Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Final report pcsirks;djsfkjlf

222 views

Published on

metallgraphy, mechanical testing and non destructive testing

Published in: Engineering

Final report pcsirks;djsfkjlf

  1. 1. 1 INTERNSHIP REPORT Submitted by: MUHAMMAD RIZWAN (2011-MM-49) University of Engineering & Technology Lahore
  2. 2. 2 Contents METALLOGRAPHY.......................................................................................................................................................5 INTRODUCTION:......................................................................................................................................................................................................................................... 5 PREPARATION OF SAMPLE: ........................................................................................................................................7 MEASURING MICROSCOPE:.............................................................................................................................. 11 ZOOM MICROSCOPE:...........................................................................................................................................................................................................................11 IMAGE ANALYZING MICROSCOPE:............................................................................................................................................................................................12 1-STANDARD TEST METHOD FOR MEASUREMENT OF METAL AND OXIDE COATING THICKNESS ......................... 13 2- GRAIN SIZE MEASURMENT.................................................................................................................................. 15 3-ANALYSIS OF WELDING DEFECTS ......................................................................................................................... 19 ON SITE METALLOGRAPHY ...................................................................................................................................... 23 NON DESTRUCTIVE TESTING ................................................................................................................................... 27 HARDNESS TESTING .......................................................................................................................................... 27 NON DESTRUCTIVE TESTING: .................................................................................................................................. 27 1-VICKER HARDNESS TEST .............................................................................................................................. 29 2-MICRO VICKER HARDNESS TEST ................................................................................................................ 32 3-ROCKWELL HARDNESS TEST:...................................................................................................................... 34 4-BRINELL HARDNESS TEST ............................................................................................................................ 37 5-SHORE HARDNESS........................................................................................................................................... 39 6-PORTABLE HARDNESS TESTER ................................................................................................................... 40 IMPORTANCE OF NDT:....................................................................................................................................... 41 1-DYE PENETRANT TESTING............................................................................................................................ 43 2-MAGNETIC PARTICLE INSPECTION (MPI).................................................................................................. 46 INTRODUCTION:.................................................................................................................................................. 46 3-ULTRASONIC TESTING................................................................................................................................... 49 4-EDDY CURRENT TESTING ............................................................................................................................. 53 5-RADIOGRAPHIC TESTING.............................................................................................................................. 56 MECHANICAL TESTING LAB ..................................................................................................................................... 59 INTRODUCTION:.................................................................................................................................................. 59 1-TENSILE TEST................................................................................................................................................... 62 2-COMPRESSION TEST ....................................................................................................................................... 69
  3. 3. 3 3-BEND TEST ........................................................................................................................................................ 72 4-IMPACT TEST.................................................................................................................................................... 77 POWDER METALLURGY:................................................................................................................................... 81 PM PARTS CLASSIFICATION SYSTEM:........................................................................................................... 86 PM WORK MATERIALS: ..................................................................................................................................... 86 LIMITATIONS AND DISADVANTAGES:.......................................................................................................... 87 REFRENCES:………………………………………………………………………………………………………………………………………………………..88
  4. 4. 4 Lab # 1 Metallography Lab Submitted To: Sir Abdul Kareem & Sir Faisal Farooq Submitted By: Muhammad Rizwan 2011-MM-49 Pakistan Institute of Technology of Minerals and Advanced Materials ____________ Signatures
  5. 5. 5 METALLOGRAPHY INTRODUCTION: Metallography has been described as both a science and an art. Traditionally, metallography has been the study of the microscopic structure of metals and alloys using optical metallographs, electron microscopes or other surface analysis equipment. More recently, as materials have evolved, metallography has expanded to incorporate materials ranging from electronics to sporting good composites. By analyzing a material’s microstructure, its performance and reliability can be better understood. Thus metallography is used in materials development, incoming inspection, production and manufacturing control, and for failure analysis; in other words, product reliability. Metallography or microstructural analysis includes, but is not limited to, the following types of analysis: • Grain size • Porosity and voids • Phase analysis • Cracks and other defects • Corrosion analysis • Coating thickness and integrity • Inclusion size, shape and distribution • Weld and heat-affected zones (HAZ) • Graphite nodularity • Carburizing thickness Some of these properties are briefly described below. GRAIN SIZE For metals and ceramics, grain size is perhaps the most significant metallographic measurement because it can be directly related to the mechanical properties of the material. Although grain size is actually a 3- dimensional property, it is measured from a 2-dimensional cross section of the material. Common grain size measurements include grains per unit area/volume, average diameter or grain size number. Determination of the grain size number can be calculated or compared to standardized grain size charts. Modern image analysis algorithms are very useful for determining grain size.
  6. 6. 6 COATING THICKNESS Coatings are used to improve the surface properties of materials. Coatings can improve temperature resistance (plasma coating), increase hardness (anodizing), provide corrosion protection (galvanized coatings), increase wear resistance, and provide better thermal expansion adherence for dielectric/metal interfaces. Metallographic analysis can provide useful information regarding coating thickness, density, uniformity and the presence of any defects. INCLUSIONS: Inclusions are foreign particles that contaminate the metal surface during rolling or other metal forming processes. Common inclusion particles include oxides, sulfides or silicates. Inclusions can be characterized by their shape, size and distribution. Weld Analysis: Welding is a process for joining two separate pieces of metal. The most common welding processes produce localized melting at the areas to be joined, this fused area is referred to as the bead and has a cast-like structure. The area or zone adjacent to the bead is also of interest and is known as the HAZ (heat affected zone). Typically the welded area will have a different microstructure and therefore different physical and mechanical properties as compared to the original metals. Analysis can also include evaluating cracks and inter diffusion of the base metals within the welded area.
  7. 7. 7 PREPARATION OF SAMPLE: The surface of a metallographic specimen is prepared by various methods of grinding, polishing, and etching. After preparation, it is often analyzed using optical or electron microscopy. Using only metallographic techniques, a skilled technician can identify alloys and predict material properties. STEPS: The standard procedure used for sample preparation is ASTM E-3. Sample preparation is carried out according to following steps 1. Sectioning 2. Mounting 3. Grinding 4. Polishing 5. Etching 6. Microscopic examination 1-SECTIONING: The first step in preparing a specimen for metallographic or microstructural analysis is to locate the area of interest. Sectioning or cutting is the most common technique for revealing the area of interest. Proper sectioning has the following characteristics: DESIRABLE EFFECTS:  Flat and cut close to the area of interest  Minimal microstructural damage UNDESIRABLE EFFECTS:  Smeared (plastically deformed) metal  Heat affected zones (burning during cutting)  Excessive subsurface damage (cracking in ceramics)  Damage to secondary phases (e.g. graphite flakes, nodules or grain pull-out) The goal of any cutting operation is to maximize the desirable effects, while minimizing the undesirable effects. . In many ways, sectioning is the most important step in preparing specimens for physical or microscopic analysis. This can be done manually using a hacksaw or automatically using cutters such as
  8. 8. 8 a diamond cutter or mecatome cutter provided with a silicon carbide cutter. Sectioning of a metallographic sample must be performed carefully to avoid altering or destroying the structure of interest. The most widely used sectioning device is the abrasive cutoff machine, ranging from units using thin diamond-rimmed wafering blades to those using wheels that are more than 1.5 mm (1/16 in.) thick, 30 to 45 cm (12 to 18 in.) in diameter, containing silicon carbide particles. Heat is generated during abrasive cutting, and the material just below the abraded surface is deformed. To minimize burning and deformation, a lubricant or coolant is typically used. Wet cutting yields a flat relatively smooth surface. However, because of the abrasion associated with cutting, the structure of the metal or alloy is damaged to a depth of approximately 1 mm (0.04 in.). The exact depth of damage depends on the type of cutoff wheel used, the cutting speed, and the hardness of the specimen. The harder the specimen, the shallower the depth of damage. This damaged layer must b removed by grinding. 2-MOUNTING: Mounting facilitates handling of the specimen. A procedure that does not damage the specimen should be selected. Because large specimens are generally more difficult to prepare than small ones, specimen size should be minimized. Standard or typical specimen mounts are right circular cylinders 25 to 50 mm (1 to 2 in.) in diameter. Mounting mediums should be compatible with the specimen regarding hardness and abrasion resistance. There are two type of mounting 1- Hot mounting 2- Cold mounting HOT MOUNTING Hot mounting involves heating epoxies and/or phenolic powders above 300°F while maintaining a constant pressure up to 4,500 psi. Cycle times are relatively short (10-15 minutes), which makes this method very attractive for labs subject to short turn-around requirements. However, due to the heat, pressure, and flow limitations associated with this process, hot mounting is a poor choice for most coating families. e. Two common mounting materials are thermosetting phenolics, such as Bakelite, and thermoplastic materials, such as methyl methacrylate (Lucite). A thermosetting polymer develops a rigid three-dimensional structure upon being heated and held at 200 to 300 °C (390 to 570 °F). A thermoplastic polymer softens when held at elevated temperatures. e. Two common mounting materials are thermosetting phenolics, such as Bakelite, and thermoplastic materials, such as methyl methacrylate (Lucite). A thermosetting polymer develops a rigid three-dimensional structure upon being heated and held at 200 to 300 °C (390 to 570 °F). A thermoplastic polymer softens when held at elevated temperatures. The main drawback to hot mounting for porous thermal spray coatings. When compared to cold mounting with a low-viscosity epoxy, hot mounting media does not penetrate porous coatings effectively. During grinding and polishing, areas of the coating not impregnated with epoxy are more susceptible to mechanical damage.
  9. 9. 9 COLD MOUNTING: Cold mounting procedure will be used to mount the specimens. Place the sample in a mounting cup with the help of mounting clips and then pour a mixture of resin mixture of two components). Now allow the resin to solidify (curing) and then take the sample out of the mounting cup. Applying release agent to the walls of the mounting cup before pouring the resin will help in easily removing the sample after curing process. The important considerations for cold mount material selection are cure time, hardness, viscosity (the ability of the material to fill inherent porosity & voids), and shrinkage. Cold mounting is the general term used to describe multi-component systems such as epoxies, acrylics, and polyesters which are mixed together and cast at (or near) room temperature. Despite the selection, very few of the available products in this area are generally recommended for mounting thermal spray coatings. Based on these requirements, several candidates can be quickly eliminated. Despite their short cure time (< 30 minutes), acrylics and polyesters generally exhibit relatively high viscosity, high shrinkage, and low hardness when compared to epoxies. Shrinkage and low hardness lead to poor edge retention and subsequently hinder coating evaluations. High viscosity limits coating impregnation, even with the assistance of a vacuum chamber. GRINDING: Grinding is generally considered the most important step in specimen preparation. Care must be taken to minimize mechanical surface damage. Grinding is generally per formed by the abrasion of the specimen surface against water-lubricated abrasive wheels (assuming water does not adversely affect the metal). Grinding develops a flat surface with a minimum depth of deformed metal and usually is accomplished by using progressively finer abrasive grits on the grinding wheels. A typical sequence might begin with 120- or 180-grit papers and pro-ceed to 240, 320, 400, and 600 grits. Scratches and damage to the specimen surface from each grit must be. removed by the next finer grinding step. The surface damage remaining, on the specimen after grinding must be removed by polishing. If this disturbed or deformed metal at the surface is not removed, microstructural observations may be obscured.Because structure and properties are so closely related, conclusions based on the structure would lead to incorrect interpretation of the anticipated behavior of the metal. Grinding of metallographic specimens is discussed in the article "Mechanical Grinding, Abrasion, and Polishing" in Volume 9 of the 9th Edition of Metals Handbook. POLISHING: Polishing of the metallographic specimen generally involves rough polishing and fine polishing. In rough polishing, the cloth covering on a wheel is impregnated with a fine (often as small as 1 txm) diamond paste or a slurry of powdered ot-A1203 in water, and the specimen is held against the rotating wheel. The cloth for rough polishing is frequently napless, providing easy access of the polishing abrasive to the specimen surface. Fine polishing is conducted similarly, but with finer abrasives (down to 0.05 ~m in diameter) on a napped cloth. Although often automated, polishing can be performed by hand. Vibratory polishing and electropolishing techniques have also been developed for many metals and alloys (see the article "Electrolytic Polishing" in Volume 9 of the 9th Editio free specimen surface, in which inclusions and other second-phase articles may be visible. Polishing damage, such as that illustrated in Fig. 3, should be recognized and avoided when preparing metallographic specimens.
  10. 10. 10 (a) (b) Fig. The effect of improper polishing on AISI 1010 steel • "Comet tails" from improper polishing. • The same material polished correctly, exhibiting small manganese sulfide inclusions ETCHING: Etching includes any process used to reveal the microstructure of a metal or alloy. Because many microstructural details are not observable on an as-polished specimen, the specimen surface must be treated to reveal such structural features as grains, grain boundaries, twins, slip lines, and phase boundaries. Etchants attack at different rates areas of different crystal orientation, crystalline imperfections, or different composition. The resulting surface irregularities differentally reflect the incident light, producing contrast, coloration, polarization, etc. Various etching techniques are available, including chemical attack, electrochemical attack, thermal treatments, vacuum cathodic etching, and mechanical treatments (see the articles "Color Metallography" and "Etching" in Volume 9 of the 9th Edition of Metals Handbook). Chemical and electrochemical attack are the most frequently used. Metallography involves many steps that can obscure or alter the structure observed during examination, leading to erroneous conclusions. Therefore, specimen preparation is not necessarily straight forward, and care must be taken to ensure that the structure observed is not an artifact. Good metallography is necessary in developing a correlation between the structure and the properties of metals and alloys. MICROSCOPIC EXAMINATION: Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye (objects that are not within the resolution range of the normal eye). Optical or light microscopy involves passing visible light transmitted through or reflected from the sample through a single or multiple lenses to allow a magnified view of the sample. The resulting image can be detected directly by the eye, imaged on a photographic plate or captured digitally. We used many microscopes in the metallography lab for the observation of microstructure. The description of some are given below.
  11. 11. 11 MEASURING MICROSCOPE: Measuring microscope is used to take measurements on microscopic level. Majorly used to measure indents, scratches, coating thickness, porosity defects and various dimensional characteristics. It differs from other microscopes in the way that it has certain coinciding marks on the eye piece and a separate panel which shows length changes in 3-dimensions. To measure a dimension, for example the thickness of coating, the center of the lens is just placed above the outer side of the coating, readings are reset to zero and the center of lens is moved to the inner side of the coating. In this way the distance moved is calculated and displayed on the panel automatically. Other specifications are listed below  The upper portion of microscope moves up and downwards for focusing, rather than the stage.  The readings are displayed in millimeters which usually converted into nanometers.  It gives real magnified image of the sample.  Total magnifications of 50-1000X.  Eye piece magnification 10X.  Objective lens magnification 5-100X. ZOOM MICROSCOPE: Zoom microscope is a special type of analyzing microscope through which one can analyze sample on macro level. This microscope is usually used to analyze welding and claddings for defects. The sample is placed beneath the objective lens and the image can also be seen on the screen attached to it with a zoom of 56X.
  12. 12. 12 Other specifications are: • It is illuminated by white light. • The upper portion of microscope moves up and downwards for focusing, rather than the stage. • It gives real magnified image of the sample. • Eye piece with 8X magnification. • Adjustable lens with magnification 0.8-7X . IMAGE ANALYZING MICROSCOPE: Image analyzing microscope as name implies is used to analyze the microstructure of the material, images can be seen as well as stored on the computer system for further analysis. These are the most used microscopes. It gives inverted magnified image of the sample. • Total magnifications of 50-1000X. • Eye piece magnification 10X • Objective lens magnification 5-100X • It is illuminated by yellow incandescent light. With the help of these microscopes provided in the metallography lab we measured coating thickness, grain size, flake size and welding defects. Detail procedure of these measurement are given below.
  13. 13. 13 STANDARD TEST METHOD FOR MEASUREMENT OF METAL AND OXIDE COATING THICKNESS SCOPE This test method covers measurement of the local thickness of metal and oxide coatings by the microscopical examination of cross sections using an optical microscope. Under good conditions, when using an optical microscope, the method is capable of giving an absolute measuring accuracy of 0.8 µm. This will determine the suitability of the method for measuring the thickness of thin coatings. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use REFERENCED DOCUMENTS: ASTM Standards: 487-85 E 3 Methods of Preparation of Metallographic Specimens SUMMARY OF TEST METHOD This test method consists of cutting out a portion of the test specimen, mounting it, and preparing the mounted cross section by suitable techniques of grinding, polishing, and etching. The thickness of the cross section is measured with an optical microscope. PROCEDURE: • First of all we prepared, mounted, polished, and etched the specimen so that: • The cross section is perpendicular to the coating; • The surface is flat and the entire width of the coating image is simultaneously in focus at the magnification used for the measurement; • All material deformed by cutting or cross sectioning is removed. • The boundaries of the coating cross section are sharply defined by no more than contrasting appearance or by a narrow, well-defined line. • Measured the width of the image of the coating cross section at 10 points distributed along a length of the microsection, and calculate the arithmetic mean of the measurements. CALCULATIONS: Mean= 10.5mm Coating thickness =mean/magnification*1000 =10.5/100*1000 Coating thickness =105micron
  14. 14. 14 FACTOR INFLUENCING COATING THICKNESS: The factors influencing oxide and coating thickness are; 1- Surface Roughness, 2- Taper of Cross Section 3- Deformation of the Coating 4- Rounding of Edge of Coating 5- Overplating 6- Magnification 7- Calibration of Stage Micrometer 8- Calibration of Micrometer Eyepiece 9- Alignment 10- Uniformity of Magnification 11- Lens Quality 12- Orientation of Eyepiece 13- Tube Length
  15. 15. 15 2- GRAIN SIZE MEASURMENT INTRODUCTION: The grain size in a metallic product is a factor which determines the hardness and ultimate tensile strength of that product. There are certain processing techniques that can be used to determine the grain size in a product, at the bulk product stage of manufacturing. As such, it is an important factor to record and use in the quality control of products. Grain size measurement is not restricted to metals and may be used in ceramics, or other situations involving grain like structures. The grain size may be expressed in terms of a grain size number: This is usually related to the number of grains per unit area by a logarithmic arithmetic relationship. The following standards describe the nature of these relationships. The grains in a metallic specimen are revealed when the specimen is polished and then etched, using a suitable etching reagent. This is due to differences in the way in which the grain is eroded by the reagent at the grain boundaries. ASTM E112 STANDARD METHOD FOR DETERMINING AVERAGE GRAIN SIZE: ASTM E112 is a basic manual method, standard issued by ASTM. It details manual procedures for use in grain sizing. The methods rate grain size in terms of ASTM grain size number. GRAIN: A grain is considered to be all that area within the confines of the original (primary) boundary. In materials having twinned grain structures a crystal and its twinned bands shall be considered as one grain. GRAIN SIZE: In materials consisting of two or more constituents, the grain size refers to the matrix. This is true, except in those materials where the second phase is of sufficient amount or size or continuity to be significant to the grain size. This may be estimated and recorded separately. Minor constituent phase’s inclusions and additives are not normally considered in the estimation of grain size. SUB GRAINS: The sizes of sub-grains may be estimated by the same methods applicable to the grains themselves. METHODS: All the methods within ASTM E112 are intended to be manual methods. They are not restricted to use for measuring grain size of metals but can be used for measuring the mean grain, crystal or cell size of non metallic materials.
  16. 16. 16 This standard contains instructions for the use of the following methods. 1- Comparison Procedure 2- Planimetric (Jeffries) Procedure 3- Lineal Intercept (Heyn) Procedure 4- Circular Intercept Procedure 1-COMPARISON PROCEDURE: This method can be applied to completely re-crystallized or cast products. The comparison procedure is a visual estimation, for which the results are generally reproducible within plus or minus a whole grain size number. When the specimen is equiaxed this method is most convenient of the three grain sizing methods, and is sufficiently accurate. Experience has shown that unless the appearance of the standard reasonably well approaches that of the sample, errors may occur. To minimize such errors the comparison charts are presented in four categories as follows. 1. Plate I: Un-twinned grains (flat etch) includes grain sizes (00, 0, ½, 1, 1½, 2, 2½, 3, 3 ½, 4, 4½, 5, 5½, 6, 6½, 7, 7½, 8, 8½, 9, 9½, 10 at 100x) 2. Plate II: Twinned grains (flat etch) includes grain size numbers 1, 2, 3, 4, 5, 3. Plate II: Twinned grains (flat etch) includes grain size numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 at 100x 4. Plate III: Twinned grains (Contrast etch) includes the nominal grain diameters 0.200, 0.150, 0.120, 0.090, 0.070, 0.060, 0.050, 0.045, 0.035, 0.025, 0.020, 0.015, 0.001, 0.005 at 75x 5. Plate IV: Austenite grains in steel (McQuaid-Ehn) Includes grain size numbers 1,2,3,4,5,6,7,8 at 100x Grain size estimations on three areas should be made, on three or more representative areas of each sample section. The small number of grains per field at the coarse end of the chart series, and the large number of grains at the fine end, may lead to errors. A more meaningful comparison can be made by changing the magnification such that the apparent grain size lies nearer the centre of the range.
  17. 17. 17 Placing the standard and measured image side by side is the traditional method, although superimposition is probably more appropriate for IA. Results of inter-laboratory grain size determinations show that there is a general bias: Ratings are generally claimed to be coarser than the actual grain size by ½ to 1 G lower than. 2-PLANIMETRIC PROCEDURE: The planimetric procedure should be treated as an estimation procedure that is only accurate to plus or minus half a grain size number, when no statistical control is applied. When sufficient measurements are made and statistically analysed to comply with the requirement of ASTM E112 section 13, the grain size can be stated to plus or minus one quarter of a grain size number. This procedure is used where a higher degree of accuracy is required over the comparison method. INTERCEPT PROCEDURE: The intercept procedure should be treated as an estimation procedure that is only accurate to plus or minus half a grain size number, when no statistical control is applied. When sufficient measurements are
  18. 18. 18 made and statistically analysed to comply with the requirement of ASTM Section 15. Then the grain size can be stated to the accuracy indicated but not normally lesser than plus or minus one tenth of a grain size number. There is no direct mathematical relationship between the ASTM grain size number (G), and the mean lineal intercept, unlike the exact relation ship between G and NAE. The relationship between the ASTM grain size number (G) and the mean lineal intercept is defined such that ASTM No.0 has a mean lineal intercept size of precisely 32.00 mm. for macroscopically determined grain size and of 32.00 mm on a field of view at 100x magnification, for the microscopically determined grain size scale. In order to measure the grain size of non-equiaxed grain structures it is necessary to make measurements on the three principle axes though the specimen and combine the results. Ref. ASTM E112 16.3. In cases of dispute, the intercept method should be the referee procedure in all cases. Section 13 of the ASTM E112 defines the Heyn lineal intercept method: This method uses straight line intercept counting. 50 intercepts are required in one visual field and the magnification should be adjusted to permit this. The precision of the grain size method is a function of the number of grain interceptions counted. Between three and five widely separated fields should be selected to make the measurement. Provided the specimen is equiaxed the measurement will be valid however if the specimen is not equiaxed then more information can be gathered by making separate measurements along the three principle axes of the specimen. See ASTM E112 section 16, Specimens with non-equiaxed grain shapes.
  19. 19. 19 3-ANALYSIS OF WELDING DEFECTS BASIC METALLURGY OF FUSION WELDING: A typical fusion welded joint varies in metallurgical structure from the fusion zone to the base material with consequential variations in mechanical properties. This is because of the fact that fusion welding processes result in melting and solidification with very high temperature gradient within a small zone with the peak temperature at the center of the fusion zone. In general, a weld can be divided in four different zones as shown schematically in fig. The fusion zone (referred to as FZ) can be characterized as a mixture of completely molten base metal (and filler metal if consumable electrodes are in use) with high degree of homogeneity where the mixing is primarily motivated by convection in the molten weld pool. The main driving forces for convective transport of heat and resulting mixing of molten metal in weld pool are: 1. Buoyancy force 2. Surface tension gradient force 3. Electromagnetic force 4. Friction force. Similar to a casting process, the microstructure in the weld fusion zone is expected to change significantly due to remelting and solidification of metal at the temperature beyond the effective liquidus temperature. The weld interface, which is also referred to as mushy zone, is a narrow zone consisting of partially melted base material which has not got an opportunity for mixing. This zone separates the fusion zone and heat affected zone. The heat affected zone (HAZ) is the region that experiences a peak temperature that is well below the solidus temperature while high enough that can change the microstructure of the material. The amount of change in microstructure in HAZ depends on the amount of heat input, peak temp reached, time at the elevated temp, and the rate of cooling. The unaffected base metal zone surrounding the HAZ is likely to be in a state of high residual stress, due to the shrinkage in the fusion zone. However, this zone does not undergo any change in the microstructure.
  20. 20. 20 The fusion zone and heat affected zone of welded joints can exhibit very different mechanical properties from that of the unaffected base metal as well as between themselves. For example, the fusion zone exhibits a typical cast structure while the heat affected zonewill exhibit a heat-treated structure involving phase transformation, recrystallization and grain growth. The unaffected base metal, on the other hand, will show the original rolled structure with a slight grain growth. DEFECTS IN WELDING: The performance of welded structure in service depends on presence or absence of defects in weld joints. In a general sense, the term weld defect refers to any departure in welded structure or welded joints from the specified requirements. According to the International Institute of Welding, the weld defects are classified into six groups as follows: • Cracks, • Cavities (blowholes, porosity, shrinkage, etc.) • Solid Inclusion • Incomplete fusion • Imperfect Shape • Miscellaneous defects. CRACKS: Cracks are the most dangerous amongst all types of defects as it reduce the performance of a welded joint drastically and can also cause catastrophic failure. Depending on the position, location and orientation these can be categorized as longitudinal cracks, transverse cracks, crater cracks, under-bead cracks, and toe cracks. These cracks are usually visible and hence, referred to surface defects in weld joints. In general, the cracks in weld joints occur due to high concentration stresses during solidification of weld, poor fit-up and incorrect welding procedures, and poor edge quality. Formation of cracks can be controlled by preheating the joints, reducing the cooling rate, taking proper precautions during post weld heat treatment. SHRINKAGE CAVITY: It is referred to the cavities which are formed due to shrinkage of weld metal during its solidification. The shrinkage cavity usually occurs during welding of thick plates in a single pass using submerged arc welding or electroslag welding processes. Proper amount of filler material has to be supplied for compensation during shrinkage to avoid this king of defect. INCOMPLETE FUSION AND PENETRATION: Incomplete fusion can occur due to inadequate welding current, offset of electrode from the axis of the weld, too high a weld speed, improper joint preparation and fit-up. It occurs between the parent metal and the weld metal and also between intermediate layers in multi-pass welding reducing the weld
  21. 21. 21 strength. Lack of penetration or inadequate penetration usually occurs at the root of the weld and also becomes a built-in crack, which can run through the base metal or weld metal or heat affected zone in actual service condition. DEFECTS WITH DESCRIPTIONS:
  22. 22. 22
  23. 23. 23 ON SITE METALLOGRAPHY INTRODUCTION: Field Metallography is most important NDT technique for assessment of plant health and life to avoid disastrous failures and to guarantee safe operations of critical equipment in petrochemical plants, power plants, cement plants, fertilizer plants, etc. When material or component used in service for long time or at high temperature or high pressure its microstructure degrade or change. On-site or field metallography can be useful for assessment of in service degradation of microstructure. Properties like mechanical, physical, metallurgical and corrosion resistance of metals and alloys all depend on the microstructure of the metals or alloys. ADVANTAGES: IN-SITU OR FIELD METALLOGRAPHY  The technique is portable and can be used on-site.  Field metallography can also be used to monitor quality of purchased components.  Field metallography can be used to monitor the evolution of microstructural changes in components during lifetime.  This is particularly useful in assessing creep damage in elevated temperature components (turbine rotor /discs, steam piping, heat exchanger, chemical reactor, pressure vessels, etc.)  The technique can be applied to a wide variety of materials.  Field metallography can complement nondestructive techniques such as ultrasonic testing. APPLICATIONS:  Metallographic examination of various metals & alloys in different forms such as castings, forgings, pipes, plates etc. non-destructively & at site.  Life assessment of equipment & components in service at high temperature & under high stress/pressure (like reactors, furnace tubes, turbine shaft, turbine discs, gas pipe lines etc.)  Failure analysis by fracture examination.  Inter-Granular Corrosion Cracking – IGCC.  Cost effectiveness of heat treatment procedures on multi-sectional parts by test on each section without cutting.  Checking welds & Heat affected zone for micro cracks, creep voids & other defects in pipelines & pressure vessels.  Heater Tubes  Boiler Tubes  Steam Piping  Tanks
  24. 24. 24 IN-SITU METALLOGRAPHY The in-situ metallography technique consists of:  Location selection,  Mechanical grinding,  Mechanical polishing/electrolytic polishing,  Chemical etching/electrolytic etching,  Microscopic examination (Capture Micrograph), and  Replication. Equipments used for in-situ metallography are below:  Fine Grinder & Polisher with a flexible shaft & variable speed / constant torque control  Electrolytic Polishing & Etching Equipment  Portable Microscope (Magnification 100X – 400X)  Digital Camera attached with portable microscope and captured micrograph at site.  Replica Kit Consumables used for in-situ metallography are listed below:  Grinding papers of different grit sizes  Polishing cloths  Diamond Paste  Etchants (solvents)  Water bottles  Replica films
  25. 25. 25 DAMAGE MECHANISM AND DEGRADATION OF MICROSTRUCTURE: Degradation of microstructures determines through Field metallography or In-situ metallography:  Creep damage  Hydrogen attack  Thermal fatigue  Intergranular corrosion  Stress Corrosion Cracking  Sigma Phase  High temperature oxidation  Carburization  Decarburization  Carbide precipitation  Graphitization
  26. 26. 26 Lab # 2 Non-Destructive Testing Lab Submitted To: Sir. Zaheer Abbas Submitted By: Muhammad Rizwan 2011-MM-49 Pakistan Institute of Technology of Minerals and Advanced Materials ____________ Signatures
  27. 27. 27 NON DESTRUCTIVE TESTING In nondestructive lab we have two portions; 1. hardness testing 2. non destructive testing HARDNESS TESTING INTRODUCTION: Hardness is measure of penetration of one material to another without fracture. However, the term hardness may also refer to resistance to bending, scratching, abrasion or cutting. There are three general types of hardness measurements 1) Scratch hardness 2) Indentation hardness 3) Rebound or dynamic hardness 1) SCRATCH HARDNESS: • The ability of material to scratch on one another • Important to mineralogists, using Mohs’scale 1= talc, 10 = diamond • Not suited for metal annealed copper = 3, martensite = 7. 2) INDENTATION HARDNESS: • Major important engineering interest for metals. • Different types : Brinell, Meyer, Vickers, Rockwell hardness tests. 3) REBOUND OR DYNAMIC HARDNESS: • The indentor is dropped onto the metal surface and the hardness is expressed as the energy of impact. • Hardness tests can be used for many engineering applications to achieve the basic requirement of mechanical property. • For examples • surface treatments where surface hardness has been much improved. • Powder metallurgy • Fabricated parts: forgings, rolled plates, extrusions, machined parts. Indentation hardness measures the resistance of a sample to permanent plastic deformation. It is the resistance offered by a material to another material during penetration. Certain load is applied on the material which leaves some impression. The study of this impression gives us the hardness of the
  28. 28. 28 material. Hardness is basically a relative term. The hardness of one material is measured with reference to another material. Hardness is dependent on • Ductility • Elastic stiffness • Plasticity • Strain • Strength • Toughness • Viscoelasticity • Viscosity
  29. 29. 29 1-VICKER HARDNESS TEST INTRODUCTION: The Vickers hardness test was developed in 1924 by Smith and Sandland. The test evaluates hardness in a manner similar to Brinell taking the ratio between the load applied and the surfacearea of the resulting impression. It was decided that the indenter shape should be one based on the following • To be capable of producing geometrically similar impressions, irrespective of size. • The resulting impression should have well defined points of measurement. • The indenter should have high resistance to self-deformation. The Vickers hardness test method consists of indenting the test material with a diamondindenter, in the form of a right pyramid with a square base and an angle of 136 degrees betweenopposite faces subjected to a load of 1 to 100 kgf. The full load is normally applied for 10 to15 seconds. The two diagonals of the indentation left in the surface of the material after removal of the load are measured using a microscope and their average calculated. The area of the sloping surface of the indentation is calculated. The Vickers hardness is the quotient obtained by dividing the kgf load by the square mm area of indentation. SPECIFICATIONS OF VICKER HARDNESS TESTER : INDENTER: All Vickers ranges use a 136° pyramidal diamond indenter that forms a square indent. MAGNIFICATION: 100x-10x eyepiece, 10x objective LOAD: 1kg-50kg DWELL TIME: 10-15 seconds VICKERS TEST METHOD:  The indenter is pressed into the sample by an accurately controlled test force.  The force is maintained for a specific dwell time, normally 10 – 15 seconds.  After the dwell time is complete, the indenter is removed leaving an indent in the sample that appears square shaped on the surface.
  30. 30. 30  The size of the indent is determined optically by measuring the two diagonals of the square indent.  The Vickers hardness number is a function of the test force divided by the surface area of the indent. The average of the two diagonals is used in the following formula to calculate the Vickers hardness. HV = Constant x test force / indent diagonal squared The constant is a function of the indenter geometry and the units of force and diagonal. It is approximately 1.85. The Vickers number, which normally ranges from HV 100 to HV1000 for metals, will increase as the sample gets harder. Tables are available to make the calculation simple, while all digital test instruments do it automatically. A typical Vickers hardness is specified as follows: 82HV5 Where 82 is the calculated hardness and 5 is the test force in kg.
  31. 31. 31 APPLICATIONS: Because of the wide test force range, the Vickers test can be used on almost any metallic material. The part size is only limited by the testing instrument's capacity. It is usually used to measure the hardness of weld materials 1) Base metal 2) Weld 3) Heat affected zone (HAZ) For sheets we prefer vicker because less sample preparation is required than microvicker. ADVANTAGES: 1- One scale covers the entire hardness range. 2- A wide range of test forces to suit every application. 3- Nondestructive, sample can normally be used. LIMITATIONS: 1- The main drawback of the Vickers test is the need to optically measure the indent size. This requires that the test point be highly finished to be able to see the indent well enough to make an accurate measurement. 2- More time required for test surface preparation and the exact measurement of the test impression 3- Diamond indenter susceptible to damage. 4- Increasing susceptibility to shocks with decreasing test load.
  32. 32. 32 2-MICRO VICKER HARDNESS TEST INTRODUCTION: The digital Vickers micro-hardness tester is especially designed to test the structure of tiny or minute metal parts, this plates, metals foil, high quality cord, thin hardening layers and electroplated layers. In addition, it can also find wide applications in testing non-metallic materials such as glass, jewelry, ceramics etc, which can hardly be measured with Rockwell or other hardness testers using relatively large test load. In particulars, it could manage to measure the internal hardness of induction hardening material or carburized material by following the metal structure. The test is performed in two steps. First, the diamond indenter is driven into the surface of the tester material by applying a known load force. Second, the user measures the diagonals(s) length of the resulting indentation and input the measured length of diagonals(s) to the integrated calculator, by which hardness value could be acquired either in Vickers scale (HV). SPECIFICATIONS: INDENTER: All Vickers ranges use a 136° pyramidal diamond indenter that forms a square indent. MAGNIFICATION: 400x-10x eyepiece, 40x objective LOAD: 10 grams-1 kg/2kg DWELL TIME: 10-15 seconds PRINCIPLE OF OPERATION: The tester will exert test forces on a specimen by using weights and a lever mechanism (force amplification). After selecting a test force, the user should press <START>. The motor drives the lever to release the weights corresponding to the selected force, then the released weights press indenter down Micro vicker hardness tester
  33. 33. 33 to make an indentation on the specimen in a specified period which is preset in the software system by the user. After the indenter has left the specimen to travel back to the starting position, the user turns the turret to 40* objective to measure to diagonals(s). The measuring microscope has adjustable filer lines. The user can adjust the lines to just touch the tips of the indentation. Now the user can press the “Reading Enter Key” to input the measured result into the integrated calculator. The calculator then computer and displays the Vickers hardness value by using formulas presented in this chapter. MICRO VICKER TEST TEST METHOD: The test method is same as used for macro vicker with only difference that this machine is softare based. First we have to set the requirement for the test. After this test is started with pressing the start button. The test will automatically provide the horizontal and vertical diameter and HV value on the screen. We took the five readings and take an average of all the results.
  34. 34. 34 3-ROCKWELL HARDNESS TEST: INTRODUCTION: The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The Rockwell test differs from the Brinell and Vickers tests is not obtaining a value for the hardness in terms of an indentation but using the depth of indentation, this depth being directly indicated by a pointer on a calibrated scale. The indenter of hardened steel ball or diamond cone can be uses in the Rockwell test. A minor load of 10 kg is applied to press the indenter into contact with the surface. A major (additional) load is then applied and causes the indenter to penetrate into the specimen. The major load is then removed and there is some reduction in the depth of the indenter due to the deformation of the specimen not being entirely plastic. The difference in the final depth of the indenter and the initial depth, before the major load was applied, is determined. This is the permanent increase in penetration e due to the major load. The Rockwell hardness number HR is then given by HR=E-e Where E is the arbitrary constant which is dependent on the type of indenter. For the diamond cone indenter E is 100, for the steel ball 130. TYPES OF ROCKWELL TEST: There are two types of Rockwell tests: 1. ROCKWELL: The minor load is 10 kgf, the major load is 60, 100, or 150 kgf. 2. SUPERFICIAL ROCKWELL: The minor load is 3 kgf and major loads are 15, 30, or 45 kgf. In both tests, the indenter may be either a diamond cone or tungsten carbide ball, depending upon the characteristics of the material being tested. PRINCIPAL OF THE ROCKWELL TEST Position the surface area to be measured close to the indenter. Applied the minor load and a zero reference position is established. The major load is applied for a specified time period (dwell time) beyond zero. The major load is released leaving the minor load applied. Deeper indentation: Softer material There are a number of Rockwell scales, the scales being determined by the indenter and the major load used.
  35. 35. 35 Scale and indenter of Rockwell hardness PROCEDURE: Rockwell testing is covered by ASTM test method E 18.  The power switch was turned ON.  The total load sequence switch was set to the AUTO position in the side panel.  The minor load from selector ring was set.
  36. 36. 36  The indenter was fixed.  The specimen was placed on the anvil.  The total load value was set by turning the selector knob.  The minor load was applied by raising the anvil by rotating clockwise the elevating handle slowly until the tip of the indenter touches the specimen.  The major load was applied for 10 seconds automatically.  The hardness value was read and recorded from the hardness indicator.  The elevating handle was turned in the reversed direction to lower the anvil and thespecimen was removed.  Three reading was taken to take an average value. ADVANTAGES OF ROCKWELL HARNESS TESTER: There are several reasons for the popularity of the Rockwell test. The test itself is very rapid. On a manually operated unit, a Rockwell test takes only five to ten seconds, depending upon the size and hardness of the specimen, as well as pre-load and dwell time. Also, the indentation is extremely small and usually does not need to be removed by machining, making this a non-destructive test. A Rockwell C scale test on hardened steel, for example, penetrates to a depth of approximately 0.0035 inch, with the diameter of the indentation only 0.019 inch, which is barely visible. The Rockwell test is applicable to a wide range of part sizes. Sheet metal as thin as 0.006 inch can be tested on the Rockwell® superficial tester, and as long as the surface area is large enough, there is no actual limitation to the size of your specimen. The Rockwell test is based on measurement of the depth of penetration with the hardness number read directly from the dial gauge or digital display that is part of every tester. In comparison, tests such as the Brinell and Knoop require optical measurement of the diameter and length respectively. Direct indication of the Rockwell hardness number is possible only because of the unique feature of the application of the minor load (preliminary test force) which seats the penetrator in the work and establishes a reference or SET position from which the depth of penetration under the heavier or major load (total test force) can be measured. This SET point establishes the same starting point with every specimen.
  37. 37. 37 4-BRINELL HARDNESS TEST INTRODUCTION: The first widely accepted and standardized indentation test, was proposed by J.A. Brinell in 1900. Brinell hardness test is mostly regarded as destructive test. This test is widely used in different industries. Brinell hardness test is macro hardness test in which large volume is displaced by hardened steel or tungsten carbide ball. Brinell hardness number is the hardness index, calculated by pressing a hardened steel ball (indenter) into test specimen under standardized load. Brinell hardness tests are used to determine hardness of metallic materials, to check quality level of products, for uniformity of samples of metals, for uniformity of results of heat treatment. The Brinell hardness test consists in indenting the metal surface with a 10-mm diameter steel ball at a load range of 500-3000kg, depending of hardness of particular materials. The load is applied for a standard time, and the diameter of the indentation is measured giving an average value of two readings of the diameter of the indentation at right angle. TEST SPECIMEN: There is no standard shape or size for a Brinell test specimen. The specimen upon which the indentation is made shall conform to the following: THICKNESS: The thickness of the specimen tested shall be such that no bulge or other marking showing the effect of the test force appears on the side of the piece opposite the indentation. As a general rule, the thickness of the specimen shall be at least ten times the depth of the indentation
  38. 38. 38 FINISH: When necessary, the surface on which the indentation is to be made shall be filed, ground, machined or polished with abrasive material so that the edge of the indentation shall be clearly defined to permit the measurement of the diameter to the specified accuracy. BRINELL TEST PROCEDURE:  All Brinell tests use a carbide ball indenter. The test procedure is as follows:  The indenter was pressed into the sample by an accurately controlled test force.  The force was maintained for a specific dwell time, normally 10 - 15 seconds.  After the dwell time was completed, the indenter was removed leaving a round indent in the sample.  The size of the indent was determined optically by measuring two diagonals of the round indent. CALCULATIONS: The Brinell hardness number is a function of the test force divided by the curved surface area of the indent. The indentation is considered to be spherical with a radius equal to half the diameter of the ball. The average of the two diagonals is used in the following formula to calculate the Brinnel hardness. The Brinell number, which normally ranges from HB 50 to HB 750 for metals, will increase as the sample gets harder. Tables are available to make the calculation simple. A typical Brinell hardness is specified as follows: 356HBW Where 356 is the calculated hardness and the W indicates that a carbide ball was used. Note- Previous standards allowed a steel ball and had an S designation. Steel balls are no longer allowed. ADVANTAGES:  Large indentation averages out local heterogeneities of microstructure.  Different loads are used to cover a wide rage of hardness of commercial metals.  Brinell hardness test is less influenced by surface scratches and roughness than other hardness tests.  Suitable for hardness tests even under rough workshop conditions.  Suitable for hardness tests on inhomogeneous materials.  Nearly All Metals Can Be Tested.  The Brinell Tests a Wider Sample of Material.  Results of the Brinell Test are Force Independent. LIMITATIONS:  Restriction of application range to a maximum Brinell hardness of 650 HBW.  Restriction when testing small and thin-walled specimens.  Restriction when testing round specimen if diameter is smaller then 1, 5 x penetrator diameter.  Relatively serious damage to the specimen due to the large test indentation.
  39. 39. 39 5-SHORE HARDNESS There are two types of shore tests. • Shore A • Shore D For rubbers we also use an additional standard • IRHD (International rubber hardness degree) • Micro IRHD It uses the both indentation and the bounce back principles at the same time. It is used to measure the hardness of hard rubber, plastic polymers and composite materials. SHORE D:- Needle like indenter and its sharp at both the edges and has an angle of 35o, with a load of 822g. The dwell time for this test is 3 sec. It is used for the materials which have hardness value more than 100. It is widely used for rubbers and soft plastics and polymers hardness. SHORE A:- In this type of test with 822kg of load, an additional load of 4.55kg is also added. It is a 10 sec test. Its indenter is needle like with a dia of 1.25mm. Tip is sharp at an angle of 30o.It uses both the indentation and bounce back phenomenon. It is widely used to find out the hardness of hard rubbers and plastic composites. IRHD:- Steel ball is used as an indenter, with a diameter of 2.5mm and 597g load is applied and it’s a 30 sec test. The reading which was taken in the lab was for rubber and it came out to be 38.69. Micro IRHD:- This test is used for extremely thick rubbers. Steel ball is used as an indenter with a diameter of .395mm. The minimum load which can be applied through this test is 15.7g and it’s a 15 sec test.
  40. 40. 40 6-PORTABLE HARDNESS TESTER RELATED THEORY: An impact body with a hard metal test tip is propelled by spring force against the surface of the test piece. Surface deformation takes place when the impact body hits the test surface, which will result in loss of kinetic energy. This energy loss is detected by a comparison of velocities vi and vr when the impact body is at a precise distance from the surface for both the impact and rebound phase of the test, respectively. Velocity measurements are achieved through a permanent magnet in the impact body that generates an induction voltage in the coil of the impact device. The signal voltage is proportional to the velocity of the impact body. Signal processing provides the hardness reading for display and storage.
  41. 41. 41 NON DESTRUCTIVE TESTING INTRODUCTION: Non-Destructive testing is the use of noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristics of an object. It is the testing of materials, for surface or internal flaws or metallurgical condition, without interfering in any way with the integrity of the material or its suitability for service. NDT can be used to ensure the quality right from raw material stage through fabrication and processing to pre-service and in-service inspection. Apart from ensuring the structural integrity, quality and reliability of components and plants, today NDT finds extensive applications for condition monitoring, residual life assessment, energy audit, etc. SOME USES OF NDT:  Flaw Detection and Evaluation  Leak Detection  Location Determination  Dimensional Measurements  Structure and Microstructure  Characterization  Estimation of Mechanical and  Physical Properties  Stress (Strain) and Dynamic  Response Measurements  Material Sorting and Chemical  Composition Determination IMPORTANCE OF NDT: NDT increases the safety and reliability of the product during operation. It decreases the cost of the product by reducing scrap and conserving materials, labor and energy. It enhances the reputation of the manufacturer as a producer of quality goods. All of the above factors boost the sales of the product which bring more economical benefits for the manufacturer. NDT is also used widely for routine or periodic determination of quality of the plants and structures during service. This not only increases the safety of operation but also eliminates any forced shut down of the plants. There are two types of Non-destructive testing; 1- Convetional methods 2- Non-conventional methods
  42. 42. 42 CONVENTIONAL METHODS:  Dye penetrant tester  Magnetic particle tester  Ultra sonic tester  Radiography tester  Eddy current hardness tester NON-CONVENTIONAL METHODS:  Flourecent dye method  Acoustic emission  Borrow scope  Infrared camera
  43. 43. 43 1-DYE PENETRANT TESTING INTRODUCTION: Liquid Penetrant Inspection is a nondestructive method of revealing discontinuities that are open to the surfaces of solid and essentially nonporous materials. Indications of a wide spectrum of flaw sizes can be found regardless of the configuration of the work piece and regardless of flaw orientations. Liquid penetrants seep into various types of minute surface openings by capillary action. Because of this, the process is well suited to the detection of all types of surface cracks, laps, porosity, shrinkage areas, laminations, and similar discontinuities. It is extensively used for the inspection of wrought and cast products of both ferrous and nonferrous metals, powder metallurgy parts, ceramics, plastics, and glass objects. In practice, the liquid penetrant process is relatively simple to utilize and control. The equipment used in liquid penetrant inspection can vary from an arrangement of simple tanks containing penetrant, emulsifier, and developer to sophisticated computer-controlled automated processing and inspection systems. The liquid penetrant method does not depend on ferromagnetism (as does, for example, magnetic particle inspection), and the arrangement of the discontinuities is not a factor. The penetrant method is effective not only for detecting surface flaws in non-magnetic metals but also for revealing surface flaws in a variety of other nonmagnetic materials. Liquid penetrant inspection is also used to inspect items made from ferromagnetic steels; generally, its sensitivity is greater than that of magnetic particle inspection. PROCESSING STEPS OF A LIQUID PENETRANT INSPECTION Liquid penetrant inspection depends mainly on a penetrant's effectively wetting the surface of a solid work piece or specimen, flowing over that surface to form a continuous and reasonably uniform coating,
  44. 44. 44 and then migrating into cavities that are open to the surface. The cavities of interest are usually exceedingly small, often invisible to the unaided eye. SURFACE PREPARATION: One of the most critical steps of a liquid penetrant inspection is the surface preparation. The surface must be free of oil, grease, water, or other contaminants that may prevent penetrant from entering flaws. The sample may also require etching if mechanical operations such as machining, sanding, or grit blasting have been performed. Use cleaner to clean the surface. These and other mechanical operations can smear metal over the flaw opening and prevent the penetrant from entering. PENETRANT APPLICATION: Once the surface has been thoroughly cleaned and dried, the penetrant material is applied by spraying, brushing, or immersing the part in a penetrant bath. PENETRANT DWELL: The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible to be drawn from or to seep into a defect. Penetrant dwell time is the total time that the penetrant is in contact with the part surface. Dwell times are usually recommended by the penetrant producers or required by the specification being followed. The times vary depending on the application, penetrant materials used, the material, the form of the material being inspected, and the type of defect being inspected for. Minimum dwell times typically range from five to 60 minutes. Generally, there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry. The ideal dwell time is often determined by experimentation and may be very specific to a particular application. EXCESS PENETRANT REMOVAL This is the most delicate part of the inspection procedure because the excess penetrant must be removed from the surface of the sample while removing as little penetrant as possible from defects. Depending on the penetrant system used, this step may involve cleaning with a solvent, direct rinsing with water, or first treating the part with an emulsifier and then rinsing with water. DEVELOPER APPLICATION: A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible. Developers come in a variety of forms that may be applied by dusting (dry powdered), dipping, or spraying (wet developers)
  45. 45. 45 INDICATION DEVELOPMENT: The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws. This development time is usually a minimum of 10 minutes. Significantly longer times may be necessary for tight cracks. INSPECTION: Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present. CLEAN SURFACE: The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable. RESULT: In different specimens crack was clear with red stain. ADVANTAGES OF DYE PENETRANT TESTING:  The method has high sensitivity to small surface discontinuities.  The method has few material limitations, i.e. metallic and nonmetallic, magnetic and nonmagnetic, and conductive and nonconductive materials may be inspected.  Large areas and large volumes of parts/materials can be inspected rapidly and at low cost.  Parts with complex geometric shapes are routinely inspected.  Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.  Aerosol spray cans make penetrant materials very portable.  Penetrant materials and associated equipment are relatively inexpensive. LIMITATIONS OF DYE PENETRANT TESTING:  Only surface breaking defects can be detected.  Only materials with a relatively nonporous surface can be inspected.  Precleaning is critical since contaminants can mask defects.  Metal smearing from machining, grinding, and grit or vapor blasting must be removed prior to LPI.  The inspector must have direct access to the surface being inspected.  Surface finish and roughness can affect inspection sensitivity.  Multiple process operations must be performed and controlled.  Post cleaning of acceptable parts or materials is required.
  46. 46. 46 2-MAGNETIC PARTICLE INSPECTION (MPI) INTRODUCTION: Magnetic Particle inspection is used to identify surface and near surface discontinuities in ferromagnetic materials such as steel and iron. The technique uses the principle that magnetic lines of force (flux) will be distorted by the presence of a discontinuity. Discontinuities (for example, cracks) are located from the flux distortion following the application of fine magnetic particles to the area under test. The part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be isually detected under proper lighting conditions. MPI PROCESS STEPS:  Pre – Cleaning  Application of background  Magnetization  Applying magnetic medium  Inspection  Post cleaning  Demagnetization The process of MPI is described below 1- PRE-CLEANING The surface of the sample was cleaned thoroughly with the help of a cloth using a cleaner usually acetone or alcohol. 2- APPLICATION OF WHITE BACKGROUND A white background was applied by spraying a white chemical so that it makes the accumulated iron particles visible during the test.
  47. 47. 47 3- MAGNETIZATION The sample was magnetized with the help of yoke or magnetizing probes. After magnetization, north and south poles appear on the edges of the samples as well as the edges of the defect. The formation of poles helps further for the identification of defects. 4- IRON PARTICLES SPRAYING (MAGNETIC MEDIUM) Afterwards a suspension of iron particles of the size 2-4 μm was sprayed on the surface of magnetized sample. Iron particles accumulate on the edges of defects due to the presence of polarity and defects become visible as dark marks. 4- INSPECTION: After the spray of iron particle the inspection of the sample was carried out. These particles were attracted to magnetic flux leakage fields and clustered to form an indication directly over the defects. This indication was visually detected under proper lighting conditions. 5- POST CLEANING Post cleaning was done to remove all the signs of test. Cleaner was used. In this we got the original properties retained even after the test was done. 6- DEMAGNATIZATION: Residual magnetism affects further operation such as welding. Demagnetization is preferably done with AC. Object was moved slowly away from coil. After demagnetization residual magnetism was checked with gauss meters.
  48. 48. 48 ADVANTAGES OF MPI:  It does not need very stringent pre-cleaning operation.  It is the best method for the detection of surface and near to the surface cracks in ferromagnetic materials.  Fast and relatively simple NDT method.  Generally inexpensive.  Will work through thin coating.  It is quicker. LIMITATIONS OF MPI:  Material must be ferromagnetic.  Orientation and strength of magnetic field is critical.  Detects surface and near-to-surface discontinuities only.  Large currents sometimes require.
  49. 49. 49 3-ULTRASONIC TESTING INTRODUCTION: Ultrasonic testing uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic examinations can be conducted on a wide variety of material forms including castings, forgings, welds, and composites. A considerable amount of information about the part being examined can be collected, such as the presence of discontinuities, part or coating thickness. This technique is used for the detection of internal surface (particularly distant surface) defects in sound conducting materials. In this method high frequency sound waves are introduced into a material and they are reflected back from surface and flaws. Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features. BASIC PRINCIPLE OF ULTRASONIC TESTING: A typical UT system consists of several functional units, such as the pulse/receiver, piezoelectric transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the piezoelectric transducer and is displayed on a screen. In the figure below, the reflected signal strength is displayed versus the time from signal generation, when a echo was received. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.
  50. 50. 50 PIEZOELECTRIC TRANSDUCER: A transducer is a device that converts energy from one form to another. Presently, piezoelectric material is commonly used as a basic component of transducers. A piezoelectric element is a crystal which delivers a voltage when mechanical force is applied between its faces, and it deforms mechanically when voltage is applied between its faces. Because of these characteristics piezoelectric element is capable of acting as both a sensing and a transmitting element. Piezoelectric transducers have been conventionally used to convert electric signals into sound wave, or to convert sound wave into electric signals. Transducers are manufactured in a variety of forms, shapes and sizes for varying applications. Transducers are categorized in a number of ways which include:  Contact or immersion  Single or dual element  Normal or angle beam COUPLANT: A couplant is a material (usually liquid) that facilitates the transmission of ultrasonic energy from the transducer into the test specimen. Couplant is generally necessary because the acoustic impedance mismatch between air and solids (i.e. such as the test specimen) is large. The couplant displaces the air and makes it possible to get more sound energy into the test specimen so that a usable ultrasonic signal can be obtained. In contact ultrasonic testing a thin film of oil, glycerin or water is generally used between the transducer and the test surface TEST TECHNIQUES: Ultrasonic inspection techniques are commonly divided into three primary classifications. 1- PULSE-ECHO AND THROUGH TRANSMISSION: (Relates to whether reflected or transmitted energy is used)
  51. 51. 51 1- NORMAL BEAM AND ANGLE BEAM: (Relates to the angle that the sound energy enters the test article) 1- CONTACT AND IMMERSION: (Relates to the method of coupling the transducer to the test article) In single crystal probe, the same crystal is used as transmitter and receiver as well. In double crystal probe, transmitter and receiver crystals act separately. In angle beam probe, beam is transmitted at a certain angle. It is usually used in weld inspection. The second part of the detector is a manipulator with a screen which consists of various function keys and a graph plotter which basically shows the output. PROCEDURE: The procedure consists of the following steps. 1. A couplant is applied on the surface of the sample. The function of this couplant is to make the surface of the sample plain and to lessen the resistance to the probe for sliding on the surface so it prevents the probe surface to wear out. Oil or grease is usually used as couplants. 2. The probe is held onto the surface of the sample and the thickness of the sample is measured. This length acts as the standard. Then the probe is sled over the whole surface. If the output shows the decrement in the traveling distance of the beam, it shows the presence of the a defect and by comparing it with the original thickness, defect can be located easily.
  52. 52. 52 ADVANTAGE OF ULTRASONIC TESTING:  Sensitive to both surface and subsurface discontinuities.  Depth of penetration for flaw detection or measurement is superior to other methods.  Only single-sided access is needed when pulse-echo technique is used.  High accuracy in determining reflector position and estimating size and shape.  Minimal part preparation required.  Electronic equipment provides instantaneous results.  Detailed images can be produced with automated systems.  Has other uses such as thickness measurements, in addition to flaw detection. LIMITATIONS OF ULTRASONIC TESTING:  Surface must be accessible to transmit ultrasound.  Skill and training is more extensive than with some other methods.  Normally requires a coupling medium to promote transfer of sound energy into test specimen.  Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult to inspect.  Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise.  Linear defects oriented parallel to the sound beam may go undetected.  Reference standards are required for both equipment calibration, and characterization of flaws.
  53. 53. 53 4-EDDY CURRENT TESTING INTRODUCTION: This method is widely used to detect surface flaws, to measure thin walls from one surface only, to measure thin coatings and in some applications to measure depth. This method is applicable to electrically conductive materials only. In this method eddy currents are produced in the product by bringing it close to an alternating current carrying coil. The main applications of the eddy current technique are for the detection of surface or subsurface flaws, conductivity measurement and coating thickness measurement. Eddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor. This magnetic field expands as the alternating current rises to maximum and collapses as the current is reduced to zero. If another electrical conductor is brought into the proximity of this changing magnetic field, the reverse effect will occur. Magnetic field cutting through the second conductor will cause an “induced” current to flow in this second conductor. Eddy currents are a form of induced currents! CRACK DETECTION: Crack detection is one of the primary uses of eddy current inspection. Cracks cause a disruption in the circular flow patterns of the eddy currents and weaken their strength. This change in strength at the crack location can be detected. GENERATION OF EDDY CURRENTS: In order to generate eddy currents for an inspection a “probe” is used. Inside the probe is a length of electrical conductor which is formed into a coil. Alternating current is allowed to flow in the coil at a frequency chosen by the technician for the type of test involved. A dynamic expanding and collapsing magnetic field forms in and around the coil as the alternating current flows through the coil. When an
  54. 54. 54 electrically conductive material is placed in the coil’s dynamic magnetic field, electromagnetic induction will occur and eddy currents will be induced in the material. Eddy currents flowing in the material will generate their own “secondary” magnetic field which will oppose the coil’s “primary” magnetic field. This entire electromagnetic induction process to produce eddy currents may occur from several hundred to several million times each second depending upon inspection frequency. Eddy currents are strongest at the surface of the material and decrease in strength below the surface. The depth that the eddy currents are only 37% as strong as they are on the surface is known as the standard depth of penetration or skin depth. This depth changes with probe frequency, material conductivity and permeability. There are three characteristics of the specimen that affect the strength of the induced eddy currents.  The electrical conductivity of the material  The magnetic permeability of the material  The amount of solid material in the vicinity of the test coil. Different type of probes The procedure of carrying EDT is as follows PROCEDURE: The procedure consists of the following steps: 1. A sample was prepared with the same composition and dimensions of original assembly to be tested. Holes of certain depths were pierced on the surface of pipe at different places. Then the probe was inserted into the pipe and travelled along its length. The data was recorded by the computer and used it as the standard. 2. After it the probe was passed into the original assembly and travelled along its length. Computer recorded the data and compared it with the standard data. In this way it figured out the type and magnitude of the defect along with its location.
  55. 55. 55 ADVANTAGES OF EDDY CURRENT INSPECTION:  Sensitive to small cracks and other defects  Detects surface and near surface defects  Inspection gives immediate results  Equipment is very portable  Method can be used for much more than flaw detection  Minimum part preparation is required  Test probe does not need to contact the part  Inspects complex shapes and sizes of conductive materials LIMITATIONS OF EDDY CURRENT INSPECTION:  Only conductive materials can be inspected  Surface must be accessible to the probe  Skill and training required is more extensive than other techniques  Surface finish and and roughness may interfere  Reference standards needed for setup  Depth of penetration is limited  Flaws such as delaminations that lie parallel to the probe coil winding and probe scan direction are undetectable
  56. 56. 56 5-RADIOGRAPHIC TESTING INTRODUCTION: Radiography Testing (RT), or industrial radiography is a nondestructive testing (NDT) method of inspecting for hidmaterials den flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials. Radiographic Testing Method is nothing but to take the shadow picture of an object onto a film by the passage of X-ray or Gamma ray through it. It is the same as the medical radiography (X-ray). Only the difference is in their wave length. RADIOGRAPHY TESTING PRNCIPLE: The principles are the same for both X and Gamma radiography. In X-radiography the penetrating power is determined by the number of volts applied to the X-Ray tube - in steel approximately 1000 volts per inch thickness is necessary. To produce an X or Gamma radiograph, the film package is placed close to the surface of the subject. The source of radiation is positioned on the other side of the subject some distance away, so that the radiation passes through the subject and on to the film. After the exposure period the film is removed, processed, dried, and then viewed by transmitted light on a special viewer. Various radiographic and photographic accessories are necessary, including such items as radiation monitors, film markers, image quality indicators, darkroom equipment, etc. Where the last is concerned there are many degrees of sophistication, including fully automatic processing units. These accessories are the same for both X and Gamma radiography systems. Also required are such consumable items as radiographic film and processing chemicals. ESSENTIAL ELEMENTS FOR RADIOGRAPHY TESTING: • A source of penetrating radiation, such as an X-ray machine. • The object to be radiographed, such as a weldment. • A recording or viewing device, usually photographic (X-ray) film enclosed in a light tight holder. • A qualified radiographer trained to produce a satisfactory exposure. • A person skilled in the interpretation of radiographs.
  57. 57. 57 The procedure for radiographic testing is as follows PROCEDURE:  The photographic paper is placed beneath the sample and then the sample is subjected to the X- rays.  Afterwards the photographic paper is removed. It is taken to the dark room for developing.  It is fixed to obtain permanent marks. Then it is developed with the help of developer. Impure water is usually used as developer.  Developed photographic paper then gives a clear image of the defects present in the sample in the form of dark marks.
  58. 58. 58 Lab # 3 Mechanical Lab Submitted To: Sir Farooq Iftikhar Submitted By: Muhammad Rizwan 2011-MM-49 Pakistan Institute of Technology of Minerals and Advanced Materials ____________ Signatures
  59. 59. 59 MECHANICAL TESTING LAB INTRODUCTION: The mechanical properties of a material are directly related to the response of the material when it's subjected to mechanical stresses. Samples of engineering materials are subjected to a wide variety of mechanical tests to measure their strength, elastic constants, and other material properties as well as their performance under a variety of actual use conditions and environments. The results of such tests are used for two primary purposes: 1. Engineering design (for example, failure theories based on strength, or deflections based on elastic constants and component geometry) and 2. Quality control either by the materials producer to verify the process or by the end user to confirm the material specifications. Mechanical tests (as opposed to physical, electrical, or other types of tests) often involve the deformation or breakage of samples of material (called test specimens or test pieces). Note that test specimens are nothing more than specialized engineering components in which a known stress or strain state is applied and the material properties are inferred from the resulting mechanical response. For example, strength is nothing more than a stress "at which something happens" be it the onset of nonlinearity in the stress-strain response for yield strength, the maximum applied stress for ultimate tensile strength, or the stress at which specimen actually breaks for the fracture strength. Mechanical properties are described as the relationship between forces (or stresses) acting on a material and the resistance of the material to deformation (i.e., strains) and fracture. This deformation, however, may or may not be evident in the metal after the applied load is removed. Different types of tests, which use an applied force, are employed to measure properties, such as elastic modulus, yield strength, elastic and plastic deformation (i.e., elongation), hardness, fatigue resistance, and fracture toughness. Because of the need to compare measured properties and performance on a common basis, users and producers of materials use standardized test methods such as those developed by the American Society for Testing and Materials (ASTM) and the International Organization for Standardization (ISO). ASTM and ISO are but two of many standards-writing professional organization in the world. These standards prescribe the method by which the test specimen will be prepared and tested, as well as how the test results will be analyzed and reported. Equipment used for mechanical testing range from simple, hand-actuated devices to complex, servo- hydraulic systems controlled through computer interfaces. Common configurations (for example, as shown in Fig) involve the use of a general purpose device called a universal testing machine. Modern test machines fall into two broad categories: electro (or servo) mechanical (often employing power screws) and servo hydraulic (high-pressure hydraulic fluid in hydraulic cylinders). Digital, closed loop control (e.g., force, displacement, strain, etc.) along with computer interfaces and user friendly software
  60. 60. 60 are common. Various types of sensors are used to monitor or control force (e.g., strain gage-based "load" cells), displacement (e.g., linear variable differential transformers ( LVDT's) for stroke of the test machine), strain (e.g., clip-on strain-gaged based extensometers). Depending on the information required, the universal test machine can be configured to provide the control, feedback, and test conditions unique to that application. Design of a test specimen is not a trivial matter. However, the simplest test specimens are smooth and unnotched. More complex geometries can be used to produce conditions resembling those in actual engineering components. Notches (such as holes, grooves or slots) that have a definite radius may be machined in specimens. Sharp notches that produce behaviour similar to cracks can also be used, in addition to actual cracks that are introduced in the specimen prior to testing.
  61. 61. 61 Fig. Geometry and loading scenarios commonly employed in mechanical testing of materials. a) tension, b) compression, c) indentation hardness, d) cantilever flexure, e) three-point flexure, f) four-point flexure and g) torsion In mechanical testing lab we have five sections: 1- Mechanical testing lab 2- Precision testing lab 3- Powder metallurgy lab 4- Metal working lab 5- Heat treatment lab In mechanical testing lab we performed the following experiments 1- Tensile test 2- Compression test 3- Bend test 4- Impact test Now we will study these 4 tests in detail.
  62. 62. 62 1-TENSILE TEST INTRODUCTION: A tensile test is a fundamental mechanical test where a carefully prepared specimen is loaded in a very controlled manner while measuring the applied load and the elongation of the specimen over some distance. Tensile tests are used to determine the modulus of elasticity, elastic limit, elongation, proportional limit, reduction in area, tensile strength, yield point, yield strength and other tensile properties. The most common type of test used to measure the mechanical properties of a material is the Tension Test. The main product of a tensile test is a load versus elongation curve which is then converted into a stress versus strain curve. Since both the engineering stress and the engineering strain are obtained by dividing the load and elongation by constant values (specimen geometry information), the load- elongation curve will have the same shape as the engineering stress strain curve. The stress-strain curve relates the applied stress to the resulting strain and each material has its own unique stress-strain curve. ELASTIC REGION: Engineering stress and strain are independent of the geometry of the specimen. In start stress and strain are in linear relationship. This is the linear-elastic portion of the curve and it indicates that no plastic deformation has occurred. In this region of the curve, when the stress is reduced, the material will return to its original shape. In this linear region, the line obeys the relationship defined as Hooke's Law where the ratio ofstress to strain is a constant. σ = Ee Where  σ = engineering stress  e = engineering strain  E = elastic modulus or young’s modulus The slope of the line in this region where stress is proportional to strain is called the “modulus of elasticity” or “Young's modulus”. The modulus of elasticity (E) defines the properties of a material as it undergoes stress, deforms, and then returns to its original shape after the stress is removed. It is a measure of the stiffness of a given material. YIELD POINT: In ductile materials, at some point, the stress-strain curve deviates from the straight-line relationship and Law no longer applies as the strain increases faster than the stress. From this point on in the tensile test, some permanent deformation occurs in the specimen and the material is said to react plastically to any further increase in load or stress. The material will not return to its original, unstressed condition when the load is removed. In brittle materials, little or no plastic deformation occurs and the material fractures
  63. 63. 63 near the end of the linear elastic portion of the curve. For most engineering design and specification applications, the yield strength is used. The yield strength is defined as the stress required to produce a small, amount of plastic deformation. S○=P(strain offset=.002)/A○ The offset yield strength is the stress corresponding to the intersection of the stress-strain curve and a line parallel to the elastic part of the curve offset by a specified strain (in the US the offset is typically 0.2% for metals and 2% for plastics while in UK offset method is 0.1% or 0.5%. Stress corresponding to 0.1% strain is known as proof strength). In some materials there is upper yield point and lower yield point. In these materials load at yield point suddenly drops this is known as yield point. After decreasing load, strain increases while load remain almost constant. This phenomena is known as yield-point elongation. After yielding stress increases the deformation occurring throughout the yield-point elongation is heterogeneous. At the upper yield point, a discrete band of deformed metal, often readily visible, appears at a stress concentration, such as a fillet. Coincident with the formation of the band, the load drops to the lower yield point. The band then propagates along the length of the specimen, causing the yield-point elongation. PLASTIC REGION: The part of the stress-strain diagram after the yielding point. At the yielding point, the plastic deformation starts. Plastic deformation is permanent. At the maximum point of the stress-strain diagram (σUTS), necking starts. ULTIMATE TENSILE STRENGTH: The ultimate tensile strength (UTS) or, more simply, the tensile strength, is the maximum engineering stress level reached in a tension test. The strength of a material is its ability to withstand external forces without breaking. In brittle materials, the UTS will at the end of the linear-elastic portion of the stress- strain curve or close to the elastic limit. In ductile materials, the UTS will be well outside of the elastic portion into the plastic portion of the stress-strain curve.
  64. 64. 64 Su=Pmax/A○ MEASURES OF DUCTILITY: The ductility of a material is a measure of the extent to which a material will deform before fracture. The amount of ductility is an important factor when considering forming operations such as rolling and extrusion. It also provides an indication of how visible overload damage to a component might become before the component fractures. In general, measurements of ductility are of interest in three ways:  To indicate the extent to which a metal can be deformed without fracture in metalworking operations such as rolling and extrusion.  To indicate to the designer, in a general way, the ability of the metal to flow plastically before fracture.  To serve as an indicator of changes in impurity level or processing conditions. Ductility measurements may be specified to assess material quality even though no direct relationship exists between the ductility measurement and performance in service. The conventional measures of ductility are the engineering strain at fracture (usually called the elongation) and the reduction of area at fracture. Both of these properties are obtained by fitting the specimen back together after fracture and measuring the change in length and cross sectional area. % elongation = Where  Lf = final length  Lo = initial length % Reduction in area = ˣ 100 Where  Ao = initial length  Af = final length RESILIENCE: Resilience is the capacity of a material to absorb energy when it is deformed elastically and then, upon unloading, to have this energy recovered TOUGHNESS: The energy per unit volume that can be absorbed by a matrial (the area under the entire stress-strain diagram) up to the point of fracture is known as toughness.
  65. 65. 65 For one, toughness (or more specifically, fracture toughness) is a property that is indicative of a material’s resistance to fracture when a crack (or other stress-concentrating defect) is present. Because it is nearly impossible (as well as costly) to manufacture materials with zero defects (or to prevent damage during service), fracture toughness is a major consideration for all structural materials. For dynamic (high strain rate) loading conditions and when a notch (or point of stress concentration) is present, notch toughness is assessed by using an impact test. NECKING: Up to maximum stress deformation is homogeneous and material deform plastically. But after maximum stress delocalized deformation takes place. After UTS stresses are concentrated at weaker portion of the specimen and a neck is formed at that there. Load bearing capacity of material decrease due to necking. Up to the point at which the maximum force occurs, the strain is uniform along the gage length; that is, the strain is independent of the gage length. However, once necking begins, the gage length becomes very important. SPECIMEN USED FOR TENSION TEST: In this lab we performed tensile test on many specimens. These include steel bars; flat specimens, copper coating wires, flat specimens, sheets, wire strips etc. But most of these were steel bars. There are three types of steel bars 1- Plain steel bars 2- Deformed steel bars 3- Tor steel UNIVERSAL TESTING MACHINE: A universal testing machine is used to test the tensile stress and compressive strength of materials and also bend type test is performed. TYPES OF GRIPS: ROUND GRIPS: Round grips used for bars.  8-12 mm  12-35 mm  35-60 mm FLAT GRIPS: Flat grips used for rectangular sheets.  0-30 mm  30-55 mm
  66. 66. 66 ROPE GRIP: Rope grips are used for rope & wires.  8-10mm  16-22 mm PROCEDURE: The standard used for tension test is A 370. The procedure is as given below:  First of all we Put gage marks on the specimen.  Measured the initial gage length and diameter  The specimen was gripped in the grips of UTM. Started the test and conducted the test until fracture.  After fracture we measured the final gage length. Recorded the yield stress and maximum load. CALCULATIONS: We performed tension test on many steel bars. As we know that the cross section of the steel bar is not uniform due to presence of ribs on the outer surface. So we measured the area and diameter of steel bars by the relation between their weight per unit length and density per unit volume. So by following method we calculated the area and diameter of steel bars. Weight of cut sample = 1360 g Length of sample = 450mm Weight per unit length = weight/length = 1360/450 = 3.02 g/mm Density of the steel sample bar = 7.85 g/cm3 = 0.00785 g/mm3 Now area can be calculated easily as Area = weight per unit length/density of steel Provided the units for both quantities are same. √
  67. 67. 67 After measuring the diameter and area of the steel bars we performed the tension test on the steel bars by fitting the sample between the grips of UTM. After performing test we noted the yield stress, max load and final gauge length and measured the yield strength, tensile strength and %elongation. Diameter of steel bar=12.71mm Area of steel bar=127mm2 Tensile strength = (74.84 KN/127 mm2 ) =589 MPa Tensile strength= 85405Psi yield strength = 54.39 KN/127mm2 =428 MPa yield strength =62060Psi %age elongation was measured as: Gage length = L○ = 200 mm Final length = Lf = 228 mm Total strain = ε = Lf - L○ = 228 – 200 = 28 mm %age elongation= %age elongation= (228-200 )/200 ×100 = 14% Load - %Elongation curve The graph is showing the relation between the applied load and %elongation. This is similar to stress- strain curve. As we can see from the graph in the initial region the load is directly proportional to the elongation. After yield point the permanent deformation starts. At UTS the applied load is maximum and after this point necking starts and material breaks at fracture point. CONCLUSION: We performed tension test on many samples.some of these were steel bars,wires,copper coating tube,rods etc. almost all of them have good tensile strength, yield strength and toughness. Only two deformed steel bars of number 3 and 4 were failed upper yeild point lower yeild point UTS fracture 0 10 20 30 40 50 60 70 80 0 5 10 15 load KN %elongation
  68. 68. 68 APPLICATION OF TENSION TEST: Tensile testing is used to guarantee the quality of components, materials and finished products within a wide range of industries. Typical applications of tensile testing are highlighted in the following sections on:  Aerospace Industry  Automotive Industry  Beverage Industry  Construction Industry  Electrical and Electronics Industry  Medical Device Industry  Packaging Industry  Paper and Board Industry  Pharmaceuticals Industry  Plastics, Rubber and Elastomers Industry  Safety, Health, Fitness and Leisure Industry  Textiles Industry

×