The document discusses several tests used to evaluate hot cracking tendency in welds, including the Murex test, Houldcroft test, and Varestraint test.
The Murex test involves making a fillet weld between two plates and then rotating one plate during welding to induce strain. Cracking indicates higher susceptibility.
The Houldcroft test uses a "fishbone" shaped test piece with slots of increasing depth. A bead-on-plate weld is made and the length of cracking shows the material's resistance to solidification cracking at different strain levels.
The Varestraint test applies a bending load to induce plastic deformation in a plate as it is welded. The amount of strain
The document discusses various weldability tests used to evaluate the suitability of materials for welding and the performance of welded joints. It describes tests such as the Murex test, Houldcroft test, ring weldability test, controlled thermal severity test, Tekken test, implant test, and Lehigh restraint test. These tests are employed to quantify weldability and provide clues on precautions needed like filler material selection, preheat, and energy input to minimize defects like hot cracking and cold cracking in welded joints.
This document discusses welding defects and their causes. It outlines the four zones in a welded joint and how they appear on an iron-carbon phase diagram. The zones are the fusion zone, weld interface zone, heat affected zone, and base metal. Solidification can be epitaxial or non-epitaxial depending on whether filler metal is used. Common welding defects include cracks, porosity, inclusions, incomplete fusion, imperfect shape, and residual stresses. Various defect types like longitudinal cracks and underbead cracks are described in more detail.
The document discusses the weldability of various stainless steel types, including austenitic, ferritic, and martensitic stainless steels. It provides information on their typical compositions and applications. It also describes various welding techniques that can be used and issues that may occur during welding like sensitization, sigma phase formation, and hydrogen cracking. Prevention methods are outlined like using stabilizers, annealing treatments, and controlling cooling rates and heat inputs during welding.
Cracks can form in welds due to stresses exceeding the metal's strength. There are two main types of cracks: hot cracks during solidification and cold cracks caused by hydrogen embrittlement. Factors like composition, thickness, restraint and hydrogen content influence cracking. Cracks are classified by location as weld metal cracks like longitudinal or transverse cracks, or base metal cracks like underbead cracks. Tests evaluate cracking susceptibility and techniques like preheating, heat input control and post heating can reduce cracking risks.
This seminar report summarizes a study on rheocasting. It defines rheocasting as a process that creates a semi-solid slurry directly from molten metal and pushes it into a mold to freeze, unlike thixocasting which reheats a billet. The report outlines the key steps in rheocasting including slurry generation techniques like stirring, dendrite fragmentation, and pressure waves. It discusses benefits like lower casting pressures/temperatures and disadvantages like needing precise control. In conclusion, the report notes potential applications for rheocasting include replacing permanent molds and producing high-strength or wear-resistant parts.
This document discusses weldability and defects in weldments. It covers various topics related to weld design, residual stresses, weld defects, and the weldability of different materials such as steels, aluminum alloys, copper alloys, titanium alloys, and magnesium alloys. The objectives are for students to understand causes of residual stresses and distortions, differentiate between weld defects, and suggest remedies. Weldability depends on factors like material composition and welding techniques. Some materials like steel are more weldable than others such as aluminum.
This document discusses hot tear defects in castings and methods to prevent them. It provides the following key points:
- Hot tears occur during solidification due to resistance to contraction from molds/cores and uneven temperature gradients. Two conditions are needed - resistance to contraction and variable temperature gradients.
- Preventing methods include using strong molds that collapse slowly, designing castings with uniform thickness, adding chills or ribs to promote faster cooling, and controlling steel chemistry to reduce hydrogen and sulfur levels.
- Case studies using computer simulations show locations of hot zones in castings and how positioning chills or changing mold materials reduces temperatures and prevents hot tears.
The document discusses various weldability tests used to evaluate the suitability of materials for welding and the performance of welded joints. It describes tests such as the Murex test, Houldcroft test, ring weldability test, controlled thermal severity test, Tekken test, implant test, and Lehigh restraint test. These tests are employed to quantify weldability and provide clues on precautions needed like filler material selection, preheat, and energy input to minimize defects like hot cracking and cold cracking in welded joints.
This document discusses welding defects and their causes. It outlines the four zones in a welded joint and how they appear on an iron-carbon phase diagram. The zones are the fusion zone, weld interface zone, heat affected zone, and base metal. Solidification can be epitaxial or non-epitaxial depending on whether filler metal is used. Common welding defects include cracks, porosity, inclusions, incomplete fusion, imperfect shape, and residual stresses. Various defect types like longitudinal cracks and underbead cracks are described in more detail.
The document discusses the weldability of various stainless steel types, including austenitic, ferritic, and martensitic stainless steels. It provides information on their typical compositions and applications. It also describes various welding techniques that can be used and issues that may occur during welding like sensitization, sigma phase formation, and hydrogen cracking. Prevention methods are outlined like using stabilizers, annealing treatments, and controlling cooling rates and heat inputs during welding.
Cracks can form in welds due to stresses exceeding the metal's strength. There are two main types of cracks: hot cracks during solidification and cold cracks caused by hydrogen embrittlement. Factors like composition, thickness, restraint and hydrogen content influence cracking. Cracks are classified by location as weld metal cracks like longitudinal or transverse cracks, or base metal cracks like underbead cracks. Tests evaluate cracking susceptibility and techniques like preheating, heat input control and post heating can reduce cracking risks.
This seminar report summarizes a study on rheocasting. It defines rheocasting as a process that creates a semi-solid slurry directly from molten metal and pushes it into a mold to freeze, unlike thixocasting which reheats a billet. The report outlines the key steps in rheocasting including slurry generation techniques like stirring, dendrite fragmentation, and pressure waves. It discusses benefits like lower casting pressures/temperatures and disadvantages like needing precise control. In conclusion, the report notes potential applications for rheocasting include replacing permanent molds and producing high-strength or wear-resistant parts.
This document discusses weldability and defects in weldments. It covers various topics related to weld design, residual stresses, weld defects, and the weldability of different materials such as steels, aluminum alloys, copper alloys, titanium alloys, and magnesium alloys. The objectives are for students to understand causes of residual stresses and distortions, differentiate between weld defects, and suggest remedies. Weldability depends on factors like material composition and welding techniques. Some materials like steel are more weldable than others such as aluminum.
This document discusses hot tear defects in castings and methods to prevent them. It provides the following key points:
- Hot tears occur during solidification due to resistance to contraction from molds/cores and uneven temperature gradients. Two conditions are needed - resistance to contraction and variable temperature gradients.
- Preventing methods include using strong molds that collapse slowly, designing castings with uniform thickness, adding chills or ribs to promote faster cooling, and controlling steel chemistry to reduce hydrogen and sulfur levels.
- Case studies using computer simulations show locations of hot zones in castings and how positioning chills or changing mold materials reduces temperatures and prevents hot tears.
The Heat-Affected Zone (HAZ) refers to the area of a material surrounding a weld that is altered by the heat of welding but not fully melted. During welding, this area experiences microstructural and property changes compared to the parent material due to elevated temperatures. These changes can include grain growth, reduced strength, and increased brittleness. As a result, failures often occur within the HAZ. The extent and properties of the HAZ depend on factors like material composition, welding process, heat input, and cooling rate. Proper welding parameters and techniques can minimize the size and negative impacts of the HAZ.
Diffusion bonding is a solid-state welding technique that joins materials together through atomic diffusion without melting. It involves applying high pressure and moderate heat to join carefully cleaned and mated surfaces. Diffusion occurs in two stages - initial metal-to-metal contact formation followed by atomic diffusion and grain growth across the interface to form a complete bond. Various factors like temperature, pressure, time and surface preparation influence the diffusion rate. Common diffusion bonding methods include gas pressure bonding, vacuum fusion bonding and eutectic bonding. Diffusion bonding finds applications in the fabrication of components for industries like aerospace, nuclear and others.
This document discusses welding metallurgy and the structure of fusion welds. It describes the different zones that make up a typical fusion welded joint, including the fusion zone, weld interface, heat affected zone, and base material. It explains how the microstructure varies across these zones due to melting and solidification processes during welding. Factors like welding parameters, heat input, and joint geometry are described as influencing weld pool shape and grain structure. The concept of thermal severity number is introduced as a way to assess cracking susceptibility based on total plate thickness.
The document discusses various types of steel and factors that influence weldability. It covers the classification of plain carbon steels based on carbon content. It also discusses alloy steels and how elements like carbon, manganese, molybdenum, and chromium influence the properties of steel. The document further summarizes different types of cracks that can occur during welding like hydrogen cracking, solidification cracking, and lamellar tearing. It explains the factors that contribute to these cracks and measures to prevent them.
1) The document discusses various defects that can occur during steel ingot solidification such as pipe, columnar structure, blow holes, and segregation.
2) It provides remedies for preventing these defects, such as using a hot top feeder head to avoid pipe formation and soaking ingots to minimize segregation.
3) The document also covers the mechanisms of ingot solidification, describing how killed, rimmed, and semi-killed steels solidify into chill, columnar, and equiaxed zones within the ingot.
Continuous casting is a process used to cast metal into a continuous length. Molten metal is poured into a mold and solidifies into a casting as it travels downward. New molten metal is continuously supplied to the mold to keep the process going and produce a casting of indefinite length. The process requires precise control of parameters like molten metal flow to ensure smooth, continuous casting.
Molten steel is tapped into a ladle and alloying elements are added before being cast into molds. Steel ingots can have square, round, or polygon cross-sections depending on their intended use - squares for rolling, rectangles for flat products, and rounds for tubes. Ingot casting molds are made of cast iron and come in two types - wide end up or narrow end up. As the steel solidifies in the mold, it forms three distinct zones - a thin chill zone against the mold walls, columnar zones of elongated crystals perpendicular to the walls, and an inner equiaxed zone of larger isotropic crystals.
This Presentation covers the basic concepts of Hot cracks and cold cracks in welding. For more information, please refer the books mentioned in the references slide.... Thank you
Diffusion welding is a solid state welding process that joins materials together without melting through the application of pressure and heat. It is commonly used to join refractory metals at temperatures just over half their normal melting point. Close tolerances and a protective atmosphere are required to accomplish the welding. The process is considered diffusion brazing when a filler material is placed between surfaces before joining. Diffusion bonding results from atomic diffusion and plastic deformation at the interface between surfaces. It is used for joining dissimilar metals and composites in applications like aerospace and nuclear industries.
Residual stresses are stresses that exist in a material after external loads have been removed. They are caused by non-uniform temperatures during welding which lead to uneven strain. Residual stresses form from mismatches in thermal expansion and contraction between the weld metal and base metal. Higher heat input welds and greater restraint during welding generally result in higher residual stresses, with tensile stresses in the weld metal and compressive stresses farther away. Residual stresses can decrease strength and increase susceptibility to cracking if not properly addressed.
This document discusses welding metallurgy and basic metallurgical concepts relevant to welding. It covers topics like crystalline structures of metals, phase transformations, alloying effects, microstructures like ferrite, pearlite, and martensite, and the influence of cooling rate on microstructure. It also discusses the heat affected zone and issues that can arise from changes in composition and cooling rate near the weld interface.
This document discusses various types of weld discontinuities and defects including misalignment, undercut, insufficient fill, excessive reinforcement, overlap, burn-through, incomplete penetration, incomplete fusion, arc strikes, and inclusions such as slag, wagontracks, and tungsten. Each discontinuity or defect is defined, potential causes are identified, methods for prevention are provided, and repair techniques are described. The document serves as a reference for identifying and addressing common weld problems and defects.
This document discusses metallurgy concepts related to welding, including:
1) It describes different types of steels like plain carbon steel, alloy steels, cast irons and how elements like carbon and manganese affect their properties.
2) It explains metallurgical phases in steel like ferrite, austenite and pearlite and how cooling rates affect their formation.
3) It discusses factors that influence weldability and properties of steels like composition, microstructure, heat treatment and service conditions.
Dissimilar Metal Welding - Issues, Solution & TechniquesVarun K M
The document discusses various challenges and considerations for welding dissimilar metals. It notes that dissimilar metals often have different physical, chemical, and metallurgical properties, requiring compromise when welding. Key factors discussed include weld metal composition and properties, dilution rates, differences in melting temperatures, thermal expansion, and heat treatments between base metals. The document provides examples of dissimilar metal welds that failed, including a superheater tube weld that cracked due to carbon migration and increased hardness. It emphasizes the importance of selecting suitable welding processes, filler metals, joint designs, preheat/post-weld heat treatments to successfully join dissimilar metals.
The document describes the Vickers hardness test. It uses a diamond pyramid indenter to make an indentation on the material being tested under a specified load ranging from 5 to 120 kg. The indentation left has a square shape regardless of load. The diagonal lengths of the indentation are measured under a microscope and used to calculate the Vickers hardness number, providing a continuous scale of hardness values. Factors like load, indentation shape, and temperature can affect the results. Advantages include consistency of indentation shape and suitability for testing a range of materials and surfaces. A disadvantage is it takes more time than other hardness tests.
This document provides an overview of welding metallurgy. It discusses the microstructure of welds and how the rapid changes in temperature during welding affect the physical characteristics and properties of metals. It examines the different zones that form in steel welds, including the fusion zone where grains are epitaxially formed, and the heat-affected zone. Problems that can occur during welding due to remelting and solidification are also summarized, such as macrosegregation, hot cracking, and cold cracking.
The document discusses various aspects of solidification processes for pure metals and alloys. It covers topics such as solidification curves, grain structure formation, mushy zone formation in alloys, segregation of elements, shrinkage during solidification, and directional solidification techniques. It also discusses the functions and design of gating systems, including elements like pouring basins, sprues, runners, gates, and risers.
This document summarizes several solid-state welding processes including cold welding, ultrasonic welding, friction welding, resistance welding, and flash welding. It provides brief descriptions of each process along with examples of applications and diagrams illustrating how each process works. The key solid-state welding processes covered are friction welding, resistance spot welding, and friction stir welding.
Fracture mechanics CTOD Crack Tip Opening DisplacementDavalsab M.L
Fracture Mechanics .Whilst the Crack Tip Opening Displacement (CTOD) test was developed for the characterisation of metals it has also been used to determine the toughness of non-metallics such as weldable plastics.
The CTOD test is one such fracture toughness test that is used when some plastic deformation can occur prior to failure - this allows the tip of a crack to stretch and open, hence 'tip opening displacement
To determine the ductility of mild steel specimens using a three-point bend test. The test involves placing steel bar specimens on a bend test machine with supports 8 times the bar diameter apart and a handle 5 times the bar diameter above the supports. A load is applied until the bar bends at 180 degrees, though some spring back was observed. No cracks were observed, indicating the material is suitable for use. The three-point bend test provides a simple way to evaluate materials' ability to resist cracking during bending.
The Heat-Affected Zone (HAZ) refers to the area of a material surrounding a weld that is altered by the heat of welding but not fully melted. During welding, this area experiences microstructural and property changes compared to the parent material due to elevated temperatures. These changes can include grain growth, reduced strength, and increased brittleness. As a result, failures often occur within the HAZ. The extent and properties of the HAZ depend on factors like material composition, welding process, heat input, and cooling rate. Proper welding parameters and techniques can minimize the size and negative impacts of the HAZ.
Diffusion bonding is a solid-state welding technique that joins materials together through atomic diffusion without melting. It involves applying high pressure and moderate heat to join carefully cleaned and mated surfaces. Diffusion occurs in two stages - initial metal-to-metal contact formation followed by atomic diffusion and grain growth across the interface to form a complete bond. Various factors like temperature, pressure, time and surface preparation influence the diffusion rate. Common diffusion bonding methods include gas pressure bonding, vacuum fusion bonding and eutectic bonding. Diffusion bonding finds applications in the fabrication of components for industries like aerospace, nuclear and others.
This document discusses welding metallurgy and the structure of fusion welds. It describes the different zones that make up a typical fusion welded joint, including the fusion zone, weld interface, heat affected zone, and base material. It explains how the microstructure varies across these zones due to melting and solidification processes during welding. Factors like welding parameters, heat input, and joint geometry are described as influencing weld pool shape and grain structure. The concept of thermal severity number is introduced as a way to assess cracking susceptibility based on total plate thickness.
The document discusses various types of steel and factors that influence weldability. It covers the classification of plain carbon steels based on carbon content. It also discusses alloy steels and how elements like carbon, manganese, molybdenum, and chromium influence the properties of steel. The document further summarizes different types of cracks that can occur during welding like hydrogen cracking, solidification cracking, and lamellar tearing. It explains the factors that contribute to these cracks and measures to prevent them.
1) The document discusses various defects that can occur during steel ingot solidification such as pipe, columnar structure, blow holes, and segregation.
2) It provides remedies for preventing these defects, such as using a hot top feeder head to avoid pipe formation and soaking ingots to minimize segregation.
3) The document also covers the mechanisms of ingot solidification, describing how killed, rimmed, and semi-killed steels solidify into chill, columnar, and equiaxed zones within the ingot.
Continuous casting is a process used to cast metal into a continuous length. Molten metal is poured into a mold and solidifies into a casting as it travels downward. New molten metal is continuously supplied to the mold to keep the process going and produce a casting of indefinite length. The process requires precise control of parameters like molten metal flow to ensure smooth, continuous casting.
Molten steel is tapped into a ladle and alloying elements are added before being cast into molds. Steel ingots can have square, round, or polygon cross-sections depending on their intended use - squares for rolling, rectangles for flat products, and rounds for tubes. Ingot casting molds are made of cast iron and come in two types - wide end up or narrow end up. As the steel solidifies in the mold, it forms three distinct zones - a thin chill zone against the mold walls, columnar zones of elongated crystals perpendicular to the walls, and an inner equiaxed zone of larger isotropic crystals.
This Presentation covers the basic concepts of Hot cracks and cold cracks in welding. For more information, please refer the books mentioned in the references slide.... Thank you
Diffusion welding is a solid state welding process that joins materials together without melting through the application of pressure and heat. It is commonly used to join refractory metals at temperatures just over half their normal melting point. Close tolerances and a protective atmosphere are required to accomplish the welding. The process is considered diffusion brazing when a filler material is placed between surfaces before joining. Diffusion bonding results from atomic diffusion and plastic deformation at the interface between surfaces. It is used for joining dissimilar metals and composites in applications like aerospace and nuclear industries.
Residual stresses are stresses that exist in a material after external loads have been removed. They are caused by non-uniform temperatures during welding which lead to uneven strain. Residual stresses form from mismatches in thermal expansion and contraction between the weld metal and base metal. Higher heat input welds and greater restraint during welding generally result in higher residual stresses, with tensile stresses in the weld metal and compressive stresses farther away. Residual stresses can decrease strength and increase susceptibility to cracking if not properly addressed.
This document discusses welding metallurgy and basic metallurgical concepts relevant to welding. It covers topics like crystalline structures of metals, phase transformations, alloying effects, microstructures like ferrite, pearlite, and martensite, and the influence of cooling rate on microstructure. It also discusses the heat affected zone and issues that can arise from changes in composition and cooling rate near the weld interface.
This document discusses various types of weld discontinuities and defects including misalignment, undercut, insufficient fill, excessive reinforcement, overlap, burn-through, incomplete penetration, incomplete fusion, arc strikes, and inclusions such as slag, wagontracks, and tungsten. Each discontinuity or defect is defined, potential causes are identified, methods for prevention are provided, and repair techniques are described. The document serves as a reference for identifying and addressing common weld problems and defects.
This document discusses metallurgy concepts related to welding, including:
1) It describes different types of steels like plain carbon steel, alloy steels, cast irons and how elements like carbon and manganese affect their properties.
2) It explains metallurgical phases in steel like ferrite, austenite and pearlite and how cooling rates affect their formation.
3) It discusses factors that influence weldability and properties of steels like composition, microstructure, heat treatment and service conditions.
Dissimilar Metal Welding - Issues, Solution & TechniquesVarun K M
The document discusses various challenges and considerations for welding dissimilar metals. It notes that dissimilar metals often have different physical, chemical, and metallurgical properties, requiring compromise when welding. Key factors discussed include weld metal composition and properties, dilution rates, differences in melting temperatures, thermal expansion, and heat treatments between base metals. The document provides examples of dissimilar metal welds that failed, including a superheater tube weld that cracked due to carbon migration and increased hardness. It emphasizes the importance of selecting suitable welding processes, filler metals, joint designs, preheat/post-weld heat treatments to successfully join dissimilar metals.
The document describes the Vickers hardness test. It uses a diamond pyramid indenter to make an indentation on the material being tested under a specified load ranging from 5 to 120 kg. The indentation left has a square shape regardless of load. The diagonal lengths of the indentation are measured under a microscope and used to calculate the Vickers hardness number, providing a continuous scale of hardness values. Factors like load, indentation shape, and temperature can affect the results. Advantages include consistency of indentation shape and suitability for testing a range of materials and surfaces. A disadvantage is it takes more time than other hardness tests.
This document provides an overview of welding metallurgy. It discusses the microstructure of welds and how the rapid changes in temperature during welding affect the physical characteristics and properties of metals. It examines the different zones that form in steel welds, including the fusion zone where grains are epitaxially formed, and the heat-affected zone. Problems that can occur during welding due to remelting and solidification are also summarized, such as macrosegregation, hot cracking, and cold cracking.
The document discusses various aspects of solidification processes for pure metals and alloys. It covers topics such as solidification curves, grain structure formation, mushy zone formation in alloys, segregation of elements, shrinkage during solidification, and directional solidification techniques. It also discusses the functions and design of gating systems, including elements like pouring basins, sprues, runners, gates, and risers.
This document summarizes several solid-state welding processes including cold welding, ultrasonic welding, friction welding, resistance welding, and flash welding. It provides brief descriptions of each process along with examples of applications and diagrams illustrating how each process works. The key solid-state welding processes covered are friction welding, resistance spot welding, and friction stir welding.
Fracture mechanics CTOD Crack Tip Opening DisplacementDavalsab M.L
Fracture Mechanics .Whilst the Crack Tip Opening Displacement (CTOD) test was developed for the characterisation of metals it has also been used to determine the toughness of non-metallics such as weldable plastics.
The CTOD test is one such fracture toughness test that is used when some plastic deformation can occur prior to failure - this allows the tip of a crack to stretch and open, hence 'tip opening displacement
To determine the ductility of mild steel specimens using a three-point bend test. The test involves placing steel bar specimens on a bend test machine with supports 8 times the bar diameter apart and a handle 5 times the bar diameter above the supports. A load is applied until the bar bends at 180 degrees, though some spring back was observed. No cracks were observed, indicating the material is suitable for use. The three-point bend test provides a simple way to evaluate materials' ability to resist cracking during bending.
The document discusses the different types of strength in concrete including compressive, tensile, shear, and bond strength. It provides details on testing procedures used to determine compressive strength, such as cube and cylinder tests. The compressive strength of concrete is the most important property and is affected by numerous factors like the type of cement, aggregates, water-cement ratio, compaction, curing temperature, and age of the concrete. Higher strengths are obtained with low water-cement ratios, well-graded aggregates, and proper compaction and curing.
Hardeninig of steel (Jominy test)-CoET- udsmmusadoto
The document describes a Jominy end-quench test experiment to measure the hardenability of two steel samples. Steel samples A and C were heated to the austenite temperature and quenched with water at one end. Hardness measurements using the Rockwell C scale were taken at intervals along the samples. Sample A showed little variation in hardness, while hardness decreased with distance from the quenched end for sample C. A graph of hardness versus distance revealed that sample A has higher hardenability, retaining hardness further from the quenched end. The hardenability indices at 50HRC were determined to be 2mm, 5mm, and 6.5mm from the graph.
1 ijcmes dec-2015-17-optimization of friction stir welding parameters for joi...INFOGAIN PUBLICATION
Friction stir welding was a promising welding technology from the same moment of its existence because of its easy use, being ecologically friendly processed and with no need for filler metal. The present paper discusses the investigate the mechanical properties in order to demonstrate the feasibility of friction stir welding for joining Al 6061 aluminum alloy welding was performed on pipe. The pipe sections, 30mm, and relatively thin walled 2, 3 and 4 mm. Wire welded as similar alloy joints using (FSW) process In order to investigate the effect of rotation speed 485,710, 910, 1120,1400 and 1800 RPM and travel speeds 4, 8 and 10 mm/min. On mechanical propertie.
This work also focuses on mathematic models such as regression analysis (RA) to predict the tensile strength, the percentage of elongation and hardness of friction stir welded 6061 aluminum alloy. The Tensile strength, the percentage of elongation and hardness of weld joints were predicted by taking the parameters Tool rotation speed, material thickness and travel speed as a function. The results obtained through regresion analysis The models have been proved to be successful in terms of agreement with experimental results ratio 94.6%.
An evaluation of haz liquation cracking susceptibility part i development of ...Henry Henao
This document discusses the development of a new methodology to quantify heat-affected zone (HAZ) liquation cracking susceptibility. The methodology characterizes a thermal crack-susceptible region (CSR) in the HAZ based on ductility data from hot-ductility testing and liquation cracking theories. Longitudinal- and spot-Varestraint tests on A-286 and Type 310 stainless steels experimentally verified the thermal CSR. This new methodology provides a material-specific measure of HAZ liquation cracking susceptibility and improves understanding of the relationship between weldability tests, material properties, and liquation cracking theories.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
All reinforced concrete beams crack, generally starting at loads well below service level, and possibly even prior to loading due to restrained shrinkage. Flexural cracking due to loads is not only inevitable, but actually necessary for the reinforcement to be used effectively. Prior to the formation of flexural cracks, the steel stress is no more than n times the stress in the adjacent concrete, where n is the modular ratio E5/Ec. For materials common in current practice, n is approximately 8.
System shear connector jakarta digunakan sebagai aplikasi dalam konstruksi bangunan untuk menghasilkan kekuatan coran beton lebih kuat dan stabil sesuai dengan perhitungan engineering civil. Dalam hal ini ada 2 hal perhitungan kekuatan secara umum yaitu kekuatan kelengketan stud pada batang baja sesudah dilas. Dan yang kedua adalah kekuatan stud bolt yang digunakan.
Experimental Investigation of Reinforced Concrete Beam with Opening for Combi...IRJET Journal
This document summarizes an experimental investigation of reinforced concrete beams with openings. Beams were cast with different sized circular openings in various locations and tested under two-point bending loads. Concrete cubes were also tested to determine compressive strength. Finite element models of beams with openings were also created in ANSYS to analyze stresses and deflections. Results showed that deflection increased with larger opening size. Additional reinforcement is needed around openings to prevent cracking. Future work will involve testing reinforced beams to validate analytical models and determine optimal reinforcement designs.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
This document summarizes a study on the effect of weld angles on butt weld joint strength. Specimens were made with V-groove weld geometries at included angles of 450, 500, 550, and 600 degrees. Tensile and fatigue tests were conducted on the specimens. The results showed that tensile strength and fatigue life increased with increasing included angle, with 600 degrees performing best. Tensile strength increased up to 76.64% and fatigue life up to 46.15% for the 600 degree angle compared to 450 degrees. Ultrasonic and magnetic testing found no defects in the welds. Therefore, the 600 degree angle provided better strength performance than the 450 degree commonly used.
This document discusses various non-destructive evaluation tests for assessing concrete structures. It describes tests for evaluating in-situ concrete strength, including rebound hammer tests, ultrasonic pulse velocity tests, pullout tests, and core sampling and testing. It also discusses tests for assessing chemical attack, corrosion activity, fire damage, and structural integrity, such as carbonation testing, half-cell potential testing, and radiography. Rebound hammer testing involves using a spring-loaded hammer to measure surface hardness as an indicator of strength, while ultrasonic pulse velocity measures the speed of ultrasonic pulses through concrete.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document describes a British standard test method for determining the static modulus of elasticity in compression of hardened concrete. It provides definitions, requirements for test specimens and apparatus, procedures for casting/preparing specimens, conducting compressive strength and elasticity tests, and calculating results. The method involves applying a stress range from 0.5 MPa to one-third of the concrete's compressive strength, while measuring strain to determine the secant modulus of elasticity.
NONLINEAR FINITE ELEMENT ANALYSIS FOR REINFORCED CONCRETE SLABS UNDER PUNCHIN...IAEME Publication
This paper presents an implementation of a three-dimensional nonlinear finite element model for evaluating the behavior of reinforced concrete slabs under centric load. The concrete was idealized by using eight-nodded solid elements. While flexural reinforcement and the shear were modeled as line elements, a perfected bond between solid elements and line elements was assumed. The nonlinear behavior of concrete in compression is simulated by an elasto-plastic work-hardening model, and in tension a suitable post-cracking model based on tension stiffening and shear retention models are employed. The steel was simulated using an elastic-full plastic model. The validity of the theoretical formulations and the program used was verified through comparison with available experimental data, and the agreement has proven to be good. A parametric study has been also carried out to investigate the influence of the slab thickness on column-slab connection response
Evaluation of concrete spall repairs by pullout testfrank collins
This document summarizes a study that evaluated concrete spall repairs using pullout tests. Concrete specimens were damaged via an initial pullout test, repaired with epoxy mortar, and subjected to a second pullout test. The tests showed that:
1) Pullout force of repaired specimens was linearly correlated with concrete cylinder compressive strength up to around 45 kN/2.26 MPa, but diminished at higher strengths.
2) Pullout force/stress of repaired specimens increased similarly to concrete specimens as age increased up to 90 days, but was lower than unrepaired concrete.
3) Higher initial pullout damage forces resulted in higher pullout forces for repaired specimens, up to around 43
Effect of the post weld heat treatments on the fatigue crack growth behavior ...eSAT Journals
Abstract
The effect of the post weld heat treatments (PWHTs) on the fatigue crack growth (FCG) behavior in the welded zone of AA6063-T5 fabricated by the friction stir process was investigated. The FCG specimens are machined in which the loading axis is put perpendicular to the welding line and the initial notches are introduced in the welded zone. The experimental results showed the FCG rates are sensitive to the PWHT solutions. The FCG resistance in the welded zone could be fully restored to that of base metal by using PWHT. While the PWHT solution solely restores the precipitates dissolved and/or coarsened during welding process has a minor effect on the FCG rates, the PWHT solution remarkably recrystallizes the grain microstructure has a significant effect here.
Keywords: Aluminum alloy, Failure assessment, Fatigue crack propagation, Friction stir welding
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
Low power architecture of logic gates using adiabatic techniquesnooriasukmaningtyas
The growing significance of portable systems to limit power consumption in ultra-large-scale-integration chips of very high density, has recently led to rapid and inventive progresses in low-power design. The most effective technique is adiabatic logic circuit design in energy-efficient hardware. This paper presents two adiabatic approaches for the design of low power circuits, modified positive feedback adiabatic logic (modified PFAL) and the other is direct current diode based positive feedback adiabatic logic (DC-DB PFAL). Logic gates are the preliminary components in any digital circuit design. By improving the performance of basic gates, one can improvise the whole system performance. In this paper proposed circuit design of the low power architecture of OR/NOR, AND/NAND, and XOR/XNOR gates are presented using the said approaches and their results are analyzed for powerdissipation, delay, power-delay-product and rise time and compared with the other adiabatic techniques along with the conventional complementary metal oxide semiconductor (CMOS) designs reported in the literature. It has been found that the designs with DC-DB PFAL technique outperform with the percentage improvement of 65% for NOR gate and 7% for NAND gate and 34% for XNOR gate over the modified PFAL techniques at 10 MHz respectively.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
Harnessing WebAssembly for Real-time Stateless Streaming PipelinesChristina Lin
Traditionally, dealing with real-time data pipelines has involved significant overhead, even for straightforward tasks like data transformation or masking. However, in this talk, we’ll venture into the dynamic realm of WebAssembly (WASM) and discover how it can revolutionize the creation of stateless streaming pipelines within a Kafka (Redpanda) broker. These pipelines are adept at managing low-latency, high-data-volume scenarios.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
2. Hot Cracking Tests
A number of tests have been devised to check the
hot cracking tendency of weldments; some of the
well known amongst them include the following.
Murex test
Houldcroft test
Varestraint test
Ring weldability test
Hot ductility test
3. Murex Text
In this test a filet weld is made between two
test plates 10-15 mm thick and of dimensions
approximately 50mm x 70mm.
These plates are rigidly fixed on two supports
one of which can be rotated about an axis in
the root of the test weld, as shown in Fig. 6.
Rotation of the movable clamp starts 5
seconds after welding begins. Although rotating
speed is of the order of 1°/Sec, but various
rotational speeds are available.
5. The drive mechanism of the machine should be such that it is not
affected by the deformation resistance of the weld metal.
Susceptibility to hot cracking is indicated by the extent to which the
weld metal cracks at various rates of applied strain during
solidification.
The strain developed is made proportional to the speed of rotation
and is a function of the V-angle, which is always initially 90°.
The maximum angle that can be obtained is 120°. Longitudinal cracks
occur during rotation however the length of a crater crack, if present,
is not included in measurement.
This test has been mainly used for assessing cracking sensitivity of
carbon and low alloy steel weld deposits made with coated electrodes.
6. Houldcroft Fishbone Test
Houldcroft Fishbone test is often used for evaluating the
solidification cracking susceptibility of sheet materials.
This test is mainly for application to TIG welding of sheet
but may be applied to other similar process.
The test can be applied to any thin plate or sheet material on
which the process is likely to be used.
A bead-on-plate weld, without filler rod, is made under
controlled conditions along the centerline of the test piece,
beginning from the end with the shortest slots and
proceeding right to the opposite end.
7. As tension builds up at the beginning of the weld a crack is likely
to start and will travel along the weld until the head build-up in
the relatively narrow plate, as represented by the distance
between the inner ends of the pairs of slots, causes the stress
intensity to fall below the critical value, as shown in Fig. 7a.
The slot at which the crack is arrested gives a measure of
weldability in a range of ten conditions (nine sets of slots)
ranging from zero weldability with cracking along the full length
to full weldability with no cracking.
The crack length from the starting edge of the test piece is an
index of solidification cracking sensitivity. The shaded area in
Fig. 7(C) is used only for starting purposes and is ignored in
estimating the result.
8. A Typical Testpiece Showing 50% Weldability by
Houldcroft Fishbone Test for Tig Welding an Aluminimum Alloy
10. The test makes use of the transverse stress pattern (Fig. 7b)
built up by a progressive fusion weld, to find the critical
heat flow condition for a particular material in a particular
thickness of sheet.
A test piece shown in (Fig 7c) is made from one piece of
material and has a series of symmetrically arranged slots of
progressively increasing depth of cut in pairs into the
opposite side of the material.
The test piece is laid flat on a sheet of carbon which rests on
a water-cooled copper block and is held in position by
Beryllium Copper clamping strip as shown in Fig. 7d.
11. 9 slots, 0.8mm wide,
7.5 mm apart
Test piece Dimensions for Houldcroft Weldability Test
13. The size of the test piece for any given material depends partly
on the thermal conductivity of the material. Also a larger test
piece is used for thicker material. Specimen width is the most
critical dimension and this should be chosen so that in a strip
of material without slots the crack would follow the entire
length of the weld bed. It is important when designing the test
piece to have some material is known crack sensitivity available
so that the right severity of test may be obtained.
14. In this test the degree of restraint diminishes from start to
finish of the weld due to the increasing depth of saw cut, so
that the length of crack has a relation to the degree of
restraint required for crack propagation.
The test is suitable for investigating the effect of parent metal
and filler metal composition on hot cracking and takes no
account whatsoever of the effect of welding variables on hot
cracking.
15. Fig. 8(A) A Schematic Representation of the Set-Up for
Vasrestraint Test
The Varestraint test
16. The varestraint test i.e., the variable restraint test requires a
metal plate 275 mm x 100 mm having a thickness of 6 to 13
mm which is fixed on one side in the welding jig as shown
in Fig. 8(a). The weld metal is then deposited right across
the middle of the plate or alternatively TIG welding process
may be employed without the use of filter.
This test like Murex test utilizes external loading to impose
plastic deformation on the test piece while weld bead is
being deposited. The load F is suddenly applied by
actuating the loading yoke, as the center of the arc passes
the point of tangency between the curved surface of the die
block and the fixed end of the specimen i.e., point A.
17. In order that the bend radius is not dependent on
the geometrical factors of the weld, the test piece is
placed on a bending block (B) of radius R.
Bending of the test plate, with the weld bead laid
on it, produces distortion of the upper fibres of the
weld bead.
The severity of deformation causing cracking can
be determined as,
The applied augemented strain,
where, t = thickness of the test piece,
R = radius of the bend.
A change in the bend radius will also cause a change
in the size of the distortion o
f the upper part of the weld bead. If the applied strain
is sufficient, cracks are formed in the weld bead.
18. Hot cracking can occur both inside and outside the weld
metal. Both, the amount of the applied strain and the crack
length (either the total length of all cracks or the maximum
crack length) serve as an index of crack sensitivity i.e., the
evaluation criterion of the test may be given by the overall
length of the cracks as a function of maximum deformation,
ε.
The relationship between ε and crack length also allows
determination of the threshold value of deformation, εcrit, at
which cracks are initiated and by virtue of this criterion
comparison of various steels or welds can be made. The
higher the value of εcrit, the more resistance, to the cracks, is
steel.
19. b) The Trans-Varestraint Test
It is a modified form of the varestraint test. While in the
varestraint test, the axis of the bend is perpendicular to the
direction of the weld and cracks occur vertically to the weld,
in the Trans-Varestraint test this axis runs parallel to the
weld, thus keeping cracks inside the weld metal resulting in
centerline cracks. The schematic representation of the set-
up for trans-varestraint test with a bilateral bend is shown in
Fig. 8b.
20. Trans-Varestraint Test Set-Up With Bilateral Bending of
Test Piece
The evaluation criterion is based on the unit of crack
susceptibility (UCS), where UCS = 10 (3 – R)
Higher values of UCS indicate low weldability.
21. Ring Weldability Test
⮚The circular patch or ring weldability test is used for studying
hot cracking in the weld metal or partially melted zone,
because it imposes a relatively high restraint in the weld zone
transverse to the weld.
⮚The stresses causing cracking are not precisely known but a
material has to be very weldable to pass the test without
cracking.
⮚Ignorance about the values of stress is of not much
consequence because in practical applications the usual
concern is not whether one weld metal composition in much
worse or only slightly worse than another, but whether or not it
cracks.
22. The test piece is made up of a square piece of sheet or plate,
with sides about 150-450 mm, out of the center of what is cut
a disc of diameter about one-third of the side of the square.
If the disc can be cut out with a very narrow cut then it can
be used in the test, but if the gap is too wide to give
reasonable representation of a weld gap then a separate
slightly larger disc has to be prepared.
Fig. 9a shows the schematic of a set-up for such a test jig
while Fig. 9b shows a set-up with zero gap for use with TIG
welding.
24. To make the test, the disc is lightly tacked into the test plate
at, say, 4 positions at regular interval so that the gap is
uniform and representative of an open square butt
preparation.
If required, single or double Vee edge preparation may also be
used. Welding is started at one of the tacks and is carried on
to complete the circle.
On welding the patch the radial and circumferential strains
imposed on the solidifying weld pool will increase with the
increase in length of the deposited weld and after some
interval both types of strain will reach a maximum, although
not necessarily simultaneously.
Thus, during welding a point is reached when, because of the
weakness of the material, the strains are sufficient to initiate a
crack. Further, it is assumed that at any instant the
circumferential strains are larger than the radial strains.
25. This implies that transverse cracks should appear before
centerline cracks; assuming that the weaknesses are uniform
throughout the weld bead.
Once a centerline crack has started it should continue until
the welding is terminated.
This is because the increased strain brought about by the
notch effect at the root of the crack will help its continuance.
A measure of the crack resistance is the angle θr, subtended
between the start of the weld and the point where the crack
first began, as shown in Fig. 9c.
Likewise the crack susceptibility is equal to
(360-θr).
Cracks at the beginning should be ignored except where it is
obvious that they from part of the main weld, since the region
at the start of the weld is not representative of the welding
conditions obtained in the main part of the weld.
26. Fig. 9(B) Jig For Ring Weldability Test in Sheet Material Using Tig
Welding Process
27. Another criterion of crack sensitivity is the occurrence of
transverse cracks; in some cases there are the only types of
cracks observed.
To a first approximation, a measure of the crack
susceptibility is the interval, measured in degrees,
between individual cracks.
This interval is in some way a function of the strain
necessary to cause cracking; the smaller the interval, the
more crack susceptible is the material.
Restrain can be varied in a given plate thickness by
adjusting the plate size and patch diameter.
Also, by using a patch on one material and a plate of
another the cracking tendencies of dissimilar metal joints
can be studied.
29. Fig. 9(D) Welding Sequence to Help Eliminate
distortion and Cracking in a Circular Weld
30. Ring weldability test is used in aluminium alloys and low
alloy steels for establishing correct welding procedures and
sequences to avoid restraint cracking.
Fig. 9d shows an example of welding sequence to help
eliminate to help estimate distortion and cracking in a
circular weld.
This may be used for comparison if the patch test shows
cracks.
31. Hot Ductility Test
The thermal cycles experienced by the workpieces during
welding can be duplicated in small specimens conveniently for
mechanical testing, by using weld thermal simulator.
By performing high-speed tensile testing during weld thermal
simulation, the elevated temperature ductility (and strength)
of metals can be evaluated. This is called the hot ductility test
and is illustrated in Fig 10a. This test can be used to
investigate the hot cracking tendency of the partially melted
HAZ in a weld. It has been used extensively for evaluating the
hot cracking susceptibility of nickel-base alloys.
32. Cold Cracking Test
Weldability is also assessed by the cold cracking
susceptibility of a weldment. Like for hot cracking, there are
a large number of tests developed to determine the cold
cracking tendency; some of the more popular amongst them
include the following.
⮚Controlled thermal severity (CTS) test.
⮚Tekken test.
⮚Lehigh restraint test.
⮚Longitudinal bead-weld test.
⮚Implant test.
33. Fig. 10(A) Illustration of Hot Ductility Test Results: (A) Haz Thermal
Cycle, and (B) Temperature Vs. Ductility Curve
34. CTS Test
The CTS test is based on the principle of the fillet welded
joint particularly for assessing weldability in relation to
steels welded by arc welding processes for establishing safe
welding procedures for low alloy steels. Under appropriate
conditions the test can assess a steel parent metal, a weld
deposit, or a process in terms of a critical cooling condition
related to the number of units of 6.25 mm (1/4 inch) of
thickness of material conducing heat away from the weld.
The test pieces of the dimensions shown in Fig. 11a are
bolted together.
Welds A and B are anchor welds and the test welds are fillet
welds of standard size laid at C and D under controlled
conditions.
35. The test piece is set up in a convenient fixture so that the test
weld can be made in the open flat position i.e., with the V in the
upright position and the line of welding horizontal; the whole
set-up is exposed only to normal still air cooling.
Each test weld is begun with the test piece at room
temperature. Thus, weld C is made under bithermal
conditions, with two thicknesses of plate conducting away the
heat, whilst weld D is made under tri-thermal conditions, with
three thicknesses conducting away the heat, whilst weld D is
made under trithermal conditions, with three thicknesses
conducting away the heat (the bottom plate conducts in two
directions).
37. The cooling rate is designated by means of a thermal severity
number (T.S.N). TSN1 is the thermal severity corresponding
to heat flow along a single steel plate 6.25mm thick.
TSN2 is obtained in a butt weld between two 6.25 mm plates
whilst in a 6.25mm T-joint, where there are three heat flow
paths, the thermal severity number is 3.
The TSN is also increased in proportion to the plate
thickness, so that CTS test pieces, which also have three heat
flow paths, in 12.5 mm plate would have TSN6.
The thicknesses t and b, of top and bottom plates
respectively, can be changed as required for successive tests,
the thermal severity number being calculated from the units
of 6.25 mm of thickness.
38. Thus, in general,
i) for bithermal welds,
(TSN)B = 1 / 6.25 (t + b)
and (ii) for tri-thermal welds,
(TSN)T = 1 / 6.25 (t + 2b)
where t and b are in mm.
Susceptibility to cracking grows with the increasing gap
between the plates, therefore a shim is often placed between
the two plates to increase the gap in the fillet weld as shown
in Fig. 11(b).
Apart from thickness of plate, the severity of the test may
also be varied by the hydrogen level in the test welds and the
composition of the weld metal. With this test, cracks occur
in the underbead zone or the weld metal.
39. The assembly is allowed to stand for a period of 72 hours
after which the welds are sectioned to prepare three test
pieces from the transverse sections, for macrostructure
study, as shown in Fig. 11 (c).
Standard known quality plates can be used to assess
weldability of particular electrode deposits and standard
weld deposits can be used to indicate weldability of
particular sheet or plate material.
Some authorities do not regard the bithermal and tri-thermal
conditions as giving any sufficiently significant differences in
information so make the test plates of a size to give two
bithermal welds instead of one of each type.
For effective location of the critical TSN it is necessary to
make several test welds under different conditions, so a
complete assessment will take several days to finish.
40. Tekken Test
This is a simple butt welding test and has found wide application
in determining cold cracking tendency of welds made by arc
welding processes including submerged arc welding.
The thickness of test plates of the dimensions shown in Fig. 7.14
are prepared for butt welding with Y-edge preparation having 2 mm
root gap, and a 60° groove angle. First symmetrical auxiliary welds
are made on both ends and then the test weld of length about 75
mm is made in the central section.
When SAW process is used, the auxiliary weld on one side is left
incomplete so as to leave room for the test weld proper. It is
reported by Japanese research workers that the intensity of the
restraint is not much affected by the dimensions of the test pieces.
Tekken test is used in selecting welding parameters for the root
run of butt joints. In this test three types of cracks, viz. a, b and c
may be noted, as shown schematically in Fig. 7.15. These are,
41. Fig. 12(A) Test Piece and Edge
Preparation Details for Tekken
Test,
The cracks of the type (a) initiating
from the fusion boundary zone of the
bottom part of the root run on the
double-bevel side of the weld edge.
These are typical cold cracks
extending to HAZ and then turn back
to extend right into the weld metal.
Fig. 12 (B) Schematic Representation of
Types Of Cracks (A, B, C) Observed in a
Tekken Test Specimen
42. Cracks of the types (b) and (c) initiate in the weld metal and
may join to become a single crack.
The test procedure involves metallographic analysis on 5
section, two of which are obtained by cutting through the
initial and final weld craters. From these analyes it is possible
to determine the percentage of crack incidence in relation to
welding parameters. For example, Fig. 12 (c) shows the
relationship between preheating temperature and percentage
of cracks. The test weld is cut for examination atleast 48
hours after welding. Tekken test is suitable for comparing the
cold cracking susceptibilities of parent materials.
Fig. 12(C) Tekken Test Data
Represented to Correlate Preheat
Temperature to Percentage of Weld
Cracks
43. Lehigh Restraint Test
The characteristic feature of this test for thick plates
is that the degree of restraint is varied by freeing the
edges of the test pieces with a series of sawcuts
extending inwards over a distance X' from the edge; the
depth of the sawcut determines the restraint.
Fig. 13(A) Dimensioned Sketch of the Test Piece for Lehigh
Weldability Test
44. A longitudinal 17-groove is milled in a plate about 300 mm x
200 mm; the shape of the groove is shown in Fig. 13(a) and its
length (L) is varied in accordance with the plate thickness for a
plate less than 25 mm thick, L = 90 mm and for a plate more than
25 mm thick, L = 140 mm.
The test piece thickness varies between 12—50 mm and the
root gap of the shaped groove measures about 1.6—2 mm.
For plates of thickness up to 25 mm, a single U-edge groove is
cut, while for thicker plates double-U groove is used. Weld metal is
deposited in the grooved preparation and explored for cracking by visual
examination or by magnetic particle testing or radiography, etc.
For steels with 0.30% C, cracks occur practically exclusively in the weld
metal but may be initiated in the root or the upper part whereas crack
sensitive higher carbon or alloy steels show cracking in the HAZ extending
into the weld metal. This test is recommended for the selection of
electrodes for use with arc welding processes.
45. Longitudinal Bead Weld Cracking Test
This test uses a bead-on-plate weld deposited on a steel test plate of the
size 150 mm x 75 mm x 25 mm, partly immersed in water to 6.25 mm of its
top surface, with the length dimension in the direction of rolling.
A bead 100 mm long is deposited in the central part of the test plate, as
shown in Fig. 14(a), with a 3.15 mm diameter electrode at a welding current
of 100 Amp and an arc voltage of 24—26 volts and a travel speed of 25.4
cm/min. ; E6010 type electrode is used for welding to provide a high
potential of hydrogen in the arc atmosphere.
Fig. 14 Longitudinal
Bead Weld Cold
Cracking Test; (A) Test
Plate Dimensions, (B)
Test Plate Cut
Longitudinally Along
Weld Axis, (C And D)
Cut and Ground Test
Pieces for Underbead
and Toe Cracks
46. The specimen is then cut longitudinally along the axis of the
weld bead, and the cross-section of one-half the test plate is
ground (Fig. 14 (b), (c)) and tested for underbead cracks by the
magnetic particle or metallographic technique.
The weld bead on the second half of the test plate is ground
flush with the plate surface (Fig. 14(d)) and then examined in
the same way for toe cracks around the edge of the weld bead.
Cracking is measured after the specimen is age 4 for 24 hours
at 15°C, and is then thermally stress relieved at 595°C for one
hour to avoid possible grinding cracks.
Results are expressed as total length of crack(s) as a
percentage of the test weld length; underbead and toe cracks
are reported separately. For a reasonable evaluation atleast ten
tests have to be conducted.
47. Implant Test
While the four cold
cracking tests described
above are self-restraint tests,
the Implant test is a forced
restraint test. In this test, a
cylindrical specimen 6 — 8
mm diameter, and the other
dimensions as shown in Fig.
15 (a), is notched and
inserted in a hole in a 20—30
mm thick plate made of the
same or similar material as
the cylindrical Component.
The detailed dimensions of
notch are also given in
Fig. 15 (a).
Fig. 15 Dimensions of the Test
Components for Implant Cold
Cracking Test
48. Fig. 15(C) The Notch in the
Cylindrical Component and its
Location in Haz in the Implant Test
A weld run is made
over the specimen, with
an electrode of the type
that is to be used in
actual fabrication,
which is located in such
a way that its top
becomes a part of the
fusion zone and the
notch lies in the HAZ, as
shown in Fig. 15(c).
49. After welding, when the temperature falls below 100°C, a load is applied to
the cylindrical specimen, and the time to failure is determined.
A plot of stress versus time to failure gives an assessment of hydrogen
cracking susceptibility. Fig.15(d) shows such plots for high strength low
alloy (HSLA) pipeline steel. In this case loading was applied to the
specimen when the weld cooled down to 125°C.
It is evident from the plots that the welds made with low-hydrogen
electrodes (E7018-Basic Coated) are less susceptible to hydrogen
cracking than the welds made with high hydrogen electrode (E7010—
cellulosic coating).
The GMA weld made with at + 2% O2 as the shielding gas was least
susceptible to cracking as the only hydrogen encountered was the residual
hydrogen in the base metal, test pieces, and the welding wire. Thus, this
test also permits the critical stress, Scrit, to be determined at which no
fracture or crack initiation will occur anymore.
50. Another possible procedure
is to fix the applied stress
equal to the yield stress of
the test piece material and to
alter the thermal conditions
like preheat, heat input,
postweld heating. In this case
it is possible to determine the
critical cooling rate, Scrit,
between 800 and 500°C,
above which no cracking
takes place. Cracking
parameter (Pc) for steel with
0.8 to 2.5 % Mn, suggested by
Tanaka and Kitada, is given
by the following equation.
Fig. 15 (D) Implant Test
Results for an HSLA
Pipeline Steel
51. Another possible procedure is to fix the applied stress equal to
the yield stress of the test piece material and to alter the thermal
conditions like preheat, heat input, postweld heating. In this case
it is possible to determine the critical cooling rate, Scrit, between
800 and 500°C, above which no cracking takes place. Cracking
parameter (Pc) for steel with 0.8 to 2.5 % Mn, suggested by
Tanaka and Kitada, is given by the following equation.
52. Nick-Break Test
One of the methods of testing a
fusion weld is to cut a strip about 20
mm wide at right angle to the weld
axis and make a saw cut down the
centre line of the weld 3 to 6 mm
deep. By holding one-half of the
specimen in a vice, Fig. 16 (a) and
giving the other half a sharp blow
with hammer or by bending in a
machine as shown in Fig. 16 (b), the
weld is broken. This test which is
required by various boiler and
pressure vessel codes, shows up any
centreline defects, such as lack of
fusion, gas pockets, slag inclusion,
and the degree of porosity in the weld
bead. The defects are generally
examined by visual examination, and
should not have a length of more
than 3 mm individually.
Fig. 16 Different Forms of Nick-Break
Test: (A) for Butt-Welded Thin
Component, (B) for Butt-Welded Thick
Plates, and (C) for a Fillet Weld
Nick-Break Test
53. Fillet welds may be similarly tested by notching and bending as shown in Fig.
16 (c).
The standard length for a specimen in the fillet nick-break test is 100 to 150
mm.
The test is carried out by simply applying force in the back of the fillet,
crushing the angle flat.
One requirement of the fillet nick-break test is that there should be no tack
welds on the other side of the fillet weld.
One small tack weld will have enough holding power to invalidate the test.
Nick-Break Test: (C) for a Fillet Weld
54. Bend Tests
The quality of the weld, in
terms of ductility of the weld
metal and HAZ as well as tests
for opening of defects
particularly lack of side wall
fusion (side bend), root fusion,
and penetration of welded joint,
are most frequently checked by
means of a bend test. Such tests
are sub-divided into three types:
•Free bend test.
•Guided bend test.
•Controlled bend test.
Bend specimens may be longitudinal or
transverse to the weld axis and may be bent in
simple three-or four point free bending as shown in
Fig. 17. The test may be carried a step further by
flattening the arms together in a press to complete a
180 0 bend as shown in Fig. 17(c, d).
Fig. 17 Free Bend
Test; (A) Three-
Point Bending, (B)
Four Point
Bending, and (C)
Press Bending to
Achieve Final U-
Shape
55. Fig. 18 Guided Bend Test Fig. 19 Controlled Bend Test Details
Due to inhomogenity of the joint, there is a tendency for free
bend test specimens to take up an irregular shape, so that the
actual radius at various points differs from the specified value.
This defect is overcome to some extent in the guided bend test,
Fig. 18, but can be avoided most effectively by the use of the
controlled bend test as shown in Fig. 19.
56. Side Bend Test: Very thick welded plates are difficult to bend in the
normal manner, and under these circumstances it may be both
permissible and desirable to make a side bend test. A slice 3 to 6 mm
thick is cut at right angles to the plate surface and to the weld axis and
is then bent in the usual way as shown in Fig. 20.
Side bend testing shows up lack of side wall fusion very well but is
somewhat less sensitive to face and root defects than the normal type
of bend test. The relative locations for cutting face, root- and side-
bend test specimens in a thick butt welded plate are as shown in Fig.
20 (a).
Fig. 20 (A) Relatived
Location of Face, Root,
and Side Bend Test
Specimens in a Butt
Welded Thick Plate