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  2. 2. Dept of MME, IITM 2 | P a g e Abhishek Radhakrishna ACKNOWLEDGEMENT The satisfaction and euphoria that accompanies the successful completion of any task would be incomplete without the mention of the people who made it possible, and whose constant guidance and encouragement helped us in completing this project successfully. We consider it a privilege to express gratitude and respect to all those who guided us throughout the course of the completion of the training. I would like to express my heartfelt thanks to Mr. Sanjeev Walvekar-head of the hydraulics quality assurance, Mr. Anathagopalan-hydraulics head for providing me with a congenial environment for carrying out the project. I express my gratitude to Mr. Sheshadri-head of the metrology lab, Mr. Gopinath-hydraulics quality assurance for their constant guidance, encouragement, support and precious advice without which this project would have never become a reality. I extend my sincere thanks to Mr. T.S Rajeev-head of Product Engineering (hydraulics), Mr. Muralidharan-head of Plant Maintenance (hydraulics) whose guidance and support has been invaluable. Last but not the least, I would like to thank my friends whose beneficial feedback helped me to improve the project results by leaps and bounds and my parents for their unending encouragement and support.
  3. 3. Dept of MME, IITM 3 | P a g e Abhishek Radhakrishna COMPANY PROFILE Larsen & Toubro Limited, or L&T, is an Indian multinational conglomerate corporation headquartered in Mumbai, Maharashtra, India. The company has business interests in engineering, construction, manufacturing, information technology and financial services. L&T is India's largest engineering and Construction Company, with a dominant presence in India's infrastructure, power, hydrocarbon, machinery and railway related projects. In recent years, L&T has expanded its global presence and international projects contributed 9% of its overall order book for the 2010–11 period. Considered to be the "bellwether of India's engineering sector", L&T was recognized as the Company of the Year in 2010. L&T has featured four times in Forbes Fab 50 list of the best public companies in the Asia-Pacific region.[7] The company ranked #14 in the 2011 Fortune India 500 list of the largest Indian companies by total revenues. L&T - Komatsu Limited Having its registered office at Mumbai, India and focusing on construction equipment and mining equipment, L&T-Komatsu Limited is a joint venture of Larsen and Toubro, India’s leading engineering, construction and technology major and Komatsu Asia Pacific Pte Limited, Singapore, a wholly owned subsidiary of Komatsu Limited, Japan. Komatsu is the world’s second largest manufacturer of hydraulic excavators and has manufacturing and marketing facilities worldwide. The plant was started in the year 1975 by L&T to manufacture Hydraulic Excavators for the first time in India. In 1998, it became a joint venture. L&T–Komatsu Limited’s manufacturing facility—The Bangalore Works—comprises Machinery Works and Hydraulics Works. Machinery Works has a modern manufacturing facility with ISO 9001:2008 accreditation for design, manufacture and servicing of earthmoving equipment. Hydraulics Works, with a precision machine shop, manufactures the complete range of high pressure hydraulic components and systems, and is ISO 9001:2000 certified for design, development, manufacturing and servicing of hydraulic pumps, motors, cylinders, turning joints, hose assemblies, valve blocks, hydraulic systems and power drives as well as allied gear boxes.
  4. 4. Dept of MME, IITM 4 | P a g e Abhishek Radhakrishna
  5. 5. Dept of MME, IITM 5 | P a g e Abhishek Radhakrishna COMPANY PRINCIPLE L&T-Komatsu Limited is a joint venture with equal equity participation by L&T and Komatsu Asia Pacific Pte Ltd., Singapore a wholly owned subsidiary of Komatsu Ltd., Japan. Komatsu is the world's largest manufacturer of hydraulic excavators and has manufacturing and marketing facilities worldwide. The plant was started in 1975 by L&T to manufacture Hydraulic Excavators for the first time in India. In 1998 it became a joint venture. L&T-Komatsu Limited's manufacturing facility - The Bangalore Works - comprises Machinery Works and Hydraulic Works. Machinery Works has a modern manufacturing facility with ISO 9001 accreditation for design, manufacture and servicing of earthmoving equipment. Hydraulics Works, with a precision machine shop, manufactures the complete range of high pressure hydraulic components and systems, and is ISO 9001 certified for design, development, manufacturing and servicing of hydraulic pumps, motors, cylinders, turning joints, hose assemblies, valve blocks, hydraulic systems and power drives as well as allied gear boxes. The products manufactured at L&T-Komatsu Limited are supplied to domestic as well as overseas customers. L&T-Komatsu Limited is certified under Environment Management System ISO 14001 : 2004 and Occupational Health & Safety Management System OHSAS 18001 : 1999.
  6. 6. Dept of MME, IITM 6 | P a g e Abhishek Radhakrishna COMPANY VISION We shall be a world class company with high standard of governance, dedicated to excellence in product, process and people. We shall be a company delighting customers by delivering on time highly reliable product which enables them to succeed. We shall be a company with very high very high safety standards, caring for safety of people committed to social responsibility and environment protection. Our business model shall drive entrepreneur zeal, growth with scale and speed our financial performance shall consistently reward our stake holders. Our people shall have passion to continual learning and engage themselves to the highest level of involvement. We shall embrace an inclusive culture that incorporates a strong and well-articulated set of values and behavioural expectations. Our supply chain shall be of the world class standard with the highest level of seamless integration bringing in quality, cost and volume flexibility.
  7. 7. Dept of MME, IITM 7 | P a g e Abhishek Radhakrishna COMPANY MISSION We shall manufacture premium range of globally competitive hydraulic excavator and hydraulic systems for domestic market. Our focus would be to attain market leadership through sustained growth, quality through product reliability and on time delivery of our product to our customer. We shall be committed to provide safe working environment, provide team working and involve employee engagement. COMPANY MILESTONES 1975- Bangalore works established, introduction of hydraulic excavator in India L&T-poclain LC 80 and L&T-poclain LY 80 models manufactured in collaboration with Poclain SA, France. 1977- Introduced L&T-Poclain 90CK model hydraulic Excavator. 1978- Introduced L&T-Poclain 300CK Hydraulic Excavator. 1979- Introduced 90CK-E Hydraulic excavator. 1979- Introduced TT900 Vibratory compactor (introduced in collaboration with Alberet, France) 1982- Established hydraulic Works- commencement of in-house manufacturing of hydraulic components. 1985- Introduced improved version of L&T poclain 90CK (model-2) 1986- Introduced L&T poclain 300CK Electric model. 1987- Introduced L&T poclain 170CK Model hydraulic excavator. 1989- Recognized as R&D house by Government of India. 1990- Bridge launcher was developed for defence application. 1990- Introduced soil and asphalt compactor W1102-in collaboration with Vibromax, Germany. 1990- Introduced wheel loader L&T case W20 and L&T case W36 in collaboration with J.I case , USA 1990- Indigenous design and development of L&T excavator. 1991- Introduced tandem compactor W752 in collaboration with Vibromax, Germany.
  8. 8. Dept of MME, IITM 8 | P a g e Abhishek Radhakrishna 1993- Development of Hydraulic drives for shunting loco, sugar mill drives, paddles feeders for coal handling equipment. 1993- Introduced L&T-DDC power generator in collaboration with Detroit diesel corporation, USA. 1994- Introduced L&T 90 Model. 1995- Transit Mixer Gear box developed. 1997-Assembly of 85 ton dump track. 1998- Formation of joint venture L&T- komastu limited. 1999- Introduction of PC 200-6 model hydraulic excavator. 2002- Introduction of PC 71 model hydraulic excavator. 2003- Introduction of PC 300LC-7 model hydraulic excavator. 2006- Introduction of PC 130-7 model hydraulic excavator. 2008- Introduction of PC 450LC-7 model hydraulic excavator
  9. 9. Dept of MME, IITM 9 | P a g e Abhishek Radhakrishna Hydraulic excavator: Schematic diagram of a hydraulic excavator Hydraulic excavators, also called as diggers are used for a variety of applications. These high performance excavators are especially useful for work areas that are more confined and less amenable to conventional equipment. Hydraulic excavators are used in applications ranging from the construction of roads and pipelines to mining and excavation of rocks containing diamonds and gold. The work equipment portion of the hydraulic excavator consists of hydraulic cylinders, revolving frame, track frame, a boom, an arm and a bucket. This work equipment is involved in the actual digging and loading. The movements of the hydraulic excavator often resemble that of an actual arm. The boom portion of the equipment acts very much like the upper portion of a human arm including the elbow and the shoulder. The arm of the excavator behaves much like the portion of the human arm that starts at the elbow and ends at the wrist. The bucket portion can be compared to a cupped hand. Though the working portion of the excavator does the digging work, it is not the only important part of the excavator. The upper structure of the excavator is important as well and can be realised as the head of the machine. It holds the engine, hydraulic pump and tank and the swing motors. These important devices are responsible for making the excavator dig and load. The lower section of the excavator is also vital. It consists of the mechanisms that make the excavator move along the road, up a hill or across the construction site. There are excavators which move by wheels and the others move by crawlers.
  10. 10. Dept of MME, IITM 10 | P a g e Abhishek Radhakrishna Most hydraulic excavators have crawlers, as they are better suited to moving along rough roads and manoeuvring along steep slopes. Crawlers are belt like tracks used in place of wheels. Hydraulic excavators with crawlers are more practical for muddy areas than those with wheels A hydraulic excavator (digger) is a large vehicle that is designed for excavation and demolition purposes. Hydraulic excavators consist of a chassis, boom, and bucket, and move via tracks or wheels. They range in size and function, an example of which is the similar but smaller “mini excavator.” All versions are generally designed for the same purposes. Hydraulic excavators weigh between 3,000 and 2 million pounds and their speed ranges between 19 HP and 4,500 HP. Advantages Hydraulic excavators have many advantages that allow them to be used in the ways that they are. For example, they are small enough to work on specific tasks within a project area and can usually be transported from one project to another by either being towed or stored on a large truck. Hydraulic excavators can also take advantage of many different attachments: a mallet for demolition purposes, a blade for scraping, or a grapple for picking up objects. Hydraulic excavators are also widely available and can be purchased new or used. Disadvantages Hydraulic excavators have few disadvantages, most of which are expected in such a vehicle. For example, hydraulic excavators are heavy and cannot simply be driven across large distances or on non-reinforced roads. Likewise, they generally use large amounts of fuel and can be a very expensive investment, the latter being countered by the fact that they can remain operable for decades. Additionally, hydraulic excavators can be difficult to repair due to their large size and many moving parts.
  11. 11. Dept of MME, IITM 11 | P a g e Abhishek Radhakrishna Parts of excavators: 1. Boom: The component that holds the arm and hydraulic cylinder and mounted on revolving frame. 2. Arm: Attached to boom at one end and to the bucket at other end. 3. Revolving frame: Component mounted on the track frame, which in turn holds the all the component of the excavator. It has flexibility to rotate in 360° horizontally. 4. Track frame: The bottom frame which carries the track over which the excavator crawler. 5. Bucket: It does the actual work of digging and loading there are also many other attachment attached to the excavator for boring, ripping, crushing, cutting etc 6. The hydraulic cylinders: carries the hydraulic fluid, adjusting the oil level in the hydraulic cylinder can change the movement accuracy of the work equipment. Hydraulic excavator
  12. 12. Dept of MME, IITM 12 | P a g e Abhishek Radhakrishna Parts of the excavator Hydraulics shop: The word "hydraulics" originates from the Greek word ὑδραυλικός (hydraulikos) which in turn originates from ὕδωρ (hydor, Greek for water) and αὐλός (aulos, meaning pipe). Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. At a very basic level hydraulics is the liquid version of pneumatics. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through most science and engineering disciplines, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behaviour and erosion. L&T Komatsu boasts of two majestic hydraulic shops which contain heavy duty machines working all round the clock. They are named as hydraulics shop 1 and hydraulic shop 2. In hydraulic shop 1, the products mainly produced are swing motors, swivel joints, gear boxes etc. whereas in the hydraulics shop 2 manufactures the cylinders and the piston rods. The components undergo line production before they are transported to the machinery and assembly units.
  13. 13. Dept of MME, IITM 13 | P a g e Abhishek Radhakrishna The different modules of the Hydraulics unit in L&T Komatsu are: 1. Supplies module. 2. Quality control module. 3. Support and service module. 4. Product engineering module. 5. Material management module. 6. Maintenance module.
  14. 14. Dept of MME, IITM 14 | P a g e Abhishek Radhakrishna FRACTURE ANALYSIS Fracture is the separation, or fragmentation of a solid body into two or more parts under the action of stress. The process of fracture can be made of two components, crack initiation and crack propagation. Fractures can be classified into two general categories, ductile fracture and brittle fracture. A ductile fracture is characterized by appreciable plastic deformation prior to and during the propagation of the crack. An appreciable amount of gross deformation is usually present at the fracture surfaces. Brittle fracture in metals is characterized by the rapid rate of crack propagation, with no gross deformation and very little micro deformation. It is akin to cleavage in ionic crystals. The tendency of brittle fracture is increased with decreasing temperature, increasing strain rate and triaxial stress conditions. Brittle fracture is to be avoided at all cost, because it occurs without warning and usually produces disastrous consequences PROCEDURE To increase the odds of completing a conclusive failure analysis while at the same time saving time and money, investigations should be carried out using a systemic approach similar to that outlined in Figure. It is important to note however, that it is often impossible to foresee results that might require the investigator to go back and repeat a test. A simple way reduce the occurrence of this is to go into a case well informed on how similar systems have failed. An excellent source of for this type of information is the ASM handbooks, particularly volume 10 on "Failure analysis and prevention". This book is an invaluable reference to the beginner and the expert and should be consulted regularly. Another important source of information are the standards by which the part was manufactured. These standards give the investigator a measuring stick by which to compare, as well as indicating areas of importance. There are many organisations that produce standards for different applications and several organisations standards can overlap. It would be a good idea for the investigators to spend some time familiarising themselves with these organisations and how the standards are used. The table below gives a brief list of the more common organisations that write standards and their general area of coverage. The first step in conducting any failure analysis is to gain a good understanding of the conditions under which the part was operating. The investigator must ask questions from those who work with, as well as those who maintain the equipment and visit the site whenever possible. Contacting the manufacturer may also be necessary. Unfortunately, in many instances the investigator will receive a failed part with little information about its history and operating conditions. In cases such as these the physical evidence will have to be more heavily relied on
  15. 15. Dept of MME, IITM 15 | P a g e Abhishek Radhakrishna Figure - Chart outlining the major steps that are usually taken when conducting a failure analysis Common standard organisations and their general area of coverage. Acronym Coverage AISI Steel composition standards ASTM Standards for materials and their manufacture API Petroleum industry standards which are used by many other industries ASME Responsible for Boiler Pressure vessel codes NACE Codes for materials exposed to corrosive environments SAE Automotive industry standards used by many other industries UNS Classification for metals and metal alloys
  16. 16. Dept of MME, IITM 16 | P a g e Abhishek Radhakrishna The second step is to conduct a visual examination, cataloguing and recording the physical evidence at the same time. This serves the functions of:  Familiarising the investigators with the evidence.  Creating a permanent record that can be referred to in light of new information. Samples should be examined, photographed and sketched taking particular care to identify and record any area of particular importance, such as fracture surfaces and surface defects. Visual examination can be aided by the use of a stereomicroscope with lights that can be easily directed. Shadows can give depth to a surface making it easier to analysis and photograph. Pieces should always be examined and recorded before any surface cleaning is undertaken. In some cases substances such as dirt, paint and Oil on the surface can themselves be important clues, indicating such things as how old the fracture surface is and in what kind of environment the piece was operating. A good general rule is to be conservative when destroying evidence of any kind. The visual examination is a good time for the investigator to examine the fracture surfaces in detail and try to identify the mode of fracture (brittle, ductile, fatigue, etc.), points of initiation, and direction of propagation. Each mode of fracture has distinct characteristics that can be easily seen with the naked eye or the use of a stereomicroscope; however, sometimes a scanning electron microscope (SEM) will have to be used. There are several good books, some listed in the bibliography, on fracture mechanism and compilations of fracture surface photographs that can be used by the investigator to identify the mechanism of fracture under investigation. As a reminder, some common fracture surface characteristics arc listed in Table with their corresponding mechanism.
  17. 17. Dept of MME, IITM 17 | P a g e Abhishek Radhakrishna Table-Fracture mechanisms and their fracture surface characteristics. Mode of Fracture Typical fracture surface Characteristics Ductile Cup and Cone Dimples Dull Surface Inclusion at the bottom of the dimple Brittle Intergranular Shiny Grain Boundary cracking Brittle Transgranular Shiny Cleavage fractures Flat Fatigue Beachmarks Striations (SEM) Initiation sites Propagation area The third step is to decide on a course of action. Based on the visual examinations and the background information the investigator must outline a plan of action, which is the series of steps that will be needed to successfully complete the case. There are several resources that an investigator can draw on to determine the cause of failure, which can classified into one of the following categories:  Macroscopic examination  Non-destructive testing (NDT)  Chemical analysis  Metallographic examination  Mechanical Testing Many of these categories will require steps that use the same equipment and therefore much time can be saved with a little forethought. The macroscopic examination is best performed when cataloguing the samples; however the investigator will often want to return to examine the part in more detail once other evidence is gathered. Use of a scanning electron microscope (SEM) is often useful at this stage because of its large range of magnifications and its large
  18. 18. Dept of MME, IITM 18 | P a g e Abhishek Radhakrishna depth of field. Since undamaged fracture surfaces are not always available, it is often a good idea to open other cracks that may be present in the piece. This often reveals good quality fracture surfaces similar to those that caused failure. Procedures for doing this can also be found in the ASM handbook volume 10. Nondestructive tests (NDT) are a good way to examine parts without causing permanent damage. Often times, results obtained from examining failed parts in the lab using NDT's can be used to examine parts in the field and remove them from service before failure occurs. There are several NDT's that are available to the investigator and it would be a good idea to read up on each ones abilities. Table below gives an outline of NDT's available and what they are able to detect. Commonly used nondestructive tests and there capabilities in detecting defects. NDT Method Capabilities Radiography  Measures differences in radiation absorption.  Inclusions, Porosity, Cracks Ultrasonic  Uses high frequency sonar to find surface and subsurface defects.  Inclusions, porosity, thickness of material, position of defects. Dye Penetrate  Uses a die to penetrate open defects.  Surface cracks and porosity Magnetic Particle  Uses a magnetic field and iron powder to locate surface and near surface defects.  Surface cracks and defects Eddy Current  Based on magnetic induction.  Measures conductivity, magnetic permeability, physical dimensions, cracks, porosity, and inclusions. Chemical analysis is done on the bulk of the material to confirm the material composition. Depending on the investigation, chemical analysis should also be done on any overlay materials or surface residues. There are several techniques that can be used to check composition, and the choice of which to use often depends on accessibility and sample type. In many cases, the
  19. 19. Dept of MME, IITM 19 | P a g e Abhishek Radhakrishna SEM can be a powerful tool for fast identification of surface materials. Care should be taken not to contaminate samples taken for chemical analysis by surface residue or cutting instruments. Metallographic examination involves the sectioning of samples to examine the microstructure. The sections that are selected for examination are dependent on the type of piece and the mode of fracture. Sections from the sample should be taken in different planes so that any differences in the microstructure can be seen. Sometimes it is useful to take a cross section through the fracture surface so that the microstructure below the fracture and the surface profile can be examined. A section running parallel to the fracture surface is also often taken for examination. Samples should be mounted, ground, and polished using metallographic techniques. They should be examined before etching for porosity, inclusions, and other defects. Microstructures should be identified and their properties researched. There are several referenced that the investigator can refer to for identification of uncertain structures. Mechanical testing is done to verify that the mechanical properties of the material conform to the standards. There are many types of mechanical testing that can be performed and their procedures can be found in the ASTM mechanical testing standards. The most common method used is hardness testing because of its relative simplicity, low cost, and the fact that for many materials tables exist to relate hardness with yield strength. A macro hardness test is usually sufficient to determine material properties; however micro-hardness measurements are helpful in determining property variations within the material. Use the micro-hardness measurement to compare the surface hardness to that of the body or to verify the microstructure. Other mechanical testing such as tensile tests and impact tests can be used; however their use is usually limited by insufficient material and high costs. Once all the data is gathered, the investigator must come to a conclusion based on the evidence present. This requires that the investigator draw heavily on background experience and research performed. This step can be difficult because when conducting the investigation clues will lead the investigator down paths that seem to be the cause but which are merely consequences. The final and most difficult step in any investigation is coming up with recommendations. Some cases will be simple, however many cases are not obvious even though the cause and theory are known. Recommendations are not to be taken lightly. Serious failures can occur if recommendations are in error. The system may have to be redesigned or a new material put in place. Sometimes all you will be able to recommend is that inspections be carried out more often.
  20. 20. Dept of MME, IITM 20 | P a g e Abhishek Radhakrishna CASE STUDY Introduction to Case Studies These case studies are actual reports submitted in response to industrial failures. The purpose of these reports is to demonstrate by example. Most of the cases mention the techniques that were used when stating the results. They were written at a basic level due to the uncertainty of background of the reader and further reading is be recommended to better understand the failure mechanism. Most of the cases that are presented here have comparable cases in the ASM failure analysis handbook. Case Study of PC 210 bucket pin fracture Introduction: A PC-210 hydraulic excavator was sold to a customer in Salem in the month of February 2012. The excavator after working for 652 hours broke down on the 28th of May, 2012. The service engineer of the region, after initial inspection of the excavator recorded that the bucket-pin which holds the bucket and the arm of the excavator was broken. This broken pin was brought to the lab for failure analysis. In the below figures the image of the broken pin is shown and also it’s 2D-drawing. A close up image of the fractured surface is also shown. The standard followed by the L&T, Komatsu is called the Komatsu engineering standards (KES). By the KES standards the material code of the bucket pin is SCM435H and the heat treatment code is 2146191100. As per the KES standards the heat treatment process is as follows;  First- induction hardening at a temperature of 840-9100 C.  Second- the induction hardened material is then tempered.  Third- hardness of 55HRC is obtained by the process of quenching.  Fourth- material hardening and tempering is carried out at 500-6000 C.  Fifth- finally tempering is done to the material at a temperature of 180-2100 C.
  21. 21. Dept of MME, IITM 21 | P a g e Abhishek Radhakrishna Drawing of the bucket-pin. Photograph of broken bucket- pin Photograph of fracture surface. Results: Observations Examination of the fracture surface revealed characteristics such as a beachmarks associated with fatigue. The zone of final fracture was located between two areas of fatigue propagation suggesting the presence of bending forces. The surface area of final fracture was approximately 12% of the total fracture surface suggesting that the bucket-pin was not overloaded. Cracks were also found between threads near the fracture surface indicating that the bucket-pin was highly susceptible to fatigue initiation. The pin has been case hardened. Case hardening is an induction hardening process where the outer surface of the material is quenched to obtain high hardness whereas no treatment is done to the inner core of the material.
  22. 22. Dept of MME, IITM 22 | P a g e Abhishek Radhakrishna Induction hardened For the concerned bucket-pin, according to the KES standards, the case hardness depth is <4mm. With the help of a micro hardness tester the actual case depth can be calculated and this experiment is called hardness survey. In this experiment the hardness of the material is recorded, using a load of 1kg, in steps of 1mm from the edge of the circumference towards to the centre of the pin. The cut-off hardness for case hardening is 450VHN. At this particular hardness number, the case depth is recorded. The observations are as follows. Polished surface for hardness survey. The following is the tabular column of the hardness survey. Distance from edge (mm) Vickers hardness number (VHN) 0.0 628 0.5 564 1.0 608 1.5 598 2.0 611 2.5 607 3.0 600 3.5 551 4.0 247 Inner core 246
  23. 23. Dept of MME, IITM 23 | P a g e Abhishek Radhakrishna Below is the graph of the hardness survey. From the graph it is clear that the hardness is highest at the edge and gradually decreases as we move towards the inner core. Beyond 4mm the hardness remains constant and is equal to the harness of the untreated material. As the cut-off is 450VHN, the case depth is measured to be 3.53mm which is well within the KES standards. A small piece of the bucket-pin was then cut out and sent for chemical analysis outside the industry. Another small section of the material was sent for mechanical properties analysis which includes yield strength, tensile strength, etc. The results were later verified with the KES standards to check whether the material had any faulty chemical composition or undesired mechanical properties. Results from chemical analyses (Table) showed that the broken bucket-pin had all the required elements well within the specifications of the KES standards. The only noteworthy information that is relevant is that the material had undesirable copper content but it has no role to play in this type of fracture. Therefore, it is safe to say that the chemical composition of the material is well within the standards and the bucket-pin did not fail due to undesirable chemical composition. 0 100 200 300 400 500 600 700 Vickers hardness number Vickers hardness number
  24. 24. Dept of MME, IITM 24 | P a g e Abhishek Radhakrishna Element Specification (in %) Test results (in % )Minimum Maximum Carbon (C) 0.320 0.390 0.360 Silicon (Si) 0.150 0.350 0.250 Manganese (Mn) 0.550 0.900 0.790 Phosphorous (P) -- 0.030 0.011 Sulphur (S) -- 0.030 0.015 Chromium (Cr) 0.850 1.250 1.120 Molybdenum (Mo) 0.150 0.250 0.220 Nickel (Ni) -- 0.250 0.020 Vanadium (V) -- -- -- MICROSCOPIC EXAMINATION: Microscopic examination of the pin was done using longitudinal and latitudinal mounts for each. The sections taken from the fractured pin were taken close to the fracture surface. Examination before etching of the two bucket pins showed no cracking or unusually large inclusions as shown in the image. The original broken bucket pin did show some flaking at the base of the threads but this is expected for a bucket pin that has been in service. Etching the sections revealed a microstructure of coarse pearlite in a matrix of ferrite. The KES standard requires that the bucket pin be quenched and tempered to conform and therefore should have a tempered martensite structure at the case hardened section. Martensite has higher material properties such as yield strength and hardness, which increases its resistance to fatigue initiation. The ferrite matrix in the inner core of the pin has low yield strength, which in turn reduces its resistance to fatigue initiation. The fracture roots are clearly visible under the lens when etched and observed very close to the fracture.
  25. 25. Dept of MME, IITM 25 | P a g e Abhishek Radhakrishna Inclusions – unetched condition. 100X Micrograph of fractured pin showing a fracture root. 2% nital 200X Micrograph of the induction hardened section. Tempered martensite. 2% nital 200X Micrograph of the inner core section. Ferrite and pearlite matrix. 2% nital 200X Mechanical tests were done on the bucket-pin to test their material properties in comparison with the standards. The results (Table) show that the yield strength and ultimate tensile strength of the broken pin compared to the specifications and it can be clearly observed that the mechanical properties were well within the standards of L&T, Komatsu. The hardness number measured here is that of the core and not the periphery were case hardening has been carried out. This conforms to the microstructural observations. Tests Specification Actual YS (kg/mm2 ) 75.00 (min) 87.45 UTS (kg/mm2 ) 90.00 (min) 94.30 %Elongation 15.0 (min) 22.00 Chropy Impact (kgM/cm2 ) 7.00(min) 8.50 Hardness number (BHN) 277 (min) 285 Therefore, with the results from chemical composition, mechanical tests and observations under the microscope, we can clearly state that the material had no issues with the material properties and therefore one has to come up with a logical solution to reason out how the bucket pin failed.
  26. 26. Dept of MME, IITM 26 | P a g e Abhishek Radhakrishna Conclusions and Recommendations: Examination revealed that the bucket-pin failed as a result of high cycle low load fatigue. Chemical analysis and tensile tests confirmed that the bucket pin did meet the KES standards required by the original design of the excavator. Since the resistance of steel to fatigue initiation in proportional to its yield strength, I believe that the specified standard for the yield strength is low in this part of the excavator because in this case left it open to fatigue initiation.
  27. 27. Dept of MME, IITM 27 | P a g e Abhishek Radhakrishna Conclusion L&T Komastu maintains a world class standard in operating excellence. The company maintains a high level of efficiency and quality The company is environment- friendly which is evident in the greenery of its premises, the company also ensures that the waste generated is disposed safety and minimizes the loss of resources and expenditure by encouraging employee in their motivation. The company also strives to minimize environment health and safety hazards. The objective of L&T Komastu is to uphold its vision, by continued excellence in all around performance with new ideas, added vigour and sustained commitment to its social culture organization and natural environment.
  28. 28. Dept of MME, IITM 28 | P a g e Abhishek Radhakrishna Bibliography  Reports of projects  Journals, manual, process sheet  L&T Komastu website   D.A. Ryder et al., "General Practice in Failure Analysis," in ASM Metals Handbook Volume 11 "Failure Analysis and Prevention", Ed. Kathleen Mill (Ohio: ASM International, 1986)  "Threaded Steel Fasteners," in ASM Metals Handbook Volume 11 "Failure Analysis and Prevention", Ed. Kathleen Mill (Ohio: ASM International, 1986)  Walter J. Jensen, "Failures of Mechanical Fasteners," in ASM Metals Handbook Volume 11 "Failure Analysis and Prevention", Ed. Kathleen Mill (Ohio: ASM International, 1986)  E. Alban, "Failures of Gears," in ASM Metals Handbook Volume 11 "Failure Analysis and Prevention", Ed. Kathleen Mill (Ohio: ASM International, 1986)  Geaorge E. Dieter, Mechanical Metallurgy (Toronto: McGraw-Hill, Inc., 1986)  William D. Callister, Jr., Materials Science and Engineering: An Introduction, Third Edition (Toronto: John Wiley & Sons, Inc., 1994)  Kathleen Mill ed. et al. ASM Metals Handbook: Metallography and Microstructures, (Ohio: ASM International, 1993)