This article provides a discussion on the structural ceramics used in gas turbine components, the automotive and aerospace industries, or as heat exchangers in various segments of the chemical and power generation industries. It covers the fundamental aspects of chemical corrosion and describes the corrosion resistance characteristics of specific classes of refractories and structural ceramics. The article also examines the prevention strategies that minimize corrosion failures of both classes of materials.

This article reviews the most common reasons for failures and the purpose of a failure investigation. It discusses the nine steps for the organization of a good failure investigation. The three basic tools that are helpful in any failure investigation, namely, a fault tree, a failure mode assessment chart, and a technical plan for resolution chart, are reviewed. The article briefly describes failure investigation pitfalls and concludes with information on the other common tools used for failure investigation and root cause determination.

Reliability-centered maintenance (RCM) is a systematic methodology for preventing failures. This article begins by discussing the history of RCM and uses Society of Automotive Engineers (SAE) all-industry standard JA1011 as its model to describe the key characteristics of an RCM process. It then expands on questions involved in RCM process, offering definitions when necessary. Next, the article describes the approach of RCM to failure modes and effects analysis (FMEA), the failure management policies available under RCM, and the criteria of RCM for deciding when a specific failure management policy is technically feasible. Then, after discussing the ways that RCM classifies failure effects in terms of consequences, it describes how RCM uses failure consequences to identify the best failure management policy for each failure mode. Next, the building blocks of RCM are put together to create a failure management program. The article ends with a discussion on some practical issues pertaining to RCM that lie outside the scope of SAE JA1011.

Reinforced polymers (RPs) are widely used in structural, industrial, automotive, and engineering applications due to their ecofriendly nature and the potential to manipulate their properties. This article addresses the technical synthesis of RPs, referring to their tribological behavior, to provide insights into the contribution and interaction of influential parameters on the wear behavior of polymers. It provides a brief discussion on the effects of significant parameters on RP tribology. The article describes abrasive and adhesive wear and provides a theoretical synthesis of the literature regarding the wear mechanisms of RPs. It also describes the synthesis of abrasive wear failure of different types of RPs and highlights the contribution of these influential parameters. The article addresses the synthesis of adhesive wear failure of different types of RPs.

The failure of a high speed steel twist drill which caused injury to the user was investigated thoroughly to settle a legal suit. The drill was being used to remove a stud that broke in the vertical wall of a metalworking machine (upsetter) after drilling a pilot hole. The drill had shattered suddenly with a bang which caused a chip to be dislodged and cause the injury. A large nonmetallic inclusion parallel to the axis near the center of the drill was revealed in an unetched longitudinal section. Carbide bands in a martensitic matrix were indicated in an etched sample. It was concluded by the plaintiff's metallurgist that the failed drill was defective as the steel contained nonmetallic inclusions and carbide segregation which made it brittle. It was revealed by the defendant that the twist drill met all specifications of M1 high-speed steel and investigated several other drills without failure to prove that the failure was caused by use in excessive conditions. It was revealed by examination that the point of the broken drill was not the original point put on at manufacture but came from regrinding. Both technical and legal details have been discussed.

Hydrogen damage is a term used to designate a number of processes in metals by which the load-carrying capacity of the metal is reduced due to the presence of hydrogen. This article introduces the general forms of hydrogen damage and provides an overview of the different types of hydrogen damage in all the major commercial alloy systems. It covers the broader topic of hydrogen damage, which can be quite complex and technical in nature. The article focuses on failure analysis where hydrogen embrittlement of a steel component is suspected. It provides practical advice for the failure analysis practitioner or for someone who is contemplating procurement of a cost-effective failure analysis of commodity-grade components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also provided.

The principal task of a failure analyst during a physical-cause investigation is to identify the sequence of events involved in the failure. Technical skills and tools are required for such identification, but the analyst also needs a mental organizational framework that helps evaluate the significance of observations. This article discusses the processes involved in the characterization and identification of damage and damage mechanisms. It describes the relationships between damage causes, mechanisms, and modes with examples. In addition, some of the more prevalent and encompassing characterization approaches and categorization methods of damage mechanism are also covered.

A Marine Corps helicopter crash was investigated. Efforts were directed to the failure of one of the main rotor blades that had apparently separated in the air. The apparent failure of a blade integrity monitor (BIM) system was also considered. The rotor blade comprised a long, hollow 6061-T651 aluminum alloy extrusion and 26 fiberglass “pockets” that provided the trailing-edge airfoil shape. Visual examination of the fracture surface of the aluminum extrusion indicated fatigue crack growth followed by ductile overload separation. Examination of the fatigue fracture region revealed several pits that appeared to have acted as fracture origin sites. Time to failure was determined using fracture mechanics. It was concluded that failure was caused by a fatigue crack that grew to critical length without detection. The crack originated at pits that resulted from the use of an improperly designed heating element used to cure fiberglass repairs.

Following an accident in which a light pickup truck left the road and overturned, one of the rear axles, made of approximately 0.30C steel, was found to be fractured adjacent to the bearing lock nut. A keyway was present in the failed area, as were threads for the lock nut. Fracture surfaces of the failed axle and exemplar fractures obtained from simulation tests were studied using scanning electron microscope. The examination showed that the outer perimeter fracture in the axle was very flat and composed of cleavage and that the interior portion was composed of both cleavage and dimples. No evidence of prior cracking was found. The exemplar specimens from the simulation impact testing failed in a manner consistent with that observed in the axle. The examination confirmed that the failure was a one-time impact overload fracture and not the result of any prior crack in the material, indicating that the axle failure did not initiate the accident.

Two type 316L stainless steel orthopedic screws broke approximately 6 weeks after surgical implant. The screws had been used to fasten a seven-hole narrow dynamic compression plate to a patient's spine. The broken screws and screws of the same vintage and source were examined using macrofractography, SEM fractography, and hardness testing. Fractography established that fracture was by fatigue and that the fatigue cracking originated at corrosion pits. Hardness while below specification, still indicated that the screws were in the cold-worked condition and notch sensitive during fatigue loading. Use of a steel with a higher molybdenum content (317L) in the annealed condition was recommended.

The types of metal components used in lifting equipment include gears, shafts, drums and sheaves, brakes, brake wheels, couplings, bearings, wheels, electrical switchgear, chains, wire rope, and hooks. This article primarily deals with many of these metal components of lifting equipment in three categories: cranes and bridges, attachments used for direct lifting, and built-in members of lifting equipment. It first reviews the mechanisms, origins, and investigation of failures. Then the article describes the materials used for lifting equipment, followed by a section explaining the failure analysis of wire ropes and the failure of wire ropes due to corrosion, a common cause of wire-rope failure. Further, it reviews the characteristics of shock loading, abrasive wear, and stress-corrosion cracking of a wire rope. Then, the article provides information on the failure analysis of chains, hooks, shafts, and cranes and related members.

A coupling in a line-shaft vertical turbine pump installed in a dam foundation fractured after a very short time. The coupling material was ASTM A582 416 martensitic stainless steel. Visual, macrofractographic, and scanning electron microscopic examination of the coupling showed that the fracture was brittle and was initiated by an intergranular cracking mechanism. The mode of fracture outside the crack initiation zone was transgranular cleavage. No indication of fatigue was found. The failure was attributed to improper heat treatment during manufacture, which resulted in a brittle microstructure susceptible to corrosion. The crack initiated either by stress-corrosion or hydrogen cracking. It was recommended that the couplings in the system be examined for surface cracking and, if present, corrective measures be taken.

The side supporting flange of the bottom platen of an 800 ton hydraulic press fractured after 9 x 10's cycles under a maximum load of 530 tons. The platen material specified in the design was cast steel 52. Metallographic examination of the fracture surface indicated that the platen had failed in fatigue as a result of a high stress concentration in a sharp 0.6 mm (0.02 in.) radius fillet. Stress analysis and fracture mechanics predictions revealed that there was also danger of fatigue failure for platens with the design radius of 10 mm (0. 4 in.) if the press operates at 800 tons. It was recommended that the remaining life of similar presses be assessed periodically controlling the cracks, their dimensions, and their propagation rates. An increase in the radius of the fillet was also recommended.

This article describes concepts and tools that can be used by the failure analyst to understand and address deformation, cracking, or fracture after a stress-related failure has occurred. Issues related to the determination and use of stress are detailed. Stress is defined, and a procedure to deal with stress by determining maximum values through stress transformation is described. The article provides the stress analysis equations of typical component geometries and discusses some of the implications of the stress analysis relative to failure in components. It focuses on linear elastic fracture mechanics analysis, with some mention of elastic-plastic fracture mechanics analysis. The article describes the probabilistic aspects of fatigue and fracture. Information on crack-growth simulation of the material is also provided.

Identification of alloys using quantitative chemical analysis is an essential step during a metallurgical failure analysis process. There are several methods available for quantitative analysis of metal alloys, and the analyst should carefully approach selection of the method used. The choice of appropriate analytical techniques is determined by the specific chemical information required, the condition of the sample, and any limitations imposed by interested parties. This article discusses some of the commonly used quantitative chemical analysis techniques for metals. The discussion covers the operating principles, applications, advantages, and disadvantages of optical emission spectroscopy (OES), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray spectroscopy, and ion chromatography (IC). In addition, information on combustion analysis and inert gas fusion analysis is provided.

Vibration analysis can be used in solving both rotating and nonrotating equipment problems. This paper presents case histories that, over a span of approximately 25 years, used vibration analysis to troubleshoot a wide range of problems.