Engineering component and structure failures manifest through many mechanisms but are most often associated with fracture in one or more forms. This article introduces the subject of fractography and aspects of how it is used in failure analysis. The basic types of fracture processes (ductile, brittle, fatigue, and creep) are described briefly, principally in terms of fracture appearances. A description of the surface, structure, and behavior of each fracture process is also included. The article provides a framework from which a prospective analyst can begin to study the fracture of a component of interest in a failure investigation. Details on the mechanisms of deformation, brittle transgranular fracture, intergranular fracture, fatigue fracture, and environmentally affected fracture are also provided.

An explosion at a food processing plant was initially attributed during scene investigation to a separated butt weld in aluminum piping associated with an ammonia-based refrigeration system. The piping failed at a weld with no obvious gross plastic deformation and, on this basis primarily, was incorrectly determined to have failed by fatigue. A series of tests on exemplar welded pipe specimens was conducted to establish fractographic characteristics for the various failure modes. Finite element stress analyses were also conducted to assist in the fracture mode determination. The results of the exemplar tests and stress analyses demonstrated that the subject weld fracture occurred via a single-event overstress due to post-explosion collapse of the adjacent roof truss.

The right-rear wheel of a full-size pickup truck involved in a single-vehicle accident was alleged to have fractured, leading to loss of vehicle control. The wheel was found fractured and partially separated from the vehicle by a distance of approximately 200 feet from the final resting point of the vehicle. The wheel was manufactured using a common casting procedure utilizing aluminum alloy A356 in the T6 condition. In subsequent litigation, the presence of porosity in the wheel was alleged to have precipitated the failure. Radiographic inspection of the wheel displayed the presence of shrinkage porosity in a quantity less than the maximum allowed according to the part specification. The recovered portions of the right-rear wheel exhibited evidence of impact overload fracture, including significant deformation. Inspection of the remaining artifacts also revealed that the right-front wheel exhibited a similar fracture as the rear.

A corroded threaded fitting on a direct-expansion ammonia fan-coil unit was found to be leaking in a refrigerated food-handling warehouse. Efforts to stop the leak by tightening the threaded connection resulted in the failure of the male fitting, causing a catastrophic release of ammonia refrigerant. Subsequent analysis of the subject threaded connection found that the threads of the male carbon steel fitting were severely deteriorated by atmospheric corrosion. The installation location of the subject fan-coil unit was such that it repeatedly experienced significant condensation and frost accumulation and, therefore, needed to be regularly defrosted. It was this combination of repeated condensation/frost accumulation and a cyclic freeze/thaw process which resulted in the accelerated atmospheric corrosion of the subject threaded connection.

Dr. Michael E. Stevenson, editor of the Journal of Failure Analysis and Prevention (JFAP), announced that the JFAP volume 11 best paper is ‘‘Failure Analysis and Prevention of Fires and Explosions with Plastic Gasoline Containers’’ by Dr. Glen Stevick, Dr. Joseph B. Zicherman, Dr. David Rondinone, and Dr. Allan Sagle. The winning article was published in the October 2011 issue of JFAP. The JFAP Volume 11 Best Paper Award was presented during the 2012 Leadership Awards Luncheon at MS&T’12 in Pittsburgh, Pennsylvania, on October 8, 2012. The award, in addition to the recognition, includes a plaque and $1000 worth of ASM International products and services. The best paper was selected by the Editorial Board of the journal from all papers published in volume 11. Dr. Glen Stevick (left) and Dr. Joseph Zicherman (right) accept the Journal of Failure Analysis and Prevention Volume 11 Best Paper Award plaque from Dr. Chris Berndt (center), then President of ASM International, during MS&T’12

Dr. Michael E. Stevenson, editor of the Journal of Failure Analysis and Prevention (JFAP), announced that the JFAP Volume 12 Best Paper is ‘‘Replaying the Fracture Process of a Failed Space Shuttle Orbiter Thruster’’ by Dr. Takao Kobayashi, Dr. Donald. A. Shockey, and Mr. Jeremy Jacobs. The winning article was published in the December 2012 issue of JFAP. The JFAP Volume 12 Best Paper Award was presented during the 2013 Leadership Awards Luncheon at MS&T ‘13 in Montreal, Canada, on October 28, 2013. The award, in addition to the recognition, includes a plaque and $1000 worth of ASM International products and services. The Best Paper was selected by the Editorial Board of the journal from all papers published in volume 12. j Dr. Gernant E. Maurer, President, ASM International (left), presents the Volume 12 JFAP Best Paper Award Plaque to Dr. Takao Kobayashi (right) during MS&T ‘13

Several radiators used for locomotive engines, manufactured from a 65/35 copper/zinc yellow brass tube, were found to have leaking problems shortly after manufacture. The radiators were found to experience widespread leaks at varying locations during pressure testing conducted before use in service. A large population of radiators produced during the same production cycle (approximately 80%) experienced leaks. The radiators were returned to the manufacturer as defective. In the months following the discovery of the leaks, a dispute regarding the cause of the leaks arose between the supplier of the yellow brass tube and the manufacturer of the radiator.

Progressive fracture occurred in a number of brazed joints on hydraulic fittings during service, resulting in a series of fires. Post-failure analysis revealed that the brazed connections that failed were of poor quality and inconsistent with properly manufactured connections of this type. The brazed connections on used, exemplar fittings removed from identical service were also examined and were found to possess similar manufacturing deficiencies. In the absence of these manufacturing deficiencies, the observed fracture modes of the fittings would not have occurred.

In the present study, the local elastic and plastic properties of the γ- TiAl and the Laves phases have been investigated in a series of γ + Laves alloys using room-temperature compression, Vickers microhardness, and nanoindentation with an emphasis on elucidating the local property changes in γ + Laves alloys deformed at room temperature. This study shows that nanoindentation can be used to provide useful information on plastic flow in multiphase intermetallic alloys.

Delayed fracture occurred to a temporary anchor supporting an overhead powerline during construction. The fracture resulted in loss of the overhead transmission line and resulted in a singe vehicle incident in the adjacent roadway. Post-failure analysis conducted as part of personal injury litigation revealed that the fracture was precipitated by a pre-existing weld related crack. Closed form and numerical stress analyses were conducted in order to assess the role of anchor installation in the failure, with the results indicating that installation was not conducted outside of the parameters intended by the anchor manufacturer.

The failure of a high-speed pinion shaft from a marine diesel engine was investigated. The shaft, which had been in service for more than 30 years, failed shortly after a service operation in which the bearings were replaced. Examination of the shaft revealed cyclic fatigue as the failure mechanism, with a substantial distribution of nonmetallic inclusions near the fracture initiation site. Fracture mechanics analysis indicated that the inclusions would be unlikely to have served as failure initiation sites if only stresses acting on the shaft were induced by normal service loads. Further examination of the bearing elements revealed an abnormal wear pattern, consistent with the application of elevated bending loads to the shaft after bearing replacement. The root cause of failure was determined to be an increase in service stresses after bearing replacement along with the presence of significant nonmetallic inclusions in the pinion shaft.

Low-carbon steel sheet used for the fabrication of automotive brake components was tearing during deep drawing. The associated mill certificates revealed that the coil met the specified chemical composition and mechanical properties. Metallographic evaluation revealed a severe variation with respect to grain size through the thickness of the steel sheet, as well as a slight segregation of pearlite. Insufficient temperature during hot rolling in combination with a high coiling temperature resulted in the observed microstructural gradient. The anisotropic mechanical properties were amplified by the slight carbon segregation.

A metallurgical failure analysis was conducted to determine the cause of cracking in several sections of copper refrigeration tubing. The tubing in question was part of a new mechanical design, implemented to mitigate fatigue failures of solder joints that had occurred in tubing systems fabricated under the previous design. A comprehensive metallurgical evaluation revealed intergranular fracture of the copper in a region of the tubing that had been significantly cold worked during manufacture. On discovery of a source of moist ammonia in the system, associated with the location of failure, intergranular stress-corrosion cracking (SCC) was identified as the failure mechanism. A modified design, incorporating annealing of the formed copper tube section, was recommended to avoid future failures.

Steel bearing plates appeared to have failed during service due to wear damage. The subsequent failure analysis revealed that the observed surface damage was the result of widespread plastic deformation and smearing associated with a network of surface crazing, rather than wear. Additionally, the majority of the bearing plates examined met microstructural specifications, although both the carbon and manganese contents were below the specified limits. The deficiencies in carbon and manganese lowered the hardenability of the alloy and may have contributed to the need for an overly severe quench during the heat treatment processing employed during manufacture.

The residual and applied stresses in u-bent copper tubing are addressed in the context of both cyclic fatigue and stress-corrosion cracking. Failures as a result of fatigue and stress corrosion cracking in u-bent copper tubing have been observed to initiate at nonintuitive locations when only the applied stresses on the component are considered. This paper presents both qualitative classical and quantitative finite-element stress analysis results for the forming of u-bends. The resulting residual stress distributions are compared to fracture patterns generated by both fatigue and stress-corrosion cracking mechanisms.

Hydrostatic pressure testing of several large gray iron castings resulted in brittle overload failures. Subsequent failure analysis on two of the failed components revealed casting imperfections associated with the failure origins. In each case, the root cause of failure was related to the casting mold. The first incident involved an imperfection that resulted in a stress concentration that reduced the normally large critical flaw size to the microstructural level. A microstructural gradient adjacent to the fracture of the second casting was the result of an inadequate mold design that allowed for rapid cooling at a thin-walled region of the casting. Material selection was a concern of the manufacturer and was also investigated.

A metallurgical failure analysis was performed on a set of carbon steel gantry crane wheels following observation of excessive damage to the central tread surfaces. Rolling contact fatigue was considered as a possible failure mechanism due to the presence of what appeared to be spalling. Metallographic evaluation and hardness testing revealed that portions of the wheel tread surface had not reached the specified case hardness during heat treatment, leaving the tread surface edges in a near normalized condition. Continual contact with the rail during service allowed for plastic flow of the softer materials across the surface, resulting in the observed damage.

A metallurgical and mechanical failure analysis was applied as part of a vehicle accident reconstruction of a multi-vehicle collision. One of these vehicles was a coal-hauling tractor-trailer. Examination of the trailer involved in the incident revealed a fatigue fracture to a primary lateral stiffener, along with a significant misalignment of the stiffener. Stress and fatigue analysis indicated that the misalignment severely degraded the fatigue life of the stiffener. Evaluation of the structural dynamics of the trailer after the fatigue fracture indicated decreased lateral stability. The decreased stability caused by fracture of the lateral stiffener allowed rollover of the trailer to occur while negotiating a curve. The failure sequence developed in this investigation proved consistent with all physical damage observed on the trailer and with witness accounts of the incident. The failure scenario developed in this investigation is compared with other conclusions made by other investigators to show that those conclusions are not consistent with all of the available evidence.

Specimens of copper tubing from an industrial scale chiller were subjected to a complete corrosion failure analysis. Nondestructive inspection of the tubing indicated substantial corrosion damage and provided the impetus for the corrosion analysis. By application of the typical methods encountered in metallurgical failure investigations, as well as additional chemical analysis techniques, the most probable cause of failure was identified to be a change in the water chemistry during the service life of the tubes. Additional items that may have contributed to the failure include the geometric design of the tube and the post-manufacture cleaning process prior to service. Recommendations were made regarding water treatment and the requirements for any replacement tubes. In addition to discussion of the specific failure(s) investigated, notes regarding the general procedures for corrosion failure analysis are also presented.