Failure analysis is a process that is performed in order to determine the causes or factors that have led to an undesired loss of functionality. This article is intended to demonstrate proper approaches to failure analysis work. The goal of the proper approach is to allow the most useful and relevant information to be obtained. The discussion covers the principles and approaches in failure analysis work, objectives and scopes of failure analysis, the planning stages for failure analysis, the preparation of a protocol for a failure analysis, practices used by failure analysts, and procedures of failure analysis.

Failure analysis is a process that is performed to determine the causes or factors that have led to an undesired loss of functionality. This article describes some of the factors and conditions that might be considered when approaching a failure analysis problem. It focuses on the key principles, objectives, practices, and procedures of failure analysis. The article provides guidelines on the preparation of a protocol for a failure analysis. It also demonstrates the proper approaches to failure analysis.

The intent of this article is to assist the failure analyst in understanding the underlying engineering design process embodied in a failed component or system. It begins with a description of the mode of failure. This is followed by a section providing information on the root cause of failure. Next, the article discusses the steps involved in the engineering design process and explains the importance of considering the engineering design process. Information on failure modes and effects analysis is also provided. The article ends with a discussion on the consequence of management actions on failures.

This article describes the methodology for performing a failure modes and effects analysis (FMEA). It explains the methodology with the help of a hot water heater and provides a discussion on the role of FMEA in the design process. The article presents the analysis procedures and shows how proper planning, along with functional, interface, and detailed fault analyses, makes FMEA a process that facilitates the design throughout the product development cycle. It also discusses the use of fault equivalence to reduce the amount of labor required by the analysis. The article shows how fault trees are used to unify the analysis of failure modes caused by design errors, manufacturing and maintenance processes, materials, and so on, and to assess the probability of failure mode occurrence. It concludes with information on some of the approaches to automating the FMEA.

A large number of electropolished copper parts showed evidence of discoloration (tinting) after electropolishing. Because these parts are used in a high-vacuum application, even trace amounts of organic materials would be problematic. Scanning electron microscopy of nondiscolored and discolored areas both showed trace amounts of residue in the form of adherent deposits. EDS, FTIR spectroscopy, XPS, and secondary ion mass spectroscopy (SIMS) analyses indicated that the discoloration to the copper components was due to the development of CuO at localized regions. It was recommended that process changes be made to completely remove residual processing fluids from the part surfaces before electropolishing. The use of more aggressive detergents was suggested, and it was recommended also that a filtering and recirculating system be considered for use in the cleaning and electropolishing tanks.

Materials selection is closely related to the objectives of failure analysis and prevention. This article briefly reviews the general aspects of materials selection as a concern in both proactive failure prevention during design and as a possible root cause of failed parts. Coverage is more conceptual, with general discussions on the following topics: design and failure prevention, materials selection in design, materials selection for failure prevention, and materials selection and failure analysis. Because materials selection is just one part of the design process, the overall concept of design is discussed. The article also describes the role of the materials engineer in the design and materials selection process. It provides information on the significance of materials selection in both the prevention and analysis of failures.

Cracking occurred within the plastic jacket (injection molded from an impact-modified, 15% glass-fiber-reinforced PET resin.) of several assemblies used in a transportation application during an engineering testing regimen which involved cyclic thermal shock (exposing the parts to alternating temperatures of -40 and 180 deg C (-40 and 360 deg F)). Prior to molding, the resin had reportedly been dried at 135 deg C (275 deg F). The drying process usually lasted 6 h, but occasionally, the material was dried overnight. Comparison investigation (visual inspection, 20x SEM views, micro-FTIR, and analysis using DSC and TGA) with non-failed parts supported the conclusion that that the failure was via brittle fracture associated with the exertion of stresses that exceeded the strength of the resin as-molded caused by the disparity in the CTEs of the PET jacket and the mating steel sleeve. The drying process had exposed the resin to relatively high temperatures, which caused substantial molecular degradation, thus limiting the part's ability to withstand the stresses. The drying temperature was found to be significantly higher than the recommendation for the PET resin, and the testing itself exposed the parts to temperatures above the recognized limits for PET.

Materials selection is an important engineering function in both the design and failure analysis of components. This article briefly reviews the general aspects of materials selection as a concern in proactive failure prevention during design and as a possible root cause of failed parts. It discusses the overall concept of design and describes the role of the materials engineer in the design and materials selection process. The article highlights the significance of materials selection in both the prevention and analysis of failures.

A steel galvanizing vat measuring 3 x 1.2 x 1.2 m (10 x 4 x 4 ft) and made of 19 mm thick carbon steel plate (ASTM A285, grade B)) at a shipbuilding and ship-repair facility failed after only three months of service. To verify suspected failure cause, two T joints were made in 12.5 mm thick ASTM A285, grade B, steel plate. One joint was welded using the semiautomatic submerged arc process with one pass on each side. A second joint was welded manually by the shielded metal arc process using E6010 welding rod and four passes on each side. The silicon content of the shielded metal arc weld was 0.54%, whereas that of the submerged arc weld was 0.86%. After being weighed, the specimens were submerged in molten zinc for 850 h. Analysis (visual inspection, chemical analysis, 100x 2% nital-etched micrographs) supported the conclusions that the vat failed due to molten-zinc corrosion along elongated ferrite bands, possibly because silicon was dissolved in the ferrite and thus made it more susceptible to attack by the molten zinc. Recommendations included rewelding the vat using the manual shielded metal arc process with at least four passes on each side.

In TAKR 300 (Bob Hope) Class transport ships, the builder observed cracking of steel cloverleaf vehicle tie-down deck sockets following installation. Sockets were made from AH36 steel plate by flame cutting and cold coining, then submerged-arc welded to the shop deck. Cracks initiated from the tip of the cloverleaf pattern in >300 cases aboard several cargo vessels in various stages of construction. Consultants who analyzed the situation concluded that the problem may have been corrosion and hydrogen embrittlement. Three possible mechanisms of failure were considered: overload failure; fatigue fracture; and, environmentally-assisted cracking. Testing indicated overload failure was the cause. Remedial actions were taken to improve the fracture properties of the deck socket. A modified manufacturing process was developed involving milling and cutting instead of coining to round the comers of the flame-cut cloverleaf lobe. This new manufacturing process solved the problem.

Cracks initiating from the tip of the cloverleaf pattern in steel cargo tiedown sockets were observed by the builder following installation aboard several cargo vessels in various stages of construction. Testing of finite element models and measurements performed in the field on cargo ships with the cracking problem supported the conclusion that the failure was caused by overload. Additional testing showed that the overload failure and the transition from ductile to brittle fracture were facilitated by a combination of high brittleness due to flame cutting, increased hardness due to the cold-working coining process, and high residual stresses created by welding. Recommendations included the removal of the brittle, carbon-rich transformed martensite layer introduced by flame cutting and the application of a localized stress-relief heat treatment process. X-ray diffraction residual-stress measurements were then performed on heat treated tiedown sockets to verify the effectiveness of the localized heat treatment process applied.

Failure analysis is an investigative process that uses visual observations of features present on a failed component fracture surface combined with component and environmental conditions to determine the root cause of a failure. The primary means of recording the conditions and features observed during a failure analysis investigation is photography. Failure analysis photographic imaging is a combination of both science and art; experience and proper imaging techniques are required to produce an accurate and meaningful fracture surface photograph. This article reviews photographic principles and techniques as applied to failure analysis, both in the field and in the laboratory. The discussion covers the processes involved in field and laboratory photographic documentations, provides a description of professional digital cameras, and gives information on photographic lighting and microscopic photography. Special techniques can be employed to deal with highly reflective conditions and are also described in this article.

This article briefly introduces the concepts of failure analysis and root cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It reviews four fundamental categories of physical root causes, namely, design deficiencies, material defects, manufacturing/installation defects, and service life anomalies, with examples. The article describes several common charting methods that may be useful in performing an RCA. It also discusses other failure analysis tools, including review of all sources of input and information, people interviews, laboratory investigations, stress analysis, and fracture mechanics analysis. The article concludes with information on the categories of failure and failure prevention.

The causes of cracking of an as-drawn 90-10 cupronickel tube during mechanical working were investigated to determine the source of embrittlement. Embrittlement was sporadic, but when present was typically noted after the first process anneal. Microstructural and chemical analyses were performed on an embrittled section and on a section from a different lot that did not crack during forming. The failed section showed an intergranular fracture path. Examination of the fracture surfaces revealed the presence of tellurium at the grain boundaries. The source of the tellurium was thought to be contamination occurring in the casting process that became concentrated in the recycled skimmings. It was recommended that future material specifications for skimmings and for externally obtained scrap copper include a trace analysis for tellurium.