The goal of using nondestructive evaluation (NDE) in conjunction with failure analysis is to obtain the most comprehensive set of data in order to characterize the details of the damage and determine the factors that allowed the damage to occur. The NDE results can be used to determine optimal areas upon which to focus for sectioning and metallography in order to further investigate the condition of the component. This article provides information on the inspection method available for failure analysis, including standard methods such as visual testing, penetrant testing, and magnetic particle testing. It covers the effects of various factors on the properties of the part that may impact failure analysis, describes the characterization of damage modes and crack sizes, and finally discusses the processes involved in application of NDE results to failure analysis.

During the pre-test inspection following the stress calculation check on a 7-ton capacity Scotch derrick crane, it was noted that threads on the back stay anchorage bolts were of unusually fine pitch (11 tpi) and that the machined faces of the nuts showed irregular pits or depressions disposed in an annular manner. When sectioned, the nuts showed a surprising method of construction. The nuts for the bolts had been made by using conventional pipe couplings inserted into sleeves made from hexagonal bar and the coupling secured to the sleeve by welding at each outer face. The ends of the sleeve bore were chamfered to form a weld preparation. After welding, the faces were machined which resulted in the removal of most of the weld metal and revealed a pronounced lack of penetration. All bolts used to anchor derrick crane back stays should be designed in accordance with the recommendations of British Standard 327:1964 (Clauses 10 and 18).

Mechanical testing is an evaluative tool used by the failure analyst to collect data regarding the macro- and micromechanical properties of the materials being examined. This article provides information on a few important considerations regarding mechanical testing that the failure analyst must keep in mind. These considerations include the test location and orientation, the use of raw material certifications, the certifications potentially not representing the hardware, and the determination of valid test results. The article introduces the concepts of various mechanical testing techniques and discusses the advantages and limitations of each technique when used in failure analysis. The focus is on various types of static load testing, hardness testing, and impact testing. The testing types covered include uniaxial tension testing, uniaxial compression testing, bend testing, hardness testing, macroindentation hardness, microindentation hardness, and the impact toughness test.

This article addresses the forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. It describes the mechanisms of corrosive attack for specific forms of corrosion such as galvanic corrosion, uniform corrosion, pitting and crevice corrosion, intergranular corrosion, and velocity-affected corrosion. The article contains a table that lists combinations of alloys and environments subjected to selective leaching and the elements removed by leaching.

This article considers two mechanisms of cavitation failure: those for ductile materials and those for brittle materials. It examines the different stages of cavitation erosion. The article explains various cavitation failures including cavitation in bearings, centrifugal pumps, and gearboxes. It provides information on the cavitation resistance of materials and other prevention parameters. The article describes two American Society for Testing and Materials (ASTM) standards for the evaluation of erosion and cavitation, namely, ASTM Standard G 32 and ASTM Standard G 73. It concludes with a discussion on correlations between laboratory results and service.

The purpose of this article is to assist the reader in understanding the role that an engineering expert witness plays in evaluating incidents related to product liability, so that he or she may become better acquainted with the role that an engineer plays in such litigation. The topics covered are admissibility of expert opinions, how to evaluate data, factual evidence, mandatory and voluntary standards, physical evidence, medical records, scientific literature, design decisions evaluation, environment of use, user's contribution, reports of opposing experts, report of findings, and deposition and trial testimonies.

Corrosion is the electrochemical reaction of a material and its environment. This article addresses those forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. Various forms of corrosion covered are galvanic corrosion, uniform corrosion, pitting, crevice corrosion, intergranular corrosion, selective leaching, and velocity-affected corrosion. In particular, mechanisms of corrosive attack for specific forms of corrosion, as well as evaluation and factors contributing to these forms, are described. These reviews of corrosion forms and mechanisms are intended to assist the reader in developing an understanding of the underlying principles of corrosion; acquiring such an understanding is the first step in recognizing and analyzing corrosion-related failures and in formulating preventive measures.

Chemical analysis is a critical part of any failure investigation. With the right planning and proper analytical equipment, a myriad of information can be obtained from a sample. This article presents a high-level introduction to techniques often used for chemical analysis during failure analysis. It describes the general considerations for bulk and microscale chemical analysis in failure analysis, the most effective techniques to use for organic or inorganic materials, and examples of using these techniques. The article discusses the processes involved in the chemical analysis of nonmetallics. Advances in chemical analysis methods for failure analysis are also covered.

A maintenance worker was injured when his 3/4 in. (19 mm) open-ended wrench failed, fracturing in overload fashion along the jaw. The failed wrench was unavailable for testing, but an identical one that failed in the same manner was acquired and subjected to hardness, chemistry, SEM, and metallurgical analyses. SEM imaging revealed microvoid coalescence within the fracture zone. The microvoids were flat and smooth edged indicating insufficient bonding. In addition, a cross sectional sample, mounted and etched using alkaline chromate, revealed an oxygen-rich zone in the jaw. It was concluded that the failures stemmed from forging laps in the jaw that broaching failed to remove.

This article presents a failure analysis of an aluminum cylinder head on an automotive engine. During an endurance test, a crack initiated from the interior wall of a hole in the center of the cylinder head, then propagated through the entire thickness of the component. Metallurgical examination of the crack origin revealed that casting pores played a role in initiating the crack. Stress components, identified by finite element analysis, also played a role, particularly the stresses imposed by the bolt assembly leading to plastic strain. It was concluded that the failure can be prevented by eliminating the bolt hole, using a different type of bolt, or adjusting the fastening torque.

Corrosive wear is defined as surface damage caused by wear in a corrosive environment, involving combined attacks from wear and corrosion. This article begins with a discussion on several typical forms of corrosive wear encountered in industry, followed by a discussion on mechanisms for corrosive wear. Next, the article explains testing methods and characterization of corrosive wear. Various factors that influence corrosive wear are then covered. The article concludes with general guidelines for material selection against corrosive wear.

A special eyebolt was used to lift prefabricated concrete panels weighing approximately 16 cwt. Two eyebolts were used with a spreader bar to give a vertical lift on each eyebolt. Following failure of one eyebolt, which resulted in dropping of the load and subsequent failure of the other one, a complete eyebolt was submitted for assessment. Microscopic examination indicated a medium carbon-manganese steel had been used for the lower screwed portion of the eyebolt. Failure may have been due to brittle fracture or to fatigue, both of which could have been initiated at cracks in the hardened material in the region of the weld securing the screwed portion to the intermediate collar and which may have formed at the time of manufacture. Out-of-squareness of the thread with the collar, as was seen in the example submitted, gave rise to bending stresses when the bolt was tightened down, and this could have been a further factor which promoted failure. It was suggested that the design and construction could be improved by either making the component in one piece or, if it was desired, to adapt a standard eyebolt.

Coaxial cable connectors made of brass were failing at a high rate after less than one year of service in an outdoor industrial environonment. The observed failures, which consisted of cracks in the body and end cap, were analyzed and found to be brittle fractures due to stress-corrosion cracking. Two common stress-corrosion cracking tests for copper materials were conducted on new connectors from the same manufacturing lot, confirming the initial determination of the fracture mode. Additional testing as was done in the investigation is often helpful when analyzing corrosion failures.

This article focuses on the general methods and approaches from the perspective of a reconstruction analyst and includes discussions relevant to materials failure analysts at the incident scene. The elements of accident reconstruction are described. These have conceptual similarity with the principles for failure analysis of material incidents that are less complex than a large-scale accident. The article provides a brief review of some general concepts on the use of modeling which can be a very powerful tool for information pertaining to the reconstruction of an accident where the model can be a physical, mathematical, or logical representation of a physical system or process.

Failure analysis is generally defined as the investigation and analysis of parts or structures that have failed or appeared to have failed to perform their intended duty. Methods of field inspection and initial examination are also critical factors for both reconstruction analysts and materials failure analysts. This article focuses on the general methods and approaches from the perspective of a reconstruction analyst. It describes the elements of accident reconstruction, which have conceptual similarity with the principles for failure analysis of material incidents that are less complex than a large-scale accident. The approach presented is that the analysis and reconstruction is based on the physical evidence. The article provides a brief review of some general concepts on the use and limitations of advanced data acquisition tools and computer modeling. Legal implications of destructive testing are discussed in detail.

This article provides information on life assessment strategies and conceptually illustrates the interplay of nondestructive evaluation (NDE) and fracture mechanics in the damage tolerant approach. It presents information on probability of detection (POD) and probability of false alarm (PFA). The article describes the damage tolerance approach to life management of cyclic-limited engine components and lists the commonly used nondestructive evaluation methods. It concludes with an illustration on the role of NDE, as quantified by POD, in fully probabilistic life management.

This article offers an overview of fatigue fundamentals, common fatigue terminology, and examples of damage morphology. It presents a summary of relevant engineering mechanics, cyclic plasticity principles, and perspective on the modern design by analysis (DBA) techniques. The article reviews fatigue assessment methods incorporated in international design and post construction codes and standards, with special emphasis on evaluating welds. Specifically, the stress-life approach, the strain-life approach, and the fracture mechanics (crack growth) approach are described. An overview of high-cycle welded fatigue methods, cycle-counting techniques, and a discussion on ratcheting are also offered. A historical synopsis of fatigue technology advancements and commentary on component design and fabrication strategies to mitigate fatigue damage and improve damage tolerance are provided. Finally, the article presents practical fatigue assessment case studies of in-service equipment (pressure vessels) that employ DBA methods.

A group of control valves that regulate production in a field of sour gas wellheads performed satisfactorily for three years before pits and cracks were detected during an inspection. One of the valves was examined using chemical and microstructural analysis to determine the cause of failure and provide preventive measures. The valve body was made of A216-WCC cast carbon steel. Its inner surface was covered with cracks stemming from surface pits. Investigators concluded that the failure was caused by a combination of hydrogen-induced corrosion cracking and sulfide stress-corrosion cracking. Based on test data and cost, A217-WC9 cast Cr–Mo steel would be a better alloy for the application.

Corrosion is the deterioration of a material by a reaction of that material with its environment. The realization that corrosion control can be profitable has been acknowledged repeatedly by industry, typically following costly business interruptions. This article describes the electrochemical nature of corrosion and provides the typical analysis of environmental- and corrosion-related failures. It presents common methods of testing of laboratory corrosion and discusses the processes involved in the prevention of environmental- and corrosion-related failures of metals and nonmetals.