Fault-tree analysis is a graphical technique that identifies all events and combinations of events that can produce an undesired event. This chapter emphasizes several fault-tree analysis concepts, examining with examples how all three categories of charting symbols (events, gates, and transfer symbols) come together to generate a fault-tree analysis.

This chapter covers special fault-tree analysis topics, including the use of transfer symbols, INHIBIT gates, sequential AND gates, state-of-the-part versus state-of-the-system considerations, and the fault tree to identify redundancy-defeating failures.

Quantifying a fault-tree analysis is a useful tool for assessing the most likely causes of a system failure. This chapter addresses fault-tree analysis event probabilities and ranking of failure causes based on these probabilities. Failure rates, failure-rate sources, probability determinations, mean times between failure, and related topics are also discussed. The discussion covers the practices observed in fault-tree analysis quantification and processes involved in calculating the probability of the top undesired event.

Failure mode assessment and assignment (FMA&A) is a tool designed to help organize the evaluation of hypothesized failure modes. This chapter begins by describing the process of preparing an FMA&A. It then describes the follow-on activities to evaluate the hypothesized failure cause. The chapter also provides information on evaluating the hypothesized potential causes.

In the second step of the four-step problem-solving process, the failure analysis team should identify all potential failure causes. This chapter discusses the steps involved in five such techniques for identifying potential causes of failure, namely brainstorming, mind mapping, Ishikawa diagrams, the “five whys” technique, and flow charting.

This chapter discusses some of the more advanced methods and procedures used in failure analysis, including in-service material sampling, in situ microstructure analysis, and a form of punch testing that can determine the fracture toughness of any material from a tiny specimen. The chapter also covers quantitative fractography, fracture surface topography analysis, and the use of oxide dating as well as fault tree and failure modes and effects analysis (FMEA) and computational techniques.

At the conclusion of a systems failure analysis, the people involved should have a much more in-depth understanding of how the system is supposed to work. The analysis should help understand shortfalls in the design, production, testing, and use of the system. The failure analysis team will have identified other potential failure causes and actions required to preclude future failures. This is valuable knowledge, and it should not be set aside or ignored when the failure analysis team concludes its activities. This chapter is a brief account of the creation of failure analysis libraries, of process guidelines based on previous failure analyses, and of troubleshooting and repair guidelines. Also provided is a listing of the various steps that should be included in a failure analysis procedure.

A system failure occurs when a system does not do what it is supposed to do when it is supposed to do it, or it does something it is not supposed to do. This chapter provides a basic understanding of how failures occur, how systems operate, and the types of failures, namely intermittent and inadvertent system failures.

In some cases, the failure analysis team finds that all components meet their requirements, the system was properly assembled, and it was not operated or tested in an out-of-specification manner, yet it still failed. When this occurs, the only conclusion the failure analysis team can reach is that it missed something in its analysis or that the design is defective. This chapter focuses on the latter possibility by discussing the various factors that a failure analysis team should consider to identify the causes of defects in system design. These include requirements identification and verification, circuit performance, mechanical failures, materials compatibility, and environmental factors. Examples that illustrate the value of design analysis are also presented.

After the fault-tree, a failure-cause identification method has identified potential failure causes and the failure analysis team has prepared a failure mode assessment and assignment (FMA&A). The team knows specifically what to search for when examining components and subassemblies from the failed system. There are numerous techniques and technologies available for examining and analyzing components and subassemblies, which are categorized as follows: optical approaches, dimensional inspection and related approaches, nondestructive test approaches, mechanical and environmental approaches, and chemical and composition analysis for assessing material characteristics. This chapter is a detailed account of the working principle and the steps involved in these techniques and technologies.

This chapter focuses on common failure characteristics exhibited by mechanical and electrical components. The topic is considered from two perspectives: one possibility is that the system failed because parts were nonconforming to drawing requirements and another possibility is that the system failed even though all parts in the system met their drawing requirements. The common failures discussed in this chapter include those associated with metallic components, composite materials, plastic components, ceramic components, and electrical and electronic components.

This chapter targets areas that determine if a change occurred and if the change induced the failure: change or what's different analysis. It describes the different sources of changes that induce process deficiencies: design, process, test and inspection, environmental, supplier lot, aging, and supplier changes. The chapter presents an example of a cluster bomb failure to explain how the failure analysis team found and corrected the failure cause.

This chapter focuses on what can cause a system to fail and addresses the challenge in approaching a system failure. It then examines the steps involved in the four-step problem-solving process: defining the problem, identifying all potential failure causes and evaluating the likelihood of each, identifying the potential solutions, and identifying the best solution. The chapter concludes by describing the responsibilities of a failure analysis team.