Search Results for system failure

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.

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.

Structural members in a radar antenna system are held together by cadmium-plated high-strength steel bolts, several of which had fractured along the fillet near the head. Investigators determined that the bolts did not seat properly, making contact only at the periphery, which subjected them to high stress concentrations in the fillet region. They also concluded that the intergranular nature of the fracture, as revealed by scanning electron fractography, pointed to hydrogen embrittlement as a contributing factor. This chapter provides a summary of the investigation along with a recommendation to consider adding spring washers to the assembly.

Contaminants can be a cause of numerous types of system failures. There are numerous techniques for confirming contaminant presence. When the presence of a contaminant is suspected, the failure analysis team must find and eliminate the contaminant source, which can be obvious or quite subtle. This chapter summarizes a few commonly encountered contaminant sources to stimulate the reader's thinking about potential contaminant sources. A case study of titanium component washing at Litton Lasers is presented to illustrate how the presence of contaminants leads to a system failure.

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.

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.

This chapter discusses the various failure analysis techniques for microelectromechanical systems (MEMS), focusing on conventional semiconductor manufacturing processes and materials. The discussion begins with a section describing the advances in integration and packaging technologies that have helped drive the further proliferation of MEMS devices in the marketplace. It then shows some examples of the top MEMS applications and quickly discusses the fundamentals of their workings. The next section describes common failure mechanisms along with techniques and challenges in identifying them. The chapter also provides information on the testing of MEMS devices. It covers the two common challenges in sample preparation for MEMS: decapping, or opening up the package, without disturbing the MEMS elements; and removing MEMS elements for analysis. Finally, the chapter discusses the aspects of failure analysis techniques that are of particular interest to MEMS.

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.

The hidden factory refers to the activities associated with scrap and rework. This chapter presents a rudimentary understanding of what sorts of things the hidden factory is doing, focusing on how to get one's arms around the rejections that occur most frequently or have the highest cost. It provides information on the use of Pareto analyses from both frequency-of-occurrence and cost perspectives to target specific areas for improvement.

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.

This appendix is a compilation of suggested analysis methods for suspected component failure causes.

Leaks can occur as the result of several failure causes. This chapter reviews the causes, features, and impact of various types of leaks, namely gasket leaks, O-ring leaks, bond-joint leaks, weld leaks, polyvinyl chloride leaks, valve leaks, and structural leaks.

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.

Corrective action means the implementation or modification of things designed to eliminate or reduce failure causes. This chapter addresses developing potential solutions and selecting the best solution. It discusses the special operations that should be used only as temporary or interim corrective actions to overcome design, process, and other failure causes. The chapter concludes by describing the process of corrective action implementation.

A product pedigree describes its design and how it was built and shows that it was built in accordance with the drawings and other documentation defining the product configuration. Evaluating the pedigree of a failed product can help to rule in or rule out hypothesized failure causes. This chapter describes various areas that can be examined by the failure analysis team to assess the pedigree of the failed system. If the failure analysis team suspects product pedigree anomalies it should confirm conformance through independent means.