Gears can fail in many different ways, and except for an increase in noise level and vibration, there is often no indication of difficulty until total failure occurs. This chapter begins with the classification of gear failure modes, followed by sections discussing the characteristics of various fatigue failures. Then, it provides information on the modes of impact fractures, wear, scuffing, and stress rupture. Next, the chapter describes the causes of gear failures and discusses the processes involved in conducting the failure analysis. Finally, the chapter presents examples of gear failure analysis.

One of the rotor bearings in an electric motor failed, producing excessive vibrate. The bearing was removed and disassembled, revealing craters and bruises on the inner ring raceway and balls along with evidence of melting and burning of metal. Scanning electron microscopy revealed metal particles near the craters, and energy-dispersive x-ray analysis showed that slivers recovered from the grease had the same composition as the bearing raceway and balls. Based on these observations, it was concluded that the bearing failed due to electrostatic discharge, which would have led to seizure if it continued. The report recommends the use of electrically conductive grease and proper grounding practices.

An aircraft went down over water some 30 minutes into a flight. The wreckage was retrieved and the elevator linkage components were dismantled, cleaned, and reassembled. As the chapter explains, both the port and starboard hinge pins had fractured at a tack welded joint along a flange. Based on visual examination, SEM fractography, and chemical analysis, investigators concluded that the hinge pins were not made from the specified steel and were not properly treated after cadmium plating. The pins failed due to hydrogen embrittlement, which may have been aggravated by welding. The chapter provides several recommendations to avoid such failures in the future.

A turbine in a fertilizer plant began to vibrate and was shut down to investigate the problem. A first stage rotor blade was found fractured and was removed along with several other blades for further examination. Based on their observations and testing, investigators concluded that the blade cracked at the tenon due to high hardness of the base material. Vibration caused the crack to grow, leading to final failure by fatigue.

This article introduces the wafer-level fault localization failure analysis (FA) process flow for an accelerated yield ramp-up of integrated circuits. It discusses the primary design considerations of a fault localization system with an emphasis on complex tester-based applications. The article presents examples that demonstrate the benefits of the enhanced wafer-level FA process. It also introduces the setup of the wafer-level fault localization system. The application of the wafer-level FA process on a 22 nm technology device failing memory test is studied and some common design limitations and their implications are discussed. The article presents a case study and finally introduces a different value-add application flow capitalizing on the wafer-level fault localization system.

A helicopter lost the outboard rib on a tail rotor blade in flight and was forced to land because of the resulting vibrations. The investigation that followed is described in this chapter along with key findings. As shown in a sketch, the rib is held in place by a set of six rivets. All of the rivets on the failed blade were missing and sections of skin were torn from most of the rivet holes. One such rivet hole was examined in a SEM, revealing corrosion on one of the tear surfaces and dimples (characteristic of ductile overload failure) on the other. In addition, the inner surface of the skin nearest the rib was found to be coated with soot, the paint on the leading edge of the top skin was abraded, and the skin in that area had thinned. Based on their findings, investigators concluded that the outboard rib separated because of stress-corrosion cracking around the rivets, and erosion may have contributed.

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.

Boiler tubes subjected to cyclic or fluctuating loads over extended periods of time are prone to fatigue failure. Fatigue can occur at relatively low stresses and is implicated in almost 80% of the tube failures in firetube boilers. This chapter covers the most common forms of boiler tube fatigue, including mechanical or vibrational fatigue, corrosion fatigue, thermal fatigue, and creep-fatigue interaction. It discusses the causes, characteristics, and impacts of each type and provides several case studies.

This chapter identifies the primary causes of service failures and discusses the types of defects from which they stem. It presents more than a dozen examples of failures attributed to such causes as design defects, material defects, and manufacturing or processing defects as well as assembly errors, abnormal operating conditions, and inadequate maintenance. It also describes the precise usage of terms such as defect, flaw, imperfection, and discontinuity.

This chapter discusses the investigation of a helicopter tail rotor blade that fractured during a test flight. It includes images of the damaged blade along with close-ups of both sides of the blade tip showing that the tip tore off at the rivets. Based on their observations, investigators concluded that the rotor blade encountered a foreign object in flight causing the tip to shear off.

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.

Compacted graphite iron (GCI) is a cast iron grade that is engineered through graphite morphology modifications to achieve a combination of thermal and mechanical properties that are in between those of flake graphite iron and ductile iron. This chapter discusses the advantages of compacted graphite iron over gray iron and ductile iron. It presents examples of low- and high-frequency thermal cycling, both of which affect the thermal stresses that castings are exposed to during temperature fluctations. Information on optimum carbon and silicon ranges as well as mechanical property standards for CGI are provided. The chapter describes the critical factors that control CGI and discusses methods of CGI manufacturing.

Root cause of failure in automotive electronics cannot be explained by the failure signatures of failed devices. Deeper investigations in these cases reveals that a superimposition of impact factors, which can never be represented by usual qualification testing, caused the failure. This article highlights some of the most frequent early life failure types in automotive applications. It describes some of the critical things to be considered while handling packages and printed circuit board layout. The article also provides information on failure anamnesis that shows how to use history, failure signatures, environmental conditions, regional failure occurrences, user profile issues, and more in the failure analysis process to improve root cause findings.

The wear caused by contact stress fatigue is the result of a wide variety of mechanical forces and environments. This chapter discusses the characteristics of four types of contact stress fatigue on mating metal surfaces: surface, subsurface, subcase, and cavitation. Features and corrective actions for these contact stress fatigue are discussed. The chapter also lists some possible ways to reduce the cavitation fatigue problem.

This chapter describes the basics of energy and entropy and “free energy.” Fundamentals of internal energy U , the enthalpy H , entropy S , free energies G , and F of a substance are presented. The chapter also presents the thermal vibration model to promote a better understanding of the U , S , and F of the crystal. It covers basic concepts of thermodynamics of magnetic transition and discusses the role and the meaning of magnetic transition in iron and steel. The chapter concludes with a general discussion on an amorphous phase from a thermodynamic viewpoint.

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.

Powder metallurgy plays a central role in the production of nearly all beryllium components. This chapter describes the primary steps in the powder metal process and the work that has been done to improve each one. It explains how beryllium powders are made and how they are consolidated prior to sintering. It also compares and contrasts the properties of beryllium products made using different methods and provides composition and particle size data on commercially available powders.

Passive components can be broadly divided into capacitors, resistors, and inductors. Failure analysis of these components helps determine the root cause and improve the overall quality and reliability of the electronic systems. This article describes different failure analysis approaches used for these components. It discusses different types of capacitors along with their constructions and failure modes. The types include tantalum, aluminum electrolytic, multi-layered ceramics, film, and super capacitors. The article then provides a discussion on the two common types of inductors, namely, common mode choke coil and surface mount powder choke coil.

Boiler tube failures associated with material defects are often the result of poor quality control, whether in primary production, on-site fabrication, storage and handling, or installation. This chapter examines quality-related failures stemming from compositional and structural defects, forming and welding defects, design defects, improper cleaning methods, and ineffective maintenance. It also includes case studies and illustrations.

This chapter provides an overview of environmental factors when studying a gear failure. Environmental factors discussed are lubrication, temperature, and mechanical stability.