This article provides details on several of the classifications of polymer wear mechanisms, using wear data and micrographs from published works. The primary goals are to present the mechanisms of polymer wear and to quantify wear in terms of wear rate. The discussion begins by providing information on the processes involved in interfacial and cohesive wear. This is followed by sections describing the wear process and applications of elastomers, thermosets, glassy thermoplastics, and semicrystalline thermoplastics. The effects of environmental and lubricant on the wear failures of polymers are then discussed. The article further includes a case study describing the tribological performance of nylon. It ends by presenting some examples of wear failures of plastics.

This article briefly reviews abrasive and adhesive wear failure of reinforced polymers and polymer composites, namely particulate-filled polymers, short-fiber-reinforced polymers, polymers with continuous fibers, and mixed reinforcements and fabrics. It includes scanning electron microscope micrographs of abraded surfaces of composites against 80-grade SiC paper and under 14 N load, and worn surfaces of abraded polyether-imide composites and polyamide 66 unidirectional composites and 66 hybrid composites.

This chapter is a detailed account of the general characteristics and effects of and the methods for preventing or reducing different categories of wear failures, namely abrasive (erosive, grinding, and gouging), adhesive, and fretting wear.

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 discusses the causes and effects of wear along with prevention methods. It covers abrasive, erosive, erosion-corrosion, grinding, gouging, adhesive, and fretting wear. It also discusses various forms of contact-stress fatigue, including subsurface-origin fatigue, surface-origin fatigue, subcase-origin fatigue (spalling fatigue), and cavitation fatigue.

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.

This chapter summarizes the various kinds of gear wear and failure and how gear life in service is estimated and discusses the kinds of flaws in material that may lead to premature gear fatigue failure. The topics covered are alignment, gear tooth, surface durability and breakage of gear tooth, life determined by contact stress and bending stress, analysis of gear tooth failure by breakage after pitting, and metallurgical flaws that reduce the life of gears. The chapter briefly reviews some components in the design and structure of each gear and/or gear train that must be considered in conjunction with the teeth to enhance fatigue life.

This chapter reviews the knowledge of the field of gear tribology and is intended for both gear designers and gear operators. Gear tooth failure modes are discussed with emphasis on lubrication-related failures. The chapter is concerned with gear tooth failures that are influenced by friction, lubrication, and wear. Equations for calculating lubricant film thickness, which determines whether the gears operate in the boundary, elastohydrodynamic, or full-film lubrication range, are given. Also, given is an equation for Blok's flash temperature, which is used for predicting the risk of scuffing. In addition, recommendations for lubricant selection, viscosity, and method of application are discussed. The chapter discusses in greater detail the applications of oil lubricant. Finally, a case history demonstrates how the tribological principles discussed in the chapter can be applied practically to avoid gear failure.

Durability is a generic term used to describe the performance of a material or a component made from that material in a given application. In order to be durable, a material must resist failure by wear, corrosion, fracture, fatigue, deformation, and exposure to a range of service temperatures. This chapter covers several types of component and material failure associated with wear, temperature effects, and crack growth. It examines temperature-induced, brittle, ductile, and fatigue failures as well as failures due to abrasive, erosive, adhesive, and fretting wear and cavitation fatigue. It also discusses preventative measures.

This chapter reviews various ways to classify failure categories and summarizes the basic types, causes, and mechanisms of damage, with particular consideration given to whether the likelihood of the types of damage can or cannot be influenced by the heat treating of steel parts. The classical organization for types of damage (failures) is as follows: deformation, fracture, wear, corrosion or other environmental damage, and multiple or complex damage. The chapter also provides some examples of lack of conformance to specification that may at first look like the heat treater did something wrong, but where other contributing factors made it difficult or impossible for the heat treater to meet the specification.

This chapter addresses the issue of die failures in hot and cold forging operations. It describes failure classifications, fatigue fracture and wear mechanisms, analytical wear models, and the various factors that limit die life. It also includes several case studies in which finite-element modeling is used to predict die failure and extend die life.

This chapter begins with a brief review of the different types of surface treatments and coatings used in industry and their effect on properties and performance. It then discusses the importance of corrosion and wear treatments and the consequences of failing to properly implement them in critical industries such as mining, energy production, transportation, and mineral and chemical processing. The chapter also describes basic approaches to dealing with corrosion and wear in steel.

This chapter briefly outlines some of the basic aspects of failure analysis, describing some of the basic steps and major concerns in conducting a failure analysis. A brief review of failure types from fracture, distortion, wear-assisted failure, and environmentally assisted failure (corrosion) is also provided.

This chapter discusses the key findings of an investigation into the failure of an aircraft engine fuel pump. It explains how investigators came to the conclusion that metal slivers from a heavily worn spring may have interrupted the flow of lubricant to one of the slipper pads, causing adhesive wear and the welding of slipper pad material onto the surface of a mating cam plate. Excessive friction between the slipper pads and cam plate, in turn, created a torsional overload that caused the camshaft to break. The chapter presents SEM images showing the wear pattern on one of the springs along with photographs of the damaged slipper pads and cam plate. It also includes an image of a copper flake found in one of the pistons and discusses the results of qualitative x-ray chemical analysis.

This article presents six case studies of failures with steel forgings. The case studies covered are crankshaft underfill; tube bending; spade bit; trim tear; upset forging; and avoidance of flow through, lap, and crack. The case studies illustrate difficulties encountered in either cold forging or hot forging in terms of preforge factors and/or discontinuities generated by the forging process. Supporting topics that are discussed in the case studies include validity checks for buster and blocker design, lubrication and wear, mechanical surface phenomenon, forging process design, and forging tolerances. Wear, plastic deformation processes, and laws of friction are introduced as a group of subjects that have been considered in the case studies.

This chapter discusses the types of failures that can occur in sheet metal forming tools and explains how to mitigate their effects. It describes the factors that influence galling and wear and the benefits of special treatments and coatings. It provides information on through hardening, case (surface) hardening, and nitriding as well as hard chrome plating, vapor deposition, and thermal diffusion coating. It explains how to measure wear resistance using various tests and provides guidelines for selecting tool materials, treatments, and coatings.

This chapter provides an overview of the tools and techniques used to examine failure specimens and the wealth of information that can be obtained from fracture surfaces, cracks, wear patterns, and other such features. It discusses the use of metallography, fractography, and optical and electron microscopy. It presents a number of images recorded using these methods and explains what they reveal about the mode of fracture and the state of the component prior to failure.

This chapter discusses the failure of an aircraft control cable and the investigation that followed. It explains how visual examination showed that the failure occurred in a heavily worn section that runs over a pulley. Further examination under a stereoscope and in a SEM found that 40 out of 49 wires had thinned and broke apart, and that the remaining nine wires failed in tension evidenced by cup and cone fracture and the presence of dimples on the fracture surface. Based on their findings, investigators concluded that cable snapped because of excessive thinning due to contact wear.

This chapter documents the key findings of an investigation into the failure of an aircraft’s main wheel bearing housing. Using annotated images and a detailed SEM fractograph, it shows what investigators observed that led them to conclude that the flange on one of the hubs broke off due to a combination of fatigue, bending stresses, and wear. It also includes a recommendation to assess the structural integrity of the bearing housing after every 100 h of service using nondestructive techniques.