Search Results for wear equations

This article provides a broad overview of sliding and adhesive wear, its processes, and its control, with special attention to three general classes of materials: metals, ceramics, and polymers. It discusses the ways in which materials can be damaged and removed during sliding contact. The article explains the physical and chemical nature of sliding surfaces. It presents wear equations, design criteria, and criteria for selection of materials. The article also describes the factors that affect wear performance of hybrid sliding systems. It concludes by providing general guidelines to prevent the sliding and adhesive wear in metals, polymers, and ceramics.

Cutting tool wear is a production management problem for manufacturing industries. It occurs along the cutting edge and on adjacent surfaces. This article describes steady-state wear mechanisms, tertiary wear mechanisms, and tool replacement. It provides information on tool failure and its consequences. The article details the modeling of tool wear by using the Taylor's tool life equation. The article concludes with information on the requirements of a successful tool life testing program: the test plan objective, designing the test, conducting the test, analyzing the results, and applying the results.

Impact wear can be defined as the wear of a solid surface that is due to percussion, which is a repetitive exposure to dynamic contact by another solid body. This article discusses the volume (or mass) removal of material either at or under engineering contact stress levels and outlines a rational, semi-empirical impact wear theory. It illustrates a linear wear mechanism that occurs in print heads and repetitive impacts that take place in metallic machine contacts. The article concludes with information on plotting a wear curve for an originally plane, massive carbon steel machine platen subjected to repetitive compound impact by a hard, nonwearing spherical-ended steel alloy component.

This article summarizes the various kinds of gear wear, including fatigue, impact fracture, wear, and stress rupture, describes how gear life in service is estimated. It presents the rules concerning lubricants in designing gearing and analyzing failures of gears. The article presents the equations for determining surface durability and life of gears. It tabulates the situations and concepts of pitting failures in gears. The article analyzes some of the more common flaws that affect the life of gear teeth. It reviews the components in the design and structure of each gear and/or gear train that must be considered in conjunction with the teeth.

This article considers the main characteristics of wear mechanisms and how they can be identified. Some identification examples are reported, with the warning that this task can be difficult because of the presence of disturbing factors such as contaminants or possible additional damage of the worn products after the tribological process. Then, the article describes some examples of wear processes, considering possible transitions and/or interactions of the mechanism of fretting wear, rolling-sliding wear, abrasive wear, and solid-particle erosion wear. The role of tribological parameters on the material response is presented using the wear map concept, which is very useful and informative in several respects. The article concludes with guidelines for the selection of suitable surface treatments to avoid wear failures.

Erosion occurs as the result of a number of different mechanisms, depending on the composition, size, and shape of the eroding particles; their velocity and angle of impact; and the composition of the surface being eroded. This article describes the erosion of ductile and brittle materials with the aid of models and equations. It presents three examples of erosive wear failures, namely, abrasive erosion, erosion-corrosion, and cavitation erosion.

This article focuses on the types of activities required for the resolution of wear problems. These include examining and characterizing the tribosystem; characterizing and modeling the wear process; obtaining and evaluating wear data; and evaluating and verifying the solution.

This article presents the mechanisms of polymer wear and quantifies wear in terms of wear rate (rate of removal of the material). Interfacial and bulk wear are discussed as well as a discussion on the wear study of "elastomers," "thermosets," "glassy thermoplastics," and "semicrystalline thermoplastics." The article also discusses the effects of environment and lubricant on the wear failures of polymers. It presents a case study on considering nylon as a tribological material and failure examples, explaining wear resistance of polyurethane elastomeric coatings and failure of an acetal gear wheel.

This article reviews the abrasive and adhesive wear failure of several types of reinforced polymers, including particulate-reinforced polymers, short-fiber reinforced polymers (SFRP), continuous unidirectional fiber reinforced polymers (FRP), particulate-filled composites, mixed composites (SFRP and particulate-filled), unidirectional FRP composites, and fabric reinforced composites. Friction and wear performance of the composites, correlation of performance with various materials properties, and studies on wear-of failure mechanisms by scanning electron microscopy are discussed for each of these types.

This article describes friction force as a function of normal force in dry forming. It focuses on metal forming operations usually classified as cold working and hot working based on metallurgical considerations. The article discusses surface flattening and roughening of workpiece asperities in metal forming. It presents advanced tribology models and results for friction in isothermal forging operations in which the tooling is maintained at a temperature close to that of the workpiece. The article provides information on heat transfer models. It discusses the effect of wear in manufacturing processes. The article concludes with information on the main categories of tool and die materials used for a variety of manufacturing application.

This article provides an overview of experimental, analytical, and numerical tools for temperature evaluation of dry and lubricated systems. It describes the analytical methods and numerical techniques for frictional heating and temperature estimation, as well as viscous heating in full-film lubrication. The article also discusses the viscous heating temperature measurements and numerical analysis of viscous heating.

Bearings are usually provided where a specific spatial relationship (alignment) must be maintained between the parts or where a force is to be transmitted from one part to the other. This article introduces the general types and configuration of sliding bearings, bearing materials, and the practical aspects and solutions in the friction, lubrication, and wear mitigation of sliding bearings. The lubrication of bearings includes thick-film lubrication, thin-film lubrication, and boundary lubrication. The article concludes with a discussion on the effects of material elasticity on the lubrication of bearings.

Through detection of the wear, risk assessment can be performed, along with a related time to failure estimation through technologies such as electrical signature analysis (ESA) and motor current signature analysis. This article discusses the principle of operation of data collectors for ESA measurements and illustrates the evaluation of broken rotor bars and a broken shaft. It describes the detection of faults in bearings using ESA and provides information on the investigation of gearboxes and related components in a wind generator.

Plastics or polymers are used in a variety of engineering and nonengineering applications where they are subjected to surface damage and wear. This article discusses the classification of polymer wear mechanisms based on the methodologies of defining the types of wear. The first classification is based on the two-term model that divides wear mechanisms into interfacial and bulk or cohesive. The second is based on the perceived wear mechanism. The third classification is specific to polymers and draws the distinction based on mechanical properties of polymers. In this classification, wear study is separated as elastomers, thermosets, glassy thermoplastics, and semicrystalline thermoplastics. The article describes the effects of environment and lubricant on the wear failures of polymers. It presents a case study on nylon as a tribological material. The article explains the wear failure of an antifriction bearing, a nylon driving gear, and a polyoxymethylene gear wheel.

This article begins with information on the fundamentals of chip formation process and general considerations for the modeling and simulation of machining processes. It focuses on smaller-scale models that seek to characterize the workpiece/tool/chip interface and behaviors closely associated with that. The article describes the advantages and disadvantages of various finite-element modeling approaches, namely, transient models, continuous cutting model, steady-state model, hybrid model, two-dimensional models, and three-dimensional models. It discusses flow stress measurements using constitutive and inverse testing methods and reviews tool design for chip removal. The article explains the effect of tool geometry on burr formation and the effect of coatings on tool temperatures. It concludes with information on tool wear, which is an unavoidable effect of metal cutting.

This article discusses the generic features of impact wear on metals, ceramics, and polymers. It describes normal impact wear and compound impact wear, as well as the features of impact wear testing apparatus such as ballistic impact wear apparatus and pivotal hammer impact wear apparatus. Most mechanical components continue to be functional beyond the zero wear limit, and their usefulness is normally connected with the loss of a specific depth of material. The article reviews the zero impact wear model and some measurable impact wear models. It presents a case study illustrating the impact of wear failure on automotive engine inlet valves and seat inserts.

Reinforced polymers (RPs) are widely used in structural, industrial, automotive, and engineering applications due to their ecofriendly nature and the potential to manipulate their properties. This article addresses the technical synthesis of RPs, referring to their tribological behavior, to provide insights into the contribution and interaction of influential parameters on the wear behavior of polymers. It provides a brief discussion on the effects of significant parameters on RP tribology. The article describes abrasive and adhesive wear and provides a theoretical synthesis of the literature regarding the wear mechanisms of RPs. It also describes the synthesis of abrasive wear failure of different types of RPs and highlights the contribution of these influential parameters. The article addresses the synthesis of adhesive wear failure of different types of RPs.

This article provides information on the nominal compositions of high-carbon bearing steels and carburizing bearing steels. It discusses the bearing fundamentals with emphasis on surface contact, stresses, and fatigue life of bearings. The article describes bearing life prediction using three factors, namely, reliability, material, and application. It analyzes the bearing damage modes and concludes with information on fatigue failure considerations.