Tribology is the science and technology of interacting surfaces in relative motion or, the study of friction, wear, and lubrication. This article focuses on friction and wear processes that aid in the evaluation and selection of materials, for polymers and some composites used in friction and wear applications. It provides information on friction, types of wear, and lubrication. The article includes a brief description of the friction and wear test methods, laboratory-scale friction, and wear testing, usually performed either to rank the performance of candidate materials for an application or to investigate a particular wear process. It describes the wear tests conducted with/without abrasives and explains the concept of PV limit (where P is contact pressure and V is velocity). The article concludes with references and tables of friction and wear test data for polymeric materials.

Total joint replacement in orthopedic surgery can be achieved by excision, interposition, and replacement arthroplasty. This article details the most common materials used in total replacement synovial joints, such as metals, ceramics, and ultrahigh molecular weight polyethylene (UHMWPE). The principal physical properties and tribological characteristics of these materials are summarized. The article discusses the pin-on-disk experiments and pin-on-plate experiments for determining friction and wear characteristics. It details the use of various types of joint simulators, such as hip joint simulators and knee joint simulators, to evaluate the performance of engineering tribological components in machine simulators. The article describes in vivo assessment of total joint replacement performance.

This article reviews the friction and wear of various dental materials that have been studied by fundamental wear measurements, simulated service wear measurements, and clinical measurements. The materials include dental amalgam, composite restorative materials, pit and fissure sealants, dental cements, porcelain and plastic denture teeth, dental feldspathic porcelain and ceramics, endodontic instruments, periodontal Instruments, and orthodontic wires. The article describes the correlations of properties, such as hardness, fracture toughness, and wear. It discusses wear mechanism such as sliding adhesive wear, two-body abrasion, three-body abrasion, erosion, and fatigue.

A cylindrical specimen compressed with friction at the die surfaces does not remain cylindrical in shape but becomes bulged or barreled. Tensile stresses associated with the bulging surface make the upset test a candidate for workability testing. This article discusses test-specimen geometry and friction conditions; strain measurements; crack detection; and material inhomogeneities, which are to be considered for performing cold upset testing. It describes test characteristics in terms of deformation, free-surface strains, and stress states for performing cylindrical compression tests. The article illustrates the fracture loci in cylindrical, tapered, and flanged upset-test specimens of aluminum alloy and type 1045 cold-finished steel.

This article discusses a number of workability tests that are especially applicable to the forging process. The primary tests for workability are those for which the stress state is well known and controlled. The article provides information on the tension test, torsion test, compression test, and bend test. It examines specialized tests including plane-strain compression test, partial-width indentation test, secondary-tension test, and ring compression test. The article explains that workability is determined by two main factors: the ability to deform without fracture and the stress state and friction conditions present in the bulk deformation process. These two factors are described and brought together in an experimental workability analysis.

This article describes the use of compression tests, namely, cylindrical compression, ring compression, and plane-strain compression tests at elevated temperatures. It discusses the effects of the temperature, strain rate, and deformation heating on metals during the cylindrical compression test, with the help of flow curves. The article illustrates the testing apparatus used in the cylindrical compression test. It describes the issues regarding friction and temperature, and strain-rate control with proper test equipment and experimental planning during the ring compression test and plane-strain compression test. The article also reviews the testing conditions, procedures, and advantages of hot plane-strain compression test.

This article contains nine tables that present useful formulas for deformation analysis and workability testing. The tables present formulas for effective stress, strain, and strain rate in arbitrary coordinates, principal, compression and tension testing of isotropic material. The article also provides formulas for flat rolling, conical-die extrusion, wire drawing, deep drawing of cups from sheet metal, and bending, and formulas for anisotropic sheet materials.

Standardization, repeatability, convenience, short testing time, and simple measuring and ranking techniques are desirable in wear and erosion tests. This article provides a brief review of the wear testing methods and wear and erosion test equipment. General elements of a wear test, namely, simulation, acceleration, specimen preparation, control, measurement, and reporting, are reviewed.

Wear is mechanically-induced surface damage that results in the progressive removal of material. Because different types of wear occur in machinery, many different types of wear tests have been developed to evaluate its effects on materials and surface treatments. This article provides an explanation on mechanisms, forms (sliding, impact, and rolling) and the causes of wear. It describes the wear measuring methods, including the mass loss method, wear width method, and scar depth method. The units used to report wear vary with type of wear and with the purpose for which the data are to be used. Listing the considerations of tribosystem analysis, the article provides information on selection of ASTM wear test methods grouped by wear type. The article concludes by tabulating the testing geometries and parameters that are commonly controlled and reported when conducting wear tests.

This article summarizes the types of hot working simulation tests such as hot tension, compression, and torsion testing used in the assessment of workability. It illustrates the use of hot torsion testing for the optimization of hot working processes. The article concludes with information on some hot torsion application examples.

Thermomechanical are used to gain insight into the causes of problems that arise during a given thermomechanical process. This article provides examples to demonstrate how significant the parameters were selected for specific tests. It examines the types of problems that can occur during a thermomechanical process. The article provides information on the thermophysical properties, which include specific heat, coefficient of thermal expansion, thermal conductivity/diffusivity, and density. It concludes with examples that illustrate how the various considerations in testing are successfully used to solve practical thermomechanical processing problems.

This article reviews the various types of mechanical testing methods, including hardness testing; tension testing; compression testing; dynamic fracture testing; fracture toughness testing; fatigue life testing; fatigue crack growth testing; and creep, stress-rupture, and stress-relaxation testing. Shear testing, torsion testing, and formability testing are also discussed. The discussion of tension testing includes information about stress-strain curves and the properties described by them.

Tensile testing of fiber-reinforced composite materials is performed to determine uniaxial tensile strength, Young’s modulus, and Poisson’s ratio relative to principal material directions, and helps in the prediction of the properties of laminates. Beginning with an overview of the fundamentals of tensile testing of fiber-reinforced composites, this article describes environmental exposures that can occur during specimen preparation and testing. These include exposures during specimen preparation, and planned exposure such as moisture, damage (impact), and thermal cycling. The article also discusses the test methods of the four major types of mechanical testing of polymer-matrix composites: tensile, compression, flexural, and shear.

In terms of their electrical properties, plastics can be divided into thermosetting and thermoplastic materials, some of which are conductive or semiconductive. This article provides detailed information on factors that affect the property of plastics. It discusses the major test methods used to determine the following dielectric properties of plastics: dielectric breakdown voltage, dielectric strength, dielectric constant, dissipation factor, arc tracking resistance, insulation resistance, volume, and surface resistivity or conductivity. The test specifications and conditions, recommended by several U.S. and foreign testing organizations for characterizing the electrical properties of plastic materials are listed. The article describes the influence of these properties on selection of plastics for insulation application. An outline of the electromagnetic shielding and testing methods of electromagnetic interference are also provided. Designations, electrical properties, and applications of elastomers are tabulated.

This article discusses the equipment design, procedures, experimental considerations, and interpretation of the torsion tests used to establish workability. It describes the application of torsion testing to obtain flow-stress data and to gage fracture-controlled workability and flow-localization-controlled failure. The article discusses the torsion test used to establish the processing parameters that are required to produce the desired microstructures.

Mechanical properties are often the most important properties in the design and selection of engineering plastics. Temperature, molecular structure, crystallinity, viscoelasticity, and effects of environment, fillers and reinforcements are considered as the basic factors affecting the mechanical properties of engineering plastics. The testing methods for determining mechanical properties, including stress-strain test, modulus-directed tensile test, strength test, strength-directed tensile test, impact test, and dynamic mechanical test are discussed.

This article describes testing and characterization methods of ceramics for chemical analysis, phase analysis, microstructural analysis, macroscopic property characterization, strength and proof testing, thermophysical property testing, and nondestructive evaluation techniques. Chemical analysis is carried out by X-ray fluorescence spectrometry, atomic absorption spectrophotometry, and plasma-emission spectrophotometry. Phase analysis is done by X-ray diffraction, spectroscopic methods, thermal analysis, and quantitative analysis. Techniques used for microstructural analysis include reflected light microscopy using polarized light, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis of X-rays, and wavelength dispersive analysis of X-rays. Macroscopic property characterization involves measurement of porosity, density, and surface area. The article describes testing methods such as room and high-temperature strength test methods, proof testing, fracture toughness measurement, and hardness and wear testing. It also explains methods for determining thermal expansion, thermal conductivity, heat capacity, and emissivity of ceramics and glass and measurement of these properties as a function of temperature.

Friction and wear are important when considering the operation and efficiency of components and mechanical systems. Among the different types and mechanisms of wear, adhesive wear is very serious. Adhesion results in a high coefficient of friction as well as in serious damage to the contacting surfaces. In extreme cases, it may lead to complete prevention of sliding; as such, adhesive wear represents one of the fundamental causes of failure for most metal sliding contacts, accounting for approximately 70% of typical component failures. This article discusses the mechanism and failure modes of adhesive wear including scoring, scuffing, seizure, and galling, and describes the processes involved in classic laboratory-type and standardized tests for the evaluation of adhesive wear. It includes information on standardized galling tests, twist compression, slider-on-flat-surface, load-scanning, and scratch tests. After a discussion on gear scuffing, information on the material-dependent adhesive wear and factors preventing adhesive wear is provided.

This article provides an overview of the fundamentals of tribology. It describes the advantages, disadvantages, and applications of pin-on-disk method, which is the most commonly used configuration for testing biomaterials and for the reproducible measurement of friction and wear. The article illustrates practical tribocorrosion setup that allows the user to perform wear tests in corrosive environments under well-defined electrochemical conditions and at controlled temperature. It describes the effect of changes in electrical contact resistance on tribological mode. The article discusses various in vivo environmental conditions in tribological tests. Some typical examples of biomaterials testing are also provided.