Search Results for microscale friction test

This chapter provides a practical overview of the tools and techniques used to assess the tribological aspects of metal forming processes. It describes test methods that have been developed to evaluate bulk deformation and sheet metal forming processes along with lubricant rheology, friction forces, and stress and strain distributions. It explains how to measure temperature between tooling and workpiece surfaces as well as surface topography and composition, film thickness, and wear. It also discusses the benefits of reduced-scale and simulation testing and the transfer of results from one process to another.

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.

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.

In contrast to most plastic deformation processes, the shape of a machined component is not uniquely defined by the tooling. Instead, it is affected by complex interactions between tool geometry, material properties, and frictional stresses and is further complicated by tool wear. This chapter covers the mechanics and tribology of metal cutting processes. It discusses the factors that influence chip formation, including tool and process geometry, cutting forces and speeds, temperature, and stress distribution. It reviews the causes and effects of tool wear and explains how to predict and extend the life of cutting tools based on the material of construction, the use of cutting fluids, and the means of lubrication. It presents various methods for evaluating workpiece materials, chip formation, wear, and surface finish in cutting processes such as turning, milling, and drilling. It also discusses the mechanics and tribology of surface grinding and other forms of abrasive machining.

This chapter examines the phenomena of deformation and fracture in metals, providing readers with an understanding of why it occurs and how it can be prevented. It begins with a detailed review of tension and compression stress-strain curves, explaining how they are produced and what they reveal about the load-carrying characteristics of engineering materials. It then discusses the use of failure criteria and the determination of yielding and fracture limits. It goes on to describe the mechanisms and appearances of brittle and ductile fractures and stress rupture, providing detailed images, diagrams, and explanations. It discusses the various factors that influence strength and ductility, including grain size, loading rate, and temperature. It also provides information on the origin of residual stresses, the concept of toughness, and the damage mechanisms associated with creep and stress rupture, stress corrosion, and hydrogen embrittlement.

This chapter describes the properties and attributes of various classes of metalworking lubricants, including mineral oils; natural oils, fats, derivatives, and soaps; synthetic fluids (olefins, esters, polyglycols, ionic liquids); compounded lubricants (oils, greases, fats); aqueous lubricants (emulsions, synthetics, solutions); and a wide range of coatings and carriers. It also discusses solid-film lubricants (oxide films, polymer films, layer-lattice compounds) and environmental and safety concerns.

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 article is a detailed account of the mechanisms of fatigue failure of polymers, namely thermal fatigue failure and mechanical fatigue failure. The mechanical fatigue failure is discussed in terms of fatigue crack initiation and fatigue crack propagation.

This chapter examines the stress-strain characteristics of metals and alloys subjected to cyclic loading and the cumulative effects of fatigue. It begins by explaining how a single load reversal can lower the yield stress of a material and how repeated reversals can cause strain hardening and softening, both of which lead to premature failure. It then discusses the stages of fatigue fracture, using detailed images to show how cracks initiate and grow and how they leave telltale marks on fracture surfaces. It goes on to describe fatigue life assessment methods and demonstrate their use on different metals and alloys. The chapter also discusses design-based approaches for preventing fatigue failures.

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 appendix focuses on procedures, techniques, and precautions associated with the investigation and analysis of metallurgical failures that occur in service. It describes the steps of an orderly failure analysis from collecting and examining samples to performing mechanical and nondestructive tests, preparing and examining fractographs and micrographs, determining failure mode, writing the report, and developing follow-up recommendations. It also examines the fundamental mechanisms of failure, why they occur, and how to identify them by their characteristic features.

Ceramic-matrix composites possess many of the desirable qualities of monolithic ceramics, but are much tougher because of the reinforcements. This chapter explains how reinforcements are used in ceramic-matrix composites and how they alter energy-dissipating mechanisms and load-carrying behaviors. It compares the stress-strain curves for monolithic ceramics and ceramic-matrix composites, noting improvements afforded by the addition of reinforcements. It then goes on to discuss the key attributes, properties, and applications of discontinuously reinforced ceramic composites, continuous fiber ceramic composites, and carbon-carbon composites. It also describes a number of ceramic-matrix composite processing methods, including cold pressing and sintering, hot pressing, reaction bonding, directed metal oxidation, and liquid, vapor, and polymer infiltration.

This chapter is a study of the microstructure of case-hardened steels. It explains what can be learned by examining grain size, microcracking, nonmetallic inclusions, and the effects of microsegregation. It identifies information-rich features, describing their ideal characteristics, the likely cause of variations observed, and their effect on mechanical properties and behaviors. The discussions throughout the chapter are aided by the use of images, diagrams, data plots, and tables.

This chapter gives a brief review of the development of additive manufacturing (AM) and the appeal of different of different AM methods.

This chapter provides details on powder-binder processing for three materials, namely precipitation-hardened 17-4 PH stainless steel, cemented carbides, and alumina. The types of powders, binders, feedstock, shaping processes, debinding, sintering cycles, compositions, microstructure, distortion, postsintering treatments, and mechanical properties are presented for each. The shaping options include powder-binder approaches such as binder jetting, injection molding, extrusion, slip and slurry casting, centrifugal casting, tape casting, and additive manufacturing. Sintering options are outlined with respect to attaining high final properties.