Ultrasonic inspection is a family of nondestructive methods in which beams of high-frequency mechanical waves are introduced into materials, using transducers, for the detection and characterization of both surface and subsurface anomalies and flaws in the material. This article describes the basic equipment in ultrasonic inspection systems, and lists the advantages and disadvantages of these systems. It discusses the applications of ultrasonic inspection and also the general characteristics of ultrasonic waves in terms of wave propagation, longitudinal waves, transverse waves, surface waves, and lamb waves. The article reviews the major variables in ultrasonic inspection, including frequency, acoustic impedance, angle of incidence, and beam intensity. It discusses the attenuation of ultrasonic beams and provides information on the pulse-echo and transmission methods for implementing ultrasonic inspection.

Fretting is the small-amplitude oscillatory movement that can occur between contacting surfaces, which are nominally at rest. This article discusses fretting wear in mechanical components and the mechanisms of fretting wear. It describes the role of fretting conditions, such as fretting duration, slip amplitude, normal load, fretting frequency, contact geometry, type of vibration, and surface finish, as well as the role of environmental conditions. The article reviews the influence of an aqueous environment on the mechanism of fretting. The steps that can be taken to reduce or eliminate damage due to fretting are extremely diverse. The article presents some general indications of how to address the fretting wear problem.

Thin-wall gray cast iron (TWGCI) can be seen as a potential material for the preparation of lightweight castings in automotive engineering applications. This article discusses the most important challenges for TWGCI: cooling rate, solidification, macrostructure, microstructure, and chilling tendency. It reviews the tensile properties and thermophysical properties of gray cast iron. The article describes the variables that influence molten iron preparation: charge materials, melting furnace thermal regime, chemical composition, modification and inoculation treatment, holding time/pouring procedure, mold properties (mold temperature, thermophysical properties of mold and mold coating), and casting design.

This article describes the unique aspects of cold isostatic pressing (CIP) in comparison with die compaction, for powder metallurgy parts. It details the components of CIP equipment, including pressure vessels, pressure generators, and tooling material. The article reviews the part shapes and their influence in determining tap density of the filled mold. It provides a discussion on process parameters, such as dwell time, depressurization rate, evaluation of green strength and density, and thermal processing, and illustrates a process flowchart for the production of CIP parts.

Heating time and holding time refer, respectively, to the time required to bring a part to temperature and the time a part is held at the required heat-treatment temperature. This article provides information on heating times and holding times with different types of furnace systems during steel hardening and tempering.

This article focuses on the frequently encountered causes of induction coil failures and typical failure modes in fabrication of hardening inductors, tooth-by-tooth gear-hardening inductors, clamshell inductors, contactless inductors, split-return inductors, butterfly inductors, and inductors for heating internal surfaces. It discusses the current density distribution and the skin effect, the proximity effect, and crack-propagation specifics. The article also describes selected properties of copper alloys, the electromagnetic edge effect of coil copper turn, and the effect of magnetic flux concentrators on coil life. It also reviews the importance of having appropriate and reliable electrical contacts.

This article provides a discussion on transformers and reactors for induction heating. It presents information on the initial considerations in the selection process and the demands of power supply and load circuits. The article describes the types of transformers and reactors used in induction heating and maintenance operations. It also provides a discussion on load matching covering the following topics: initial considerations in the load-matching process, understanding the load circuit and the power supply circuit, selecting the desired operating point, adjusting the value of components, and testing the setup.

This article provides information on single-shot and scanning, the two types of induction heat treating processes that are based on whether the induction coil is moving relative to the part during the heating process. It describes the effect of the frequency of induction heating current on the induction coil and process design, and the control of heating in different areas of the inductor part. The article reviews three main tools for adjustment of coil design and fabrication: coupling gap, coil copper profile, and magnetic flux controllers. It examines the method of holding a part and presenting it to the inductor during the initial inductor design. The article provides information on coil leads/busswork and contacts that mechanically and electrically connect the induction coil head to the power supply. It concludes with a discussion on flux and oxide removal, leak and flow checking, silver plating, and electrical parameter measurement.

Scanners are the most versatile and flexible of the equipment available to the heat treating industry for induction hardening. This article provides a general overview of scanners, and describes various critical factors, including scan speeds, rotational speeds, and center total indicator runout of vertical scanners. It presents information on the frequency selection parameters for scanning applications. The article also discusses the critical parameters and production rates in specifying and developing a tooth-by-tooth hardening process.

This article provides a detailed discussion on the components of a high-performance induction crucible furnace system, namely, furnace body, power supply, and peripheral components. The furnace body contains refractory lining, coil and transformer yokes, and tilting frame and furnace cover. The power supply consists of the following: transformers, frequency converters, capacitor banks, and power cables and furnace coils. The peripheral components comprise recooling device, charging system, and skimming devices. The article also presents a three-dimensional representation of the induction crucible furnace system.

An induction channel furnace consists of a tiltable furnace vessel with refractory lining onto which an inductor or several inductors are flange mounted. This article includes a discussion on the design for holding and dosed-pouring of the iron melts, design for melting the materials, and refractory lining of furnace vessel. It provides information on the structural changes and refractory lining of channel inductors. The article also includes a discussion on power supplies deployed in channel inductor furnaces: line-frequency power supply for melting iron, and converter power supply for melting nonferrous metals. It concludes with an overview of the inductor cooling circuit.

Estimation of process parameters for selective heating and heat treating of simple- and complex-shaped workpieces in induction hardening can be accurately carried out using numerical simulation techniques such as the finite-element analysis and the finite-different method. Along with the significant benefits of modern numerical simulations, it is important to be able to use rough estimation techniques to develop a general understanding of the critical parameters of a particular induction heating system. This article discusses such numerical techniques for estimating the critical parameters: workpiece power estimation; estimation of electrical and thermal efficiency of the coil; and frequency selection for heating solid cylinders, tubes, pipes, slabs, plates, strips, and rectangular workpieces.

This article provides a rough estimate of the basic parameters, including coil efficiency, power, and frequency in induction heating of billets, rods, and bars. It focuses on the frequency selection for heating solid cylinders made of nonmagnetic metals, frequency selection when heating solid cylinders made from nonmagnetic alloys, and frequency selection when heating solid cylinders made from magnetic alloys. The article describes several design concepts that can be used for induction billet heating, namely, static heating and progressive/continuous heating. It presents the four major factors associated with the location and magnitude of subsurface overheating: frequency, refractory, final temperature, and power distribution along the heating line. The article summarizes the pros and cons of using a single power supply. It also reviews the design features of modular systems, and concludes with information on the temperature profile modeling software.

Induction hardening of steel components is the most common application of induction heat treatment of steel. This article provides a detailed account of electromagnetic and thermal aspects of metallurgy of induction hardening of steels. It describes induction hardening techniques, namely, scan hardening, progressive hardening, single-shot hardening, and static hardening. The article discusses the techniques used to control the heat pattern, and provides a brief review of quenching techniques used in the induction hardening. It provides guidelines for selecting the frequency and power for induction hardening, and describes common methods for measuring case depth, such as optical and microhardness, and surface hardness. It provides information on some complications and ambiguities associated with these measurements. The article also discusses the commonly used non-destructive testing methods, namely, magnetic particle testing, ultrasonic testing, and eddy current testing to evaluate induction-hardened components.

This article describes the significance of the three variables that affect the resistance spot welding process: welding current, electrode force, and welding time. It presents the effects of weld spacing and surface preparation on weld quality. The article elaborates the typical sequence of steps for determining the satisfactory conditions for spot welding and the mechanical aspects that affect this process. It considers the effects of process variables on the weld lobe. The article reviews surface preparation, part fit-up, electrode drives, weld parameters, and tests associated with seam welding. It concludes with a discussion on the welding equipment and other factors associated with resistance spot and seam welding.

This article describes the results obtained by Volmer, Weber, Farkas, Becker, and Doring, which constitute the classical nucleation theory. These results are the predictions of the precipitate size distribution, steady-state nucleation rate, and incubation time. The article reviews a nucleating system as a homogeneous phase using the classical nucleation theory, along with heterophase fluctuations that led to the formation of precipitates. It discusses the gas cluster dynamics using the kinetic approach to describe nucleation. The article presents key parameters, such as cluster condensation and evaporation rates, to describe the time evolution of the system. The predictions and extensions of the classical nucleation theory are discussed. The article also provides the limitations of classical nucleation theories in cluster dynamics.

This article reviews the factors that have a significant effect on the selection and interpretation of results of different hardness tests, namely, Brinell, Rockwell, Vickers, and Knoop tests. The factors concerned include hardness level (and scale limitations), specimen thickness, size and shape of the workpiece, specimen surface flatness and surface condition, and indent location. The article focuses on the selection for specific types of materials, such as steels, cast irons, nonferrous alloys, and plastics, and industrial applications, of hardness tests.

This article discusses the underlying concepts and basic techniques for performing ultrasonic fatigue tests and describes test equipment design, specimen design, and effective control over test variables. It reviews the results obtained with ultrasonic fatigue test methods with respect to strain-rate-dependent material behavior. The article also provides information on the applications of the ultrasonic fatigue test.

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.

Porcelain enamels are glass coatings applied primarily to products or parts made of sheet steel, cast iron, and aluminum to improve appearance and to protect the metal surface. This article describes the types of porcelain enamels, and details enamel frits for these materials. It provides a list of steels suitable for porcelain enameling and discusses the most important factors considered in the selection of steel for porcelain enameling. The article briefly presents the preparation methods of these materials for porcelain enameling and covers the methods, and furnaces of porcelain enameling. It examines the role of coating thickness, firing time and temperature, metal substrate, and color on the performance of enameled surfaces. The article concludes with a discussion on the properties of enameled surfaces, factors considered in process control, and test procedures for evaluating the quality of enameled surfaces.