Eddy-current inspection is based on the principles of electromagnetic induction and is used to identify or differentiate among a wide variety of physical, structural, and metallurgical conditions in electrically conductive ferromagnetic and nonferromagnetic metals and metal parts. This article discusses the advantages and limitations of eddy-current inspection, as well as the development of the eddy-current inspection process. It reviews the principal operating variables encountered in eddy-current inspection: coil impedance, electrical conductivity, magnetic permeability, lift-off and fill factors, edge effect, and skin effect. The article illustrates some of the principal impedance concepts that are fundamental to understanding of and effective application of eddy-current inspection. It discusses various types of eddy-current instruments, such as the resistor and single-coil system, bridge unbalance system, induction bridge system, and through transmission system. The article concludes with a discussion on the inspection of aircraft structural and engine components.

This article focuses on nondestructive inspection of steel bars. The primary objective in the nondestructive inspection of steel bars and wire is to detect conditions in the material that may be detrimental to the satisfactory end use of the product. The article discusses various types of flaws encountered in the inspection of steel bars, including porosity, inclusions, scabs, cracks, seams, and laps. Inspection methods, such as magnetic-particle inspection. liquid penetrant inspection, ultrasonic inspection, and electromagnetic inspection, of steel bars are also described. The article provides a discussion on electromagnetic systems, eddy-current systems, and magnetic permeability systems for detection of flaws on steel bars. It concludes with a description of nondestructive inspection of steel billets.

Magnetic-particle inspection is a method of locating surface and subsurface discontinuities in ferromagnetic materials. This article discusses the applications and advantages and limitations of magnetic-particle inspection. It describes magnetic fields in terms of magnetized ring, magnetized bar, circular magnetization, longitudinal magnetization, and effects of flux direction. General applications, advantages, and limitations of the various magnetizing methods used in magnetic-particle inspection are listed in a table. The article discusses the items that must be considered in establishing a set of procedures for the magnetic-particle inspection of a specific part: type of current, type of magnetic particles, method of magnetization, direction of magnetization, magnitude of applied current, and equipment. It concludes with a discussion on demagnetization after magnetic-particle inspection.

This article focuses on different aspects of wear particle analysis. It discusses the different wear regimes in the wear rate versus time (bathtub) curve. The article explains the essence of condition monitoring and how to properly sample lubricants for condition monitoring. It also discusses in-service lubricant analysis for condition monitoring, focusing on the spectrometric oil analysis program. The article describes the characteristics of wear particles and analytical techniques for characterizing them. It also describes the characteristics of different types of wear particles and the mechanisms by which they are generated. The article concludes with a summary of the major applications of wear particle analysis.

This article discusses the influence of microstructure and chemical composition on the physical properties of cast iron. The physical properties include density, thermal expansion, thermal conductivity, specific heat, electrical conductivity, magnetic properties, and acoustic properties. The article describes the properties of liquid iron in terms of surface energy, contact angles, and viscosity. The conductive properties such as thermal and electrical conductivity, of the main metallographic phases present in cast iron are presented in a table. The article discusses the magnetic properties of cast iron in terms of magnetic intensity, magnetic induction, magnetic permeability, remanent magnetism, coercive force, and hysteresis loss. It concludes with a discussion on the acoustic properties of cast iron.

In some phase diagrams, the appearance of several reactions is the result of the presence of intermediate phases. These are phases whose chemical compositions are intermediate between two pure metals, and whose crystalline structures are different from those of the pure metals. This article describes the order-disorder transformation that typically occurs on cooling from a disordered solid solution to an ordered phase. It provides a table that lists selected superlattice structures and alloy phases that order according to each superlattice. The article informs that spinodal decomposition has been particularly useful in the production of permanent magnet materials, because the morphologies favor high magnetic coercivities. It also describes the theory of spinodal decomposition with a simple binary phase diagram.

This article describes the fundamental concepts of heat treatment simulation, including the physical events and their interactions, the heat treatment simulation software, and the commonly used simulation strategies. It summarizes material data needed for heat treatment simulations and discusses reliable data sources as well as experimental and computational methods for material data acquisition. The article provides information on the process data needed for accurate heat treatment simulation and the methods for their determination. Methods for validating heat treatment simulations are also discussed with an emphasis on the underlying philosophy for the selection and design of validation tests. The article also discusses the applications, capabilities, and limitations of heat treatment simulations via selected industrial case studies for a better understanding of the effect of microstructure, distortion, residual stress, and cracking in gears, shafts, and bearing rings.

Magnetic-particle inspection is a nondestructive testing technique used to locate surface and subsurface discontinuities in ferromagnetic materials. Beginning with an overview of the applications, advantages, and limitations of magnetic-particle inspection, this article provides a detailed account of the portable power sources available for magnetization, and the different ways of generating magnetic fields using yokes, coils, central conductors, prod contacts, direct-contact, and induced current. In addition, the article discusses the characteristics and classification, and properties of magnetic particles and suspended liquids. Finally, the article outlines the types of discontinuities (surface and subsurface) that can be identified by magnetic-particle inspection and the importance of demagnetization after inspection.

Eddy-current inspection is a nondestructive evaluation method based on the principles of electromagnetic induction. Eddy-current methods are used to identify or differentiate a wide variety of physical, structural, and metallurgical conditions in electrically conductive ferromagnetic and nonferromagnetic metals and metal parts. Giving a brief introduction on the uses of eddy-current inspection, this article discusses the operating principles and the principal operating variables encountered in eddy-current inspection, including coil impedance, electrical conductivity, magnetic permeability, lift-off and fill factors, edge effect, and skin effect. It further describes different aspects of eddy current testing such as the selection of inspection frequencies and the types and configurations of inspection coils. The article also deals with the eddy current instrumentation and the discontinuities that are detectable by eddy-current methods.

Ferromagnetic resonance (FMR) is used in the identification of the magnetic state of materials, the quantitative determination of static magnetic parameters, and the determination of microwave losses. This article describes the theory of ferromagnetic resonance and provides information on reflection spectrometers, microwave spectrometers, and ferromagnetic anti-resonance spectrometers used for measuring FMR. It also discusses the applications of FMR and provides several detailed examples.