The goal of using nondestructive evaluation (NDE) in conjunction with failure analysis is to obtain the most comprehensive set of data in order to characterize the details of the damage and determine the factors that allowed the damage to occur. The NDE results can be used to determine optimal areas upon which to focus for sectioning and metallography in order to further investigate the condition of the component. This article provides information on the inspection method available for failure analysis, including standard methods such as visual testing, penetrant testing, and magnetic particle testing. It covers the effects of various factors on the properties of the part that may impact failure analysis, describes the characterization of damage modes and crack sizes, and finally discusses the processes involved in application of NDE results to failure analysis.

Electromagnetic signals at microwave and millimeter-wave frequencies are well suited for inspecting dielectric materials and composite structures in many critical applications. This article presents a partial list of reported nondestructive testing (NDT) application areas for microwaves. It discusses the advantages and limitations of inspection with microwaves. The article discusses the physical principles, including reflection and refraction, absorption and dispersion, scattering, and standing waves. It provides a discussion on terahertz (THz) imaging for nondestructive evaluation (NDE). The article concludes with information on ground-penetration radar (GPR) that uses electromagnetic radiation and detects the reflected signals from subsurface structures.

This article describes the basic features of electromagnetic acoustic transducers (EMATs) and discusses their existing and some potential uses within the field of ultrasonic nondestructive evaluation (UNDE). It provides sufficient basic and practical information to make an informed choice when considering the transducer to be used for any particular UNDE application. The article describes how different types of EMATs operate and presents their fundamental and some practical limitations. It summarizes the representative literature for electromagnetic acoustic transducer UNDE applications. Some successful uses of EMATs are mentioned to illustrate the depth, range, and potential of commercial EMAT applications. The article concludes with information on the commercial sources for EMAT systems and components.

Additive manufacturing (AM) is the process of joining materials to make parts from three-dimensional (3D) model data, usually layer upon layer, as opposed to subtractive manufacturing and formative manufacturing methodologies. This article discusses various defects in AM components, such as porosity, inclusions, cracking, and residual stress, that can be avoided by using vendor recommended process parameters and approved materials. It describes the development of process-structure-property-performance modeling. The article explains the practical considerations in nondestructive evaluation for additively manufactured metallic parts. It also examines nondestructive testing (NDT) inspection and characterization methods for each of the manufacturing stages in their natural order. The article provides information on various inspection techniques for completed AM manufactured parts. The various electromagnetic and eddy current techniques that can be used to detect changes to nearsurface geometric anomalies or other defects are also discussed. These include ultrasonic techniques, radiographic techniques, and neutron imaging.

The potential for introducing defects during processing becomes greater as the relative density of pressed and sintered powder metallurgy (PM) parts increases and more multilevel parts with complex geometric shapes are produced. This article discusses the potential defects in pressed and sintered PM parts: density variations, compaction and ejection cracks, microlaminations, poor degree of sintering, and voids from prior lubricant agglomerates. It describes the various methods applicable to green compacts: direct-current resistivity testing, radiographic techniques, computed tomography, and gamma-ray density determination. The article also discusses the methods for automated nondestructive testing of pressed and sintered PM parts: acoustic methods-resonance testing, eddy current testing, magnetic bridge comparator testing, ultrasonic techniques, radiographic techniques, gamma-ray density determination, and visual inspection.

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.

This article provides information on the application of nondestructive examination (NDE) technologies to tube and pipe products. These include modeling and simulation methods, eddy-current methods, magnetic methods, acoustic methods, and physical methods. A summary of nondestructive examination methods based on flaw type and product stage is presented in a table. The article also discusses in-service inspection of tubular products and presents an example that illustrates the importance of nondestructive testing (NDT) for welds in austenitic stainless steel tubing.

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.

Nondestructive inspection (NDI) methods for cast iron are used to ensure that the parts supplied perform as required by the purchaser. This article focuses on the principal nondestructive methods used to inspect for anomalies in cast irons and to determine if the volume, shape, size, or number of these anomalies exceeds the maximum allowed by the purchaser. The nondestructive methods include visual inspection, dimensional inspection, liquid penetrant inspection, magnetic-particle inspection, eddy-current inspection, radiographic inspection, ultrasonic inspection, resonant testing, and leak testing. The technique, strengths, and weaknesses of each of the nondestructive methods are also discussed.

Induction hardening involves multiple processing steps of heating and quenching which presents opportunity for errors and defects. This article discusses the common problems associated with induction hardening of shafts as well as the methods to diagnose, inspect, and prevent them. In addition to the major defects such as laps and seams that remain after induction hardening, microstructural transformation, decarburization, residual stress, and grain size, as well as variations in carbon content, composition, or microstructure can also affect the hardened part.

Inspection involves two types of testing, namely, destructive and non-destructive. This article provides an overview of the various inspection plans, such as first-article inspection and periodic tests done by destructive metallurgical testing and the final inspection done by the application of non-destructive technology. It describes the processes involved in destructive methods, such as surface hardness measurement, induction hardening pattern and heat-affected zone inspection, and the examination of microstructure before and after induction hardening. It also discusses non-destructive evaluation techniques for defect detection and microstructure characterization as well as non-destructive evaluation for real-time monitoring of induction process.

This article presents the different hardness test methods used to measure the effectiveness of surface carbon control in carburized parts of steel. Common test methods include Rockwell hardness measurements, superficial Rockwell 15N testing, and microhardness testing. The article provides information on the microscopic method used to detect smaller variations in carbon content, and reviews consecutive cuts analysis and spectrographic analysis that are used to accurately evaluate the carbon concentration profile of carburized parts. It describes procedures of and precautions to be undertaken during shim stock analysis, which is used to measure the atmosphere carbon potential. The article includes a discussion on the electromagnetic nondestructive tests that are used to evaluate the case depth of case-hardened parts.

After solidification and cooling, further processing and finishing of the castings are required. This article describes the general operations of shakeout, grinding, cleaning, and inspection of castings, with particular emphasis on automation technology. It illustrates the vertical core knockout machine and the A-frame core knockout machine and lists the advantages and disadvantages of these machines. The article describes the general factors in automated or manual gate removal process. It concludes with discussion on the various types of inspection, such as the liquid penetrant inspection, pressure testing, radiographic inspection, magnetic particle inspection, and ultrasonic inspection.

Powder forging is an extension of the conventional press and sinter powder metallurgy process, which is recognized as an effective technology for producing a variety of parts to net or near-net shape. This article focuses on the material considerations, such as powder characteristics, alloy development, and inclusion assessment; and process considerations, such as process stages, tool design, and secondary operations; of ferrous alloy powder forging. The mechanical properties of powder forged materials are also reviewed. The article discusses the quality assurance tests for powder forged materials: the part dimensions and surface finish measurement, magnetic particle inspection, metallographic analysis, and nondestructive testing. It concludes with a discussion on the applications of powder forged parts with examples.

This article focuses on the methods that are being developed for detecting and monitoring corrosion: electrochemical methods, electromagnetic or sound wave methods, fiber-optic technology, fluorescence methods, and the Diffracto Sight method. It reviews the importance of data management and the Corrosion Expert System. It concludes with information on the simulation and modeling for incorporating the mechanisms of corrosion prevention into military hardware systems design and operation.

Microwave and guided wave (GW) nondestructive evaluation (NDE) techniques are capable of detecting corrosion damage, cracks, and other defect types in inaccessible areas. This article describes the operation principles of the techniques and provides information on hidden corrosion detection and the applications of microwave NDE devices and GW ultrasonic NDE devices.

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.

Magnetic field testing includes some widely used nondestructive evaluation methods to inspect magnetic materials for defects such as cracks, voids, and inclusions and to assess other material properties, such as grain size, texture, and hardness. This article discusses the principles of such defect detection, providing details on the origin, generation, and assessment of leakage field data. In addition, it discusses the metallurgical and magnetic properties of magnetic materials and the applications of magnetic field testing.

Microwaves (or radar waves) are a form of electromagnetic radiation with wavelengths between 1000 cm and 1 mm in free space. One of the first important uses of microwaves in nondestructive evaluation was for components such as waveguides, attenuators, cavities, antennas, and antenna covers (radomes). This article focuses on the microwave inspection methods that were subsequently developed for evaluation of moisture content in dielectric materials; thickness measurements of thin metallic coatings on dielectric substrates; and detection of voids, delaminations, macroporosity, inclusions, and other flaws in plastic or ceramic materials. It also discusses the advantages and disadvantages and the general approaches that have been used in the development of microwave nondestructive inspection.