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.

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.

This article provides an overview of the characteristics of Rayleigh waves plus methods for generation and detection of waves, including using piezoelectric transducers or noncontact techniques such as lasers, electromagnetic acoustic transducers, or air-coupled ultrasonics. It reviews the methods for using Rayleigh waves for defect detection and materials characterization, alongside nonlinear ultrasonic inspection and surface acoustic wave (SAW) microscopy. The article concludes with information on the standards that use Rayleigh waves for nondestructive evaluation (NDE) of different structures.

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.

This article presents abbreviations and symbols related to fractography.

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.

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 provides a discussion on general nondestructive evaluation (NDE) science and considerations for specific technique selection. It explains the basic concept of flaw detection and evaluation and probability of detection. The article provides an overview of NDE methods with their applications, limitations, and advantages. It includes details on NDE codes, calibration standards, inspection frequency, guidance on how to perform inspections, applicability, and mandatory and nonmandatory practice. The article also provides tips on where to focus inspections in order to align with the likely areas of damage or degradation and a number of other aspects of inspection.

This article discusses the inspection/reference standards that are absolutely critical for proper application of ultrasonic inspection systems. Many of the standards and specifications for ultrasonic inspection require the use of standard reference blocks. The article lists the variables that should be considered when selecting standard reference blocks and describes the three types of standard blocks ordinarily used for calibration or reference: area-amplitude blocks, distance-amplitude blocks, and blocks of the type sanctioned by the International Institute of Welding. It reviews the determination of area-amplitude and distance-amplitude curves of a straight-beam pulse-echo ultrasonic inspection system. The article discusses the three principal conventional manual ultrasonic sizing techniques: 6 dB drop technique, maximum-amplitude technique, and 20 dB drop technique. It provides information on the dimension-measurement applications of ultrasonic inspection 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.

This article discusses the fundamentals and operating principles of the following acoustic microscopy methods: scanning laser acoustic microscopy, C-mode scanning acoustic microscopy, and scanning acoustic microscopy. It describes the applications of acoustic microscopy for detecting defects in metals, ceramics, glasses, polymers, and composites with examples.

Ultrasound is an ideal modality for nondestructive evaluation (NDE) because it enables the interior of objects to be assessed without the safety and access issues associated with radiography. This article summarizes the history of array usage in NDE and its relationship to medical applications. It discusses the mathematics behind classical beamforming, full matrix capture, and total focusing methods of imaging. The article shows how ultrasonic array data can be simulated by direct numerical methods (most commonly using finite-element methods), analytical methods, or hybrid methods. It also considers various methods of comparing the performance of arrays and imaging algorithms. The article provides a comparison of various advanced and nonlinear imaging algorithm and looks at some practical industrial applications of arrays. It concludes with some future perspectives for arrays in NDE.

Impact tests are used to study dynamic deformation and failure modes of materials. This article discusses low-velocity impact experiments in single-stage gas guns. It describes surface velocity measurements with laser interferometric techniques. The article details plate impact soft-recovery experiments, pressure-shear friction experiments, and low-velocity penetration experiments. It reviews two types of plate impact soft-recovery experiments: normal plate impact and pressure-shear plate impact experiments. The article provides information on low-velocity penetration experiments, which include the setup for direct penetration experiment (rod-on-plate) and the reverse penetration experiment (plate-on-rod). It also considers high-temperature plate impact testing and impact techniques with in-material stress and velocity measurements.

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.