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.

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.

Leak testing is used to determine the rate at which a liquid or gas penetrates from inside a component or assembly to the outside, or vice versa. This article discusses the type of leaks, namely real leaks, and virtual leaks. It describes the leak testing of fluid systems at pressure through acoustic method and bubble testing. The article gives a short note on types of leak detectors, sulfur hexafluoride detectors and mass-spectrometer. It tabulates the pressure and vacuum system leak-testing methods and discusses the application of gas detectors in leak testing.

This article presents the basic principle, characteristics, advantages, and disadvantages of resonant ultrasound spectroscopy (RUS) methods in additive manufacturing. It focuses on the two types of RUS methods: the swept-sine method and the impulse excitation method. Representative significant results for additively manufactured complex parts obtained with the different RUS systems are also shown. The article also presents the basic principle and examples of nonlinear RUS methods.

Acoustic-emission inspection detects and analyzes minute acoustic-emission signals generated by discontinuities in materials under applied stress. This article discusses the types of acoustic emissions (continuous-type emissions and burst-type emissions) and applications, including laboratory testing, production testing, and structural testing. The article includes a section in which the characteristics of acoustic emission inspection are compared with other nondestructive testing methods. Further, it briefly reviews the key elements of the acoustic-emission instrumentation, which includes the acoustic-emission resonant sensor.

Acoustic emission is the generation of stress waves by sudden movement in stressed materials. This article begins with a comparison of acoustic emission from most other nondestructive testing (NDT) methods, and discusses the range of applicability of acoustic emission. It describes the instrumentation principles of acoustic emission and reviews the role of acoustic emission in materials studies. The article illustrates the testing of metal-matrix composites (MMCs) using acoustic emission and the use of acoustic emission inspection in production quality control. It concludes with information on the structural test applications of acoustic emission inspection to find defects and to assess or ensure structural integrity.

This article describes the test techniques that are available for monitoring crack initiation and crack growth and for obtaining information on fatigue damage in test specimens. These techniques include optical methods, the compliance method, electric potential measurement, and gel electrode imaging methods. The article discusses the magnetic techniques that are primarily used as inspection techniques for detecting fatigue cracks in structural components. It details the principles and operation procedures of the liquid penetrant methods, positron annihilation techniques, acoustic emission techniques, ultrasonic methods, eddy current techniques, infrared techniques, exoelectron methods, and gamma radiography. The article explains the microscopy methods used to determine fatigue crack initiation and propagation. These include electron microscopy, scanning tunneling microscopy, atomic force microscopy, and scanning acoustic microscopy. The article also reviews the X-ray diffraction technique used for determining the compositional changes, strain changes, and residual stress evaluation during the fatigue process.

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.

Holography is basically a two-step process for creating a whole three dimensional image of a diffusely reflecting object having some arbitrary shape. This article discusses the advantages, disadvantages and applications of using the optical holography method in nondestructive evaluation. It also discusses the types of acoustical holography, including liquid-surface acoustical holography and scanning acoustical holography. The article concludes by comparing liquid-surface and scanning systems.

This article introduces the principal methodologies and some advanced technologies that are being applied for nondestructive evaluation (NDE) of fiber-reinforced polymer-matrix composites. These include acoustic emission, ultrasonic, eddy-current, computed tomography, electromagnetic acoustic transducer, radiography, thermography, and low-frequency vibration methods. The article also provides information on NDE methods commonly used for metal-matrix composites.

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.

Acoustical holography is the extension of holography into the ultrasonic domain. The basic systems for acoustical holography are the liquid-surface type and the scanning type. This article discusses the applications for acoustical holography, including inspection of large composite parts, through-transmission breast imaging system, inspection of welds in thick materials, and inspection of sleeve-bearing stock. It describes the basic system for liquid-surface acoustical holography and scanning acoustical holography. A comparison between these techniques is also provided.

This article covers defect formation and classification, followed by a brief description of the most common nondestructive testing (NDT) methods used for postbuild inspection. Descriptions of the established and emerging NDT techniques for in-process monitoring (IPM) and in-process inspection (IPI) in additive manufacturing (AM) also are provided, highlighting the advantages and limitations. The article concludes with a list of the main NDT methods and techniques used. As qualification and certification of AM parts is an urgent matter for the AM industry, a description of the current work carried out for developing standards is also included.

Ultrasonic inspection is a nondestructive method in which beams of high-frequency acoustic energy are introduced into a material to detect surface and subsurface flaws, to measure the thickness of the material, and to measure the distance to a flaw. This article provides a detailed account of ultrasonic flaw detectors, including ultrasonic transducers and types of search units and couplants. The article describes pulse-echo and transmission inspection methods and data interpretation. The general characteristics of ultrasonic waves and the factors influencing ultrasonic inspection are also addressed. The article concludes with a review of the advantages and disadvantages of ultrasonic inspection compared with other methods applications of the technique.

Adhesive-bonded joints are extensively used in aircraft components and assemblies where structural integrity is critical. This article addresses the problem of how to inspect bonded assemblies so that all discrepancies are identified. It describes several inspection techniques and presents drawbacks and limitations of these techniques. Generic flaw types and flaw-producing mechanisms are listed in a table. The article discusses metal-to-metal defects, adherend defects, honeycomb sandwich defects, repair defects, and in-service defects. It reviews the methods applicable to the inspection of bonded structures, including visual inspection, ultrasonic inspection, X-ray radiography, and neutron radiography. The evaluation and correlation of inspection results are also discussed. The article concludes with information on the effects of ultrasonic wave interference in the ultrasonic inspection of adhesive-bonded joints.

Mechanical and environmental loadings cause a variety of failure modes in composites, including matrix cracking, fiber-matrix debonding, delamination between plies, and fiber breakage. This article summarizes visual analysis and nondestructive testing methods for the failure analysis of composites. These methods include radiography, ultrasonic techniques, acoustic emission, and thermograph. The article also provides information on destructive test techniques.

This article introduces the principal methodologies and some technologies that are being applied for nondestructive evaluation of composite materials. These include ultrasonic testing (UT), air-coupled UT, laser UT, ultrasonic spectroscopy, leaky lamb wave method, acousto-ultrasonics, radiography, X-ray computed tomography, thermography, low-frequency vibration methods, acoustic emission, eddy current testing, optical holography, and shearography. The article presents some examples are for fiber-reinforced polymer-matrix composites. Many of the techniques have general applicability to other types of composites such as metal-matrix composites and ceramic-matrix composites.