Digital radiography is a technique that uses digital detector arrays (linear or area) to capture an X-ray photonic signal and convert it to an electronic signal for display on a computer. This article begins with an overview of real-time radiography and provides a schematic illustration of a typical radioscopic system using an X-ray image intensifier. It discusses the advantages and limitations of real-time radiography. Computed radiography (CR) is one of the radiography techniques that utilizes a reusable detector comprised of photostimuable luminescence (PSL) storage phosphor. The article provides a schematic illustration of a typical storage phosphor imaging plate. It concludes with a discussion on the benefits of digital radiography.

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 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.

Computed tomography (CT) is an imaging technique that generates a three-dimensional (3-D) volumetric image of a test piece. This article illustrates the basic principles of CT and provides information on the types, applications, and capabilities of CT systems. A comparison of performance characteristics for film radiography, real-time radiography, and X-ray computed tomography is presented in a table. A functional block diagram of a typical computed tomography system is provided. The article discusses CT scanning geometry that is used to acquire the necessary transmission data. It also provides information on digital radiography, image processing and analysis, dual-energy imaging, and partial angle imaging, of a CT system.

Metal transparency and interaction with X-rays have been recognized as obvious candidate principles from which methods for in situ monitoring of solidification processes could be developed. This article describes the use of X-ray imaging-based techniques to investigate interface morphology evolution, solute transport, and various process phenomena at spatiotemporal resolutions. It discusses the three viable imaging techniques made available by synchrotron radiation for the real-time investigation of solidification microstructures in alloys. These include two-dimensional X-ray topography, two-dimensional X-ray radiography, and ultra-fast three-dimensional X-ray tomography.