The field of non-destructive testing (NDT) is a very broad area. It plays a critical role in assuring that structural components and systems perform their function in a reliable and cost effective fashion. NDT is a part of the quality control process. Non-destructive testing (NDT)/non-destructive inspection (NDI)/non-destructive evaluation (NDE) is a wide group of analysis techniques used in science and industry to detect surface or internal flaws of a material, component or system without causing damage. Since NDT does not permanently alter the article being inspected, it is a highly valuable method that can save both money and time in product evaluation, troubleshooting and research. NDT is not just a method for rejecting sub-standard materials; it is an assurance that the supposedly good is really good. NDT is a commonly used tool in forensic engineering, mechanical engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, metallurgical engineering, electronic engineering, medicine, and art. In this chapter, we shall discuss the basic principle involved in NDT and very briefly, the methods of NDT.
Objectives of NDT
NDT provides an excellent balance between quality control and cost-effectiveness. There are NDE applications at almost any stage in the production or life cycle of a component.
i. To assist in product development.
ii. To screen or sort out incoming materials.
iii. To assist in product development.
iv. To monitor, improve or control manufacturing processes.
v. To verify proper processing such as heat treatment.
vi. To verify proper assembly.
vii. To inspect in-service damage.
NDE may be used to determine material properties such as fracture toughness, ductility, conductivity, and other physical characteristics. NDT are used in
i. Flaw detection and evaluation.
ii. Leak detection.
iii. Location determination.
iv. Dimensional measurements.
v. Structure and microstructure characterization.
vi. Estimation of mechanical and physical properties.
vii. Stress/Strain and dynamic response measurements.
viii. Material sorting and chemical composition determination.
Methods of NDT
The NDT technique uses a variety of scientific principles. The list of NDT methods that can be used to inspect components and make measurements is large and continues to grow. Researchers continue to find new ways of applying principles of physics and other scientific disciplines to develop better NDT methods. However, there are six NDT methods that are used most often.