Nondestructive testing or Non-destructive testing (NDT)

 Nondestructive testing or Non-destructive testing (NDT)

Nondestructive testing or Non-destructive testing (NDT) is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component surface & subsurface without causing damage or effect to their future performance or properties. Non-destructive testing is used to detect abnormalities in physical, chemical or electrical characteristics.

NDT provides an edge over conventional methods as it is a fast, cheap and easy process. In 1930s, non destructive testing, where it had been heard of at all, was generally considered an evil. Later it became a necessary evil. For a number of years now NDT has been a necessary aid. NDT has saved uncounted thousands of lives. Non destructive testing is not confined to crack detection. Other discontinuities include porosity, wall thinning from corrosion and many sorts of disbond.
originally found here:- http://www.ndtindia.org/application.html

CLASSIFICATION OF NDT TEST METHODS

CLASSIFICATION OF NDT TEST METHODS

Basic Categories	Objectives
Mechanical and optical	color, cracks, dimensions, film thickness, gaging, reflectivity, strain distribution and magnitude, surface finish, surface flaws, through-cracks
Penetrating radiation	cracks, density and chemistry variations, elemental distribution, foreign objects, inclusions, microporosity, misalignment, missing parts, segregation, service degradation, shrinkage, thickness, voids
Electromagnetic and electronic	alloy content, anisotropy, cavities, cold work, local strain, hardness, composition, contamination, corrosion, cracks, crack depth, crystal structure, electrical and thermal conductivities, flakes, heat treatment, hot tears, inclusions, ion concentrations, laps, lattice strain, layer thickness, moisture content, polarization, seams, segregation, shrinkage, state of cure, tensile strength, thickness, disbonds
Sonic and ultrasonic	crack initiation and propagation, cracks, voids, damping factor, degree of cure, degree of impregnation, degree of sintering, delaminations, density, dimensions, elastic moduli, grain size, inclusions, mechanical degradation, misalignment, porosity, radiation degradation, structure of composites, surface stress, tensile, shear and compressive strength, disbonds, wear
Thermal and infrared	bonding, composition, emissivity, heat contours, plating thickness, porosity, reflectivity, stress, thermal conductivity, thickness, voids
Chemical and analytical	alloy identification, composition, cracks, elemental analysis and distribution, grain size, inclusions, macrostructure, porosity, segregation, surface anomalies

originally found here:- http://www.ndtindia.org/classification-of-ndt-methods.html