What Is Nondestructive Testing (NDT)?
What Is Nondestructive Testing (NDT)?
Nondestructive testing (NDT) is the process of inspecting, testing, or evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the part or system. In other words, when the inspection or test is completed the part can still be used.
In contrast to NDT, other tests are destructive in nature and are therefore done on a limited number of samples ("lot sampling"), rather than on the materials, components or assemblies actually being put into service.
These destructive tests are often used to determine the physical properties of materials such as impact resistance, ductility, yield and ultimate tensile strength, fracture toughness and fatigue strength, but discontinuities and differences in material characteristics are more effectively found by NDT.
Today modern nondestructive tests are used in manufacturing, fabrication, and in-service inspections to ensure product integrity and reliability, to control manufacturing processes, lower production costs, and to maintain a uniform quality level. During construction, NDT is used to ensure the quality of materials and joining processes during the fabrication and erection phases, and in-service NDT inspections are used to ensure that the products in use continue to have the integrity necessary to ensure their usefulness and the safety of the public.
It should be noted that while the medical field uses many of the same processes, the term "nondestructive testing" is generally not used to describe medical applications.
How many kinds of NDT mothods?
Test method names often refer to the type of penetrating medium or the equipment used to perform that test. Current NDT methods are: Acoustic Emission Testing (AE), Electromagnetic Testing (ET), Ground Penetrating Radar (GPR), Guided Wave Testing (GW), Identification of Materials (IM), Laser Testing Methods (LM), Leak Testing (LT), Liquid Penetrant Testing (PT), Magnetic Flux Leakage (MFL), Magnetic Particle Testing (MT), Microwave Testing (MW), Neutron Radiographic Testing (NR), Predictive Maintenance (PdM), Radiographic Testing (RT), Thermal/Infrared Testing (IR), Ultrasonic Testing (UT), Vibration Analysis (VA), and Visual Testing (VT).
What is visual testing (NDT)?
Visual testing is the most commonly used test method in industry.?Because most test methods require that the operator look at the surface of the part being inspected, visual inspection is inherent in most of the other test methods.?As the name implies, VT involves the visual observation of the surface of a test object to evaluate the presence of surface discontinuities.?VT inspections may be by Direct Viewing, using line-of sight vision, or may be enhanced with the use of optical instruments such as magnifying glasses, mirrors, boroscopes, charge-coupled devices (CCDs) and computer-assisted viewing systems (Remote Viewing).?Corrosion, misalignment of parts, physical damage and cracks are just some of the discontinuities that may be detected by visual examinations.
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