Non Destructive Testing

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Non Destructive Testing (NDT)

Nondestructive testing (NDT) is a profession that blends quality assurance and materials science. NDT is used to inspect and evaluate materials, components, or assemblies without destroying their serviceability. Through a set of test methods, technicians identify cracks, voids, inclusions, and weld discontinuities, as well as identify misassembled subcomponents.

NDT is used to ensure product integrity and reliability, control manufacturing processes, lower production costs, and maintain a uniform quality level. Without it, the safety and reliability of components can be seriously jeopardized. This makes NDT crucial to help prevent catastrophic failures such as airplane and locomotive crashes, pipeline leaks and explosions, nuclear reactor failures, and ships sinking.

Industries that utilize NDT include:

  • Aerospace
  • Manufacturing
  • Energy (oil and gas, nuclear)
  • Chemical
  • Infrastructure (Bridges, Highways, Buildings)
  • Transportation (Automotive, Railways)
  • Maritime
  • Construction

Ultrasonic Testing (UT)

Ultrasonic Non-Destructive Testing is the process of transmitting high-frequency sound waves into a material in order to identify changes in the material’s properties.

Ultrasonic soundwaves are transmitted through the tested material. The sound propagates through the component and reflects off the rigid surface placed at the opposite end of the transmitter. The time required to transmit and receive the sound waves is measured. The variance in the time at different sections of the component can be used to identify the defects in the material. 

Different types of ultrasonic testing modes can be used to identify different defects, cavities, material deterioration, etc. Mechanical components that operate with heavy workloads are regularly tested with ultrasonic testing. A good example of ultrasonic testing is testing to identify defects and deformation in the wheels and axles of railway carriages.

Ultrasonic Testing (UT)

Magnetic Particle Inspection:

MPI is used to detect near-surface defects in ferromagnetic materials. The test piece is kept between the two poles of an electromagnet and a suspension of magnetic particles is poured over the test piece. This testing method is based on the effect of a magnetic field on ferromagnetic materials.

The defects on the surface of the material will be highlighted as the magnetic particles cluster near defects and cracks. For better visibility, ultraviolet light is used to observe defects.

Magnetic Particle Inspection

Dye Penetrate Testing

Dye Penetrant testing can be used where magnetic particle testing is not feasible. A clean work surface is required to conduct penetrant testing. 

During a penetrant inspection, a liquid dye penetrant is sprayed over the area to be tested and left untouched in the open air. The time required to leave the penetrant to work (a.k.a. dwell time) on the surface could be anywhere from 10 minutes to an hour. It depends on the characteristics of the tested material.

Dye liquid penetrant is removed from the work surface with a dry lint-free cloth. A light application of developer liquid is sprayed over the tested work surface. If there are defects on the tested surface, the liquid dye will be brought to the surface after the developer liquid is applied. 

Dye Penetrate Testing