Ultrasonic testing is done in materials to determine

Explanation:

To detect such defects without damaging the weld, several techniques are employed, known as non-destructive testing (NDT).

Some commonly used NDT methods are outlined below.

• Magnetic particle test
• Liquid penetrant test
• Radiography (X-ray/Gamma ray) test
• Ultrasonic test

Ultrasonic test: 

• Sound waves of high frequency are used in this test.
• This test is used to find out the discontinuities in the weldment.
• The sound waves can penetrate from a very small thickness of plate to 6 to 10 m of steel.

Liquid penetrant test: This test is based on the principle that colored liquid dyes and fluorescent liquid penetrate into the cracks and are used to check for surface defects in metals, plastics, ceramics and glass.

X-ray test: In this test internal photographs of the welds are taken. The test specimen is placed in between the X-ray unit and film. Then the X-ray is passed. If there is any hidden defect, that will be seen in the film after developing it.

Gamma ray test: These rays penetrate greater thickness of steel than x-rays and the chief advantage of this process is portability. These tests are used on high quality jobs like boilers and high-pressure vessels and penstock pipes and nuclear vessels.