Essay On Ultrasonic Testing

This test is a non destructive testing techniques based on the propagation of ultrasonic waves in the material tested. It uses very short ultrasonic pulse and waves with center frequencies ranging from 0.1-15 MHz.

Ultrasonic testing is often performed on steel and other metal alloys, though it can be used on other materials like wood, concrete etc. Figure 3: Principle of ultrasonic testing

Principle of ultrasonic testing. LEFT: A probe sends a sound wave into a test material. There are two indications, one from the initial pulse of the probe, and the second due to the back wall echo. RIGHT: A defect creates a third indication and simultaneously reduces the amplitude of the back wall indication. The depth of the defect is determined

Brinell Hardness Test The purpose of the Brinell hardness test is to measure the hardness of the material. In this test, surface of the sample which will measure the hardness is made suitable and oxides are removed from the surface of the sample. Smooth and bright surface are important for the Brinell hardness test. Therefore, grinding and polishing processes are applied on the sample's surface. The test is processed at room temperature and normal atmospheric pressure to obtain more reliable results inasmuch as mechanical properties of metals change with temperature and pressure. In the light of the test results, the values which are obtained from the inner part of the sample have low hardness value while the values of the sample taken from the end regions have high hardness value. The outer part of the sample cools down faster than the inner part of the sample and it can cause hardness differences. I could not get any parameter about this type of hardness test and could not see any sample about it. They did not use very often so I just explain the