Testing of Metals used in Mechanical Engineering

When metals are used in mechanical engineering, they have to be tested for different properties like strength, hardness, toughness, ductility and resistance against impact. To adjudge the suitability of the metal for intended application, different tests are performed using metal testing instruments like Brinell hardness tester, tensile tester, impact tester, etc. Varied metals are used for fabrication of mechanical engineering components. Right metal is picked after testing it for different properties like capacity to bear the load, stress bearing capacity, working under stress and pressure. Various tests like are performed according to the different test standards to certify that their efficient performance.

What are different mechanical properties that need to be tested?

Strength – This property is tested by using tensile tester and compression tester. The aim of this test is to determine the strength of sample to analyze the behavior when tensile force and compressive force is applied. In this test, the sample to be tested is fixed in the vice of the fixture. A movable plate attached with the lead screw will move up and down to apply force on the sample. Depending upon the test type, the mode of the machine can either be set on tension mode or compressive mode.

Ductility – This property is again determined by tensile testing machine. If the test material is ductile, sample will get elongated without getting fractured. On the other hand, the brittle metal will develop cracks.

Hardness – This property is tested by using Brinell hardness tester. The aim of this test is to determine the resistance of test material against wear and tear, corrosion and erosion. These machines imply the principle of creating and indention with a known load the test sample and measuring the area of indention thereafter. To perform the test, the sample is clamped in the fixture under a hydraulic operated ram. The load is applied for 10 secs to 30 secs. After the test is completed, the depth of indention is measured. From the dimension of indention, further calculations can be made by referring the relative tables.

Resistance against impacts – When subjected to sudden force, what is the tendency of the test sample? Will it break or deform or stand tall? It is important to perform this test to see how metal will behave after processing like casting, heating and machining. Charpy impact test or Izod impact test can be performed on the machine to determine the resistance. The sample is placed on the fixture after making a v-notch over it. A free fall force is applied via pendulum. The force applied by the pendulum on the sample is measured by the machine and displayed on the screen.