Impact hardness

  We have been speaking about tensile toughness. Tensile toughness can be defined as the resistance offered by material to plastic deformation i.e. the ability to resit indentation and penetration or abrasion. Here, the load is applied slowly and the strain rate is quite slow too.

But in real life materials are also subjected to sudden blows. The resistance offered by materials to such blows (or impacts) can be called as impact toughness.

Hard, strong materials with good tensile toughness also falter under sudden impacts and exhibit brittle nature and undergo brittle fracture. The brittleness of materials and the reliability of materials under impacts can be studied using Charpy test and Izod test.

The tests are described in the further sections of this blog. Please do take time to go through the same.

Don't forget to grab a copy of Material Science and Engineering book, which is essential for preparing for AMIE, Material Science.

with warm regards

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Rockwell Hardness Test

    The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load (60Kgf - 200Kgf) compared to the penetration made by a preload (10Kgf). There are different scales, which are denoted by a single letter, that use different loads or indenters. The result, which is a dimensionless number, is noted by HRX where X is the scale letter.

      The determination of the Rockwell hardness of a material involves the application of a minor load followed by a major load, and then noting the depth of penetration, vis a vis, hardness value directly from a dial, in which a harder material gives a higher number. The chief advantage of Rockwell hardness is its ability to display hardness values directly, thus obviating tedious calculations involved in other hardness measurement techniques. 

This method is widely used in Industry as the reading is available easily & quickly. 

The above info is taken from Wikipedia. Please do refer to them for more info. 

With warm regards 

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