Question

1. Use your own words, define engineering strain and true strain in words and equation

2. What are the mechanical properties you can learn about materials under tensile tests without an extensometer? (name at least 2)

3. What 3 properties cannot be accurately measured without an extensometer?

Answer 1

1. Engineering strain is defined as the ratio of change in dimension to original (initial) dimension. In case of axial strain, it is the ratio of change in length to initial length.

True strain is the natural log of ratio of current length to original length.

2. Mechanical properties that we can learn without extensometer are ultimate tensile strength, rupture strength.

3. 3 properties that cannot be measured accurately without extensometer are....a) yield strength b) elastic strength c) Proof stress