Tuesday 22 December 2015

experimental physics - Young's modulus and geometry of test material


When measuring Young's modulus in a material, does the geometry of the material actually matter? I have seen several references recommend that I use cylindrical pieces. But, wouldn't the tests work just as well using non-cylindrical(ex. rectangular pieces)?




Answer



Young's modulus of a material doesn't depend on geometry. It is a mechanical property of material and depend on its structure. But, we cannot determine Young's modulus of a material by its structural properties experimentally. We (in your case) want to determine $E$ (Young's modulus) by using $E=\large{\frac{PL}{A\delta}}$ in a tension test ($P$ is the tension force,$L$ is the initial length, $A$ is the cross sectional area and $\delta$ is the elongation). So, we should make our experiment conditions ideal as much as possible. For example, we should use a shape that doesn't make stress concentration as much as we can and for this aim cylindrical pieces are better than rectangular pieces.


No comments:

Post a Comment

Understanding Stagnation point in pitot fluid

What is stagnation point in fluid mechanics. At the open end of the pitot tube the velocity of the fluid becomes zero.But that should result...