Tangent Modulus

Tangent modulus is the slope of the stress strain curve. Below the proportional limit the tangent modulus is equivalent to the young's modulus. Hence tangent modulus is most useful above proportional limit (i.e: in the plastic range). Refer to the stress strain curve below:

Note that the tangent modulus is very useful when it comes to calculation of allowables in the plastic strain region

Disclaimer: The content on this site is provided as general information only and should not be taken as engineering advice. All site content, including advertisements, shall not be construed as a recommendation to specifically analyze a stress problem. The ideas expressed on this site are solely the opinions of the author(s) and do not necessarily represent the opinions of sponsors or firms affiliated with the author(s). Any action that you take as a result of information, analysis, or advertisement on this site is ultimately your responsibility. Consult professional adviser before making any engineering decisions. 

Stress Strain Curves Explained

Most stress strain curves are determined by testing coupon material in axial loading, hence stress strain curves are sometimes describe as "axial stress strain curves" because this better represents what is tested. Understanding the relation between stress and strain is one of the foundation for every stress engineer. one example of stress strain curve is shown below. the source of this figure is from Wikipedia.

the "flat top" (i.e: strain beyond point 2) is a plastic zone in which the strain is not linearly proportional to the stress.

Disclaimer: The content on this site is provided as general information only and should not be taken as engineering advice. All site content, including advertisements, shall not be construed as a recommendation to specifically analyze a stress problem. The ideas expressed on this site are solely the opinions of the author(s) and do not necessarily represent the opinions of sponsors or firms affiliated with the author(s). Any action that you take as a result of information, analysis, or advertisement on this site is ultimately your responsibility. Consult professional adviser before making any engineering decisions.