Hooke's Law and Elastic Limit

From the stress-strain curve of a material, a number of necessary mechanical properties of the material might be studied. While you look at the stress-strain curve you might recognize segments of different nature. The first segment of the curve is steep and straight and the strain in this range is proportional to the stress. Therefore, the terminal stage of this range is called as proportional limit. At this stage, we discover some small fluctuations followed by a horizontal segment, mentioning that the strain in the solid is continuously enhancing without any enhance in stress. Here the material yields at the end of proportional limit & exhibits plasticity (that means being strained without enhance in stress) on further pulling. This range of strain is called as plastic range, and is approximate 12 to 13 times the proportional range of strain. The stage on which point proportional range ends & plastic range starts is called as yield point.

While the end of plastic range is attained, further loading results in enhances of both stress and strain. However here the stress-strain curve is not as steep as in the initial range &it is also non-linear. The material along exhibited plasticity once again hardens to take added stress and therefore this range is called as strain hardening range. Straining further leads to final failure by rupture.