which law says elastic limits strain produced is proportional to the stress called
Stress-strain Diagram An arbitrary strain of 0.05 mm/mm is frequently taken as the dividing line between these two classes. Stress-strain diagram of a medium-carbon structural steel. Proportional Limit (Hooke's Law) From the origin O to the point called proportional limit, the stress-strain curve is a straight line. This linear relation between elongation and the axial force causing was first noticed by Sir Robert Hooke in 1678 and is called Hooke's Law that within the proportional limit, the stress is directly proportional to strain or