For no obvious yield a metal material, to produce a predetermined residual strain of 0.2% of its yield limit stress value, known as the yield strength or proof stress.
For metal materials withno apparent yield, the stress value of 0.2% residual deformation is specified to be its yield limit, called the condition yield limit or yield strength.
For metal materials without obvious yield, the stress value of 0.2% residual deformation is defined as the yield limit, which is called conditional yield limit or yield strength.<br>