The constraint effect A2 has to be evaluated within plastic region near
crack tip front using opening displacement. Plastic boundary and stress or
strain conditions in the vicinity of the crack tip using recrystallization heat
treatment was represented. It was found that the plastic deformation boundary
by recrystallization heat treatment method was the true strain of εt =
0.05mm/mm. With the estimation of constraint effects A2, the region of proper
displacement measurement point near crack tip was between 0mm and 1mm
distance toward direction of crack propagation, and was between 1mm to 3mm
distance toward direction of load line.