Abstract
Plastic deformation zones of deep double edge notched tension (DENT) paper specimens under in-plane stress were estimated exactly in terms of the linear elastic fracture mechanics (LEFM), and further in terms of thermal image. Comparing the size of the estimated zone with that of the circular plastic deformation zone assumed in the “Essential Work of Fracture (EWF)” method to measure fracture toughness, fracture works were corrected to correspond with the circular case. As a result, corrected experimental plots of the EWF method to obtain fracture toughness for large ligament specimens were almost on the same linear relationship obtained from the uncorrected experimental plots for small ligament specimens. The results show the uniqueness of the fracture toughness obtained from small ligament specimens, which experimentally satisfy the prerequisite of the EWF method.
