COMPARISON OF MICROSHEAR TOUGHNESS AND MODE-II FRACTURE-TOUGHNESS FOR STRUCTURAL-STEELS

In the present work, a concept of microshear toughness was proposed, and the microshear test was carried out for determining microshear toughness. Asymmetrical four point bend specimens and J(II)-integral vs crack growth resistance curve technique were used for determining the mode II elastic-plastic fracture toughness of steels. J(II)-integral expression of the specimen was calibrated by finite element method. Both the microshear and four point bend specimen tests were conducted on structural steels with both L-T and T-L orientations. The results indicate that there is an excellent correlation between the microshear toughness and mode II fracture toughness. The basis of the correlation is because there exists the same stress triaxiality ahead of the crack tip and the same fracture mechanisms between the microshear and asymmetrical four point bend specimens. Therefore, the microshear test may be successfully used to predict the mode II elastic-plastic fracture toughness, and the microshear test is very simple and inexpensive.