COMPARISON OF MICROSHEAR TOUGHNESS AND MODE-II FRACTURE-TOUGHNESS FORSTRUCTURAL-STEELS

In the present work, a concept of microshear toughness was proposed, a nd the microshear test was carried out for determining microshear toug hness. Asymmetrical four point bend specimens and J(II)-integral vs cr ack growth resistance curve technique were used for determining the mo de II elastic-plastic fracture toughness of steels. J(II)-integral exp ression of the specimen was calibrated by finite element method. Both the microshear and four point bend specimen tests were conducted on st ructural steels with both L-T and T-L orientations. The results indica te that there is an excellent correlation between the microshear tough ness and mode II fracture toughness. The basis of the correlation is b ecause there exists the same stress triaxiality ahead of the crack tip and the same fracture mechanisms between the microshear and asymmetri cal four point bend specimens. Therefore, the microshear test may be s uccessfully used to predict the mode II elastic-plastic fracture tough ness, and the microshear test is very simple and inexpensive.