FRACTURE TOUGHNESS TESTING DEVICE AND FRACTURE TOUGHNESS TESTING METHOD

摘要

When there is thermal residual stress in a test piece obtained by joining different types of materials, a fracture toughness testing device 10 according to this invention is capable of evaluating the fracture toughness of the test piece in a pure mode in which the effect of the thermal residual stress has been removed. This fracture toughness testing device 10 comprises a testing load application means 17 for applying a prescribed testing load to a test piece 11 having thermal residual stress and a cancelling load application means 18 for applying a cancelling load to the test piece 11 so as to cancel the thermal residual stress of the test piece 11. The cancelling load application means 18 comprises a pressing force application unit 23 for operating so as to apply a pressing force to the test piece 11 as the cancelling load and a pressing force determination unit 24 for determining the magnitude of the pressing force. The pressing force determination unit 24 uses a formula that has been stored in advance to calculate a pressing force magnitude for making an energy release rate component corresponding to an in-plane-shear-type crack deformation state zero.