MATERIAL TESTING DEVICE

PROBLEM TO BE SOLVED: To efficiently perform a test for calculating a J1Cvalue, in a material testing device. SOLUTION: This material testing device is equipped with: a loading means 1 for loading a test piece TP to which a crack is preliminarily formed by a tensile testing force P and removing the tensile testing force P at a target load removing point; a testing force detecting means 2 for detecting the tensile testing force P for loading the test piece TP; a displacement detecting means 3 for detecting the opening displacement v of the test piece TP; an arithmetic means 4 for calculating compliance at the target load removing point on the basis of detection results of the testing force detecting means 2 and the displacement detecting means 3 to calculate not only the crack developing length Δa of the test piece TP but also a J integrated value being the development parameter of the crack at the target load removing point; and a load removing point setting means 4 for setting the load removing point so that the number of the calculation data of the crack developing length Δa and J integrated value calculated by the arithmetic means 4 becomes the predetermined target number or larger in predetermined regions A-C on a J-Δa curve showing the relation of the crack developing length and the J integrated value. COPYRIGHT: (C)2010,JPO&INPIT