PURPOSE: To enable accurate determination of the intensity of ceramics at a high temperature, by making a chuck for supporting a test piece out of shape memory alloy to grab the test piece recovering the shape of the chuck for testing.
CONSTITUTION: In a chuck 2, a support 1b of a test piece 1 is fitted into a concave 2a thereof at a low temperature and further, the outside thereof is fitted into a support hole 3a of a pull rod 3. In other words, at the test preparation step, there are left clearances with the respective side walls. Under such a condition, as the test piece 1 or the chuck 2 is heated with heater, the chuck 2 is returned to a shape it memorizes before the working at a low temperature. Then, the concave 2a contracts inward to press and grasp the support section 1b of the test piece 1 while the circumference thereof is abutted on the support hole 3a of the pull rod 3 so that it will expand outward to make the pull rod 3 grasp the chuck 2 itself. Thus, regardless of a tension applied to the test piece 1, there is concentration of stress at any part of the test piece 1 thereby enabling accurate testing.