SMALL-SCALE NONDESTRUCTIVE STRESS-STRAIN AND CREEP TESTS FEASIBLE DURING IRRADIATION

By the use of suitable cylindrical indenters with flat surface and con stant penetration rates, load versus penetration depth curves are obta ined which show correspondence with the stress-strain curves of the te nsile tests for some materials examined. After an initial linear stage , a limit load of sigma(U) is reached after which a stage of work-hard ening occurs with a trend comparable to the one of the tensile test. T he limit load sigma(U) congruent to 3 sigma(y), sigma(y) being the yie lding load of the tensile test. For penetration rates = 100 mu m/min, the loads of the work-hadening stage above sigma(U) tend to saturation values comparable to the loads of hardness only for some of the mater ials examined. With larger penetration rates, loads are reached well i n excess above those of hardness. With metal-matrix composite alloys a stage with drops of load has been observed at the level of the loads of hardness. Besides those with constant penetration rates, tests with constant load have been also made on the same materials, with the res ults interpreted on the basis of the penetration rate effects.