Small-scale nondestructive stress-strain and creep tests feasible during irradiation

Abstract By the use of suitable cylindrical indenters with flat surface and constant penetration rates, load versus penetration depth curves are obtained which show correspondence with the stress-strain curves of the tensile tests for some materials examined. After an initial linear stage, a limit load of σU is reached after which a stage of work-hardening occurs with a trend comparable to the one of the tensile test. The limit load σ U ⋟ 3σ y , σ y being the yielding load of the tensile test. For penetration rates = 100 μm/min, the loads of the work-hadening stage above σU tend to saturation values comparable to the loads of hardness only for some of the materials examined. With larger penetration rates, loads are reached well in 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 results interpreted on the basis of the penetration rate effects.