STRESS-STRAIN RESPONSE OF AUSTENITIC STEEL-316L IN CYCLIC STRAINING

Cylindrical specimens of austenitic stainless steel 316L were cycled in a computer controlled electrohydraulic testing machine. Plastic strain amplitude was kept constant and stress amplitude and the shape of the hysteresis loop was measured. Loop shape parameter was also evaluated. Fatigue hardening-softening curves depend on the plastic strain amplitude. Three regimes were observed and are also reflected on the shape of the cyclic stress-strain curve. In regime I (epsilon(ap) < 2 x 10(-4)) either saturation or slight hardening is observed and cyclic stress-strain curve has low fatigue hardening exponent. In regime II (2 x 10(-4) < epsilon(ap) < 1.5 x 10(-3)) original hardening is followed by softening and there is a plateau on the cyclic stress-strain curve. In regime III (epsilon(ap) > 1.5 x 10(-3)) continuous hardening was found and cyclic stress-strain curve exhibit high hardening exponent. Fatigue-life curves were measured and appropriate numerical parameters characterising the cyclic plastic stress-strain response and fatigue life were evaluated.