HARDENING INTERACTION IN CYCLIC CREEP OF A TYPE-316 STAINLESS-STEEL AT 20-DEGREES-C AND 500-DEGREES-C

The development of anisotropic material properties due to torsional cy clic plastic straining of tubes with sustained axial loads was examine d for a type 316 stainless steel at room temperature and at 500 degree s C. The effect of the cyclic strains and the cumulative ratchetting s trains on the axial tensile properties was determined and the results show a significant increase in the tensile strength at both 20 degrees C and 500 degrees C, with more pronounced hardening at the higher tem perature. The cyclic shear stress-strain response of the material is s hown to be extremely temperature dependent and the hardening ratio is much greater at 500 degrees C, which is consistent with the dynamic st rain ageing observed previously for this material. The ratchetting str ains are controlled by the cyclic shear strain hardening, by the axial hardening resulting from the cyclic shear and the cumulative axial st rains, and by the ratio of the secondary shear stress to the primary a xial stress.