Cyclic Stress-Strain Behavior of Two Alloys at High Temperature

The cyclic stress-strain curve is useful in the design of structural components that are subjected to cyclic plastic deformation. Since the incremental step test has been used successfully to approximate cyclic stress-strain curves of metals at room temperature, the objective of this study is to evaluate its usefulness in describing the cyclic deformation behavior of two alloys at elevated temperature.

Constant strain rate incremental step tests were conducted on nickel-iron-chromium Alloy 800 and Type 304 austenitic stainless steel in air at temperatures between 70 and 1400 F. This experimental technique provided a useful method of determining cyclic stress-strain curves for these two alloys over that temperature range. Alloy 800 cyclically hardened by factors between 2 and 5, with a maximum amount of hardening at 1200 F. Type 304 stainless steel cyclically hardened by factors between 2 and 3, with a maximum amount of cyclic hardening at 1000 F. Strain rate and maximum strain range were shown to influence cyclic hardening of the Type 304 stainless steel at both 1000 and 1200 F. Results indicated that the cyclic stress-strain curve obtained from an incremental step test is most useful for estimating the cyclic stress-strain response of a material under variable-amplitude loading.