Time Dependence in Biaxial Yield of Type 316 Stainless Steel at Room Temperature

This paper describes two biaxial experiments which investigated time and rate effects in the yield and deformation behavior of type 316 stainless steel at room temperature. The first experiment was aimed at determining the effect of probing rate on small-offset yield behavior. The primary aim of the second experiment was to investigate time-dependent flow after loading beyond initial yield. An additional aim was to investigate the effect of radial (3 σ12 = σ11) and nonradial preloads on the yield and hardening behavior. The first experiment showed that for the limited range investigated, 100 to 500 με/min, the probing rate had little effect on yield behavior. The small differences observed in the size and position of certain yield surfaces were shown to be related to the sequence in which the yield loci were determined. The second experiment showed that yield surfaces suffered considerable distortion from their initial near-circular form after both radial and nonradial preloads beyond initial yield. It also showed that the hardening behavior was predominantly kinematic for both types of preload. The strain-time data obtained after the preloads in this experiment showed characteristics typical of creep curves. A transient flow period was observed with high initial strain rates diminishing one or two orders of magnitude during the 0.5-h hold periods. This means that in detailed mechanical modeling of this material, careful attention should be given to time-dependent effects, even at room temperature.