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

Abstract

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.

Evolution of yield surface in the 2D and 3D stress spaces

“…There were also experimental results which showed contraction first and then expansion with increasing plastic pre-strains (Helling et al, 1986;Shiratori et al, 1973;Williams and Svensson, 1971). More information about the evolution of yield surface was reported in Ellis et al (1983), Boucher et al (1995), Lissenden and Lei (2004), and in the book (Wu, 2005).…”

“…In probing yield surfaces, the strain rates were about _ e zz ¼ 2 Â 10 À6 s À1 and _ c ¼ 2 _ e zh ¼ 5:5 Â 10 À6 s À1 . Note that it was mentioned by Ellis et al (1983) and Wu and Yeh (1991) that the probing rate had little effect on the yield surface determination. This automated process of yield stress determination required less manipulation by the operator and it had higher efficiency and decreased artificial errors.…”

Reversible Phase Transformation in Polycrystalline TRIP Steels Induced by Cyclic Indentation Performed at the Nanometric Length Scale

“…A magnification of several loading‐unloading cycles (N) is represented in Figure b, where the maximum deformation takes place for the initial P‐h cycles; when the indentation cycle increases, the aperture of the P‐h cycles decreases. This effect has been previously appreciated under conventional dynamic tests at the macroscopic length scale, which is mainly attributed to the ratcheting strain accumulation effect. Within this context, the open loops for low cyclic cycles observed in Figure b, may be described because of increasing the dislocation activity during the indentation process.…”

Dynamic Deformation of Metastable Austenitic Stainless Steels at the Nanometric Length Scale

“…Crystal orientation in the region where the micromechanical properties were loading sequence, remaining thus significant amount of dislocations in the substructure which cause the increase in dislocation density [19]. This phenomenon, also known as ratcheting strain accumulation effect, has been previously observed for austenitic stainless steels under conventional fatigue testing, as reported elsewhere [15,17,20,21,22,23]. Misra et al [24] found the same trend described above at the local scale by using the nanoindentation technique for austenitic grains, whereas the loops for the martensite phase were close.…”