An experimental and numerical study of the strain rate effects on mild steel for cyclic loading

Strain Rate Effects on a Ductile Moment Resisting Frame with RBS Connection Subjected to Seismic Ground Motions

“…Monotonic tensile tests at constant strain rates from of 10 3.8 to 3.11 as static stresses were not given by Walker (2012). It can be seen that the amplification factor is higher at the initial stage of strain hardening and decreases with strain.…”

“…However, the isotropic yield stress is expected to always increase with strain. These humps were produced because only two kinematic hardening terms for back stress were used by Walker (2012). It is expected that the hump in the isotropic stress-strain curve to become less distinct or be eliminated as more kinematic hardening terms are used to better represent the back stress evolution.…”

“…to ensure that the hump to be less distinct or be eliminated. Another condition is that the saturated isotropic yield stress versus plastic strain curve by Walker (2012) show the back stress and isotropic yield stress versus true plastic strain curves with calibrated parameters listed in Table 3.4 for three kinematic hardening terms. It can be seen that the increase in the back stress at low strain for 3 kinematic hardening terms over back stress for Although further improvement on the elimination of the hump can be expected with more kinematic hardening terms, only 4 kinematic hardening terms will be considered as to limit the complexity in the calibration of the kinematic hardening parameters.…”

“…Similar to material H, the differences between the generated curves byWalker (2012) and Eq. (3.6) are not big even though the yield plateau length varies with strain rate(Walker 2012) while it is taken to be constant at a plastic strain of 0.13 for curves generated with Eqs. (3.6),(3.14) and(3.15).…”

“…and cyclic loading byWalker (2012). One set of cyclic loading tests consisted of specimens cyclically loaded at decreasing engineering strain ranges of ±2% and ±0.5% for 10 cycles at each range and then pulled to fracture.…”