Cyclic Yield Characterization for Low-Carbon Steel with HAZ Microstructures

To characterize the relationship between the cyclic yield and monotonic tensile properties of HAZ microstructures, incremental step tests were carried out on a total of eight microstructures of low-carbon steel that had been subjected to several simulated HAZ heat treatments. The results showed that most of the cyclic stress-strain relationships evaluated using incremental step tests roughly agreed with those from constant-stress amplitude tests. Furthermore, the cyclic yield stresses of simulated HAZ microstructures were proportional to these tensile strengths, similar to ordinary carbon and low-alloy steels. Although cyclic yield coefficients were also proportional to these tensile strengths, the slope of the proportional line is steeper than that of ordinary steels. Approximation formulas using monotonic tensile stress to calculate cyclic hardening coefficients for simulated HAZ were therefore determined as the least-squares line compiled from the experimental data.