Effect of High Strain Rate on Low-Cycle Fatigue Behavior of Steel Welded Joints During Earthquake Loading

This study aims to investigate the effects of strain rate on the low-cycle fatigue strength of steel welded joints. Load-carrying cruciform joints with different material mismatch ratios were fabricated in order to observe the effects of material mismatching. A series of displacements that generate low-cycle fatigue damage were applied to the specimens. The experiment was conducted by fast cyclic loading and displacement control, using feedback from a displacement transducer. The feedback control algorithm was found to be critical. Thus, a non-linear feedback control algorithm, i.e., PID control, was implemented in the testing machine. An experimental setup capable of fast cyclic loading was developed. Fatigue life based on the load drop curve indicated that higher strain rates caused lower fatigue life. Failure behavior regarding the strain rate effects of steel welded joints was observed.