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A combined cycle fatigue(CCF) testing system with ultrasonic frequency component was developed to evaluate the CCF properties of S350 steel welded joints in this study. The fatigue testing results indicated that the S-N curves of CCF did not have fatigue limit, which agreed with those of pure high frequency fatigue of welded joints. The S-N curves showed that the CCF strength of welded joints dropped greatly with the increasing interaction between high and low frequency fatigue loading. An approximation design method of CCF was presented using amplitude envelope as the stress range.
A combined cycle fatigue (CCF) testing system with ultrasonic frequency component was developed to evaluate the CCF properties of S350 steel welded joints in this study. The fatigue testing results indicated that the SN curves of CCF did not have fatigue limit, which agreed with those of pure high frequency fatigue of welded joints. The SN curves showed that the CCF strength of welded joints dropped greatly with the increasing interaction between high and low frequency fatigue loading. An approximation of design method of CCF was presented using amplitude envelope as the stress range.