Fatigue life extension of the prefatigued welded joints by ultrasonic impact treatment

Abstract

The demand for life extension of existing steel infrastructures motivates the authors to investigate the effect of ultrasonic impact treatment (UIT) on fatigue life extension of in-service Q345 welded cruciform joints experimentally. This study examines the welding residual stress, local weld geometry, fatigue strain and failure surface to quantify the beneficial mechanism of UIT and proposes the two-reduction-factors to quantify the decreasingly beneficial effect of UIT with increasing prefatigued cycles. Through utilizing the nonlinear damage accumulation law and Paris' law to quantify fatigue crack initiation and propagation, respectively, the theoretical relationship of the two-reduction-factors has been developed.