Abstract:

Some weld defects, such as undercuts, often exist in the surface at the weld toe. These defects greatly affect the capability of the weld subjected to dynamic loading and fatigue cracks usually initiate from these zones with defects. At present, no method using ultrasonic peening technique to treat weld structure with defects and to improve fatigue strength has ever been reported yet at home. Combining with low alloy middle strength steel 16Mn,a study of increasing the fatigue strength and raising fatigue life was carried out. Compared with specimens without defects, the fatigue strength of specimens with undercuts has been increased by 10%~20%. It also shows that with ultrasonic peening treatment, the fatigue strength of the cruciform weld joint of steel 16Mn has been increased by 66%, and the fatigue life by 10~40 times. Compared with as welded specimens with no defects, the fatigue strength has been increased by 32%, and the fatigue life by 2~7 times. Undercuts have adverse effects on fatigue property of weld joints under peening conditions.

Key words: fatig ue st rengt h, w elded joint s, undercut, ultr asonic peening