Estimation of Fatigue Life in Butt-Welded Zone of SM45C Steel Rod

Oh, Byung-Duck; Lee, Yong-Bok

Journal of KWJS 2008;26(3):45-50.
Published online July 31, 2008.

강 봉(SM45C) 맞대기 용접부의 피로수명 평가

Estimation of Fatigue Life in Butt-Welded Zone of SM45C Steel Rod

Abstract

SM45C steel rods being used generally for power transmission shafts and machine components was selected and welded by Butt-GMAW(Gas Metal Arc Welding) method. An estimation of fatigue life was studied by constructing S-N curve. Fatigue strength of base metal zone showed higher values than one of weld zone in low cycles between 10⁴ and 10?cycles. However, significant decrease in fatigue strength of base metal was found around 10?cycles, which were almost same as one of heat affected zone. This decrease was attributed that initial residual stress of the steel rods distributed by drawing process was diminished by continually applied load, and resulted in softening of base metal. The fatigue limit of the weld zone was highest in the boundary between deposited metal zone and heat affected zone, and followed by in the order of deposited metal zone, base metal zone, and heat affected zone. Based on these results, it is revealed that the stress for safety design of machine components using SM45C butt-welded steel rods must be selected within the region of the lowest fatigue limit of heat affected zone.

Key Words: SM45C steel rod, Machine components, Fatigue life, Fatigue strength, Fatigue limit, Base metal zone, Compressive residual stress, Drawing process, Alternating stress