CO₂ 레이저 용접 이종재료강의 피로파괴거동에 관한 연구

A Study on Fatigue Fracture Behavior of Laser Beam Welding and Steel with Different Materials

  In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2㎜ thickness of cold-rolled metal sheet(SPCSD) and 2.0㎜ thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0㎜ TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0㎜ and 1.2+1.2㎜ thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0㎜ thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range (ΔK) region and faster in high ΔK region than that of the base metal specimens. The slant crack angle slightly influenced the crack propagation of the TB specimen of 2.0+2.0㎜ thinkness.