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자동차 차체용 SPFC590강 레이저 용접판재의 피로특성
한문식(Moonsik Han),전성민(Sungmin Jeon),서정(Jung Suh),이제훈(Jeohoon Lee) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
For the Tailor Welded Blank Sheet, the characteristics of the fatigue crack initiation and propagation behavior of laser welded sheet used for vehicle body pannels are investigated. Used are three types of specimens which were machined of the same base metal: one is 1.4㎜ thick, another is 1.6㎜ thick and the third is laser-welded of the l.4㎜ thick specimen and 1.6㎜ thick specimen(TB specimen). The results of tensile and hardness test indicate that the yield strength of the TB specimen is the highest, and hardness around welding bead was greater tha that of base metal. Fatigue strength and fatigue limit of the TB specimen before 10? cycles are much superior to those of the base metal. The fatigue crack propagation, of the heat-affected zone of the TB specimen is slower than that of the base metal. Welding bead has the fastest crack propagation in the low stress intensity factor range( △K) region, but the lowest in the high △K region. Therefore, the fatigue propagation characteristic of the laser-welded TB specimen relatively stable compared with that of the base metal in the high △K region around over 28㎫√m.<br/>