In applying laser welded joints to automobile components, there are two main areas of suspicious in material strength: 1. Fatigue crack starting from notch tip at root of weld, 2. For some components, fatigue life over 107 cycles is needed. The purpose of this paper is to understand the fatigue strength properties of laser welded joints. In this paper, the fatigue tests for three types of laser welded joints, lap, butt and fillet joints, were performed. Some of the joints were tested at the range of the fatigue life over 107 cycles. The fatigue strength properties of these three types of laser welded joints were evaluated by DeltaK0max. Materials and experiment method are outlined. Results of the experiments and the evaluation of fatigue strength properties by DeltaK0max are discussed. The following conclusions are drawn: 1. The fatigue strength of laser welded joints, lap, butt and fillet joints, continues decreasing with increasing Nf even in the range from 107 to 108 cycles. This is different from the fatigue properties for bulk steels whose S-N diagrams remain horizontal over about 107 cycles. 2. The fatigue strength properties of the laser welded joints were well characterized by DeltaK0max under mixed mode. 3. If DeltaK0max value is smaller than 2.0 MPam1/2, fatigue cracks do not start from the notch tip. Also the value accords with the threshold values of stress intensity factor range DeltaKth which were obtained by the fatigue crack growth test for general arc welded structures.
Study for fatigue strength of laser welded joints
Untersuchung der Dauerfestigkeit von lasergeschweißten Verbindungen
JSAE Review ; 22 , 2 ; 231-233
2001
3 Seiten, 7 Bilder, 7 Quellen
Aufsatz (Zeitschrift)
Englisch
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