Improvement on the Fatigue Performance of BIW by Using Mechanical Clinching Joining Method

The stiffness of autobody largely depend on the joint strength of welding spots. Weak welding joints lead to inferior stiffness, which lowers vehicle performance such as ride & handling and NVH(Noise Vibration Harshness). Resistance spot welding, major joining method of autobody, produces superior joint strength but its fatigue limit(fatigue strength at 10⁷ cycle) is inferior, which implies that joint strength may be greatly affected by the fatigue. Mechanical clinching, on the other hand, has lower joint strength but its fatigue limit is higher than that of spot welding.

This paper focused on the behavior of joint strength under cyclic loading in both resistance spot welding and mechanical clinching. The deterioration of joint strength during fatigue testing was examined by measuring monotonic shear tension force as a function of fatigue cycles at a given cyclic load. It was found that the joint strength of spot welding decreased with fatigue cycles but the mechanical clinching showed no signs of deterioration at all. Thus the mechanical clinching is found to be a very effective method to improve the durability of the body under low cyclic load level which is expected to emerge during normal driving conditions.