预开孔对钢铝热熔自攻丝接头力学性能的影响

Effect of Pilot Hole on Mechanical Properties of Steel/Aluminum Flow Drill Screw Joint

热熔自攻丝技术(Flow Drill Screw,FDS)作为混合材料车身中单边连接的主要连接方式,在上层板材预开孔是其常用的辅助连接方法。以HC340/590DP高强钢和6063-T6挤压铝合金为研究对象,通过剪切拉伸实验,研究了上层板材厚度及预制孔尺寸对接头剪切强度及失效模式的影响。结果表明,当上层钢板厚度为0.8 mm,预制孔直径为5.5 mm时,FDS接头剪切峰值载荷及吸能能力大大降低。当预制孔直径小于5.5 mm时,相同预制孔直径下FDS接头吸收能量能力随上层板厚度增大呈减小趋势。此外,上层钢板厚度与预制孔直径之比f影响FDS接头失效模式及力学性能,当f大于0.27时,FDS接头失效模式为螺钉断裂,剪切峰值载荷基本不变;当f小于0.27时,FDS接头失效模式为上板撕裂,剪切峰值载荷随f增大而增大。

Flow Drill Screw(FDS)is the main connection method of single side connection in multi-material vehicle body,and machining pilot hole in upper plate is the common auxiliary connection method.Taking HC340/590DP high-strength steel and 6063-T6 extruded aluminum as the research objects,the effects of the thickness of the upper plate and the size of the pilot hole on the shear strength and failure mode of the joint were studied by shear tensile test.The results show that when the thickness of the upper steel plate was 0.8 mm and the diameter of the pilot hole was 5.5 mm,the shear failure load and energy absorption capacity of the FDS joints were greatly reduced.When the diameter of the pilot hole was smaller than 5.5 mm,the energy absorption capacity of the FDS joints decreased with the increase of the thickness of the upper steel plate under the same diameter of the pilot hole.Moreover,the ratio of the thickness of the upper steel plate to the diameter of the pilot hole(f)affect the failure mode and mechanical properties of the FDS joint.When f was greater than 0.27,the failure mode of the FDS joints was screw fracture and the shear failure load was basically unchanged.When f was less than 0.27,the failure mode of FDS joint was upper plate tearing,and the shear failure load increased with the increase of f value.