Study On Structural Parameters And Mechanical Properties Of Clinched Joint With Galvanized Steel

As one of most important programs,Made in China 2025 was proposed on May 8,2015.The plan not only required digital,networking and intelligent manufacturing,but also required breaks in the limitation of environment and resource,especially for energy conservation and emissions reduction.And energy saving and new energy vehicle was one of ten key sectors of the plan.Lightweight structure will be a effective way for us to manufacture energy saving vehicle.However,if lightweight structure was needed,the joining technologies of lightweight metal will be a problem.In recent years,some new joining technologies have been studied,including the key point of this paper:mechanical clinching.The former studies of mechanical clinching were focus on the mechanical properties and the similarities or differences of clinched joint with different materials.However,these studies were lack of the rule of failure process and failure modes of clinched joint.In this study,main test object is clinched joint.By a large scale of tests,the researches of failure modes have done and its laws were founded.The details of study were as follow.1)On the basis of definition of traditional failure modes,the primary reason cause of different failure modes was a fight between the strength of neck of upper sheet and the interlock.Hybrid failure mode was separated from traditional failure modes and was considered as prefect one.2)Besides,according to former researches and experience of practical experiments,the structural parameters s was presented which was the quotient of thickness of neck and undercut.3)The test results of galvanized steel joints showed that failure mode of clinched joint could be predicted by using structural parameters s.When s<0.5,failure modes of all joints were neck fracture mode.When 2.35<s<7.00,failure modes of all joints were almost hybrid failure mode.When 8.60<s,failure modes of joints changed from hybrid failure mode to button separation mode gradually.Increased value of s caused a linear decrease of joints with neck fracture mode.Increased value of s caused a parabolic trend of joints with hybrid failure mode.Increased value of s caused a linear increase of joints with button separation mode.The joint with hybrid failure mode had best performance in tensile and shear strength.When s=4.40,the joint had best performance in load bearing capacities.When s=5.70,the joint had best performance in energy absorption.At same time,the load bearing capacities and energy absorption of eight groups changed as the value of s changed with a parabolic trend.4)When the laws of failure modes and the value of s were got,three groups of specimens were made which were prepared to verify the laws we got.The results showed that the joint with same material like DP590-DP590 and SPCC-SPCC would follow the trend,but to the joint with different materials the laws would not applicable to.5)After statics mechanical experiments,the joints with three different failure modes were picked up.The results of fatigue tests showed that the joint with neck fracture mode had better performance in fatigue property.Besides,the smaller of value of s the better performance in fatigue property.When s=0.50,galvanized steel joints get the best performance in fatigue property.