Study On Mechanical Properties And Fretting Mechanism Of Aluminum Alloy Clinched Joints

Lightweight body plays an important role in energy saving and environmental protection.Aluminum alloy is the first choice material for realizing lightweight body,with excellent characteristics such as light weight and high strength.Aluminum alloy clinching joints obtained by clinch technology have better performance.The clinched connection technology is a mechanical cold forming connection technology.The material flow formed a solid interlocking point to achieve plate connection.It has the advantages of simplicity,environmental protection,etc,and is suitable for the connection of new light thin plates of the same or different species.Clinched connection technology has broad application prospects in the automotive,aerospace,home appliance and other mechanical industry fields.Exploring the mechanism of fatigue failure and fretting wear of clinched joints has important guiding significance for solving the damage failure of actual engineering mechanical structural parts.This article takes same material aluminum alloy and different material joints as the research object,studied the joint fretting behavior and fatigue failure mechanism.The main work and research results are summarized as follows:(1)Tensile-tensile fatigue tests were conducted on same material aluminum alloy clinched joints and different material aluminum alloy /galvanized steel clinched joints,respectively,to obtain the fatigue life of the specimen under different load conditions,and the fatigue data of the two groups of joints.The combined fatigue life curve showed a high degree of fit.The analysis curve found that the different material joint of aluminum alloy / galvanized steel has low sensitivity to the load value.The same fatigue load value was applied to the two sets of joints,andthe life of different material aluminum alloy / galvanized steel joints has always been longer than that of same material aluminum alloy joints.The fatigue failure analysis of the clinched joint showed that the wear of the different material joint was more prone to wear,and the wear was more serious.(2)The article explored the fretting behavior of the specimen during the fatigue test,and studied the fretting mechanism from the aspects of normal load,number of cycle,and material that has fretting behavior.The results showed that the failure mode was affected by the fatigue load value,and the two failure modes,neck fracture and substrate fracture,are determined by competition.Generally,neck fracture are likely to occur under high load conditions,and substrate fracture is apt to occur under medium and low load conditions;the larger the load value,the greater the damage to the test piece every cycle,if the same damage is caused to the test piece,the low load state requires more cycles of damage accumulation;compared with the same material aluminum alloy clinched joint,the damage of the different material joint is more serious in each cycle of the cycle.(3)In this paper,the fatigue life and energy loss values of same material aluminum alloy clinched joints and different material aluminum alloy / galvanized steel clinched joints were statistically analyzed,and the Ed-N curves of the two groups of joints were obtained by straight-line fitting.It was found that the energy loss value of the two sets of joints is proportional to the fatigue life,the proportionality coefficient is determined by the contact pair material,and the dynamic failure energy loss value of the clinched joint is not related to the static performance.