Application Of Self Piercing Riveting Connection Technology For Aluminiumm Alloy Body

At present,automobile lightweight is the key direction of automobile technology development.The steel body used in traditional automobiles has the problem of overweight,which has great pressure on fuel consumption and exhaust emissions.The test proves that the automobile quality is reduced by 50%,and the fuel consumption can be saved by 50%.In the new energy automobile industry,the reduction of vehicle quality is directly related to the mileage of the new energy automobile.Relevant research shows that the mileage can be increased by 2.5 km for every 10 kg reduction of vehicle weight.In the electric vehicle industry,taking a car for example,the whole weight has increased 200 kg for the battery replaceing engine.Therefore,to ensure the vehicle mileage,lightweight body is particularly critical.Aluminum alloy has a wide application prospect in light weight car body because of its light weight ratio.Due to the limitations of aluminium alloy welding technology,self-piercing riveting(SPR)has become a common method for joining aluminium alloy and other materials.However,the application of self-piercing riveting technology in automobile manufacturing has just started.The influences of each parameter on the quality of riveted joint need to be studied.In this paper,two samples of BJ5182 aluminium alloy with 1.5mm thickness are joined by self-piercing riveting.The mechanical properties of self-piercing riveting joints with different riveting die shapes(including flat bottom riveting die A,punch riveting die B and C),different riveting forces and different holding time are discussed by orthogonal design method.The mechanical properties of self piercing riveting and the resistance spot welding mechanical properties of the same base metal were compared.The details are as follows:Taking BJ5182 aluminium alloy sheet as the experimental object,the orthogonal experimental design method was adopted.The influence of three parameters(the shape of riveting die,holding time and riveting force)on the self-locking quantity,bottom thickness,rivet opening degree and joint tension-shear strength of self-piercing riveted joint were analyzed through range method and variance method.The results show that riveting force has the greatest influence on the self-locking quantity,but has no correlation.The height of riveting die is proportional to the self-locking quantity.The main factors affecting the bottom thickness are the shape of riveting die.The bottom thickness is proportional to the height of riveting die.The analysis of variance shows that the height of riveting die is the main factor affecting the bottom thickness,the riveting force is the main factor affecting the rivet opening,and the riveting force obtained by variance analysis is the significant factor affecting the rivet opening.Under the same holding time and riveting force,the hardness distribution and failure modes of the surrounding structures of self-piercing riveted joints with different riveting die shapes were studied.The tensile shear performance of convex riveting die is the most stable And the cross-section hardness of the joint by three different riveting dies was tested.It was found that the material around the rivet had big plastic deformation,and the plastic deformation of the joint by the convex riveting die was larger than that by the plain riveting die.Comparing the mechanical properties of self-piercing riveting and resistance spot welding of the same kind of aluminium alloy sheet,it is found that the tensile and shear strength and peeling strength of self-piercing riveted joint are stronger than spot welding joint,and the energy absorption of self-piercing riveted joint is higher than spot welding,so it has more toughness.