Simulation Study On The Clinching Joint Quality Of Three-layer Steel And Aluminum Alloy Dissimilar Materials

The use of lightweight materials is an important means for the rapid development of automobile industry and the realization of lightweight vehicles.Multi-material body, especially steel and aluminum alloy hybrid body is used in the most of the car body. So steel and aluminum alloy hybrid body structure has become one of the main research directions of automotive lightweight. The clinching is a new type of mechanical connection technology, which can effectively achieve the connection of dissimilar sheets. And the connection form of three or more layers is adopted in many parts of the car body now. Therefore, study on the clinching of three-layer sheets has a very important practical value.First of all, ordinary SPCC steel is selected as the research object, the clinching process of three-layer SPCC steel sheets and the factors influencing joint quality are analysized based on DEFORM. The results show that the load of punch increases with the increase of the displacement, and the load of die is larger than that of punch and blank holder. In the process of joining, the neck of sheet is first subjected to stress and strain, and stress and strain of the neck are the largest. The factors affecting joint quality are the neck thickness t_N1 and t_N2, the undercut t_U1 and t_U2, the bottom thickness X.Secondly, the effect of different combinations of steel and aluminum alloy materials on the joint quality is explored by using A16061-T6 instead of SPCC and the failure of joints under different combinations is studied. It can be seen from the results that the clinching joint is best when the aluminum alloy is in the middle for aluminum alloy, steel and steel combination. The clinching joint is best when the steel sheet is on the bottom for aluminum alloy, aluminum alloy and steel combination. But the neck thickness is small,it is best to adjust the thickness of sheets to further research. The joint can bear the maximum failure load when the aluminum alloy is in the middle of two steel sheets. The lightweight body can be effectively realized after replacing steel with aluminum alloy.Next, the punch radius, die depth, groove depth and groove width are selected as the variable parameters. The influence of different die parameters on the neck thickness and the undercut of steel and aluminum alloy dissimilar materials joint is studied. The results show that the influence of different die parameters on the joint quality is not identical. When the die parameters are not appropriate, there will be many defects. For example, the groove is not completely filled, the sheet has been over clinched or there is agap between sheets and soon.In the end, the four factors of die depth, groove depth, groove width and punch radius are used as test factors and the maximum failure load of joints is taken as the response. Multi-objective optimization of the die parameters is carried out by the center composite design. The variance analysis and regression analysis are performed combining with finite element simulation. The effects of various factors and the interaction between factors on joint strength are studied. And the visualization models of the influence of each factor on joint strength are provided.Finally, the optimal combination of die parameters under the optimum test conditions is obtained.