| The rapid development of automobile industry in recent years has led to the problem of energy and the environmental issues has becoming increasingly serious. As an important technical means to alleviate these problems. Automotive lightweight getting more and more people’s attention. Advanced high-strength steel and aluminum as superior lightweight materials are increasingly used in automobile production, so how better to resolve connectivity issues between them has become an important research focus. Now the ultimate tensile AHSS used on automobile production are prevalent more than 1500Mpa, but connections between such high intensity steel and aluminum can’t be achieved by the traditional clinch technology. Therefore, the study is significant for the clinch technology of AHSS.This paper studies the sticky elastic-plastic material model that applicable for 22MnB5 AHSS, and because they do not consider the effect of temperature on the mechanical properties of aluminum alloy 7075, so I studied the piecewise linear plastic material model, established for 22MnB5 advanced on the basis of high-strength steel and 7075 aluminum rivet-free connection FEM simulation model. Based on this model,the clinch joints were analyzed at the stress and strain changes in the process under the punch punching force, get in the important parameters of the shape and size of clinch joints include the neck thicker value Tn, self-locking value Tu and bottom thickness value X. Also I observed the impact of forming to the joint at different arrangement of the plate member, the temperature changes in advanced high strength steel member during the clinch process and the changes of punch punching force at different initial temperatures.I research on the Akerstrom’s mathematical model that the decomposition of austenite phase because of boron steel cooling. Then use the experimental research methods for advanced high strength precursor steel to do heat treatment test, compared to the mechanical properties of advanced high strength steel under air cooling, air-cooled, water-cooled, oil-cooled four cooling way, resulting in mechanical properties of advanced high-strength steel clinch joints under different cooling way; at the same time using the finite element analysis method to obtained AHSS martensite content distribution under different cooling rates, and test results come as expected conclusions after contrast.After analysis of the clinch and subsequent quenching process, through the establishment of the one-way stretch and the cross shear mechanical finite element model, the resist axial load capability was determined as a standard to the mechanical properties of the joint. At the same time research the impact of the size of different mold parameters including punch radius, groove radius and die depth on clinch joints size parameters, design orthogonal experiment to complete die size parameter optimization and obtained optimal parameters of die size for the thickness of 2mm plate between advanced high strength steel and aluminum alloy. After determining in the size of the mold parameters, research the impact of process parameters include the coefficient of friction, punch stroke, the initial temperature of the plate, blank holding force to the size parameters of clinch joints, the same orthogonal test was designed to determine the optimal process parameters.Finally, according to the optimal mold dimensions parameters obtained by simulation design mold, build the test platform based on the optimized process parameters to complete clinch test between advanced high strength steel and aluminum on the basis of existing test conditions. |
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