Study On Forming Technology, Microstructure And Mechanical Properties Of A SUV Roof

The car body panel is one of the most important parts in car body, the level of press for car body panel and the quality of panel are very important in the car industry.As we all know, most of the automotive body panel and structure are made by sheet metal stamping. In the present study, on the one hand, the formability of an automotive roof and the effect of main parameters on forming process was studied by using 3D analyzing software Autoform. On the other hand, we study the properties and microstructures of materials. Drawing forming is the key process in manufacture of the car body panels. Quality of the drawn parts wills affect directly quality of the manufacture in subsequent processes. Several conclusions are reached as below:(1) Through the geometry modeling, finite element modeling, meshing, proper choosing of the analyzing parameter and material model, we simulate the drawing progress. The simulation result is verified by the thickness of measured results, so the simulated result proves its reliability. The simulation of drawing process has been realized with Autofrom, the possible causes of defects and the material flow during the stamping process have been estimated by analyzing the FLD, thickness distribution.(2) we put forward improved design structure of stiffeners against the problem above inadequate deform of mobile coping. Numerical simulation technique is used to simulate the forming process of optimization structure. The results show the problem of inadequate deform is improved better. The shape optimization based on stamping formability, not only can we used to improve forming quality of mobile coping, but also the reference value for the similar autobody structure optimization.(3) Mechanical distributions of mobile coping are analyzed by hardness test. the evaluates high strength steel's dent resistance is obtained by simulating experiment,with the reduction of thinning ratio, dent resistance of roof smaller and smaller.(4) Texture, grain boundaries and disorientation of the specimens were investigated by electron back-scatter diffraction(EBSD). The DC05 sheets with different stamping deformation degree all have a strong {111}//ND fiber texture composed of {111} <110> and {111} <112>. The {111} texture is beneficial to deep drawability, so the DC05 have good formability under different stamping deformation degree. The results also showed that the average grain size decreases with the decrease of the thickness. What's more, the decrease of the thickness also makes the number of low angle grain boundaries(<15°) increase continuously, so the average disorientation decrease steadily. The yield strength increased of material due to refined grain, so the DC05 have higher yield strength and better plasticity with the increase of thinning ratio.