高强钢轧制变厚度板热冲压成形破裂预测及其回弹研究

For both energy-saving emission reduction and security are required for modern vehicles，the aim of automobile lightweight also becomes higher and higher. Hot stamped parts of high strength steel tailor rolled blank (TRB) have special advantages for reducing weight, so they will be used widely in the field of modern cars. Because of the variable cross-section of TRB, mechanical and hot stamping theories based on equal cross-section will not be suitable. In the research, isothermal tensile tests for high strength steel TRB will be carried out by Gleeble3500 thermo-simulator, the constitutive relation will be built at high temperature, and the ductile fracture criterion for hot forming will be built based on Lemaitre damage theory. Through theoretical analysis, numerical simulation and experiments, the fracture mechanism of automobile B pillar of high strength steel TRB in hot stamping will be lucubrated, and effect of process parameters on the springback of formed part in hot stamping will be obtained. Then the mechanism of springback compensation for hot-stamping parts will be studied. It has importmant practical value and significance for state-owned auto industry, and it is an essential application of basic research to carry out this research. It has not only high academic value, but also important economic and strategic significance to further promote the development and use of domestic panel, which can improve the competitveness of domestic autobody panel marke, and revitalization of the steel and automotive industries.

对现代汽车提出节能减排和安全性的双重要求，使汽车轻量化的目标也越来越高。高强钢轧制变厚度板（TRB）热冲压件具有突出的减重优势，将会在现代汽车领域得到广泛应用。 TRB的变截面使得以往基于等截面的力学以及热冲压成形理论无法适用，其冷成形的相关理论在热冲压成形时亦不能适用。本研究拟采用Gleeble3500热模拟试验机进行高强钢TRB等温拉伸实验，建立其高温下的本构关系，基于Lemaitre损伤理论建立其热成形韧性断裂准则。通过理论分析、数值模拟和工艺试验相结合的方法深入研究高强钢TRB汽车B柱热冲压成形破裂机理和工艺参数对其热冲压成形回弹的影响规律，并研究其回弹补偿机制。通过该项目的研究，探索高强钢TRB的热冲压成形性能及其热冲压模具的设计理论，为高强钢TRB热冲压件在现代汽车领域的应用奠定理论基础。对于国产板材的开发利用、提高国产板材的市场竞争力、振兴钢铁和汽车工业，具有重要战略意义。

由于高强钢TRB热冲压件具有较好的减重优势，在汽车轻量化领域具有广泛的应用前景。通过Gleeble3500热拉伸试验机在不同温度和应变速率下对不同厚度的B1500HS钢板进行不同应变形式下的应力应变曲线测定，并基于曲线拟合建立高强钢TRB材料本构关系模型；同时利用混合法在Lemaitre韧性断裂准则的基础上获得了适用于高强钢热成形的韧性断裂准则。然后，通过二次开发将其应用于高强钢TRB热冲压成形过程的破裂预测。. 为了研究高强钢TRB热冲压件的回弹规律，设计了高强钢TRB热冲压模具，并进行了高强钢TRB热冲压过程仿真分析。通过数值模拟和试验研究，获得了工艺参数对高强钢TRB热冲压成形回弹的影响规律，验证了设计的高强钢TRB热冲压模具满足成形件的性能要求，并获得了高强钢TRB热冲压合适的工艺参数。高强钢TRB热冲压成形技术研究为高强钢TRB在汽车轻量化领域的应用奠定了理论基础且对生产实践具有指导意义。