薄壁结构棱边强化效果
Effect of ridgeline strengthening in thin-walled structure

基于方管理想化折叠单元模型、塑性挤压过程能量耗散分解法与棱边强化薄壁方管在轴向静态压溃作用下的能量平衡修正方程,分别导出了棱边强化薄壁方管的平均压溃力、吸能预测与棱边强化效果的理论表达式。建立了系列棱边强化薄壁方管准静态轴向压溃有限元模型,导入LS-DYNA程序进行弹塑性动力学仿真,获得了平均压溃力,分析了棱边应力强化的敏感性。将棱边强化技术应用于某车前保横梁和吸能盒相应棱边强度设计中,采用超高应力强化棱边和普通延性钢板组合去置换较高强度钢薄壁结构,在冲击试验验证过的有限元模型基础上,建立了棱边强化前保险杠子结构独立评价有限元模型,分别进行了棱边强化模型和原始模型的50 km？h-1正碰仿真试验。仿真结果表明:导出的平均压溃力公式可以预测棱边与平板屈服强度比为1～4的棱边强化薄壁方管轴向压溃力学特性,仿真结果与理论结果的最大偏差不超过5.66%; 由前保险杠子结构正碰仿真结果得到了棱边强化前后近似的塑性变形模式与传力路径,能量吸收差值不超过0.3 kJ。可见,选择性棱边应力强化后的普通延性钢前保险杠子结构有望实现等效置换较高强度钢前保险杠子结构。
The theoretical expressions of mean crushing force, energy absorbing prediction and ridgeline strengthening(RS)effect of thin-walled RS square tube were respectivelyderived out based on the ideal folding element model of square tube, the energy dissipation decomposition method during its plastic deformation process, and the modified energy balance equation of thin-walled RS square tube subjected to static axial crushing effect. A series of finite element models of thin-walled RS square tube subjected to quasi-static axial crushing were built, and imported into LS-DYNA program to conduct elastic-plastic dynamics simulation. The mean crushing forces were obtained, and the sensivity of ridgeline stress strengthening was investigated. The ridgeline strengthening technology was applied to the ridgeline strength design of front bumper beam and crashboxes for a vehicle. The corresponding thin-walled structures with higher strength steel were replaced by the assembly of ultra stress strengthened ridgelines and general mild steel plates. The finite element model of front bumper substructure system with strengthened ridgelines for individual evaluation was set up based on the existing finite element model verified by crash test. At 50 km？h-1, the front crash simulation tests were conducted with the ridgeline strengthening model and the original model respectively. Simulation result indicates that the axial cushing force property of thin-walled RS square tube with the yield strength ratios of ridgeline to plate ranging from 1 to 4 can be predicted by using the mean crushing force formula, and the maximum deviation between theoretical result and simulation result is lower than 5.66%. Front crash simulation result comparison of the front bumper substructure before and after ridgeline strengthening shows similar plastic deformation modes and force transmission routes, and the energy absorption deviation is lower than 0.3 kJ. So, the general mild steel front bumper substructure with selective stress strengthened ridgelines can equivalently replace the corresponding higher strength steel