Crashworthiness assessment of square aluminum extrusions considering the damage evolution

Combining the pivotal tests and FEM technology, crashworthiness of aluminum extrusions was studied for an automobile safety plan. Experiments under static axial loading conditions were carried out for square thin-walled tubes with different thicknesses, section dimensions, with various impact velocities were conducted as well. Crush behavior of this structure under axial static and dynamic loads was studied. FEM code was used for crash analysis, which gave deformation and load prediction. Geometric imperfection and damage model were introduced to simulation. Results show that experiment and numerical model have good agreement with each other.     

动态显式有限元方法在车架耐撞性能分析中的应用

应用动态显式有限元方法对车辆纵向碰撞中车架的大变形过程进行了计算机模拟。文中介绍了显式有限元方法基本理论 ,运用 PAM-CRASH软件预测了车架变形状况和内能吸收能力 ;提出了优化方案 ,并进行对比。结果表明 :改进后的车架耐撞性能有明显的提高 ,达到要求的吸能能力。这种设计方法对整车的设计提供了指导性的参考 ,同时印证了动态显式有限元方法具有的优越性     

Multiobjective optimization of multi-cell sections for the crashworthiness design

Plastic deformation of structures absorbs substantial kinetic energy when impact occurs. For this reason, energy-absorbing components have been extensively used in the structural design of vehicles to intentionally absorb a large portion of crash energy to reduce the severe injury of occupants. On the other hand, high peak crushing force may to a certain extent indicate the risk of structural integrity and biomechanical damage of occupants. For this reason, it is of great significance to maximize the energy absorption and minimize the peak force by seeking for optimal design of these components. This paper aims to design the multi-cell cross-sectional thin-walled columns with these two crashworthiness criteria. An explicit finite element analysis (FEA) is used to derive higher-order response surfaces for these two objectives. Both the single-objective and multi-objective optimizations are performed for the single, double, triple and quadruple cell sectional columns under longitudinal impact loading. A comparative analysis is consequently given to explore the relationship between these two design criteria with the different optimization formulations.     

直升机整体抗坠毁设计的简化力学模型

基于直升机结构件的力学性能研究,根据试验和有限元分析结果,提出了进行直升机抗坠毁设计的简化力学模型.模型主要用于在垂直坠毁过程中的最大冲撞力的预测和关键抗坠毁构件的能量吸收设计.利用此简化模型,对直升机10.2 m/s速度垂直撞击地面这一工况进行了计算,得到了起落架吸收的能量(塑性功)占初始动能的百分比,等效机体的动能衰减曲线等重要结果,与有限元结果对比,吻合较好.     

On the response of thin-walled CFRP composite tubular components subjected to static and dynamic axial compressive loading: experimental

In this work the crushing response and crashworthiness characteristics of thin-wall square FRP (fibre reinforced plastic) tubes that were impact tested at high compressive strain rate are compared to the response of the same tubes in static axial compressive loading. The material combination of the tested specimens was carbon fibres in the form of reinforcing woven fabric in epoxy resin, and the tested tubes were constructed trying three different laminate stacking sequences and fibre volume contents on approximately the same square cross-section. Comparison of the static and dynamic crushing characteristics is made by examining the collapse modes, the shape of the load–displacement curves, the peak and average compressive load and the absorbed amount of crushing energy in both loading cases. In addition, the influence of the tube geometry (axial length, aspect ratio and wall thickness), the laminate material properties-such as the fibre volume content and stacking sequence-and the compressive strain rate on the compressive response, the collapse modes, the size of the peak load and the energy absorbing capability of the thin-wall tubes is extensively analysed.     

Multiobjective optimization for crash safety design of vehicles using stepwise regression model

In automotive industry, structural optimization for crashworthiness criteria is of special importance. Due to the high nonlinearities, however, there exists substantial difficulty to obtain accurate continuum or discrete sensitivities. For this reason, metamodel or surrogate model methods have been extensively employed in vehicle design with industry interest. This paper presents a multiobjective optimization procedure for the vehicle design, where the weight, acceleration characteristics and toe-board intrusion are considered as the design objectives. The response surface method with linear and quadratic basis functions is employed to formulate these objectives, in which optimal Latin hypercube sampling and stepwise regression techniques are implemented. In this study, a nondominated sorting genetic algorithm is employed to search for Pareto solution to a full-scale vehicle design problem that undergoes both the full frontal and 40% offset-frontal crashes. The results demonstrate the capability and potential of this procedure in solving the crashworthiness design of vehicles.     

A multipoint version of space mapping optimization applied to vehicle crashworthiness design

In this paper, space mapping (SM) technique is combined with response surface methodology (RSM). SM is an optimization method well suited for very costly problems to find an improved design with fulfilled constraints. The SM technique use less costly models, which complements the correct models. The theory is established and compared to the corrected RSM. A multipoint version of SM is presented, where a separate evaluation is done in each iteration to improve the mapping function. Using this additional evaluation to update the mapping function, generally, the number of iterations to find the optimum solution can be reduced. Thus, the elapsed time to solve the optimization problem can be reduced if a parallel computer is utilized. Finally, one engineering optimization problem is solved to illustrate the application of SM in vehicle crashworthiness structural optimization.     

泡沫填充夹芯墙多胞结构的耐撞性多目标优化设计

泡沫填充管由于其优秀的能量吸收性能引起越来越多的关注。根据对丝瓜结构的研究,提出一种与丝瓜横截面类似的泡沫填充夹芯墙多胞结构。基于非线性有限元软件LS-DYNA,建立此种泡沫填充夹芯墙多胞结构的轴压分析有限元模型。基于多项式代理模型,采用多目标粒子群优化算法对不同截面形状的多胞结构进行了优化设计。根据优化结果对不同结构的选择给出指导性意见,使结构在满足峰值力限制的情况下拥有最好的吸能特性。本文提出的新型结构在车辆工程及航空航天等领域具有很好的应用前景。     

基于逐步回归模型的汽车碰撞安全性多目标优化

汽车结构的耐撞性及碰撞吸能优化是现代汽车工业的重要研究内容。面对传统优化方法难以找到汽车结构耐撞性问题多目标参数最优解的难题,在汽车结构碰撞安全性问题的研究中,结合试验设计、响应表面模型和有限元仿真程序提出一种基于逐步回归模型的多目标优化设计方法。利用该方法对以汽车前端结构的加强件作为设计变量,以整车质量、脚踏板在碰撞过程中的侵入量和整车碰撞加速度积分值作为目标函数的汽车100%正面碰撞以及40%正面偏置碰撞的多目标优化问题进行仿真优化研究,结果表明该方法对于汽车结构碰撞安全性的优化具有明显的效果。     

直升机抗坠毁仿真软件现状研究

直升机的抗坠毁技术是直升机研制中的五大关键技术之一,而抗坠毁仿真软件是突破这一技术的重要工具。该文对目前国外研究抗坠毁仿真软件的公司、其软件产品、功能以及成功的应用案例进行了详细介绍,对国内进行抗坠毁研究的几个单位及其研究工作进行了简单介绍,分析了其不足。指出直升机抗坠毁仿真软件研究是今后仿真软件研究的一个重要方向。