基于承载式客车的正面碰撞性能仿真研究

以某型承载式大客车为研究对象,利用有限元法和非线性理论建立整车有限元模型,通过通用显式动力分析软件对其100％正面碰撞进行仿真计算,研究该承载式车身骨架结构的变形大小以及变形特点,并对乘员的生存空间进行分析比较,评价该客车耐撞性与安全性能,并为进一步研究改进客车耐撞性能提供相关参考。     

长淮卫淮河大桥船撞设防标准研究

以长淮卫淮河大桥为依托工程,介绍桥梁船撞设防标准的确定方法。基于风险的思想,参考《重庆市三峡库区跨江桥梁船撞设计指南》,对长淮卫淮河大桥在2012年、2022年和2050年通航密度下进行船撞风险分析,并根据风险分析结果,提出进一步降低桥墩船撞风险的建议和措施,为桥梁船撞设计提供技术支撑。     

基于前车运动状态的运动学安全距离完善研究

根据前车的加速度大小及其变化率对前车的运动状态进行判断,当前车处于紧急制动或持续加速时,对基于车辆制动过程运动学分析的安全距离模型进行修正完善。在双轮模型的基础上进行了仿真实验,结果表明:当前车出现撞车时,完善后的模型依然能够达到避撞目的,当前车处于持续加速时,完善后模型在保证安全的前提下改善了道路的通过性。     

船舶与桥墩碰撞的数值模拟

利用有限元软件,模拟4种不同载重吨位的船舶以不同的速度与某桥墩发生碰撞的过程,演示有限元法仿真计算船桥碰撞问题的一般过程,着重分析船舶和桥墩的损伤程度.在此基础上,归纳出撞深速度、撞击时间-速度和桥墩的应力分布.     

Damage assessment of a tunnel-type structure to protect submarine power cables during anchor collisions

The dynamic characteristics of a tunnel structure used to protect underwater power cables, the so-called A-duct, were determined for anchor collisions to provide a procedure for damage assessment and recommendations. The required physical quantities of five target anchors, including the drag coefficient, were obtained using an element-based finite-volume method and ANSYS-CFX software. The terminal velocities of the anchors were then calculated to maximize the colliding kinetic energy. For collision analysis, four parameters (anchor type, ground condition, collision velocity, and collision point) were considered, and the A-duct was modeled based on the Riedel–Hiermaier–Thoma concrete model using ANSYS-Autodyn software. Our analysis results indicated severe damage (D = 1) for most of the gauge points; the damaged area and level increased with the anchor weight. The results showed that the damage was concentrated in the collision area for stock anchors; however, for stockless anchors, damage was also evident in adjacent areas (i.e., damage propagation) due to the anchor head shape as well as the transfer mechanism provided by its reinforcing nets. Accordingly, the 2-ton stock anchor caused more damage at the gauge points near the collision location than the 2-ton stockless anchor. Second, regardless of the ground conditions and rotation angle of the anchor heads with respect to the vertical axis, the damage levels were almost identical. Fixed boundary conditions and non-rotational angle were sufficient for the model used. Third, the damaged areas became smaller when the anchor collision locations deviated from the reference gauge point (P1), i.e., the center of the A-duct. Finally, a comparison of the field-test results to equivalent numerical collision simulations indicated that the size of the predicted and experimentally observed damaged areas were in agreement within 7%.     

Simplified analytical method for evaluating web girder crushing during ship collision and grounding

The paper presents a simplified analytical method to examine the crushing resistance of web girders subjected to local static or dynamic in-plane loads. A new theoretical model, inspired by existing simplified approaches, is developed to describe the progressive plastic deformation behaviour of web girders. It is of considerable practical importance to estimate the extent of structural deformation within ship web girders during collision and grounding accidents. In this paper, new formulae to evaluate this crushing force are proposed on the basis of a new folding deformation mode. The folding deformation of web girders is divided into two parts, plastic deformation and elastic buckling zones, which are not taken into account for in the existing models. Thus, the proposed formulae can well express the crushing deformation behaviour of the first and subsequent folds. They are validated with experimental results of web girder found in literature and actual numerical simulations performed by the explicit LS-DYNA finite element solver. The elastic buckling zone, which absorbs almost zero energy, is captured and confirmed by the numerical results. In addition, the analytical method derives expressions to estimate the average strain rate of the web girders during the impact process and evaluates the material strain rate sensitivity with the Cowper-Symonds constitutive model. These adopted formulae, validated with an existing drop weight impact test, can well capture the dynamic effect of web girders.     

A comparative analysis of the fluid-structure interaction method and the constant added mass method for ice-structure collisions

The constant added mass (CAM) method and the fluid-structure interaction (FSI) method are widely used to simulate ship-ship and ship-ice collisions. In the CAM method, the hydrodynamic effect of the surrounding water is treated as a constant added mass, whereas in the FSI method the surrounding fluid flow is explicitly modelled. The objective of the paper is to compare the two methods and to explain the causes of the differences in the results. We considered collision between a freshwater ice mass and a floating steel structure. For both methods, the numerical simulations were performed with the LS-DYNA software. The behaviour of the ice mass was modelled using an elliptic yield criterion and a strain-based pressure-dependent failure criterion. To ensure realistic ice behaviour, the ice model was calibrated using general trends found in laboratory and in-situ indentation tests with focus on the laboratory-grown ice and the fluid model in the LS-DYNA was verified by comparing the added mass coefficients for a spherical body and a rectangular block with the corresponding WADAM results. To validate and benchmark the numerical simulations, experimental data on ice-structure interactions in water were used, including the acceleration of the floater wall measured with the dynamic motion unit (DMU), the relative velocity between the ice mass and the floater before the impact and some images extracted from video recording of the test. The comparisons indicated that the FSI method yields better results for the motion of the floater, i.e., the acceleration of the floater wall caused by the ice mass’s impact and the relative velocity were in reasonably good agreement with experimental measurements. It was also found that the CAM method was faster but predicted a higher peak contact force and more dissipated energy in the ice mass than in the FSI method.     

基于驾驶人瞳孔直径的追尾冲突辨识方法研究

以提高交通冲突辨识与驾驶人认知一致性为目的,以驾驶人心理负荷对瞳孔直径变化的影响为理论基础,以追尾冲突下瞳孔直径在时序上的变化为研究对象,使用傅里叶变换在频谱层面对数据进行逐点扫描并完成模板瞳孔直径数据曲线和全程瞳孔直径数据曲线的匹配,最终提取出与模板数据对应时间车辆运行状态相似度较高的时段,辨识结果相对人工同步录像辨识结果的准确率为71.4％.证明了基于驾驶人瞳孔直径的追尾冲突辨识方法的可行性和有效性,为提高交通冲突辨识与驾驶人认知的一致性提供了崭新而有效的方法.     

城市客车座椅动态碰撞的仿真与试验研究

使用MADYMO软件构建了某城市客车正面碰撞乘客约束系统的仿真模型,通过仿真计算分析确认所测假人各部分伤害值均满足法规要求。对某城市客车塑料座椅进行了动态碰撞试验,试验结果与仿真结果对比分析表明,仿真结果接近标准要求,从而验证了本文所建模型的正确性和可行性。     

基于弹性绳理论的自主车辆防碰撞的路径规划

基于人工势场的引导策略,通过建立包括车道边界和障碍车的道路危险势场,采用弹性绳模型实现了车辆在高速公路上的车道保持和紧急避障功能。为了保证车辆在高速情形下避障的安全性,在障碍车辆原有势场基础上,在障碍车辆的前后各增加一个引导势场,使车辆能够提前避障,从而避障过程更安全。再结合Carsim仿真,在车辆的路径跟随过程中观察主车的横摆角速度的变化来判断车辆的稳定性。对直道和弯道两种情形进行避障仿真对比分析,结果表明:在障碍车辆前后添加引导势场能提前避障,从而使避障过程更安全。