镁合金方向盘疲劳试验的计算机模拟

通过利用有限元技术对镁合金方向盘疲劳试验的主要过程加以模拟,分析产品的几种主要受力状态。作为模拟分析的重要技术,CAE可以进行高效、快速的分析,便于对试验结果做出预先判定、优化产品设计。     

Finite element analysis of collapse of front side rails with new types of crush initiators

Today’s vehicles are designed with lighter weight to increase performance and to lower fuel consumption, while at the same time meeting the demands of safety requirements. Reducing the cross-section of structural elements to achieve weight reduction can lead to adverse effects on passive safety of the vehicle. In such cases, necessary design modifications must be created to overcome the adverse effects. For this purpose, front rail columns with crush initiators are used in the front zone of cars. These shock-absorbing elements act as energy consuming devices that convert impact energy (kinetic energy) into plastic deformation energy. Simulation of this energy conversion phenomenon is the subject of this paper. The primary objective of this study is to computationally determine how various crush initiators can reduce the maximum crushing force and how different types of structural modifications affect the observed folding form. The ribs near the crash area are placed in two rows and four different configurations on all facing sides of the column in order to decrease reaction forces and absorb more kinetic energy. These structures are analyzed under axially loaded crushing forces using the explicit nonlinear finite element analysis solver ANSYS/LS-DYNA.     

浅谈隧道浅埋软弱地质段塌方处理技术

文章以十天高速公路石庄隧道施工为例,对该隧道浅埋软弱地质段的塌方冒顶情况进行了介绍,分析了塌方产生的原因,提出了内外结合的塌方处理方案,并阐述了方案的关键技术措施及注意事项。     

车载接触网运行状态检测装置系统设计及应用

接触网作为电气化铁路牵引供电的关键设备,其状态好坏直接影响铁路运行安全。为了在运营动车组上装备一套接触网运行状态检测装置对接触网运行状态进行全程监控,从系统的设计要求、设计原则、设计方案着手,引入非接触式的图像处理、机器视觉以及红外测温关键技术,完成装置的系统设计,同时通过静态和动态试验验证装置的性能。试验和现场的实际应用反馈表明,装置满足技术条件要求,同时装置对接触网的检测结果能够为接触网检修提供依据。     

Influence of boundary conditions on the collapse behaviour of stiffened panels under combined loads

A series of finite element analyses are conducted to investigate the influence of boundary conditions and geometry of the model on the predicted collapse behaviour of stiffened panels. Periodic and symmetric boundary conditions in the longitudinal direction are used to calculate the ultimate strength of stiffened panels under combined biaxial thrust and lateral pressure. The calculated ultimate strength of stiffened panels are compared with those by different FEM (finite element method) code and are assessed. The periodic boundary condition in the longitudinal direction for two spans or bays model provides an appropriate modelling to a continuous stiffened panel and can consider both odd and even number of half waves and thus, is considered to introduce the smaller model uncertainty for the analysis of a continuous stiffened panel.     

加筋球冠结构在静动载荷作用下的动响应分析

借助ANSYS/LS-DYNA程序,分析加筋球面艏端隔壁在静动载荷作用下的动响应,求得了静动载荷作用下的球面艏端隔壁结构的动力响应;分析潜艇发射雷弹时发射管的转角变形,给出了潜艇发射雷弹时发射管转角变形的规律。分析时选用顺序求解法,即借助ANSYS对艏端隔壁结构进行静力分析,将其结果作为艏端隔壁结构动力作用下的初始条件,然后再借助LS-DYNA进行艏端隔壁结构的动力响应分析。通过大量的数值实验,并结合理论分析,最终给出了潜艇发射雷弹时发射管的转角变形规律。     

Model-scale experiments of symmetric ship collisions

This study was initiated due to the lack of experimental data on ship collisions. The feasibility of model-scale ship collision experiments was examined and a series of model-scale ship collision experiments is presented. The theoretical background for the analysis of experiments is given together with the principles of scaling. Proper scaling should assure physical similarity to the large-scale experiments conducted in the Netherlands. The Froude scaling law was followed, resulting in the improper scaling of some forces: the effects of this are discussed. The study concentrates on the dynamics of collisions. The structural response, properly scaled from the large-scale experiments, was modelled using polyurethane foam as the ship’s side structure. The collision process was analysed and the results of model-scale tests, large-scale experiments, and a simple analytical model were compared, showing that there was both quantitative and qualitative agreement in the results of the experiments conducted at different scales. The analytical model yielded good quantitative assessment of the deformation energy.     

地裂时桥梁倒塌过程研究

利用LS-DYNA程序建立数值分析模型，再现土耳其Arifiye大桥在1999年地震中由于地裂引起倒塌的过程，并与真实的倒塌场景进行比较，验证了分析模型的正确性。有限元分析中，墩台和上部结构均采用平面应力单元，忽略弹性支座的影响；墩台与上部结构之间采用接触算法；结构动力分析采用显式有限元法进行。从对桥梁上部结构破坏过程中梁体位移的动力响应分析可知，梁体坠落过程中没有与相邻墩台发生明显的撞击。对地裂发生位置和上部结构形式对倒塌影响的研究表明，结构完整性能够明显阻止结构发生连续性倒塌破坏；在阻止地裂引起桥梁破坏方面，连续结构形式优于简支结构形式，可有效减轻地裂发生瞬间桥梁破坏造成的生命财产损失。     

铁路土质边坡滑坍抢修技术的研究

通过对铁路土质边坡上不同土质、不同地形、不同入土深度、不同材质(钢或木)的128根打入桩的水平静载试验研究,得到不同条件下各种长度钢、木抗滑桩所能承受的水平力,为土质边坡滑坍抢修时如何选择适当长度、排数的钢桩或木桩提供参考。试验结果表明,边坡上抗滑桩的水平极限承载力与坡脚平地上抗滑桩的水平极限承载力相比,并没有规律性地减少,水平值相差不大;在均匀土层中,不同桩型、不同土质抗滑桩的水平极限承载力与其埋深基本成正比线性关系。     

On the handling performance of a vehicle with different front-to-rear wheel torque distributions

ABSTRACT

The handling characteristic is a classical topic of vehicle dynamics. Usually, vehicle handling is studied by analyzing the understeer coefficient in quasi-steady-state maneuvers. In this paper, experimental tests are performed on an electric vehicle with four independent motors, which is able to reproduce front-wheel-drive, rear-wheel-drive and all-wheel-drive (FWD, RWD and AWD, respectively) architectures. The handling characteristics of each architecture are inferred through classical and new concepts. The study presents a procedure to compute the longitudinal and lateral tire forces, which is based on a first estimate and a subsequent correction of the tire forces that guarantee the equilibrium. A yaw moment analysis is performed to identify the contributions of the longitudinal and lateral forces. The results show a good agreement between the classical and new formulations of the understeer coefficient, and allow to infer a relationship between the understeer coefficient and the yaw moment analysis. The handling characteristics vary with speed and front-to-rear wheel torque distribution. An apparently surprising result arises at low speed: the RWD architecture is the most understeering configuration. This is discussed by analyzing the yaw moment caused by the longitudinal forces of the front tires, which is significant for high values of lateral acceleration and steering angle.