History of wheel/rail contact mechanics: from Redtenbacher to Kalker

The history of wheel/rail contact mechanics is an integrated part of contact mechanics. Problems of wheel/rail contact (damage phenomena and influence of contact mechanics on vehicle dynamics, especially on vehicle stability) have been investigated since the middle of the 19th Century. In 1855, Redtenbacher was the first to consider head checking. Stability investigations started with Boedecker (1887) and were continued by Carter (1916); however, they were not recognized at that time. Stability analysis was only considered to be an integrated step in vehicle design in about 1955 when stability problems started to occur in practice. The scientific foundations of our present investigations are based on Heinrich Hertz, Frederick William Carter and Hans Fromm. The key contributors to research in the last fifty years in the field of wheel/rail contact mechanics are Joost Kalker and Ken Johnson.     

Approximate weight functions of stress intensity factor for a wide range shapes of surface and an embedded elliptical crack

This paper describes the application of weight function for stress intensity factor in a surface crack with a wide range of crack shapes. Based on the weight function representation proposed by Wang and Glinka (2009), an extended formulation of the weight function for surfaces and embedded cracks is performed. The unknown parameters in the formulations were determined from reference values of stress intensity factor for a surface and an embedded crack given by finite element analysis with the J integral method. The effectiveness of the proposed weight functions has been verified by comparing with the stress intensity factors given by finite element analysis and available approximated solutions under several loading conditions.     

基于逆向工程轿车保险杠设计及曲面评价

在对汽车外形的局部改型中,由于逆向设计具有设计精度高、开发周期短及节约成本等优点,逐渐得到厂家的广泛采用。文章根据原型车前后保险杠造型,运用逆向工程原理以及CATIA软件中的模块构建出新的保险杠造型,依据曲线几何连续性条件,利用曲面断面线法、斑马线法及曲面反射性分析法来评价曲面的质量。最终得到更加美观的轿车保险杠外表面造型。该方法大大提高了轿车外表面改型的开发效率。     

SMS水动力学软件

简要介绍了水动力学软件SMS的基本功能,并用简单实例对其前后处理功能做了展示。     

The effect of weld residual stress on fracture toughness at the intersection of two welding lines of offshore tubular structure

Due to the spatial complexity and fabrication characteristics of offshore platforms, it is inevitable to encounter overlaps or proximity of weld lines in tubular joints. Several international standards such as American Petroleum Institute (API), American Welding Society (AWS), and American Institute of Steel Construction (AISC) regulate the minimum distance between primary weld beads; however, any logical and detailed background of this limitation has not been presented. For a non-compliant weld joint where the regulation is not met, fracture toughness calculation is a typical index to verify the structural integrity.This research consists of two parts. First, weld residual stress distributions are calculated by a 3D thermo-mechanical nonlinear Finite Element Analysis. Two crossing welds, a T-weld crossing on a butt weld, are simulated in one model. A separate tee and a butt welding simulations are also performed for a comparative purpose. Second, SIFs and J-integral values are calculated at the surface and deepest crack tip locations for four different types of semi-elliptical surface cracks. Four cracks are embedded into the weld model and the residual stress distribution from the 3D thermo-mechanical FEA are mapped to a 3D FE crack model as initial conditions. An additional axial tensile load is also imposed. SIF values are compared with those using the weighting function method for the butt weld model subject to three load cases, i.e., tensile stress only, weld residual stress only, and both of them. From the simulation, a tubular joint containing a chord girth weld intersected with weld beads of brace is found to show lower the SIF values than that having only a girth weld on chord.     

动面生锈对低里程制动抖动现象的影响研究

基于某车型持续出现的低里程制动抖动现象的调查研究,分析了该车型出现低里程制动抖动的可能性原因。通过盐雾处理模拟制动盘自然锈蚀过程,并实车路试再现了该车型低里程制动抖动发生过程,提出了制动面生锈不均匀是造成低里程制动抖动的主要原因的结论。     

电动汽车用永磁同步电机永磁体最佳工作点分析

永磁同步电机应用在电动汽车及混合动力汽车上已经十分普及,不仅因为永磁同步电机具有尽可能宽广的弱磁调速范围,能够在电机最大功率不变的条件下提高电动汽车的起动加速能力及低速爬坡能力,而且永磁同步电机具有较高的功率密度比。应用在电动汽车上,更为有效地降低电动汽车的质量,从而提高电动车效率。     

汽车内饰零件表面油漆工艺分析及质量控制

汽车内饰塑料零件采用表面喷油漆工艺是当今轿车内饰设计中的亮点,也是一种趋势。通过对汽车内饰零件表面油漆工艺进行分析,从素材及油漆的选取、前处理的要求、空气洁净度要求、工艺流程规划、工艺参数控制及常见缺陷分析等各方面,找出了该工艺中关键的影响因素,只有加强对这些特殊特性的监控,才能保证稳定的生产过程,杜绝油漆色差、开裂及磨损等质量问题的发生,从而提高企业的制造水平及市场竞争力。     

基于CATIA的轿车前翼子板曲面造型与质量分析

针对轿车前翼子板不易划分基础曲面和桥接曲面的情况,提出了一种基于CATIAV5的快速建模与曲面质量评价方法。首先应用Generative Shape Design模块生成单个曲面,再利用Free Style、Automotive Class A等模块对模型进行分割,最后分别应用等照度线和多截面曲率梳工具对轿车前翼子板曲面质量进行评价。结果表明,该模型达到了A级曲面的各项要求,为后续的加工制造提供了可靠的理论依据。     

自由曲面数控加工技术的研究进展

数控加工是自由曲面高质量和高效率的加工方法，生成无干涉过切刀具轨迹是自由曲面数控加工技术的关键。随着高速加工技术的发展，高速机床生成的刀具轨迹越来越受到重视，本综述了刀具轨迹生成过程中的关键技术，加工仿真以及在高速加工中自由曲面的数控编程问题，分析了商用系统的现状及不足，最后探讨了自由曲面CAPP的关键技术及其策略。