前轮转角和车轮制动状态对汽车轨迹模拟的影响

对于碰撞后失去动力的汽车，建立其运动轨迹的计算机模型需要碰撞后汽车的初始速度和前轮转角，制动情况等初始值作为轨迹模型的输入参数，以便观察碰撞发生后的汽车运动情况。分析了碰撞后汽车车轮的受力情况，给出不同初始值情况下的轨迹模拟模型。分析结果得出，车轮在自由状态下，前轮的转角对汽车的运动距离有较大影响；当前轮转角为零时，汽车的质心运动几乎为一条直线；当车轮未完全抱死且前轮转角不为零时，汽车的质心运动为一条曲线。     

高速铁路对区域经济的影响分析——以京津城际铁路为例

高速铁路凭借其显著的技术优势,对沿线地区的经济发展起到了很大的推动作用。此文在阐述国内外研究成果的基础上,分析高速铁路对沿线区域经济的影响,主要包括提高沿线线路运输能力、提高区域可达性、推动区域经济发展、优化产业结构、促进就业等几个方面。并采用有无高速铁路的对比法,分析和评价京津城际铁路对京津地区社会经济发展带来的影响。不管在生产总值、各产业增加值、就业人数、环境污染治理等方面都做出了贡献。并提出发展高速铁路的建议及促进区域经济发展注意的问题。     

The role of the contact geometry in wheel–rail impact due to wheel flats

A thorough investigation of wheel–rail impact due to wheel flats is presented, together with a quantitative characterization of the main mechanisms and parameters. A criterion for the speed with respect to contact loss between wheel and rail is derived. In the subcritical speed regime, the magnitude of the impact force is shown to be directly related to the geometry of the flat, whereas in the transcritical speed regime a fictitious or effective flat depth exists, which decreases with the second order of the speed. In this domain, the position of impact shifts towards the end of the flat with increasing speed. The impact force increases with the second order of the speed in the subcritical speed regime and approximately the first order of the speed in the transcritical speed regime. The magnitude of the impact force is inversely proportional to the minimum circumferential curvature of the wheel tread defect in the subcritical speed regime, and to the effective minimum curvature in the transcritical case. The variation with the flat depth is less; the impact varies with the square root of the flat depth. The presented theory is in accordance with measurements reported in the literature and explains characteristic features in them.     

摩托车铝合金车轮冲击试验研究

对摩托车铝合金车轮冲击试验常用3个标准ISO 8644—1988、JSAO T203—1985和QC/T 211—1996规定冲击试验方法进行比较研究,发现QC/T 211标准冲击试验后车轮变形量最大,ISO 8644标准次之,JASO T203—1996标准最小。为了使车轮按照各标准冲击试验后变形量接近一致,提出修订QC/T 211—1996标准冲击试验冲击锤下落高度h和试验强化系数k的建议。     

Impact scenario models for probabilistic risk-based design for ship–ship collision

A number of authors have proposed probabilistic risk based ship design for ship–ship collision, conditional to the local trading area of a vessel. The probability of collision and consequences are determined based on the traffic conditions in which a vessel is expected to operate. This paper investigates the adequacy of currently available models for impact scenarios, i.e. models linking the traffic conditions to the conditions at the moment of collision. An exploratory statistical model is presented to establish such a link. A probabilistic risk based design case study is performed for a fleet of RoPax vessels trading on a specified route in the Gulf of Finland. The available impact scenario models from the literature are compared with the developed probabilistic evasive maneuvering model. The results show that the impact scenario models have a very significant influence to the calculated hull breach probabilities. No well-justified impact scenario models are presently available and also the presented probabilistic evasive maneuvering model is burdened with uncertainty. Hence, to move toward a probabilistic risk based ship design paradigm for ship–ship collision in a local trading area, more focus and research is needed to establish a credible link.     

钢桥面铺装层弹性模量与铺装层厚度对铺装体系受力影响分析

采用美国环氧沥青、日本环氧沥青两种钢桥面铺装材料在不同厚度下分析铺装层受力变形规律。推导出铺装层最大拉应力、剪应力与弹性模量、铺装层厚度的数学模型。结果表明：铺装层最大拉应力、剪应力同铺装层弹性模量均可用多项式4次方程拟合,铺装层表面横向最大拉应力随着铺装层厚度的增加而减小,横向最大层间剪应力不随铺装层厚度增加而减小,而是在铺装层厚度处在40～50 mm之间有一个峰值,而后随厚度的增加而逐渐减小。     

冲击载荷作用下隧道逃生管动力响应研究

为保证隧道塌方时施工人员有足够的逃生空间,结合具体工程,介绍了隧道逃生管设计要点,并对其在冲击荷载作用下的动力响应进行了弹塑性数值模拟。研究表明,逃生管变形随着落石尺寸的增大而增大,随着逃生管壁厚的增大而减小,随着与逃生管端部距离的增大而减小。     

冲击压实在公路湿陷性黄土地基处理中的应用

结合工程实例,介绍了冲击压实在高等级公路湿陷性黄土地基处理中的应用情况,阐述了冲击压实法的工作原理,指出冲击压实是处理湿陷性黄土地基的一种良好方法,其优点是施工效率高,适合于大面积地基处理.     

某商用车摆锤冲击安全性CAE分析与改进设计

针对某商用车在执行欧洲经济委员会法规<关于对商用车驾驶室乘员保护方面的车辆认证的统一规定>(ECE R29)的试验中出现的驾驶室与车架连接机构断裂的情况,建立了该商用车驾驶窜正面摆锤撞击的有限元分析模型,按ECE R29要求进行了虚拟试验.经计算分析,提出了改进悬置结构和增加吸能器2种驾驶室结构改进方案,并存仿真分析中得到了验证,为改进该商用车的被动安全性提供了依据.     

薄壁方管在冲击载荷下的应变及应变率特性

在汽车碰撞模拟过程中,材料的应变率效应已经得到越来越多地关注和应用,要求更全面地认识材料应变率效应对模拟结果的影响情况。本文选择具有应变率效应的材料以及薄壁方形管件为研究对象,通过模拟分析验证了材料应变率效应的引入对计算结果的影响,同时分析了冲击载荷下的方管典型区域的有效塑性应变及塑性应变率分布情况。