Estimation of wheel–rail friction for vehicle certification

In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. However, in associated test runs the wheel–rail friction condition is difficult to handle because the friction coefficient needs to be fairly high and the friction is also generally hard to assess. This is an issue that has been studied in the European project DynoTRAIN and part of the results is presented in this paper. More specifically, an algorithm for estimating the wheel–rail friction coefficient at vehicle certification tests is proposed. Owing to lack of some measurement results, the algorithm here is evaluated in a simulation environment which is also an important step towards practical implementation. A quality measure of the friction estimate is suggested in terms of estimated wheel–rail spin and total creep. It is concluded that, tentatively, the total creep should exceed 0.006 and the spin should be less than 1.0 m^?1 for the algorithm to give a good friction estimate. Sensitivity analysis is carried out to imitate measurement errors, but should be expanded in further work.     

老旧散货船营运缺陷与管理探讨

针对老旧散货船在营运中安全问题,阐述了加强老旧散货船的营运管理,做好安全防范,采取正确的管理措施是确保船舶营运安全的前提。重点探讨了老旧散货船的营运缺陷,分析了缺陷可能产生的后果,提出了营运中应采取的管理措施及建议。     

A railway vehicle multibody model for real-time applications

Hardware in the loop (HIL) techniques are widely used for fast prototyping of control systems, electronic and mechatronic devices. In the railway field, several mechatronic on board subsystems are often tested and calibrated following the HIL approach. The accuracy of HIL tests depends on how the simulated virtual environment approximates the physical conditions. As the computational power available on real-time hardware grows, the demand for more complex and realistic models of railway vehicles for real-time application increases. In past research activities, the authors worked on the implementation of simplified real-time models for several applications and in particular for an HIL test rig devoted to the type approval of wheel slide protection systems. The activity has then been focused on the development of a three-dimensional model of the dynamics of a railway vehicle for more complex applications. The paper summarises the features and the results of the study.     

双垂直线路桥大型箱梁运输施工技术

为满足施工需要,根据现场实际情况对两种施工方案进行比对分析,选择了小半径大角度转弯运输箱梁的方案。通过对传统轮胎式运梁小车改进,特制出五轴轮胎式运梁小车。采用该运梁小车成功解决了大吨位大跨度大型箱梁在小转弯半径上实现大角度转弯的技术难题。结果表明,特制五轴轮胎式运梁小车是解决狭小施工场地内大角度运梁的有效方法。     

Handling performance control for hybrid 8-wheel-drive vehicle and simulation verification

In order to improve handling performance of a hybrid 8-Wheel-Drive vehicle, the handling performance control strategy was proposed. For armoured vehicle, besides handling stability in high speed, the minimum steer radius in low speed is also a key tactical and technical index. Based on that, the proposed handling performance control strategy includes ‘Handling Stability’ and ‘Radius Minimization’ control modes. In ‘Handling Stability’ control mode, ‘Neutralsteer Radio’ is defined to adjust the steering characteristics to satisfy different demand in different speed range. In ‘Radius Minimization’ control mode, the independent motors are controlled to provide an additional yaw moment to decrease the minimum steer radius. In order to verify the strategy, a simulation platform was built including engine and continuously variable transmission systems, generator and battery systems, independent motors and controllers systems, vehicle dynamic and tyre mechanical systems. The simulation results show that the handling performance of the vehicle can be enhanced significantly, and the minimum steer radius can be decreased by 20% which is significant improvement compared to the common level of main battle armoured vehicle around the world.     

赛车轮毂多功能集成化设计新方法

由于传统制造工艺在复杂曲面和集成化加工的局限性,导致方程式赛车轮毂的多功能集成化一直被制约,以至于传统赛车轮毂总成普遍存在体积硕大、重量大、传动效率低等问题。文章基于集成化设计原则,在保留传统赛车轮毂总成所需功能的前提下,改变赛车外球笼、轮毂、轮辐等的结构以进行集成化设计从而得到多功能集成化赛车轮毂。所获得的集成化赛车轮毂体积重量明显减小且传动效率明显提高,达到了通过集成化以实现轻量化的目标。     

机械差速器耦合轮对轨道车辆导向性能分析

目前对称样式的差速器广泛应用于旋转车轮轨道车辆中,左右车轮差速控制的装置,成为时下研究的一个热点问题。研究学者在动力学的基础上对机械差速耦合轮对运行车辆的影响建立了模型进行分析,其中包含刚性的车轮和独立旋转的车轮,通过模型分析对比研究了机械差速耦合轮对车辆直线和曲线行驶导向性能的研究。研究发现,机械差速耦合装置独立旋转的车轮在车轮在复位对中有着积极的影响,对独立车轮导向能力差有了很好的解决办法。和刚性车轮进行比较,机械差速在通过性能上有着更好的安全性和导向性能。在城市轨道交通领域有着很好的应用。文章通过讨论车轮导向的原理,研究了机械差速耦合装置对轨道交通车辆导向性能的影响。     

引汉济渭秦岭隧洞高磨蚀性硬岩TBM滚刀磨损试验研究

引汉济渭工程秦岭输水隧洞TBM掘进施工在试掘进段因遭遇高磨蚀性硬岩地层,滚刀发生严重磨损,致使施工进度严重滞后。为降低刀具磨损,节约施工成本,加快施工进度,必须对刀具磨损进行准确预测。针对高磨蚀性地层,开展滚刀磨损预测研究; 通过课题组前期研究结果,建立滚刀磨损理论预测模型; 通过室内实验,建立滚刀磨损实验预测模型; 通过现场试验,对室内实验模型及课题组前期研究建立的理论预测模型进行验证。结果表明,实验预测结果具有较高的准确性,相对误差在10%以内。     

Sensitivity of the wheel–rail contact interactions and Dang Van Fatigue Index in the rail with respect to irregularities of the track geometry

This paper investigates the effects of the track geometry irregularities on the wheel–rail dynamic interactions and the rail fatigue initiation through the application of the Dang Van criterion, that supposes an elastic shakedown of the structure. The irregularities are modelled, using experimental data, as a stochastic field which is representative of the considered railway network. The tracks thus generated are introduced as the input of a railway dynamics software to characterise the stochastic contact patch and the parameters on which it depends: contact forces and wheelset–rail relative position. A variance-based global sensitivity analysis is performed on quantities of interest representative of the dynamic behaviour of the system, with respect to the stochastic geometry irregularities and for different curve radius classes and operating conditions. The estimation of the internal stresses and the fatigue index being more time-consuming than the dynamical simulations, the sensitivity analysis is performed through a metamodel, whose input parameters are the wheel–rail relative position and velocity. The coefficient of variation of the number of fatigue cycles, when the simulations are performed with random geometry irregularities, varies between 0.13 and 0.28. In a large radius curve, the most influent irregularity is the horizontal curvature, while, in a tight curve, the gauge becomes more important.     

A linear complementarity method for the solution of vertical vehicle–track interaction

A new method is proposed for the solution of the vertical vehicle–track interaction including a separation between wheel and rail. The vehicle is modelled as a multi-body system using rigid bodies, and the track is treated as a three-layer beam model in which the rail is considered as an Euler-Bernoulli beam and both the sleepers and the ballast are represented by lumped masses. A linear complementarity formulation is directly established using a combination of the wheel–rail normal contact condition and the generalised-α method. This linear complementarity problem is solved using the Lemke algorithm, and the wheel–rail contact force can be obtained. Then the dynamic responses of the vehicle and the track are solved without iteration based on the generalised-α method. The same equations of motion for the vehicle and track are adopted at the different wheel–rail contact situations. This method can remove some restrictions, that is, time-dependent mass, damping and stiffness matrices of the coupled system, multiple equations of motion for the different contact situations and the effect of the contact stiffness. Numerical results demonstrate that the proposed method is effective for simulating the vehicle–track interaction including a separation between wheel and rail.