Circuit racing,track texture,temperature and rubber friction

ABSTRACT

Some general observations relating to tyre shear forces and road surfaces are followed by more specific considerations from circuit racing. The discussion then focuses on the mechanics of rubber friction. The classical experiments of Grosch are outlined and the interpretations that can be put on them are discussed. The interpretations involve rubber viscoelasticity, so that the vibration properties of rubber need to be considered. Adhesion and deformation mechanisms for energy dissipation at the interface between rubber and road and in the rubber itself are highlighted. The enquiry is concentrated on energy loss by deformation or hysteresis subsequently. Persson's deformation theory is outlined and the material properties necessary to apply the theory to Grosch's experiments are discussed. Predictions of the friction coefficient relating to one particular rubber compound and a rough surface are made using the theory and these are compared with the appropriate results from Grosch. Predictions from Persson's theory of the influence of nominal contact pressure on the friction coefficient are also examined. The extent of the agreement between theory and experiment is discussed. It is concluded that there is value in the theory but that it is far from complete. There is considerable scope for further research on the mechanics of rubber friction.     

Performance evaluation of slim low-risk-deployment dual-type passenger airbag system with dispersed inflation pressure

Motor vehicle passenger airbags have been proven to be effective for reducing the possibility of passenger injury during a crash. However, the inflation of the airbag sometimes causes serious injury when a passenger is positioned close to the airbag. The United States Federal Motor Vehicle Safety Standard (FMVSS) 208 requires the use of a low-riskdeployment (LRD) passenger airbag system. This paper proposes a newly developed airbag system comprising two slim airbags mounted on the instrument panel. A series of tests were conducted using the FMVSS 208 test procedures to demonstrate the effectiveness of the proposed system. It was found that the system not only satisfied the injury criteria of FMVSS 208, but was also effective for protecting passengers of all sizes.     

多功能远洋渔船主推进系统和电站配置研究综述

明确了多功能远洋渔船的发展前景及意义,结合中国远洋渔船发展现状提出了中国多功能远洋渔船主推进系统设计的四种可行性方案。分析了典型的多功能远洋渔船运行工况,并以此为基础给出了柴油机推进方案,电力推进方案,轴带发电机方案,以及混合电力推进方案研究方法。强调了每种设计方案的重点,并分析了每种方案优缺点,为后继开展更为深入的研究和实际工程应用提供了借鉴与参考。     

宏基因组学及其技术的研究进展

宏基因组学是研究生态群体基因功能和其相互作用的新科学领域,以特定生态环境中微小生物遗传物质的总和作为研究对象,基本研究策略是通过克隆、异源表达,筛选出有用的新基因及其产物。宏基因组学为生命学科和药学研究提供了一个强有力的新技术,并在包括医学在内的许多领域取得了新成就。本述评对宏基因组学的概念、技术和应用作了简要介绍。     

Two- and three-dimensional hydroelastic modelling of a bulker in regular waves

The relatively high rates of bulk carrier casualties in recent years, as well as structural features such as large deck openings, make this vessel type a suitable example for investigating the influence of hydroelastic modelling on predicting wave-induced loads and responses. Two- and three-dimensional fluid–flexible structure interaction models, due to their different degree of complexity and associated data requirements, can be used at different stages of the design process when estimating wave-induced loads, namely preliminary and detailed design stages, respectively.

In this paper, therefore, two- and three-dimensional hydroelasticity theories are applied to predict and compare the dynamic behaviour of a bulk carrier hull, based on OBO MV Derbyshire, in waves. Both symmetric and antisymmetric motions and distortions are incorporated in these investigations. The three-dimensional structural model consists entirely of shell finite elements, representing all major external and internal structural components, whilst the two-dimensional model is generated using Timoshenko beam finite element and finite difference discretisations. Issues relevant to the structural modelling stage, for both idealisations, are discussed. The in vacuo dynamic characteristics are compared for all models, with particular emphasis on the influence of hatch openings, shear centre and warping on the antisymmetric dynamics of the structure. For the wet analysis the fluid–flexible structure interaction is carried out using two-dimensional (Timoshenko beam and strip theory) and three-dimensional (beam and shell finite element idealisations combined with potential flow analysis based on pulsating source distribution over the mean wetted surface) analyses. Comparisons are made between steady-state responses predicted by two- and three-dimensional models in bow quartering regular waves.

It is shown that whereas the predicted symmetric dynamic responses obtained from two- and three-dimensional models are in good agreement, differences are observed for the antisymmetric dynamic characteristics. It is thought that this may be due to inadequacies in the beam models employed when simulating the global dynamic behaviour of this highly non-prismatic hull girder whilst allowing for the effects of warping.     

Bayesian kriging regression for the accuracy improvement of beam modeled T-junctions of buses and coaches structures with a methodology based on FEM behavioral analysis

This paper has been developed in the framework of the alternative beam T-junction solution previously propoused by the authors (Alcalá et al., 2013), with the scope of optimizing the behavior of buses and coaches upper structures modeled with beam type elements. The alternative beam T-junction model proposed by the authors, had a total of six elastic elements at the junction level allowing to modify the localized rigidity of any modeled T-junctions, therefore improving their behavior and avoiding the well known rigidity issue these elements have. A fundamental aspect behind the use of these alternative beam models is related to the necessity of correctly estimating the rigidity values of the elastic elements for each modeled T-junction. In this context, we propose applying a surrogate model for the reference calculations which is based on statistical Bayesian kriging predictors. Statistical predictions have the added value, with respect to deterministic solutions, of providing a quantification of uncertainty. The development of the kriging predictors has required the application of a statistical methodology including computer experiment design, computation of moments of inertia, graphical and Entry&sortOrder=relevance' class='reference-link webtrekk-track' gaCategory="internal-link" gaLabel="ANOVA" gaAction="reference keyword">ANOVA type sensitivity analysis and Monte Carlo computation of Bayesian inference. The results of the application have been a very satisfactory trade-off between accuracy of approximation (prediction) and computational cost. The surrogate kriging models also provide an useful tool for a better understanding of the input-output relationships involved in the reference computations.     

Evaluation of safety benefits of automatic crash information notification systems on freeways

The automatic crash information notification system (ACINS) is an effective technology to enhance the potential for saving crash victims by reducing the crash response time (CRT) of emergency medical services. Shorter CRT results in a greater potential to save the lives and to alleviate the severity of injuries for crash victims. To fully operate the ACINS, reliable assessments of the safety benefits would be needed for justifying public investment. This study proposed a methodology for quantifying the effectiveness of the ACINS and applied the methodology to the Korean freeway system. The proposed methodology consists of three steps. The first step is to develop a statistical model for predicting injury severity of crash victims using ordered logistic regression. The second step is to estimate the amount of reduced CRT by applying ACINS. The effectiveness of the ACINS, which are defined as the number of reduced fatalities and severe injuries, were evaluated with the consideration of the market penetration rate (MPR) in third step. It has been found that approximately 9.4–15.4% of fatalities can be reduced with 100% MPR when the proposed methodology is applied to 2011 freeway crash data. The outcomes of this study support decision making for public investments and for establishing relevant traffic safety policies.     

竖井对高铁隧道内接触网风致振动的影响

高速铁路接触网属于复杂的空间耦联体系,其支持结构一直是我国高速铁路系统的薄弱环节.为给高铁隧道内接触网的设计和施工进一步提供理论依据,基于三维不可压缩N-S方程和标准k-ε两方程湍流模型理论,建立隧道-竖井-列车-空气三维CFD数值模型.基于ANSYS Workbench平台,结合流固耦合计算方法等手段,确定竖井对交叉...