美国通用汽车公开“雪佛兰(Chevrolet)HHR”2006年款的图片,该车为将于2005年上市的新型多功能轿车(Cross-over Vehicle)。HHR是Heritage High Roof的简称.以1940年代后半期由雪佛兰制造的车辆为主题,并融合了“Suburban”1949年款式和...美国通用汽车公开“雪佛兰(Chevrolet)HHR”2006年款的图片,该车为将于2005年上市的新型多功能轿车(Cross-over Vehicle)。HHR是Heritage High Roof的简称.以1940年代后半期由雪佛兰制造的车辆为主题,并融合了“Suburban”1949年款式和现行“SSR”的设计。HHR将从2005年夏开始生产,将加入2005年款“Cobalt”和2004年款“Aveo”等的小型车产品线。展开更多
Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameter...Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameters had been made. Fractal geometry was introduced in the present work to accurately simulate transect contour curves of pervious concrete specimens through fractal interpolation. It is proved that its fractal dimension (D) can be adopted to measure the skid resistance on pervious concrete pavement, overcoming the shortcomings of both macrotexture depth (DT ) and British portable pendulum number (NBP). Combined with Fujikawa-Koike tire/road contact model, the optimization method of all surface textures was recommended for designing and constructing excellently skid-resistant and noise-absorptive pervious concrete pavement. In addition, evaluating of the abrasion process and attenuation of the surface textures on concrete pavement slabs was also the focus of this work based on accelerated abrasion test. Results show that the surface textures on pervious concrete pavement slabs is extremely durable, compared to those on conventional grooved or exposed aggregate concrete pavement slabs.展开更多
This paper covers why measurements at various speeds with CFME （continuous friction measurement equipment） are not able to measure the speed-friction gradient of the pavement as determined by the macro-textural feat...This paper covers why measurements at various speeds with CFME （continuous friction measurement equipment） are not able to measure the speed-friction gradient of the pavement as determined by the macro-textural features of the surface. Most CFMEs measure friction in the slip ratio range of 10% to 18%. In this range, it is shown that the friction versus slip speed of these devices are mainly determined by the coupled properties of the surface micro-texture and relevant tire properties and to a minimal extent only by pavement macro-texture properties. The determinacy of low slip ratio friction measurements on the macro-textural features of the pavement surface are shown to be so low that they are inadequate to capture macro-texture caused speed degradation of friction. It is also shown in the paper that close to 100% slip ratio measurements at a relatively wide speed scale or direct macro texture measurements are needed to adequately determine the speed gradient if friction caused by the pavement macro-texture. The data and analysis in this paper provide strong and compelling evidence that the EFI （European Friction Index） or EFI developed by the HERMES （Harmonization of European Routine and Research Measuring Equipment for Skid Resistance） project sponsored by FEHRL （Forum of European National Highway Research Laboratories） is strongly affected by the lack of consideration of this phenomenon. It is recommended that the results of the HERMES project are reviewed taking into account the findings of the present paper. Based on the results of the presented paper it is suggested that CFME＇s only measure friction at a fixed speed with a standard tire and use a macro-texture measuring device to obtain the pavement speed gradient.展开更多
文摘美国通用汽车公开“雪佛兰(Chevrolet)HHR”2006年款的图片,该车为将于2005年上市的新型多功能轿车(Cross-over Vehicle)。HHR是Heritage High Roof的简称.以1940年代后半期由雪佛兰制造的车辆为主题,并融合了“Suburban”1949年款式和现行“SSR”的设计。HHR将从2005年夏开始生产,将加入2005年款“Cobalt”和2004年款“Aveo”等的小型车产品线。
基金Project(kfj080205) supported by Key Laboratory of Road Structure and Material of Ministry of Transport of Changsha, China
文摘Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameters had been made. Fractal geometry was introduced in the present work to accurately simulate transect contour curves of pervious concrete specimens through fractal interpolation. It is proved that its fractal dimension (D) can be adopted to measure the skid resistance on pervious concrete pavement, overcoming the shortcomings of both macrotexture depth (DT ) and British portable pendulum number (NBP). Combined with Fujikawa-Koike tire/road contact model, the optimization method of all surface textures was recommended for designing and constructing excellently skid-resistant and noise-absorptive pervious concrete pavement. In addition, evaluating of the abrasion process and attenuation of the surface textures on concrete pavement slabs was also the focus of this work based on accelerated abrasion test. Results show that the surface textures on pervious concrete pavement slabs is extremely durable, compared to those on conventional grooved or exposed aggregate concrete pavement slabs.
文摘This paper covers why measurements at various speeds with CFME （continuous friction measurement equipment） are not able to measure the speed-friction gradient of the pavement as determined by the macro-textural features of the surface. Most CFMEs measure friction in the slip ratio range of 10% to 18%. In this range, it is shown that the friction versus slip speed of these devices are mainly determined by the coupled properties of the surface micro-texture and relevant tire properties and to a minimal extent only by pavement macro-texture properties. The determinacy of low slip ratio friction measurements on the macro-textural features of the pavement surface are shown to be so low that they are inadequate to capture macro-texture caused speed degradation of friction. It is also shown in the paper that close to 100% slip ratio measurements at a relatively wide speed scale or direct macro texture measurements are needed to adequately determine the speed gradient if friction caused by the pavement macro-texture. The data and analysis in this paper provide strong and compelling evidence that the EFI （European Friction Index） or EFI developed by the HERMES （Harmonization of European Routine and Research Measuring Equipment for Skid Resistance） project sponsored by FEHRL （Forum of European National Highway Research Laboratories） is strongly affected by the lack of consideration of this phenomenon. It is recommended that the results of the HERMES project are reviewed taking into account the findings of the present paper. Based on the results of the presented paper it is suggested that CFME＇s only measure friction at a fixed speed with a standard tire and use a macro-texture measuring device to obtain the pavement speed gradient.
