Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. ...Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.展开更多
With TEM、SEM, various high temperature deformed structures in W9Mo3Cr4V steel were investigated. The sub structures,recrystallized nuclei, as well as the dynamic precipitation were also studied and analyzed. The r...With TEM、SEM, various high temperature deformed structures in W9Mo3Cr4V steel were investigated. The sub structures,recrystallized nuclei, as well as the dynamic precipitation were also studied and analyzed. The relationship between recrystallized structures and dynamic precipitation was discussed. The results showed that the deformed structures in W9Mo3Cr4V steel are more complicated than those in low alloy steels. Because W9Mo3Cr4V steel is a high speed steel, there are a large number of residual carbides on the matrix. Also, much dynamic precipitating carbides will precipitate during deformation at high temperature.展开更多
高温超导磁悬浮(High Temperature Superconducting,HTS)列车因其自悬浮导向自稳定特性被认为是未来超高速交通运输中较为理想的运行方式之一。作为高温超导磁悬浮列车最重要的部件之一,悬浮架的结构至关重要。因此有必要对不同方案的...高温超导磁悬浮(High Temperature Superconducting,HTS)列车因其自悬浮导向自稳定特性被认为是未来超高速交通运输中较为理想的运行方式之一。作为高温超导磁悬浮列车最重要的部件之一,悬浮架的结构至关重要。因此有必要对不同方案的悬浮架结构建立车桥耦合模型,从运行平稳性、舒适度、振动传递率等方面对不同结构设计的悬浮架进行对比。研究结果表明:3种结构的悬浮架在动力学性能方面存在一定共性,双层悬浮架结构下车辆平稳性与舒适度指标更好,双层结构受空簧刚度影响最大。垂向减振器阻尼对3种结构的振动传递率影响均为阻尼越大,低频传递率越低,高频传递率越高。在车辆动态载荷作用下,桥梁跨中垂向位移的变化均为先略有上翘再下挠,而后呈现较大幅度的上翘与下挠,最后恢复正常。双层结构的悬浮架引起的桥梁跨中垂向加速度变化最为平顺。单层结构的悬浮架产生的跨中垂向加速度明显大于其余2种结构。桥梁的上挠随着车辆运行速度的增加呈现增大趋势,桥梁的下挠则是速度越大垂向位移越小。所得的结果是在特定的结构参数、负载条件下的仿真分析结果,可以为高温超导磁悬浮列车悬浮架结构的设计与选择提供一定的参考。展开更多
基金Projects(51478484,51308551,51678571)supported by the National Natural Science Foundation of ChinaProject(2016zzts063)supported by Fundamental Research Funds for the Central Universities,China
文摘Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.
基金Project Sponsored by Ministry of Science and Technology of China(G1998061513)
文摘With TEM、SEM, various high temperature deformed structures in W9Mo3Cr4V steel were investigated. The sub structures,recrystallized nuclei, as well as the dynamic precipitation were also studied and analyzed. The relationship between recrystallized structures and dynamic precipitation was discussed. The results showed that the deformed structures in W9Mo3Cr4V steel are more complicated than those in low alloy steels. Because W9Mo3Cr4V steel is a high speed steel, there are a large number of residual carbides on the matrix. Also, much dynamic precipitating carbides will precipitate during deformation at high temperature.
文摘高温超导磁悬浮(High Temperature Superconducting,HTS)列车因其自悬浮导向自稳定特性被认为是未来超高速交通运输中较为理想的运行方式之一。作为高温超导磁悬浮列车最重要的部件之一,悬浮架的结构至关重要。因此有必要对不同方案的悬浮架结构建立车桥耦合模型,从运行平稳性、舒适度、振动传递率等方面对不同结构设计的悬浮架进行对比。研究结果表明:3种结构的悬浮架在动力学性能方面存在一定共性,双层悬浮架结构下车辆平稳性与舒适度指标更好,双层结构受空簧刚度影响最大。垂向减振器阻尼对3种结构的振动传递率影响均为阻尼越大,低频传递率越低,高频传递率越高。在车辆动态载荷作用下,桥梁跨中垂向位移的变化均为先略有上翘再下挠,而后呈现较大幅度的上翘与下挠,最后恢复正常。双层结构的悬浮架引起的桥梁跨中垂向加速度变化最为平顺。单层结构的悬浮架产生的跨中垂向加速度明显大于其余2种结构。桥梁的上挠随着车辆运行速度的增加呈现增大趋势,桥梁的下挠则是速度越大垂向位移越小。所得的结果是在特定的结构参数、负载条件下的仿真分析结果,可以为高温超导磁悬浮列车悬浮架结构的设计与选择提供一定的参考。
