Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduce...Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduced a computational model for analyzing probabilistic dynamic responses of three-dimensional(3D)coupled train-ballasted track-subgrade system(TBTSS),where the coupling effects of uncertain rail irregularities,stiffness and damping properties of ballast and subgrade layers were simultaneously considered.The number theoretical method(NTM)was employed to design discrete points for the multi-dimensional stochastic parameters.The time-histories of stochastic dynamic vibrations of the TBSS with systematically uncertain structural parameters were calculated accurately and efficiently by employing the probability density evolution method(PDEM).The model-predicted results were consistent with those by the Monte Carlo simulation method.A sensitivity study was performed to assess the relative importance of those uncertain structural parameters,based on which a case study was presented to explore the stochastic probability evolution mechanism of such train-ballasted track-subgrade system.展开更多
A model of vibrating device coupling two pendulums (VDP) which is highly nonlinear was put forward to conduct vibration analysis. Based on energy analysis, dynamic equations with cubic nonlinearities were established ...A model of vibrating device coupling two pendulums (VDP) which is highly nonlinear was put forward to conduct vibration analysis. Based on energy analysis, dynamic equations with cubic nonlinearities were established using Lagrange's equation. In order to obtain approximate solution, multiple time scales method, one of perturbation technique, was applied. Cases of non-resonant and 1:1:2:2 internal resonant were discussed. In the non-resonant case, the validity of multiple time scales method is confirmed, comparing numerical results derived from fourth order Runge-Kutta method with analytical results derived from first order approximate expression. In the 1:1:2:2 internal resonant case, modal amplitudes of Aa1 and Ab2 increase, respectively, from 0.38 to 0.63 and from 0.19 to 0.32, while the corresponding frequencies have an increase of almost 1.6 times with changes of initial conditions, indicating the existence of typical nonlinear phenomenon. In addition, the chaotic motion is found under this condition.展开更多
近年来,部分特高压换流变压器在运行中相继发生电弧短路故障并引发爆炸、起火事故,严重威胁直流系统安全稳定运行。充油设备故障冲击下的结构失效机制尚不明确,且缺乏成熟的数值计算方法,制约故障防爆技术的发展。基于此,该文提出一套...近年来,部分特高压换流变压器在运行中相继发生电弧短路故障并引发爆炸、起火事故,严重威胁直流系统安全稳定运行。充油设备故障冲击下的结构失效机制尚不明确,且缺乏成熟的数值计算方法,制约故障防爆技术的发展。基于此,该文提出一套适用于高能电弧故障冲击的结构失效仿真计算方法。首先,建立有限腔体内油中电弧能量持续注入的气泡动力学模型,准确描述故障气泡的脉动膨胀行为;其次,提出自适应有限元-光滑粒子流体动力学(finite element method-smoothed particle hydrodynamics,FEM-SPH)耦合方法,利用SPH粒子继承失效前的物理信息参与FEM计算;进行不同能量、不同位置的电弧故障仿真计算,获得换流变压器结构的薄弱区域及其破裂行为,复现了油箱结构失效行为。研究发现,油箱顶盖两侧及侧壁转角接缝位置容易发生应力集中现象。一旦结构出现裂缝,将在极短时间内沿着应力集中方向快速发展,最终导致壁面整体撕裂。可知,该方法揭示的结构失效行为可为改进变压器设计和提高设备安全性提供依据。展开更多
基金Projects(51708558,51878673,U1734208,52078485,U1934217,U1934209)supported by the National Natural Science Foundation of ChinaProject(2020JJ5740)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(KF2020-03)supported by the Key Open Fund of State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures,ChinaProject(2020-Special-02)supported by the Science and Technology Research and Development Program of China Railway Group Limited。
文摘Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduced a computational model for analyzing probabilistic dynamic responses of three-dimensional(3D)coupled train-ballasted track-subgrade system(TBTSS),where the coupling effects of uncertain rail irregularities,stiffness and damping properties of ballast and subgrade layers were simultaneously considered.The number theoretical method(NTM)was employed to design discrete points for the multi-dimensional stochastic parameters.The time-histories of stochastic dynamic vibrations of the TBSS with systematically uncertain structural parameters were calculated accurately and efficiently by employing the probability density evolution method(PDEM).The model-predicted results were consistent with those by the Monte Carlo simulation method.A sensitivity study was performed to assess the relative importance of those uncertain structural parameters,based on which a case study was presented to explore the stochastic probability evolution mechanism of such train-ballasted track-subgrade system.
基金Projects(50574091, 50774084) supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions+1 种基金Project(CXLX12_0949) supported by Research and Innovation Project for College Graduates of Jiangsu Province, ChinaProject(2013DXS03) supported by the Fundamental Research Funds for the Central Universities, China
文摘A model of vibrating device coupling two pendulums (VDP) which is highly nonlinear was put forward to conduct vibration analysis. Based on energy analysis, dynamic equations with cubic nonlinearities were established using Lagrange's equation. In order to obtain approximate solution, multiple time scales method, one of perturbation technique, was applied. Cases of non-resonant and 1:1:2:2 internal resonant were discussed. In the non-resonant case, the validity of multiple time scales method is confirmed, comparing numerical results derived from fourth order Runge-Kutta method with analytical results derived from first order approximate expression. In the 1:1:2:2 internal resonant case, modal amplitudes of Aa1 and Ab2 increase, respectively, from 0.38 to 0.63 and from 0.19 to 0.32, while the corresponding frequencies have an increase of almost 1.6 times with changes of initial conditions, indicating the existence of typical nonlinear phenomenon. In addition, the chaotic motion is found under this condition.
文摘近年来,部分特高压换流变压器在运行中相继发生电弧短路故障并引发爆炸、起火事故,严重威胁直流系统安全稳定运行。充油设备故障冲击下的结构失效机制尚不明确,且缺乏成熟的数值计算方法,制约故障防爆技术的发展。基于此,该文提出一套适用于高能电弧故障冲击的结构失效仿真计算方法。首先,建立有限腔体内油中电弧能量持续注入的气泡动力学模型,准确描述故障气泡的脉动膨胀行为;其次,提出自适应有限元-光滑粒子流体动力学(finite element method-smoothed particle hydrodynamics,FEM-SPH)耦合方法,利用SPH粒子继承失效前的物理信息参与FEM计算;进行不同能量、不同位置的电弧故障仿真计算,获得换流变压器结构的薄弱区域及其破裂行为,复现了油箱结构失效行为。研究发现,油箱顶盖两侧及侧壁转角接缝位置容易发生应力集中现象。一旦结构出现裂缝,将在极短时间内沿着应力集中方向快速发展,最终导致壁面整体撕裂。可知,该方法揭示的结构失效行为可为改进变压器设计和提高设备安全性提供依据。
