In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj...In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.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
Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock ma...Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.展开更多
A kinetic model of the rigid and flexible coupling system for terminally sensitive submunition is set up with Kane's method. The parachute is considered as a flexible body, the flexible displacement is expressed w...A kinetic model of the rigid and flexible coupling system for terminally sensitive submunition is set up with Kane's method. The parachute is considered as a flexible body, the flexible displacement is expressed with modal spread method, the position of the parachute is expressed with a hybrid coordinate method, and the kinematics of the terminally sensitive submunition is analyzed. Ten generalized coordinates relative to the attitude of the terminally sensitive submunition are chosen, and the correlative generalized active forces, the generalized inertial forces, the generalized internal forces are calculated in turn. On the base of the Kane's method, the ten degrees of freedom dynamic equations for the coupled terminally sensitive submunition are finally set up. This model can be used to expediently simulate and analyze accurately the exterior ballistic trajectory of terminally sensitive submunition, and provide the overall design of the terminally sensitive submunition with some helpful references.展开更多
采煤机摇臂壳体是采煤机的重要部件及薄弱环节,其寿命直接影响采煤机的工作性能。为研究采煤机截割复杂煤层时滚筒所受载荷对其摇臂壳体寿命的影响,以MG325型采煤机截割兖州矿区杨村煤矿17层含夹矸煤壁为工程背景,通过虚拟样机技术和离...采煤机摇臂壳体是采煤机的重要部件及薄弱环节,其寿命直接影响采煤机的工作性能。为研究采煤机截割复杂煤层时滚筒所受载荷对其摇臂壳体寿命的影响,以MG325型采煤机截割兖州矿区杨村煤矿17层含夹矸煤壁为工程背景,通过虚拟样机技术和离散单元法-多柔体动力学(Discrete Element Method-Multi Flexible Body Dynamics,DEM-MFBD)双向耦合技术,利用离散元仿真软件EDEM和多体系统动力学仿真软件RecurDyn,基于实际工况获得采煤机螺旋滚筒的外负载。在RecurDyn仿真平台中,建立采煤机摇臂三维实体模型并进行边界条件的设置及摇臂壳体的柔性化,通过软件本身的Durability疲劳耐久分析模块,计算摇臂壳体的疲劳寿命。利用专业绘图软件Origin绘制2个软件后处理的载荷曲线图,发现其走势较为一致,其后处理数据均值,标准差等相接近,证明两者耦合效果较好。结果表明:MG325型采煤机以滚筒转速83.5 r/min,截深600 mm,牵引速度5 m/min截割复杂煤层时,滚筒所受载荷具有较为强烈的载荷波动现象,由等效应力云图可得摇臂壳体的最大等效应力为230.51 MPa,且应力较大处集中位于壳体的各个齿轮轴孔处、凹槽处以及上下耳过渡处,经应力疲劳分析后得其最小寿命位于壳体的齿轮轴孔处,循环次数为8.3215×10~6次。本研究方法可为复杂条件下工矿装备大型结构件的优化设计提供参考。展开更多
Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is stron...Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.展开更多
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
Due to the current trend towards lightweight design in automotive industry,hollow stepped gear shafts for automobile and its radial forging process are widely investigated.Utilizing coupled finite element thermo-mecha...Due to the current trend towards lightweight design in automotive industry,hollow stepped gear shafts for automobile and its radial forging process are widely investigated.Utilizing coupled finite element thermo-mechanical model,radial forging process of a hollow stepped gear shaft for automobile was simulated.The optimal combination of three process parameters including initial temperature,rotation rate and radial reduction was also selected using orthogonal design method.To examine the strain inhomogeneity of the forging workpiece,the strain inhomogeneity factor was introduced.The results reveal that the maximum effective strain and the minimum effective strain appeared in the outermost and innermost zones of different cross sections for the hollow stepped gear shaft,respectively.Optimal forging parameters are determined as a combination of initial temperature of 780°C,rotation rate of 21°/stroke and radial reduction of 3 mm.展开更多
严寒地区冰雪飞溅问题对高速铁路运营安全性有直接影响,现场调研发现多处冰块脱落击打应答器的现象,而国内外对此研究尚未见文献报道。采用基于离散元-多柔性体动力学-计算流体力学(discrete element method-multi flexible body dynami...严寒地区冰雪飞溅问题对高速铁路运营安全性有直接影响,现场调研发现多处冰块脱落击打应答器的现象,而国内外对此研究尚未见文献报道。采用基于离散元-多柔性体动力学-计算流体力学(discrete element method-multi flexible body dynamics-computational fluid dynamics, DEM-MFBD-CFD)耦合分析法,建立车厢底板结冰脱落击打应答器模型,并借助风洞和现场试验结果,验证了模型的可靠性;基于建立的分析模型研究不同列车速度、风压变化、冰块质量等因素对应答器击打的受力影响。结果表明:应答器受到的最大应力随列车运行速度呈现幂函数增长关系,当行车速度增大到350 km/h时,最大应力达15.591 MPa,约为150 km/h时的3.5倍;且随冰块质量增加应答器最大应力呈现先迅速增加后缓慢增长趋势;当横风风速为5~20 m/s作用时,应答器表面所受到的最大应力相差不大,表明横风对冰雪击打应答器作用可忽略不计;为减小冰雪飞溅击打应答器危害,可采取除融雪手段、列车降速等措施。展开更多
In order to solve the disadvantages caused by mechanical slide rheostat that has big errors and low precision,a novel voltage regulation method for high voltage DC power supply was introduced.The key of this method we...In order to solve the disadvantages caused by mechanical slide rheostat that has big errors and low precision,a novel voltage regulation method for high voltage DC power supply was introduced.The key of this method were digital potentiometer MAXIM 5455 and linear photoelectric coupling LOC110,and application programs were compiled using Visual Basic which was graphical compiling language,furthermore the communication between exterior and computer was carried out by ICP7044D module,in consequence the output value of high voltage DC power supply could be regulated with computer.The measured results showed that this method could accurately,conveniently and rapidly regulate the output value of high voltage DC power supply.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supported by the National Natural Science Foundation of China(Grant Nos.U2141254 and U23B6009)。
文摘In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.
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.
基金Project(2010CB732101) supported by the National Basic Research Program of ChinaProjects(51079145,51379201) supported by the National Natural Science Foundation of China
文摘Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.
文摘A kinetic model of the rigid and flexible coupling system for terminally sensitive submunition is set up with Kane's method. The parachute is considered as a flexible body, the flexible displacement is expressed with modal spread method, the position of the parachute is expressed with a hybrid coordinate method, and the kinematics of the terminally sensitive submunition is analyzed. Ten generalized coordinates relative to the attitude of the terminally sensitive submunition are chosen, and the correlative generalized active forces, the generalized inertial forces, the generalized internal forces are calculated in turn. On the base of the Kane's method, the ten degrees of freedom dynamic equations for the coupled terminally sensitive submunition are finally set up. This model can be used to expediently simulate and analyze accurately the exterior ballistic trajectory of terminally sensitive submunition, and provide the overall design of the terminally sensitive submunition with some helpful references.
文摘采煤机摇臂壳体是采煤机的重要部件及薄弱环节,其寿命直接影响采煤机的工作性能。为研究采煤机截割复杂煤层时滚筒所受载荷对其摇臂壳体寿命的影响,以MG325型采煤机截割兖州矿区杨村煤矿17层含夹矸煤壁为工程背景,通过虚拟样机技术和离散单元法-多柔体动力学(Discrete Element Method-Multi Flexible Body Dynamics,DEM-MFBD)双向耦合技术,利用离散元仿真软件EDEM和多体系统动力学仿真软件RecurDyn,基于实际工况获得采煤机螺旋滚筒的外负载。在RecurDyn仿真平台中,建立采煤机摇臂三维实体模型并进行边界条件的设置及摇臂壳体的柔性化,通过软件本身的Durability疲劳耐久分析模块,计算摇臂壳体的疲劳寿命。利用专业绘图软件Origin绘制2个软件后处理的载荷曲线图,发现其走势较为一致,其后处理数据均值,标准差等相接近,证明两者耦合效果较好。结果表明:MG325型采煤机以滚筒转速83.5 r/min,截深600 mm,牵引速度5 m/min截割复杂煤层时,滚筒所受载荷具有较为强烈的载荷波动现象,由等效应力云图可得摇臂壳体的最大等效应力为230.51 MPa,且应力较大处集中位于壳体的各个齿轮轴孔处、凹槽处以及上下耳过渡处,经应力疲劳分析后得其最小寿命位于壳体的齿轮轴孔处,循环次数为8.3215×10~6次。本研究方法可为复杂条件下工矿装备大型结构件的优化设计提供参考。
文摘Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.
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(51774054,51974050)supported by the National Natural Science Foundation of China。
文摘Due to the current trend towards lightweight design in automotive industry,hollow stepped gear shafts for automobile and its radial forging process are widely investigated.Utilizing coupled finite element thermo-mechanical model,radial forging process of a hollow stepped gear shaft for automobile was simulated.The optimal combination of three process parameters including initial temperature,rotation rate and radial reduction was also selected using orthogonal design method.To examine the strain inhomogeneity of the forging workpiece,the strain inhomogeneity factor was introduced.The results reveal that the maximum effective strain and the minimum effective strain appeared in the outermost and innermost zones of different cross sections for the hollow stepped gear shaft,respectively.Optimal forging parameters are determined as a combination of initial temperature of 780°C,rotation rate of 21°/stroke and radial reduction of 3 mm.
基金Project Supported by National Natural Science Foundation of China（50637020）.
文摘In order to solve the disadvantages caused by mechanical slide rheostat that has big errors and low precision,a novel voltage regulation method for high voltage DC power supply was introduced.The key of this method were digital potentiometer MAXIM 5455 and linear photoelectric coupling LOC110,and application programs were compiled using Visual Basic which was graphical compiling language,furthermore the communication between exterior and computer was carried out by ICP7044D module,in consequence the output value of high voltage DC power supply could be regulated with computer.The measured results showed that this method could accurately,conveniently and rapidly regulate the output value of high voltage DC power supply.
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。
