In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum...In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum response surface method(ERSM) is produced based on the previous deterministic analysis results with the finite element model(FEM). In this work, many key nonlinear factors, such as the dynamic feature of the temperature load, the centrifugal force and the boundary conditions, are taken into consideration for the model. The changing patterns with time of bladed disk assemblies about stress distribution and total deformation are obtained during the deterministic analysis, and at the same time, the largest deformation and stress nodes of bladed disk assemblies are found and taken as input target of probabilistic analysis in a scientific and reasonable way. Not only their reliability, historical sample, extreme response surface(ERS) and the cumulative probability distribution function but also their sensitivity and effect probability are obtained. Main factors affecting stress distribution and total deformation of bladed disk assemblies are investigated through the sensitivity analysis of the model. Finally, compared with the response surface method(RSM) and the Monte Carlo simulation(MCS), the results show that this new approach is effective.展开更多
This paper proposes a new dynamic model for the study of friction-induced self-excited vibration of a disc brake system,where the pad’s motions in both radial and circumferential/tangential directions are included,wh...This paper proposes a new dynamic model for the study of friction-induced self-excited vibration of a disc brake system,where the pad’s motions in both radial and circumferential/tangential directions are included,which is in stark contrast to the previous studies that normally consider the pad’s motion in the tangential/circumferential direction only.The non-smooth dynamics of the system including three different states of motion,i.e.,stick,slip and separation,is investigated.Both the linear stability analysis and the transient dynamic analysis are performed.The numerical results in the linear stability analysis indicate that the inclusion of pad’s radial motion in the present brake model significantly expands the ranges of operating parameters for dynamic instability than the brake model with only circumferential/tangential motion for the pad.For the transient dynamic analysis,two different methods,i.e.,the time integration method and the shooting method,are employed for the calculation of steady-state response.The accuracy and efficiency of the shooting method are subsequently examined.The numerical results show rich bifurcation behaviours of the steady-state response in the present brake model with the variations of brake pressure N_(0) and disc speedΩ,and that k_(ir)(the stiffness of the inclined spring in the radial direction)is a key parameter for controlling the occurrence of chaotic vibration in the system.展开更多
For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalanc...For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings（FRBs）, the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.展开更多
The post-tensioned energy dissipating(PTED)connection for steel frames has drawn many researchers'attention for its good seismic performance.This particular cable is one of the key components of post-tensioned con...The post-tensioned energy dissipating(PTED)connection for steel frames has drawn many researchers'attention for its good seismic performance.This particular cable is one of the key components of post-tensioned connections.However,the value of cable force can decrease due to creep in the cable and anchor systems.To evaluate seismic response by means of transient dynamic analysis,a simplified numerical model with a friction-damped,post-tensioned connection is used.The evolution patterns of the seismic response of friction-damped,post-tensioned steel frames(FDPT),along with a decrease in cable force,is systematically investigated.The interaction mechanisms between structural displacement and post-tensioning force variations were rigorously analyzed by utilizing advanced nonlinear simulations.The influence of initial PT force and friction force are revealed through parametrical analysis.Spectral decomposition techniques were employed to evaluate vibration characteristics across different excitation frequency bands.The results indicate that the intensity of seismic response generally increases with a decrease in cable force,especially for the condition in which the cable force approaches zero.The degradation of cable force caused by the creep of a cable and anchor system should be seriously considered.展开更多
基金Projects(51375032,51175017,51245027)supported by the National Natural Science Foundation of China
文摘In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum response surface method(ERSM) is produced based on the previous deterministic analysis results with the finite element model(FEM). In this work, many key nonlinear factors, such as the dynamic feature of the temperature load, the centrifugal force and the boundary conditions, are taken into consideration for the model. The changing patterns with time of bladed disk assemblies about stress distribution and total deformation are obtained during the deterministic analysis, and at the same time, the largest deformation and stress nodes of bladed disk assemblies are found and taken as input target of probabilistic analysis in a scientific and reasonable way. Not only their reliability, historical sample, extreme response surface(ERS) and the cumulative probability distribution function but also their sensitivity and effect probability are obtained. Main factors affecting stress distribution and total deformation of bladed disk assemblies are investigated through the sensitivity analysis of the model. Finally, compared with the response surface method(RSM) and the Monte Carlo simulation(MCS), the results show that this new approach is effective.
基金supported by the Hong Kong Innovation and Technology Commission(Project No.MRP/030/21 under PiH/026/23)The Chinese University of Hong Kong(Project ID:3134167)the Research Grants Council(Project No.CUHK14211823)of Hong Kong Special Administrative Region,China.
文摘This paper proposes a new dynamic model for the study of friction-induced self-excited vibration of a disc brake system,where the pad’s motions in both radial and circumferential/tangential directions are included,which is in stark contrast to the previous studies that normally consider the pad’s motion in the tangential/circumferential direction only.The non-smooth dynamics of the system including three different states of motion,i.e.,stick,slip and separation,is investigated.Both the linear stability analysis and the transient dynamic analysis are performed.The numerical results in the linear stability analysis indicate that the inclusion of pad’s radial motion in the present brake model significantly expands the ranges of operating parameters for dynamic instability than the brake model with only circumferential/tangential motion for the pad.For the transient dynamic analysis,two different methods,i.e.,the time integration method and the shooting method,are employed for the calculation of steady-state response.The accuracy and efficiency of the shooting method are subsequently examined.The numerical results show rich bifurcation behaviours of the steady-state response in the present brake model with the variations of brake pressure N_(0) and disc speedΩ,and that k_(ir)(the stiffness of the inclined spring in the radial direction)is a key parameter for controlling the occurrence of chaotic vibration in the system.
基金Supported by National Natural Science Foundation of China(Grant Nos.51575176,51375162)Scientific Research Foundation of Hunan Provincial Education Department of China(Grant No.15B085)Postgraduate Innovation Foundation of Hunan University of Science and Technology,China(Grant No.S140020)
文摘For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings（FRBs）, the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.
基金Basic Scientific Research Project of Liaoning Provincial Education Department under Grant No.JYTMS20230795Scientific Research Project of Shaanxi Provincial Transportation Department under Grant No.23-49K+1 种基金Scientific Research Project of Housing and Urban-Rural Development Department of Shaanxi Province under Grant No.2023-K21the Natural Science Foundation of Liaoning Province under Grant No.2022-MS-399。
文摘The post-tensioned energy dissipating(PTED)connection for steel frames has drawn many researchers'attention for its good seismic performance.This particular cable is one of the key components of post-tensioned connections.However,the value of cable force can decrease due to creep in the cable and anchor systems.To evaluate seismic response by means of transient dynamic analysis,a simplified numerical model with a friction-damped,post-tensioned connection is used.The evolution patterns of the seismic response of friction-damped,post-tensioned steel frames(FDPT),along with a decrease in cable force,is systematically investigated.The interaction mechanisms between structural displacement and post-tensioning force variations were rigorously analyzed by utilizing advanced nonlinear simulations.The influence of initial PT force and friction force are revealed through parametrical analysis.Spectral decomposition techniques were employed to evaluate vibration characteristics across different excitation frequency bands.The results indicate that the intensity of seismic response generally increases with a decrease in cable force,especially for the condition in which the cable force approaches zero.The degradation of cable force caused by the creep of a cable and anchor system should be seriously considered.
