The strong vibration responses of the cab system can be restrained by the damper force and the friction of the suspensions for trucks.After the failures of dampers,especially in the case of the complete failure,the an...The strong vibration responses of the cab system can be restrained by the damper force and the friction of the suspensions for trucks.After the failures of dampers,especially in the case of the complete failure,the anti vibration effect of the friction is prominent.However,the nonlinear vibration response characteristics of the cab subject to the damper complete failure have not been revealed.In order to reveal the nonlinear vibration response characteristics,a dynamic model of the cab system was established and its vibration equations were given.The friction forces existing in the suspensions were determined by the bench test.The influences of the friction forces on the cab vibration under different amplitude harmonic inputs were investigated when the dampers completely fail.The cab vertical displacement changes with the excitation amplitude and the vibration represents various motion states,including the periodic motion,the quasi-periodic motion,and the chaotic motion.The simulation results show that when the dampers fail,the proper friction forces help to suppress the quasi-periodic motion and the chaotic motion of the cab and to reduce the amplitude of the periodic motion.The proper friction forces can make the cab movement far away from the chaos area.They also help to avoid the fatigue damage of the cab floor and suspension parts to improve the service life of the suspension parts and to reduce the maintenance cost of the cab suspensions.展开更多
In order to find out the sensitivity of the thermophysical and structural parameters to the thermodynamic characteristics of twin-tube hydraulic shock absorbers,based on the bench test,a method for calculating the tim...In order to find out the sensitivity of the thermophysical and structural parameters to the thermodynamic characteristics of twin-tube hydraulic shock absorbers,based on the bench test,a method for calculating the time-varying rate of the external work on the shock absorber oil is proposed.And then,a thermodynamic model of the twin-tube hydraulic shock absorber is established by using the basic thermodynamic principles.By analyzing the influence of each parameter on the thermodynamic characteristics of the shock absorber,it can be seen that,the radius of the working cylinder outer wall has the greatest influence on the temperature rise of the shock absorber,followed by the thermal conductivity of the oil,the height of the oil,the heat transfer length of the cylinder barrel,the radius of the oil storage cylinder outer wall,the emissivity of the oil storage cylinder outer wall,the height of the nitrogen,the thermal conductivity of the nitrogen,the specific heat capacity of the oil,the density of the oil,the thermal conductivity of the cylinder,and the mass of the working oil.The kinematic viscosity of the oil has the least influence on the temperature rise of the shock absorber.The research can provide an effective theoretical guidance and reference for the design of the twin-tube hydraulic shock absorber.展开更多
In this paper,using the theoretical analysis method,according to the actual structure of the hanging leaf spring of the traction motor mounted on the frame,the lateral force model of the hanging leaf spring of the tra...In this paper,using the theoretical analysis method,according to the actual structure of the hanging leaf spring of the traction motor mounted on the frame,the lateral force model of the hanging leaf spring of the traction motor was established.Then,through theoretical deduction,the deformation analytical calculation formula and the stress analytical calculation formula of the hanging leaf spring were established.The correctness of the leaf spring’s lateral force model was established and its deformation and stress analytical formulae were verified using ANSYS finite element analysis software.Based on this,according to the deformation analytical formula and the stress analytical formula of the leaf spring established,the influence of the main structural parameters on the mechanical characteristics of the leaf spring was discussed,and the reliability of the analytical analysis method of the lateral mechanical characteristics of the traction motor hanging leaf spring was verified by the loading–unloading test.The results show that the deformation and the load of the leaf spring change linearly.The changes of leaf spring’s stress at different positions can be considered as being composed of three sections:a linear change section in the root,a nonlinear change section in the middle,and a nonlinear change section in the end.In the structural parameters,the end thickness h2 has the greatest influence on the stiffness and the stress of the leaf spring,and the maximum thickness of the leaf spring eye h1 has the least influence on the stiffness and the stress of the leaf spring.The influence degree of other parameters on the stiffness of the leaf spring is h_(3),L_(1),L_(3),L_(2) in order,and the influence degree on the stress of the leaf spring is h_(3),L_(1),L_(2),L_(3) in order.In addition,when the root thickness h_(3) is greater than a certain value,the maximum stress point of the leaf spring appears at the end position L_(2).This study can provide a useful reference for the intelligent forward design and the rapid analysis of the mechanical characteristics of high-speed train traction motor hanging leaf spring.展开更多
To make a rapid comfort assessment and a reasonable dynamic parameters choice of wheelchair robots,this paper proposes a dynamic comfort coefficientκand analytically optimizes the cushion damping.Firstly,a traveling ...To make a rapid comfort assessment and a reasonable dynamic parameters choice of wheelchair robots,this paper proposes a dynamic comfort coefficientκand analytically optimizes the cushion damping.Firstly,a traveling vibration model of the occupantwheelchair system for wheelchair robots running on random roads was created.Secondly,the analytic formula of the occupant RMS(root mean square)acceleration was deduced.Moreover,the dynamic coefficientκwas proposed and its influence laws were revealed.Finally,the cushion system optimal damping ratio was calculated based onκ.The results show that theκvalue is only determined by the parameters of the occupant-wheelchair system.The smaller theκvalue is,the better the dynamic comfort is for wheelchair robots running on random roads.By minimizingκ,the occupant-wheelchair system can achieve a statistically optimal dynamic comfort effect.展开更多
In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively,this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the car...In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively,this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the carriage,and establishes a vertical dynamic model of railway vehicles by considering the influence of the coupling vibration effect between the passenger and the car body.The correctness of the model is verified by the real vehicle test.Then,the influence of the passengers on the vertical vibration characteristics of railway vehicles is analyzed,and the influence of the railway vehicle vibration on the vertical vibration characteristics of passengers is discussed in this paper.The research made in this paper can provide an effective model reference for the analysis of the vertical random vibration characteristics of railway vehicles and passengers,and for the optimization design of the suspension system parameters.展开更多
The friction inevitably exists in the nonlinear suspension system for seats.It affects dynamic characteristics of the seat with the nonlinear suspension system.Analysis of the influences of the friction on the seat vi...The friction inevitably exists in the nonlinear suspension system for seats.It affects dynamic characteristics of the seat with the nonlinear suspension system.Analysis of the influences of the friction on the seat vibration responses is helpful to improve comfort.Moreover,it is also an important part of promoting the industrialization application of the nonlinear suspension system for seats.In order to verify the influences,a model of the seat with the nonlinear suspension system considering friction effects was established by combining experiments.Based on the model,by using the harmonic balance method,the analytical formulas of the seat frequency-domain vibration response considering friction effects were deduced,and the influences of the friction on the frequency response characteristics of the system were simulated and analyzed.Moreover,the influences of the friction on the time-domain response characteristics were investigated.The results show that the existence of the friction can help to reduce the vibration in the peak region and to increase the system stability,however,it is not conducive to the improvement of the seat comfort under random road conditions.展开更多
To define the application fields of the traditional cab system model and the seat–cab coupled model,this paper mainly aims to investigate the differences of the vibration characteristics of the two models.First,the t...To define the application fields of the traditional cab system model and the seat–cab coupled model,this paper mainly aims to investigate the differences of the vibration characteristics of the two models.First,the two models and their motion equations were introduced.Then,based on the mechanical parameters of the seat and cab system for a truck,the transmissibility characteristics of the two models were analyzed.The results show that the traditional model can relatively accurately predict the pitch and roll vibration characteristics of the real seat–cab system.However,it overvalues the vertical vibration transmitted from the front suspensions of the cab.Third,the typical excitation conditions and the measuring points were selected.Finally,under the typical excitation conditions,the dynamic responses of the measuring points were calculated.The results show that under the vertical excitation condition,the dynamic responses of the two models have obvious differences.Under the roll excitation condition and the pitch excitation condition,the roll responses and the pitch responses of the cab between the two models show almost no obvious difference.Under the random excitation condition,the vertical acceleration responses have relatively larger deviations between the two models,however,the angular acceleration responses are almost the same.For the preliminary design of the cab system,the traditional cab system model can be used.However,for the accurate design and the optimization of the seat–cab system,the seat–cab coupled model is recommended.展开更多
The seat-cabin system of fork lift trucks has a great influence on ride comfort.On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck,a seat-cabin system vertical ...The seat-cabin system of fork lift trucks has a great influence on ride comfort.On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck,a seat-cabin system vertical dynamic model was created.The vertical dynamic responses of the model under the random irregularities excitation were calculated.The calculated responses including the seat dynamic response and the cabin dynamic responses at the four corners are very close to the field measurement data and the relative deviations of the(root mean square)RMS acceleration responses are all less than 6.0%.The results show that the vertical dynamic model is acceptable and can truly describe the basic mechanical behavior of the seat-cabin system.The model provides a good basis for investigating the relations between the dynamic parameters and the vibration attenuation characteristics of the seat-cabin system to further improve ride comfort.展开更多
基金supported by the National Natural Science Foundation of China(51575325)Scientific Research Starting Foundation for Doctors:419067School-Enterprise Cooperation Project:2018-KJ-4.
文摘The strong vibration responses of the cab system can be restrained by the damper force and the friction of the suspensions for trucks.After the failures of dampers,especially in the case of the complete failure,the anti vibration effect of the friction is prominent.However,the nonlinear vibration response characteristics of the cab subject to the damper complete failure have not been revealed.In order to reveal the nonlinear vibration response characteristics,a dynamic model of the cab system was established and its vibration equations were given.The friction forces existing in the suspensions were determined by the bench test.The influences of the friction forces on the cab vibration under different amplitude harmonic inputs were investigated when the dampers completely fail.The cab vertical displacement changes with the excitation amplitude and the vibration represents various motion states,including the periodic motion,the quasi-periodic motion,and the chaotic motion.The simulation results show that when the dampers fail,the proper friction forces help to suppress the quasi-periodic motion and the chaotic motion of the cab and to reduce the amplitude of the periodic motion.The proper friction forces can make the cab movement far away from the chaos area.They also help to avoid the fatigue damage of the cab floor and suspension parts to improve the service life of the suspension parts and to reduce the maintenance cost of the cab suspensions.
基金supported by the National Natural Science Foundation of China(51575325).
文摘In order to find out the sensitivity of the thermophysical and structural parameters to the thermodynamic characteristics of twin-tube hydraulic shock absorbers,based on the bench test,a method for calculating the time-varying rate of the external work on the shock absorber oil is proposed.And then,a thermodynamic model of the twin-tube hydraulic shock absorber is established by using the basic thermodynamic principles.By analyzing the influence of each parameter on the thermodynamic characteristics of the shock absorber,it can be seen that,the radius of the working cylinder outer wall has the greatest influence on the temperature rise of the shock absorber,followed by the thermal conductivity of the oil,the height of the oil,the heat transfer length of the cylinder barrel,the radius of the oil storage cylinder outer wall,the emissivity of the oil storage cylinder outer wall,the height of the nitrogen,the thermal conductivity of the nitrogen,the specific heat capacity of the oil,the density of the oil,the thermal conductivity of the cylinder,and the mass of the working oil.The kinematic viscosity of the oil has the least influence on the temperature rise of the shock absorber.The research can provide an effective theoretical guidance and reference for the design of the twin-tube hydraulic shock absorber.
基金This work is supported by the National Natural Science Foundation of China(51575325)Key R&D Projects in Shandong Province(GG201703070088).
文摘In this paper,using the theoretical analysis method,according to the actual structure of the hanging leaf spring of the traction motor mounted on the frame,the lateral force model of the hanging leaf spring of the traction motor was established.Then,through theoretical deduction,the deformation analytical calculation formula and the stress analytical calculation formula of the hanging leaf spring were established.The correctness of the leaf spring’s lateral force model was established and its deformation and stress analytical formulae were verified using ANSYS finite element analysis software.Based on this,according to the deformation analytical formula and the stress analytical formula of the leaf spring established,the influence of the main structural parameters on the mechanical characteristics of the leaf spring was discussed,and the reliability of the analytical analysis method of the lateral mechanical characteristics of the traction motor hanging leaf spring was verified by the loading–unloading test.The results show that the deformation and the load of the leaf spring change linearly.The changes of leaf spring’s stress at different positions can be considered as being composed of three sections:a linear change section in the root,a nonlinear change section in the middle,and a nonlinear change section in the end.In the structural parameters,the end thickness h2 has the greatest influence on the stiffness and the stress of the leaf spring,and the maximum thickness of the leaf spring eye h1 has the least influence on the stiffness and the stress of the leaf spring.The influence degree of other parameters on the stiffness of the leaf spring is h_(3),L_(1),L_(3),L_(2) in order,and the influence degree on the stress of the leaf spring is h_(3),L_(1),L_(2),L_(3) in order.In addition,when the root thickness h_(3) is greater than a certain value,the maximum stress point of the leaf spring appears at the end position L_(2).This study can provide a useful reference for the intelligent forward design and the rapid analysis of the mechanical characteristics of high-speed train traction motor hanging leaf spring.
基金the National Natural Science Foundation of China(51575325).
文摘To make a rapid comfort assessment and a reasonable dynamic parameters choice of wheelchair robots,this paper proposes a dynamic comfort coefficientκand analytically optimizes the cushion damping.Firstly,a traveling vibration model of the occupantwheelchair system for wheelchair robots running on random roads was created.Secondly,the analytic formula of the occupant RMS(root mean square)acceleration was deduced.Moreover,the dynamic coefficientκwas proposed and its influence laws were revealed.Finally,the cushion system optimal damping ratio was calculated based onκ.The results show that theκvalue is only determined by the parameters of the occupant-wheelchair system.The smaller theκvalue is,the better the dynamic comfort is for wheelchair robots running on random roads.By minimizingκ,the occupant-wheelchair system can achieve a statistically optimal dynamic comfort effect.
基金This work is supported by the National Natural Science Foundation of China(51575325).
文摘In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively,this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the carriage,and establishes a vertical dynamic model of railway vehicles by considering the influence of the coupling vibration effect between the passenger and the car body.The correctness of the model is verified by the real vehicle test.Then,the influence of the passengers on the vertical vibration characteristics of railway vehicles is analyzed,and the influence of the railway vehicle vibration on the vertical vibration characteristics of passengers is discussed in this paper.The research made in this paper can provide an effective model reference for the analysis of the vertical random vibration characteristics of railway vehicles and passengers,and for the optimization design of the suspension system parameters.
基金This work is supported by National Natural Science Foundation of China(51575325)Scientific Research Starting Foundation for Doctors(419067).
文摘The friction inevitably exists in the nonlinear suspension system for seats.It affects dynamic characteristics of the seat with the nonlinear suspension system.Analysis of the influences of the friction on the seat vibration responses is helpful to improve comfort.Moreover,it is also an important part of promoting the industrialization application of the nonlinear suspension system for seats.In order to verify the influences,a model of the seat with the nonlinear suspension system considering friction effects was established by combining experiments.Based on the model,by using the harmonic balance method,the analytical formulas of the seat frequency-domain vibration response considering friction effects were deduced,and the influences of the friction on the frequency response characteristics of the system were simulated and analyzed.Moreover,the influences of the friction on the time-domain response characteristics were investigated.The results show that the existence of the friction can help to reduce the vibration in the peak region and to increase the system stability,however,it is not conducive to the improvement of the seat comfort under random road conditions.
基金This work is supported by National Natural Science Foundation of China(51575325).
文摘To define the application fields of the traditional cab system model and the seat–cab coupled model,this paper mainly aims to investigate the differences of the vibration characteristics of the two models.First,the two models and their motion equations were introduced.Then,based on the mechanical parameters of the seat and cab system for a truck,the transmissibility characteristics of the two models were analyzed.The results show that the traditional model can relatively accurately predict the pitch and roll vibration characteristics of the real seat–cab system.However,it overvalues the vertical vibration transmitted from the front suspensions of the cab.Third,the typical excitation conditions and the measuring points were selected.Finally,under the typical excitation conditions,the dynamic responses of the measuring points were calculated.The results show that under the vertical excitation condition,the dynamic responses of the two models have obvious differences.Under the roll excitation condition and the pitch excitation condition,the roll responses and the pitch responses of the cab between the two models show almost no obvious difference.Under the random excitation condition,the vertical acceleration responses have relatively larger deviations between the two models,however,the angular acceleration responses are almost the same.For the preliminary design of the cab system,the traditional cab system model can be used.However,for the accurate design and the optimization of the seat–cab system,the seat–cab coupled model is recommended.
文摘The seat-cabin system of fork lift trucks has a great influence on ride comfort.On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck,a seat-cabin system vertical dynamic model was created.The vertical dynamic responses of the model under the random irregularities excitation were calculated.The calculated responses including the seat dynamic response and the cabin dynamic responses at the four corners are very close to the field measurement data and the relative deviations of the(root mean square)RMS acceleration responses are all less than 6.0%.The results show that the vertical dynamic model is acceptable and can truly describe the basic mechanical behavior of the seat-cabin system.The model provides a good basis for investigating the relations between the dynamic parameters and the vibration attenuation characteristics of the seat-cabin system to further improve ride comfort.
