Automotive dry clutches have been found to produce a low frequency sliding noise in many applications,which challenges the ride comfort of vehicles.In order to study this clutch sliding noise,a detailed finite element...Automotive dry clutches have been found to produce a low frequency sliding noise in many applications,which challenges the ride comfort of vehicles.In order to study this clutch sliding noise,a detailed finite element model including both a pressure plate assembly and a driven plate assembly was developed.Based on this model,a complex eigenvalue analysis is performed in this research.The effect of several major factors on the clutch sliding noise,such as the coefficient of friction,the clamping force,the geometric imperfection of the friction plate,and the thermal deformation of the pressure plate,were investigated numerically.A vehicle road test with clutch sliding noise was conducted for several different conditions.The leading frequencies of the clutch sliding noise in the testing were obtained and compared with the frequencies predicted by the numerical model.The simulation results show the same tendency as the road test.It is found that the clutch sliding noise can be reduced by decreasing the coefficient of friction.With the presence of the surface bumping of the friction plate,the propensity of the clutch sliding noise greatly increases and the corresponding squeal frequencies fall into the range lower than 1 kHz.With the consideration of the thermally introduced deformation of the clutch pressure plate,the possibility of clutch sliding noise is significantly reduced.It is concluded that the model with the incorporation of the thermal deformation of the pressure plate is more effective for the frequency prediction of clutch sliding noise.展开更多
The design and fabrication of semiconductor photocatalysts have attracted much attention. Herein, the effect of pH value and soluble salt additives on crystal structure, morphology and photocatalytic properties of WO3...The design and fabrication of semiconductor photocatalysts have attracted much attention. Herein, the effect of pH value and soluble salt additives on crystal structure, morphology and photocatalytic properties of WO3 was investigated in detail. It was found that the phase structure of WO3 changed from monoclinic to hexagonal phase when pH value of the solution increased. The ultraviolet-visible absorption spectra show that the monoclinic and hexagonal WO3 had absorbance from 600 nm to the ultraviolet-visible region. Hexagonal WO3 with nanofiber bundle morphology was successfully synthesized through Na2SO4 and Zn（CH3COO）2.2H2O-assisted hydrothermal method when pH value was 0.8. It exhibits the highest photocatalytic efficiency and better than that of cubic-shaped rnonoclinic WO3. The shuttle-like hexagonal WO3 prepared at pH 1.4 gives much lower activity. The morphology is a decisive parameter for the photocatalytic properties of WO3.展开更多
基金support for this work from the National Natural Science Foundation of China(NSFC)(No.51965012)the Key Research and Development Plan of Guangxi Province of China(No.AB18126002).
文摘Automotive dry clutches have been found to produce a low frequency sliding noise in many applications,which challenges the ride comfort of vehicles.In order to study this clutch sliding noise,a detailed finite element model including both a pressure plate assembly and a driven plate assembly was developed.Based on this model,a complex eigenvalue analysis is performed in this research.The effect of several major factors on the clutch sliding noise,such as the coefficient of friction,the clamping force,the geometric imperfection of the friction plate,and the thermal deformation of the pressure plate,were investigated numerically.A vehicle road test with clutch sliding noise was conducted for several different conditions.The leading frequencies of the clutch sliding noise in the testing were obtained and compared with the frequencies predicted by the numerical model.The simulation results show the same tendency as the road test.It is found that the clutch sliding noise can be reduced by decreasing the coefficient of friction.With the presence of the surface bumping of the friction plate,the propensity of the clutch sliding noise greatly increases and the corresponding squeal frequencies fall into the range lower than 1 kHz.With the consideration of the thermally introduced deformation of the clutch pressure plate,the possibility of clutch sliding noise is significantly reduced.It is concluded that the model with the incorporation of the thermal deformation of the pressure plate is more effective for the frequency prediction of clutch sliding noise.
基金the financial support provided by the Foundation of Liaoning Educational Committee (No.L2016004)Natural Science Foundation of Liaoning Province (No.2015020209)+1 种基金the financial support provided by the National Natural Science Foundation of China (Nos.91545119, 21773269 and 21761132025)Youth Innovation Promotion Association CAS (No.2015152)
文摘The design and fabrication of semiconductor photocatalysts have attracted much attention. Herein, the effect of pH value and soluble salt additives on crystal structure, morphology and photocatalytic properties of WO3 was investigated in detail. It was found that the phase structure of WO3 changed from monoclinic to hexagonal phase when pH value of the solution increased. The ultraviolet-visible absorption spectra show that the monoclinic and hexagonal WO3 had absorbance from 600 nm to the ultraviolet-visible region. Hexagonal WO3 with nanofiber bundle morphology was successfully synthesized through Na2SO4 and Zn（CH3COO）2.2H2O-assisted hydrothermal method when pH value was 0.8. It exhibits the highest photocatalytic efficiency and better than that of cubic-shaped rnonoclinic WO3. The shuttle-like hexagonal WO3 prepared at pH 1.4 gives much lower activity. The morphology is a decisive parameter for the photocatalytic properties of WO3.
