The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident ...The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident toolbox. Then parametric model was established by adopting the subsection linearization method, and the damp value was estimated. The curve and function of damp changing with speed ratio was also established by fitting. In order to validate the identification results, the experimental output was compared with the output of the model in which torque was chosen as input signal and speed as output signal in Matlab/Ident toolbox. It was shown that model output is in good agreement with experimental output.展开更多
Using magnetorheological (MR) fluids in hydraulic engine mount for damping vehicle noise and vibration is opposed firstly, the structure of passive type and its mechanical model are described. The analysis of the expe...Using magnetorheological (MR) fluids in hydraulic engine mount for damping vehicle noise and vibration is opposed firstly, the structure of passive type and its mechanical model are described. The analysis of the experimental data show that the dynamic characteristics of MR mount such as dynamic stiffness and loss angles vary distinctly as the excitation frequency, and MR fluids as one type of attracting controllable fluids are fit for hydraulic engine mounts. The author advises to work out potentialities of MR fluids, the semi control or active control MR fluids filled hydraulic engine mount must be developed.展开更多
Static and dynamic numerical simulations of high recording density disk drivers are presented in this paper. The shear thinning effect on the viscosity is taken into account in the lubricant rheological model. The per...Static and dynamic numerical simulations of high recording density disk drivers are presented in this paper. The shear thinning effect on the viscosity is taken into account in the lubricant rheological model. The perturbation theory and short bearing theory are employed to set up the static and dynamic lubrication model on the head disk interface. Close solutions are given for the pressure distribution, load capacity and the dynamic characteristics such as stiffness and damping coefficients, which provide a simple method to analyze the dynamic response of the slider supported by the ultra thin fluid film lubricated bearing. Based on the close solutions the static and dynamic responses of the IBM 3380 slider are simulated. Some interesting results are obtained for the analysis of the slider’s flying stability.展开更多
In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respectively, were subjected to blow tests using a Split Hopkinson Pressure Bar(SHPB) system at a pressure of 0.4 atmosph...In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respectively, were subjected to blow tests using a Split Hopkinson Pressure Bar(SHPB) system at a pressure of 0.4 atmospheres. In this paper, we have analyzed the effect of slenderness ratio on the mechanical properties and energy dissipation characteristics of red sandstone under high strain rates. The processes of compaction, elastic deformation and stress softening deformation of specimens contract with an increase in slenderness ratio, whilst the nonlinear deformation process extends correspondingly. In addition, degrees of damage of specimens reduced gradually and the type of destruction showed a transformation trend from stretching failure towards shear failure when the slenderness ratio increased. A model of dynamic damage evolution in red sandstone was established and the parameters of the constitutive model at different ratios of length to diameter were determined. By comparison with the experimental curve, the accuracy of the model, which could reflect the stress–strain dynamic characteristics of red sandstone, was verified. From the view of energy dissipation, an increase in slenderness ratio of a specimen decreased the proportion of energy dissipation and caused a gradual fall in the capability of energy dissipation during the specimen failure process. To some extent, the study indicated the effects of slenderness ratios on the mechanical properties and energy dissipation characteristics of red sandstone under the high strain rate, which provides valuable references to related engineering designs and academic researches.展开更多
Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds： 1.275, 3.287, 6.251, and ...Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds： 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following： the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.展开更多
The influence of vegetation and sediment on flow characteristics in open channels cannot be neglected. To study the flow variability under the effects of the instream natural vegetation and sediment supply, experiment...The influence of vegetation and sediment on flow characteristics in open channels cannot be neglected. To study the flow variability under the effects of the instream natural vegetation and sediment supply, experiments were conducted with varied water and sediment supply in a movable bed of a river prototype. The instantaneous threedimensional velocities near two types of vegetation patches(the shrub and the weed) and along the centerline of the main channel with vegetation belts were measured using a 3-D side-looking acoustic Doppler velocimetry. The experimental results show that both the instream vegetation and sediment supply strongly affect the flow and turbulence characteristics. In the case of vegetation patches, both the shrub and weed have a considerable influence on the distribution of the streamwise velocity and turbulence intensity of their surrounding water. The streamwise velocity distribution followed as J-shape and linear shape around the weed and shrub under different experimental conditions. The turbulence intensity was large at the top of the weed and shrub;the shrub had its greatest influence on the downstream water flow. In the case of vegetation belts,the streamwise velocity along the centerline of the main channel exhibited an S-shape, J-shape and linear shape at different locations under varied water,vegetation structures and riverbed configurations.The turbulence intensity along the centerline of the main channel ranged from 0.0 to 0.1. The upstream turbulence intensity was affected considerably by a sediment supply, while the downstream turbulence intensity changed with the varied vegetation characteristics and riverbed topography. The second flow coefficient M-value increased longitudinally and was almost positive along the centerline of the main channel, implying that the rotational direction of the secondary current cell was clockwise.展开更多
Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping chara...Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids(D50,r/D50,s) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10-4% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D50,r/D50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.展开更多
A new CVT(continuously variable transmission) design which is a traction drive variator has been introduced. Analytical predictions and experimental results of the steady state which demonstrate higher efficiencies an...A new CVT(continuously variable transmission) design which is a traction drive variator has been introduced. Analytical predictions and experimental results of the steady state which demonstrate higher efficiencies and power capacities of the new design are presented. The traction and power loss are then predicted by using models including evaluation of creep and spin in the contact patch. Analytical predictions of the transmission reach reasonable agreement with the experimental data, and the transmission efficiency of the system increases as the input torque increases while the input speed is certain. The research results can be further used in hydraulic traction drive CVT design and optimization.展开更多
文摘The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident toolbox. Then parametric model was established by adopting the subsection linearization method, and the damp value was estimated. The curve and function of damp changing with speed ratio was also established by fitting. In order to validate the identification results, the experimental output was compared with the output of the model in which torque was chosen as input signal and speed as output signal in Matlab/Ident toolbox. It was shown that model output is in good agreement with experimental output.
文摘Using magnetorheological (MR) fluids in hydraulic engine mount for damping vehicle noise and vibration is opposed firstly, the structure of passive type and its mechanical model are described. The analysis of the experimental data show that the dynamic characteristics of MR mount such as dynamic stiffness and loss angles vary distinctly as the excitation frequency, and MR fluids as one type of attracting controllable fluids are fit for hydraulic engine mounts. The author advises to work out potentialities of MR fluids, the semi control or active control MR fluids filled hydraulic engine mount must be developed.
文摘Static and dynamic numerical simulations of high recording density disk drivers are presented in this paper. The shear thinning effect on the viscosity is taken into account in the lubricant rheological model. The perturbation theory and short bearing theory are employed to set up the static and dynamic lubrication model on the head disk interface. Close solutions are given for the pressure distribution, load capacity and the dynamic characteristics such as stiffness and damping coefficients, which provide a simple method to analyze the dynamic response of the slider supported by the ultra thin fluid film lubricated bearing. Based on the close solutions the static and dynamic responses of the IBM 3380 slider are simulated. Some interesting results are obtained for the analysis of the slider’s flying stability.
基金Financial support for this work, provided by the National Basic Research Program of China (No. 2013CB227900)the National Natural Science Foundation of China (No. 51074166), the National Natural Science Foundation for Young (Nos. 51304200, 51304201 and 51104128)+3 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120095110013)the Open Fund of the State Key Laboratory of Coal Resource and Safe Mining (No. 10F08)the Colleges and Universities in Jiangsu Province Plans to Graduate Research and Innovation (No. CXLX13_935)the College Students’ Innovative Entrepreneurial Foundation of China University of Mining and Technology (No. 2013DXS03)
文摘In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respectively, were subjected to blow tests using a Split Hopkinson Pressure Bar(SHPB) system at a pressure of 0.4 atmospheres. In this paper, we have analyzed the effect of slenderness ratio on the mechanical properties and energy dissipation characteristics of red sandstone under high strain rates. The processes of compaction, elastic deformation and stress softening deformation of specimens contract with an increase in slenderness ratio, whilst the nonlinear deformation process extends correspondingly. In addition, degrees of damage of specimens reduced gradually and the type of destruction showed a transformation trend from stretching failure towards shear failure when the slenderness ratio increased. A model of dynamic damage evolution in red sandstone was established and the parameters of the constitutive model at different ratios of length to diameter were determined. By comparison with the experimental curve, the accuracy of the model, which could reflect the stress–strain dynamic characteristics of red sandstone, was verified. From the view of energy dissipation, an increase in slenderness ratio of a specimen decreased the proportion of energy dissipation and caused a gradual fall in the capability of energy dissipation during the specimen failure process. To some extent, the study indicated the effects of slenderness ratios on the mechanical properties and energy dissipation characteristics of red sandstone under the high strain rate, which provides valuable references to related engineering designs and academic researches.
文摘Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds： 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following： the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.
基金supported by the National Key Research and Development Program of China (2016YFC0402304 and 2017YFC1502504)the National Natural Science Foundation of China (51639007 and 51579163)
文摘The influence of vegetation and sediment on flow characteristics in open channels cannot be neglected. To study the flow variability under the effects of the instream natural vegetation and sediment supply, experiments were conducted with varied water and sediment supply in a movable bed of a river prototype. The instantaneous threedimensional velocities near two types of vegetation patches(the shrub and the weed) and along the centerline of the main channel with vegetation belts were measured using a 3-D side-looking acoustic Doppler velocimetry. The experimental results show that both the instream vegetation and sediment supply strongly affect the flow and turbulence characteristics. In the case of vegetation patches, both the shrub and weed have a considerable influence on the distribution of the streamwise velocity and turbulence intensity of their surrounding water. The streamwise velocity distribution followed as J-shape and linear shape around the weed and shrub under different experimental conditions. The turbulence intensity was large at the top of the weed and shrub;the shrub had its greatest influence on the downstream water flow. In the case of vegetation belts,the streamwise velocity along the centerline of the main channel exhibited an S-shape, J-shape and linear shape at different locations under varied water,vegetation structures and riverbed configurations.The turbulence intensity along the centerline of the main channel ranged from 0.0 to 0.1. The upstream turbulence intensity was affected considerably by a sediment supply, while the downstream turbulence intensity changed with the varied vegetation characteristics and riverbed topography. The second flow coefficient M-value increased longitudinally and was almost positive along the centerline of the main channel, implying that the rotational direction of the secondary current cell was clockwise.
文摘Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids(D50,r/D50,s) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10-4% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D50,r/D50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.
基金Project(A2220060029)supported by the National Ministries of Basic Scientific Research Fund Project,ChinaProject(9140C340201113403)supported by the Foundation of the National Key Laboratory of Vehicular Transmission,China
文摘A new CVT(continuously variable transmission) design which is a traction drive variator has been introduced. Analytical predictions and experimental results of the steady state which demonstrate higher efficiencies and power capacities of the new design are presented. The traction and power loss are then predicted by using models including evaluation of creep and spin in the contact patch. Analytical predictions of the transmission reach reasonable agreement with the experimental data, and the transmission efficiency of the system increases as the input torque increases while the input speed is certain. The research results can be further used in hydraulic traction drive CVT design and optimization.
