In this paper a new physical model for studying stick-slip is established. Based on the dynamics system of the model,the state equation of the system is presented. And simulation analysis on the influential factors of...In this paper a new physical model for studying stick-slip is established. Based on the dynamics system of the model,the state equation of the system is presented. And simulation analysis on the influential factors of stick-slip is carried out. The relationship between stiffness ( horizontal and normal) ,dampness,mass, difference of static and kinetic coefficients of friction,driving velocity,and amplitude in normal direction is analyzed and parameters of stick-slip are evaluated. Results show that stick-slip can be reduced by improving horizontal stiffness,decreasing dampness,reducing mass,cutting down the difference of static and kinetic coefficients of friction,properly choosing the vertical stiffness and properly inducting the normal oscillation.展开更多
A new method for the determination of the critical slip surfaces of slopes is proposed in this paper. In this paper, the original critical slip field method is extended in terms of the total residual moment, values of...A new method for the determination of the critical slip surfaces of slopes is proposed in this paper. In this paper, the original critical slip field method is extended in terms of the total residual moment, values of residual work as well as the unbalanced thrust force at the exit point for a given non-circular slip surface. The most critical slip surface with the maximum representative value for a prescribed factor of safety will be optimized and located using the harmony search algorithm. The prescribed factor of safety is modified with certain tiny interval in order to find the critical slip surface where the maximum representative value is zero. The aforementioned approach to the location of the critical slip surface is greatly different from the traditional limit equilibrium procedure. Three typical soil slopes are evaluated by use of the proposed method, and the comparisons with the classical approaches have illustrated the applicability of the proposed method.展开更多
Hydrodynamic lubrications between two plane plates with an intersection angle θ have been investigated us- ing the boundary slippage theory, and relations are obtained between dimensionless pressures and coordinate x...Hydrodynamic lubrications between two plane plates with an intersection angle θ have been investigated us- ing the boundary slippage theory, and relations are obtained between dimensionless pressures and coordinate x, between bearing capacity, friction force, friction coefficient and di- mensionless slipping size factor. The results show that bear- ing capacity of two plane plates without boundary slippage significantly increases with increasing intersection angle θ when 0 〈 θ 〈 1°, whereas decreases with increasing in- tersection angle 0 when θ 〉 1°. The results also show that negative pressure occurs in fluid entrance region and bearing capacity decreases, and friction force and friction coefficient increase with the increase of dimensionless slipping size fac- tor.展开更多
The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were ...The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.展开更多
文摘In this paper a new physical model for studying stick-slip is established. Based on the dynamics system of the model,the state equation of the system is presented. And simulation analysis on the influential factors of stick-slip is carried out. The relationship between stiffness ( horizontal and normal) ,dampness,mass, difference of static and kinetic coefficients of friction,driving velocity,and amplitude in normal direction is analyzed and parameters of stick-slip are evaluated. Results show that stick-slip can be reduced by improving horizontal stiffness,decreasing dampness,reducing mass,cutting down the difference of static and kinetic coefficients of friction,properly choosing the vertical stiffness and properly inducting the normal oscillation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51008167 and 51274126)the S&T Plan Project of Shandong Provincial Education Department (Grant No. J10LE07)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20103721120001)the Research Project Council of the Hong Kong SAR Government(Grant No. PolyU 513808)
文摘A new method for the determination of the critical slip surfaces of slopes is proposed in this paper. In this paper, the original critical slip field method is extended in terms of the total residual moment, values of residual work as well as the unbalanced thrust force at the exit point for a given non-circular slip surface. The most critical slip surface with the maximum representative value for a prescribed factor of safety will be optimized and located using the harmony search algorithm. The prescribed factor of safety is modified with certain tiny interval in order to find the critical slip surface where the maximum representative value is zero. The aforementioned approach to the location of the critical slip surface is greatly different from the traditional limit equilibrium procedure. Three typical soil slopes are evaluated by use of the proposed method, and the comparisons with the classical approaches have illustrated the applicability of the proposed method.
文摘Hydrodynamic lubrications between two plane plates with an intersection angle θ have been investigated us- ing the boundary slippage theory, and relations are obtained between dimensionless pressures and coordinate x, between bearing capacity, friction force, friction coefficient and di- mensionless slipping size factor. The results show that bear- ing capacity of two plane plates without boundary slippage significantly increases with increasing intersection angle θ when 0 〈 θ 〈 1°, whereas decreases with increasing in- tersection angle 0 when θ 〉 1°. The results also show that negative pressure occurs in fluid entrance region and bearing capacity decreases, and friction force and friction coefficient increase with the increase of dimensionless slipping size fac- tor.
基金the National Natural Science Foundation of China(20476014,51376030)
文摘The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.
