MODELING, VALIDATION AND OPTIMAL DESIGN OF THE CLAMPING FORCE CONTROL VALVE USED IN CONTINUOUSLY VARIABLE TRANSMISSION

Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dynamic model is set up by means of mechanism analysis. For the purpose of checking the validity of the modeling method, a prototype workpiece of the valve is manufactured for comparison test, and its simulation result follows the experimental result quite well. An associated performance index is founded considering the response time, overshoot and saving energy, and five structural parameters are selected to adjust for deriving the optimal associated performance index. The optimization problem is solved by the genetic algorithm （GA） with necessary constraints. Finally, the properties of the optimized valve are compared with those of the prototype workpiece, and the results prove that the dynamic performance indexes of the optimized valve are much better than those of the prototype workpiece.

Variational approximation methods for long-range force transmission in biopolymer gels

The variational principle of minimum free energy(MFEVP) has been widely used in research of soft matter statics.The MFEVP can be used not only to derive equilibrium equations(including both bulk equations and boundary conditions),but also to develop direct variational methods(such as Ritz method) to find approximate solutions to these equilibrium equations. We apply these variational methods to study long-range force transmission in nonlinear elastic biopolymer gels.It is shown that the slow decay of cell-induced displacements measured experimentally for fibroblast spheroids in threedimensional fibrin gels can be well explained by variational approximations based on the three-chain model of biopolymer gels.

Statistics and Analysis on Reliability of HVDC Transmission Systems of SGCC

Reliability level of HVDC power transmission systems becomes an important factor impacting the entire power grid.The author analyzes the reliability of HVDC power transmission systems owned by SGCC since 2003 in respect of forced outage times,forced energy unavailability,scheduled energy unavailability and energy utilization eff iciency.The results show that the reliability level of HVDC power transmission systems owned by SGCC is improving.By analyzing different reliability indices of HVDC power transmission system,the maximum asset benef its of power grid can be achieved through building a scientif ic and reasonable reliability evaluation system.

Vibration isolation performance analysis of a bilateral supported bio-inspired anti-vibration control system

To achieve better anti-vibration performance in a low frequency region and expand the range of vibration isolation,a bilateral supported bio-inspired anti-vibration(BBAV)structure composed of purely linear elements is proposed,inspired by the motion form of bird legs and the nonlinear extension and compression of muscles and tendons.The kinematic relations and nonlinear dynamic model considering vertical and rotational vibrations are established.The loading capacity and equivalent stiffness are investigated with key parameters.The amplitude-frequency characteristics and force transmissibility are used to evaluate the stability and anti-vibration performance with the effects of the excitation amplitude,rod length,installation angle,and spring stiffness.The results show that the loading requirements and resonant characteristics of the BBAV structure are adjustable,and superior vibration isolation performance can be achieved readily by tuning the parameters.The X-shaped vibration structure is sensitive to the spring stiffness,which exhibits a wider vibration isolation bandwidth with smaller spring stiffness.Besides,depending on the parameters,the nonlinear behavior of the BBAV system can be interconverted between the softening type and the hardening type.The theoretical analysis in this study demonstrates the advantages and effectiveness of the vibration isolation structure.

Development of an Adjustable Bed for a Micro-Turbine Electric Power Generator Plant

An adjustable bed is a supporting structure designed to provide a seating base or platform, for a 5.0 KW micro steam turbine generator plant prior to its mounting on a block-type concrete foundation. The design of the bed frame and flanges was carried out by considering the predetermined weights of the turbine and generator (alternator) [1]. On this basis, steel materials of U-channels and angle irons were used in the fabrication of the generator bed. The bed was designed to be adjustable by accommodating direct coupling of the turbine with the generator, and the belt drive. Fabrication was carried out by welding, machining, and assembly. During assembly, the bed was made to accommodate damping materials in order to reduce the vibration of the plant [2]. The performance of the unit with or without vibration isolator when they are axially connected with flexible flange coupling or transversely connected with sets of belt and pulley, in succession respectively. The results showed that a reduction in the force transmitted to the supporting structure occurred when the vibration produced by the unit is isolated from its base by the use of a vibration isolator, maximum reduction of 99.95% achieved when axially coupled and 99.91% when transversely connected with belt and pulley system [3].

Reducing force transmissibility in multiple degrees of freedom structures through anti-symmetric nonlinear viscous damping

In the present study, the Volterra series theory is adopted to theoretically investigate the force transmissibility of multiple degrees of freedom （MDOF） structures, in which an isolator with nonlinear anti-symmetric viscous damping is assembled. The results reveal that the anti-symmetric nonlinear viscous damping can significantly reduce the force trans- missibility over all resonance regions for MDOF structures with little effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to solve the dilemma occurring in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant frequencies but increases the transmissibility over non-resonant frequency regions. This work is an extension of a previous study in which MDOF structures installed on the mount through an isolator with cubic nonlinear damping are considered. The theoretical analysis results are also verified by simulation studies.

A quasi-zero-stiffness isolator with a shear-thinning viscous damper

Quasi-zero-stiffness(QZS)vibration isolators have been widely studied,because they show excellent high static and low dynamic stiffnesses and can effectively solve low-frequency and ultralow-frequency vibration.However,traditional QZS(T-QZS)vibration isolators usually adopt linear damping,owing to which achieving good isolation performance at both low and high frequencies is difficult.T-QZS isolators exhibit hardening stiffness characteristics,and their vibration isolation performance is even worse than that of linear vibration isolators under a large excitation amplitude.Therefore,this study proposes a QZS isolator with a shear-thinning viscous damper(SVD)to improve the vibration isolation performance of the T-QZS isolators.The force-velocity relation of the SVD is obtained,and a dynamic model is established for the isolator.The dynamic responses of the system are solved using the harmonic balance method(HBM)and the Runge-Kutta method.The vibration isolation performance of the system is evaluated using force transmissibility,and the isolator parameters are analyzed.The results show that compared with the T-QZS isolators,the proposed QZS-SVD isolator achieves the lower initial vibration isolation frequency and peak value,and exhibits better vibration isolation performance at medium and high frequencies.Moreover,the proposed isolator can withstand a large excitation amplitude in the effective vibration isolation range.

Effects of anti-symmetric nonlinear viscous damping on the force transmissibility of multi-degree of freedom structures

In the present study, the concept of the output frequency response function is applied to theoretically investigate the force transmissibility of multi-degree of freedom (MDOF) structures with a nonlinear anti-symmetric viscous damping. The results reveal that an anti-symmetric nonlinear viscous damping can significantly reduce the transmissibility over all resonance regions for MDOF structures while it has almost no effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to overcome the dilemma in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant region but increases the transmissibility over non-resonant regions.

Time-domain hydrodynamic analysis of pontoon-plate floating breakwater

The hydrodynamic behaviors of a floating breakwater consisting of a rectangular pontoon and horizontal plates are studied theoretically. The fluid motion is idealized as two-dimensional linear potential flow. The motions of the floating breakwater are assumed to be two-dimensional in sway, heave, and roll. The solution to the fluid motion is derived by transforming the governing differential equation into the integral equation on the boundary in time domain with the Green＇s function method. The motion equations of the floating breakwater are established and solved with the fourth-order Runge-Kutta method to obtain the displacement and velocity of the breakwater. The mooring forces are computed with the static method. The computational results of the wave transmission coefficient, the motion responses, and the mooring forces of the pontoon-plate floating breakwater are given. It is indicated that the relative width of the pontoon is an important factor influencing the wave transmission coefficient of the floating breakwater. The transmission coefficient decreases obviously as the relative width of the pontoon increases. The horizontal plates help to reduce the wave transmission over the floating breakwater. The motion responses and the mooring forces of the pontoon-plate floating breakwater are less than those of the pontoon floating breakwater. The mooring force at the offshore side is larger than that at the onshore side.

An Investigation into the Isolation Performance of Mono-and Bi-stable Systems

Motivated by the need for improving the isolation performance, many research studies have been performed on isolators with nonlinear characteristics. Based on the shape of their phase portrait, such devices can be configured as either a mono-or bi-stable isolator. This paper focuses on investigating the relative performance of these two classes under the same excitations. Force transmissibility is used to measure the isolation performance, which is defined in terms of the RMS of the ratio of the transmitted force to the excitation force. When the system is subjected to harmonic excitation, it is found that the maximum reduction of the force transmissibility in the isolation range using Quasi-Zero stiffness is achieved. When the system is subjected to random excitation, it has the same effect of Quasi-Zero stiffness. Further, optimum damping can be changed with stiffness and has minimum value.

Isolation performances and optimization of triple quasi-zero stiffness isolators

In this paper,triple quasi-zero stiffness(QZS)passive vibration isolators whose restoring force curve has a three-stage softening effect are proposed.Multi-coupled SD oscillators with three independent geometrical parameters are used as negative stiffness mechanisms to achieve QZS characteristics at the origin and symmetrical positions on both sides of the origin.Isolation performances of different triple QZS isolators are analyzed to show influences of the selection of QZS regions away from the origin on the range of isolation regions.Pareto optimizations of system parameters are carried out to get a larger range of small restoring force regions and small stiffness regions.Isolation performances of two triple QZS isolators are discussed to show the influence of different Pareto optimization solutions through the comparisons with single and double QZS isolators.Results showed that triple QZS isolators have both the advantages of single and double QZS isolators which results in better isolation performances under both small and large excitation amplitudes.An improvement in isolation performances for triple QZS isolators is found with the decrease in average stiffness due to the appearance of two symmetrical QZS regions away from the origin.Larger displacements of QZS regions away from the origin result in better isolation performances when excitation amplitude is large,and triple QZS characteristics are similar to double QZS isolators at this time.Smaller restoring forces of QZS regions away from the origin lead to better isolation performances when excitation amplitude is small,and triple QZS characteristics are similar to single QZS isolators at this moment.Compared with the decrease in average stiffness,the improvement of isolation performances shows a hysteresis phenomenon due to the difference between static and dynamic characteristics.

Study on force chain evolution of rice straw with different length during vibrational compression

This paper explores the mechanism of force chain evolution and voidage change under vibrational and non-vibrational compression conditions of rice straw of different lengths.Simulations were used to explore the force chain evolution and voidage variation mechanism under different conditions.The re-sults show that under non-vibrational compression,the strong force chain passes from top to bottom in vertical direction and from center to periphery in tangential direction.Under vibrational compression,the force chain passes from top and bottom to center in vertical direction and the force chain evolves from outer ring to interior and exterior in tangential direction.The number of strong chains,voidage and standard deviation of the mean pressure under vibratory compression are lower than the values under non-vibratory compression.Vibration promotes stress transfer and enhancement,velocity enhancement and density enhancement.This study analyzes the mechanical properties of different lengths straw during vibrational and non-vibrational compression from a detailed viewpoint.

Liquid metal hydraulics paradigm:Transmission medium and actuation of bimodal signals

In this article,room temperature gallium-based fluids(RTGFs)with unique thermal and conductive properties are proposed as a transmission fluid for the force carrying medium of hydraulics,which rectify the lack of the multi-functional hydraulic roles of liquid metal(LM).The typical physical properties of RTGFs and comparative conventional hydraulic fluids(commercial hydraulic oil and deionized water),such as thermal stability and rheological characteristics,are evaluated.Experimental and numerical methods,then,were adopted to clarify the force transmission performance of RTGFs and commercial hydraulic oils,as well as the influence of temperature fields on the viscosity of fluids.The results disclosed that the advantages of inherent flame resistance,wide liquid temperature range,and the viscosity changing slightly with temperature made RTGFs potential in finding efficient application in the hydraulics as new working fluids.Finally,for illustration,the rigid and flexible actuators driven by RTGFs were designed as hydraulic fluid and demonstrated their capabilities in grasping objects with various shapes and weights,respectively.And the tunable stiffness of such a flexible actuator was enabled via the solid-liquid phase change of LM.Additionally,a frequency-adjustable antenna was manufactured and showcased owing to the introduced transformable electromagnetic behaviors of LM.Overall,the gallium-based LM fluids with thermoelectrical and mechanical multimodal signal medium would serve as a potential candidate for future complex multifunctional signal transmission systems.

Forced vibrational power flow input and transmission in a fluid-filled shell

The characteristics of vibrational power flow in an infinite elastic cylindrical shell filled with fluid are investigated. The simple harmonic motion of the shell and the pressure field in the contained fluid are described by the Fltigge shell equations and Helmholtz equation respectively. The vibrational equation of this system is obtained by using the coupling of shell and fluid. The dispersion curves are discussed for different circumferential orders. By using Fourier transform and its inverse transform, the input power into this coupled system excited by a simple harmonic linearly distributed driving force is studied. Along the shell, the transmission of the power flow carried by different shell internal forces and by the contained fluid are discussed