Papers by Author: Hua Ling Chen

Abstract: Temperature can significantly affect the performance of a viscoelastic dielectric elastomer (DE). In the current study, we use a thermodynamic model to characterize the influence of temperature on the viscoelastic electromechanical response undergoing a constant electric load by taking into account the temperature dependent elastic modus and dielectric constant. Due to the significant viscoelasticity in the dielectric elastomer, DE membrane creeps in time and the inelastic stretch of DE is smaller than that of the total stretch. The results show that the total stretch of the viscoelastic electromechanical deformation increases with the increasing temperature until suffering electromechanical instability at a high temperature; the actuation performance is dominated by the moduli of the elastomer. This may be used to guide the design of dielectric elastomer actuators undergoing temperature variation.

Abstract: Focusing on the quantitative research on feed system with installation errors, a theoretical analyses model is developed to analyze the influence of parallelism error and coaxiality error of the system. The change law of stress, deformation and contact angle is discussed based on the analysis with hertz contact theory. The theoretical analysis is verified by the simulation with FEM software. The result shows that bias load, deformation of guide and compress variation of the ball decrease as the deviation from bearing for the coaxiality error, while these changes remain small for the first half stroke and dramatically increase later for the parallelism error. The analysis above may be helpful for the installing of the ball screw and for improving the machining accuracy.

Abstract: The vibration of pipe systems not only worsens their working environment, but also may result in the loosening of mechanical connections between pipelines, as well as the structural fatigue damages. This paper presents a new method for vibration control of pipe systems, by specially designing some pipe structures based on two vibration reduction mechanisms of phononic crystals, for the vibration frequency in the actual tests. Some numerical analyses are then performed about the effects of the parameters of vibrator, for instance, the ratio of material components, and the numbers of period. The simulation results demonstrate that the proposed phononic crystals structures can reduce the vibration of pipe systems effectively.

Abstract: This paper presents the design of a novel shape memory alloys (SMAs) damper, and its application in the vibration control of transmission towers. Firstly, based on a brief introduction for the essential properties of SMAs, a kind of constitutive model, i.e., the Brinson model is established to describe the unique behaviors of the material, combined with the experiments results. And then, a novel SMA damper, with the functions of displacement amplification and re-centering, is specifically designed by utilizing SMAs’ damping capacity. To verify and evaluate the device’s performance, the FEM model of an actual transmission tower is subsequently built in ANSYS, and by embedding the theoretical model of the damper into its analysis process, the responses of the tower subjected to the natural wind are numerically calculated. The results show that under the reasonable installations, the proposed SMA damper has a good effect on the wind-induced response control of the transmission tower.

Abstract: Finite element equation of the nonlinear dimensionless Reynolds equation, based on the Galerkin finite element method, was derived. Three key points of solving the equation was studied in detail, i.e. Boolean matrix was calculated under the nonlinear conditions, and a method of integrating discrete element equations was provided; Nonlinear algebraic equations set, resulted from integrated finite element equations, was obtained and a method how to substitute boundary conditions into the algebraic equations was presented; A method of calculating the Jacobi matrix of the equations set were described in this paper. All of them are crucial to solve the nonlinear Reynolds equation and helpful for promoting the further research on compliant foil gas bearing.

Abstract: In this article, a metal diaphragm coupling is introduced. It is assembled by interference fit with the shafts. Based on two axial vibration styles, self-exited vibration and external exited vibration, of the coupling, physical model of the coupling is established. Stiffness and damping of the coupling are also solved and analyzed. Then, natural vibration of the coupling is researched and natural frequencies are acquired by analyzed and simulated method. Finally, axial vibration response of the coupling was presented based on a calculation example. Techniques are presented which permit the coupling designer to predictably modify the coupling and thereby make in-place retrofits should an axial resonance condition occur in the field.

Abstract: Recently, we develop a new method for reducing vibration named liquid film damping (LFD) which combines the mechanism of vibrational energy dissipation of liquid viscous damping (LVD) and air film damping (AFD). This paper use experiment to compare the capacities of vibration decreasing of LFD and the pore viscous damping (PVD) which is an extensive applied type of LVD. The results of experiment present LFD has better ability than traditional LVD in reducing vibration of structures in not only higher frequency but lower frequency.

Abstract: In this paper, reverberation chamber high-frequency vibration-acoustic problem for an aircraft cabin is investigated with two methods. One is combining energy finite element analysis (EFEA) and energy boundary element analysis (EBEA); another is boundary element method by SYSNOISE. Comparison is performed between these two methods.

Abstract: Distribution of static interference pressure between a thin-wall flexible cup and a flexible shaft fluctuates heavily along the axis of the cup and is quite different from pressure distribution of common interference styles. In this article, aiming at solving distribution of static interference pressure between a thin-wall flexible cup with much thicker bottom and a hollow flexible shaft, mechanical model and mathematical model of solving the problem were built based on classic thin shell theory. Special difference is that precise special solution of bending equation of thin cylindrical shell was used to substitute the special solution which is original from bending deformation of thin cylindrical shell in no moment status. And a brand new general solution, the relational expression between bending deformation of thin wall of the cup and distribution of the static interference pressure, was obtained. Then, a method used to solve the pressure distribution was presented by solving integral equation and applying superposition principle for the first time. Through using the method to solve an example and comparing calculated results with FEM results, it was proved that the method is correct and effective.

Abstract: Ionic polymer-metal composites (IPMCs) show great potential in a large variety of engineering fields as actuator materials. They mainly consist of electrodes and ionic polymer as the substrate material. Many metal materials can be used as the electrode material of IPMCs. In this paper palladium was adopted to get a compromise between the cost and the stability, and Pd-Nafion IPMC was fabricated by chemical plating as test sample. Preliminary experiments were accomplished with satisfactory result using a suit of self-made measurement setup. The results showed that palladium was a good electrode material. Although some previous work has investigated on the elastic modulus of IPMCs by tensile test, a simple method based on the cantilever beam theory to estimate the modulus is still proposed here, which does not need a tensile testing machine. By the method we got that the elastic modulus of the sample is 362.35MPa.