Advanced Materials Research Vols. 139-141

Abstract: The effect of surface friction on the dynamic response of spur gear pair is investigated in this paper. Firstly, surface friction during the mesh is described briefly, and realistic time-varying tooth stiffness and realistic static transmission error are introduced. Subsequently, the differential equation of the torsional vibration of gear transmission is developed in which the realistic time-varying stiffness and realistic static transmission error are incorporated. Finally, using the numerical simulation method, the solutions in time domain and spectrum graphs of the nonlinear system are obtained. Results show that surface friction has great influences on the dynamic responses nearby the pitch point but less influences far away the pitch point. Surface friction may also bring sudden change to the dynamic responses at pitch point when the rotational speed is low.

Abstract: In order to research dynamic natures of a three knife-shape-tooth star-wheel loading mechanism, a mechanical model and a solid model of the star-wheel loading mechanism are established by means of updated-Lagrange and ANSYS software in the paper, equivalent stress clouds and displacement responding curves of the star-wheel at different excitation frequencies are obtained through harmonic response analyses. Model analysis shown that the star-wheel loading mechanism doesn’t take place resonance when the excitation frequency locates between 1.8 and 2.4 Hz, and the star-wheel works stability when the rotation speed is from 36 r/min to 48 r/min. These conclusions from study lay a theoretical foundation for improving the design of a three knife-shape-tooth star-wheel loading mechanism and make better its dynamic behavior.

Abstract: A comparison of contact forces between the constrained gripper and the under-constrained gripper to grip the same work-piece is analyzed. The new type heavy forging grippers with constrained rods are designed to improve the contact status. The main difference between the new grippers with constrained tongs and the traditional grippers with under-constrained tongs is that the constrained gripper has constrained rods to keep the two tongs parallel. A gripping model has been presented in which the gripping operation is equivalent to the grasp of multi-fingered robot hands with friction contact point model. The models for calculating contact forces with constrained tongs and under-constrained tongs are presented with different constraint functions based on gradient flow optimization algorithms, and the constraint functions describe the definite state of the tongs during forging operation. By comparing the simulation and experiment results of the contact and gripping forces, it shows that the contact forces are different when the gripping in different rotation angles and the contact forces with constrained tongs is much smaller than that with under-constrained tongs, especially in the vertical position.

Abstract: Shape Memory Alloy(SMA)has advantages of great recovery stress and elastic modulus varied with the temperature, so it can be embedded in composite structure to active control structure deformation and vibration. In this paper, we have deducted the recovery stress at different temperature by modifying the phase-change coefficient Ω of Liang Constitutive Model[1], then base on = /E equation, the recovery stress is translated into recovery strain. By using finite element software ANSYS, the natural frequency of composite plate at influence of recovery stress can be obtained under both ends of fixed conditions at three configurations. The steady-state vibration response of the composite plate embedded SMA fibers is also simulated. The results show that recovery stress of SMA can increase the natural frequency and can suppress vibration effectively.

Abstract: A kind of adaptive searching optimization active vibration control system of smart structure with piezoelectric materials was put forward, and the smart flexible cantilever structure was analyzed, the active vibration control system was realized in the lab. The result proved the methods’ feasibility and practicability.

Abstract: A composite piezoelectric energy converter intended for Micro-electromechanical Systems (MEMS) from background vibrations is presented. The converter is composed of a piezoelectric circular plate bonded to a brass substrate with different diameters. The vibration of the structure is analyzed based on the thermal-piezoelectric-elastic theory and Kirchhoff’s assumption. The vibration solutions and the relation between the vibration and output charge are obtained. The effects of geometric characteristics and environment temperatures on the electrical energy generation are numerically discussed. The numerical results show that the vibration-induced voltage is proportional to the excitation frequency and the thickness of the device, but is inversely proportional to the temperature of the environment. The experimental data show good agreement with the energy conversion analytical model.

Abstract: Based on the LuGre friction model, the nonlinear dynamic characteristic of a sucker-rod pumping system of deviated well is simulated. Firstly, the LuGre friction model is introduced, and the values of its six model parameters, which satisfy the engineering’s needs, are obtained according to handbook and computation. Then, the vibration of the rod of sucker-rod pumping system is regarded as an axial vibration of multi-segment flexible rod. The loads analysis of rod element is accomplished by means of the finite element method, and recurrence formulas of load and elastic deformation are derived through the finite difference method. The boundary and initial conditions of the load and deformation are evaluated. In the end, a numerical example is given, where a comparison between the elastic deformation of pumping piston obtained based on LuGre friction model and that obtained based on classical Coulomb friction model is made to show that the LuGre friction model describe the friction of sucker-rod pumping system better.

Abstract: For improving the bonding strength of chip and vibration stability, propagation characteristics of ultrasonic wave across contact interface in wire bonding transducer was investigated in this paper. The rough contact interface is studied. The propagation characteristic is equivalent to the spring-mass model. The spring-mass model of ultrasonic propagation through contact interface was established. The reflection coefficient and transmission coefficient of ultrasonic is related to the stiffness of the contact interface. Aluminum wire bond experiments were performed on a laboratory test bench. The vibration velocities of the capillary and bond strength of chip were obtained at different tightening torque. The results show that the tightening torque in a moderate condition can the highest velocity of capillary and the largest bond strength be reached. Measuring of velocity of capillary can be a method of forecasting the bond strength of chip

Abstract: The application of vibration analysis in fault diagnosis of rotary machine becomes more and more popular. Aiming at an abnormal high frequency vibration of a stern bearing, this paper proposed a method of fault diagnosis based on the analysis of vibration characteristics and the spectral analysis. From the gathered vibration data of a stern shaft bench through Pulse Vibration Analysis Platform, using the speed spectrum array to determine the characteristics of vibration source, with the analysis of vibration characteristics of the bench, it concluded that the abnormal high frequency vibration source of the stern bearing is a weak rigidity part of bench─ tacho-torque meter. The vibration data of again test after strengthening the part illustrated the validity of this diagnostic mode.

Abstract: Agitator as a key component of fracturing unit, its dynamic characteristic has great influence on performance of fracturing fluid and operation of sand blender, so it is necessary to get the dynamic characteristic of agitator. In this study, we conduct the experimental modal test of agitator by using uTeKL dynamic signal analysis system. The modal test system structure, the procedure and the technique of modeling and testing is presented in detail. Also the finite element modal analysis of agitator is carried out with SolidWorks software. Modal test and finite element analysis reveal similar results with the maximum natural frequency error is 5.15% and corresponding modal shapes are nearly same, which means the method and technique of modal test proposed in this paper is correct, the result is confident, and the finite element modal analysis of the agitator is feasible.