Applied Mechanics and Materials Vols. 300-301

Abstract: An important part of the numerical simulation is the grid which the quality has great influence on the calculation precision, and also the influence often is crucial factor in most of situation. Water-entry at high speed is a complex unsteady process, and its numerical simulation needs to take consider of natural cavitation as well as rotation of the underwater body. In this paper, a new meshing method was given with using the Layering, Smoothing and Remeshing for calculating the unsteady flow field. Numerical simulation shows that the mesh given in this paper has better quality, and can be used to calculate the multi-phase mode of water-entry at the high speed.

Abstract: To predict the vibration characteristics of the rotor-bearing system by using the scale model and the associated scaling laws may significantly reduce the time and money required by the experiments. To this end, the dynamic similarity criteria are investigated inferring from the model behavior of rotor-bearing system to the vibration response of the prototype. The similar relationship was established by combining method of dimensional analysis and equation analysis based on similarity theory, and the effectiveness was verified through the finite element method. The result provide the theoretical rational for further study of the similarity design of the rotor-bearing system.

Abstract: In this study, we analyze the influence of passive joint viscous friction on modal space decoupling for a class of symmetric spatial parallel mechanisms. The Jacobian matrix relating the platform movements to each passive joint velocity is first gained by vector analysis and the passive joint damping matrix is then derived by applying the Kane method. Next, an analytic formula index measuring the damping non-proportionality is proposed using classical modal analysis of dynamic equations in task space. Based on the index, a new optimal design method is found which establishes the kinematics parameters for minimizing the non-proportional part of damping and achieves optimal fault tolerance for modal space decoupling. To illustrate the effectiveness of the theory, the new method was used to redesign two configurations of an actual group manipulator.

Abstract: For the buckling problems of slender columns, size effects on buckling behaviors have been studied based on the modified couple stress theory. The governing equations are obtained by using variational statement and the buckling loads of slender columns are assessed. The results show that the buckling loads predicted by the new model are size-dependent.

Abstract: In this paper, a comparison of two kinds of acceleration models under temperature and humidity joint stress is given. The traditional generalized Arrhenius model and Eyring Model give two ways to describe the accelerated life of products. First, through some mathematical transformation and synthesizing of these two models we have concluded two acceleration models under temperature and humidity joint stress which are described in detail in this paper. Estimations of model parameters are also given. Secondly, by comparing accelerated life coefficient and coefficient of variations, we can take a glimpse of the models in their fitness of actual conditions. Then, since the models presented in this paper follow the features of nested models, a likelihood ratio test is conducted which takes a further step in the work of model selection. At last, these two models are compared through an application example – Smart Electricity Meter.

Abstract: In order to study the thermal stability of PPS (polyphenylene sulfide) filter media, by means of thermogravimetry(TG), thermal degradation kinetics behavior of two kinds of PPS filter media were analyzed. The kinetic parameters of PPS filter media were obtained according to Flynn-Wall-Ozawa method. Thermal stability of PPS filter media was discussed. It was found that the initial decomposition temperature and activation energy of N3 sample are all higher than B1 sample, the thermal stability of N3 sample is better than B1 sample, and kinetic analysis can be used as an important method to evaluate the thermal stability of filter media.

Abstract: The operating performance of micro-gyroscope may be easily influenced by various factors, which changes the dynamic response accordingly. Generally, the influences can’t be quantified because of the complexity, and the accurate sensitivity and linearity measuring of micro-gyroscope meets enormous difficulties. In order to accomplish corresponding measuring and analysis accurately and efficiently, input excitation waves are designed based on mathematical analysis of the measuring principles and vibration response, and each measuring of sensitivity and linearity can be analyzed in a single test. In this way, the influences from manual operation and variation of measuring environment are well eliminated, and some key parameters of the dynamic response are obtained, such as sensitive voltage, response function, linearity error, etc. In addition, problems about imbalance in double drive vibration, design of the minimum excitation voltage and evaluation of the measuring error are also described. Therefore, some important references are provided for subsequent design, experiment and engineering application.

Abstract: This paper adopts Finite Volume Method, with the aid of GT-POWER platform, building the joint model of engine with cracking sound attenuation coupler. Based on the correctness of verification model, we research the cracking sound attenuation coupler’s influence on exhaust noise with engine performance. The results show that the muffler causes little power loss for engine at low and medium speed. At high speed the muffler brings power loss to engine mainly coming from muffler tail. Comparing with original muffler in the aspects of noise elimination performance and engine performance is not obvious effect and at the meantime providing a feasible technology method for realizing high efficiency and cleaning burning of methanol.

Abstract: A linear viscoelastic plastic creep model of mica-quartzose schist is established by using the method of establishing combined-linear-component model based on triaxial creep test. The micro-structural changes of mica-quartzose schist during triaxial creep process are observed by using the scanning electron microscope test, based on that, the relation of macro-stress and macro-strain with porosity and damage variable are established through statistical damage theory and simplified mechanical model respectively, the creep damage variable is obtained by further derivation on the basis of above study. The creep damage variable is simplified according to the whole creep process curve, substitutes the simplified creep damage to the estabilished linear viscoelastic plastic creep model of mica-quartzose schist, considering the change of modulus and viscosity during creep process, a viscoelastic plastic damage model of mica-quartzose schist is established. The model parameters are got by segment fitting, the good consistency of the test curves and the fitted curves shows the right and reasonable of the creep model, it also shows that the model can well describe the nonlinear accelerated creep stage. Sensitivity analysis shows that parameter m has greater influence on the accelerated creep deformation than parameter a.

Abstract: The electromagnetic force produced by air-gap eccentricity magnetic field includes kinds of frequencies, and excites multiform magnetism and solid coupling vibrations of stator system. In this paper, based on the improved model of double-shell system of asynchronous machine, the magnetism and solid coupling vibration equations of double-shell system are obtained. Considering the air-gap eccentricity, an improved expression of electromagnetic force is derived. Then the method of multiple scales is applied to solve the nonlinear parametric resonance. Through the numerical calculation, the influence of electromagnetic and mechanic parameters on amplitude- frequency characteristics is analyzed.