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Table of Content

    15 February 2018, Volume 40 Issue 1
    Review
    ADVANCE OF EXPERIMENTAL TECHNOLOGIES FOR STRUCTURAL MODAL TEST IN HIGH TEMPERATURE ENVIRONMENTS
    YU Kaiping, BAI Yunhe, ZHAO Rui, ZHOU Haotian
    2018, 40(1):  1-12.  DOI: 10.6052/1000-0879-17-288
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    Since the hypersonic vehicle is acted by a serious aerodynamic thermal load caused by the flight through the atmosphere, it is necessary to consider the effect of the high temperature in the ground test of the vehicle structures. But the structural modal experiment in a high temperature environment is far more complex than the normal modal experiment with many technical difficulties to be solved. In this paper, the advance of the thermal modal test technology is reviewed. The characteristics and the applicability of the excitation and measurement techniques to be used in the high temperature environment are discussed in detail. The development direction and the research focus of the structural modal test technology in the high temperature environment are suggested.

    Applied Research
    OPTIMAL DAMPING MATCHING Of SHOCK ABSORBER FOR A LIGHT TRUCK SUSPENSION SYSTEM
    LI Shaohua, ZHAO Junwu, ZHANG Zhida
    2018, 40(1):  13-17.  DOI: 10.6052/1000-0879-17-342
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    Damping matching is a key issue in the design of shock absorber for a vehicle suspension system. For light trucks, a half vehicle model for the optimal design of suspension damping is established in MATLAB.Using the root mean square value of the vertical and pitching accelerations of the vehicle body and the tire dynamic load as the evaluation index, the objective function of the damping ratio optimization design is established through the linearity-weighted-sum method. Under the stochastic road roughness excitation, the suspension damping ratio is optimized and analyzed, and the result is verified by the real car experiment. It is shown that the optimal design of the suspension damping ratio effectively improves the vehicle ride comfort, and thus provides a useful reference for the dynamic design of the vehicle suspension.
    AN EXPERIMENTAL METHOD BASED ON ENERGY RELEASE RATE OF INTERFACIAL FRACTURE
    WANG Shuo, ZHANG Zheng
    2018, 40(1):  18-23.  DOI: 10.6052/1000-0879-17-225
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    Based on commonly used experimental methods in fracture mechanics, with special consideration of the features of the interface fracture, an experimental method for the interface crack is established in the framework of fracture mechanics. With this method, the critical energy release rate can be obtained through the measurement of the load and the displacement of the specimens, for a given length of a crack. Related experiment data verify the robustness of this method, and the qualified consistency between the set of experimental results and the corresponding ones obtained by this method. Further, with this method, the maximum load capacity of the structure can be predicted according to the impedance energy curve. So, this analytic method is a powerful experimental method for the determination of the strength of the interface crack through the energy release rate with wider applications.

    A RHEOLOGICAL CONSOLIDATION MODEL FOR SOFT CLAY WITH CONSIDERATION OF TEMPERATURE AND THE ANALYTICAL
    GUO Hua, LIU Ganbin, XUE Chuancheng
    2018, 40(1):  24-29.  DOI: 10.6052/1000-0879-17-346
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    Based on the four element rheological model, a rheological consolidation model for the Ningbo soft clay is established with consideration of the influence of temperature, and the analytical solution for the rheological consolidation of the saturated soft clay under instantaneous loading conditions is obtained by Laplace transform. Based on the rheological consolidation test results of soft clay in different temperatures, the parameters in the rheological Ningbo soft clay four element model are determined. And the theoretical values are compared with the experimental values. It is shown thatthe model can well reflect the rheological consolidation characteristics of the Ningbo soft clay,and the calculated results are in good agreement with the experimental results. The increase of the temperature leads to an increase of the permeability coefficient, and the pore pressure dissipates at the same time, leading to an accelerated consolidation.
    STRUCTURAL RESPONSE ESTIMATION AND CONTROL OPTIMIZATION BASED ON WHITE NOISE MODELS
    LIU Yufei, FAN Jiansheng
    2018, 40(1):  30-38.  DOI: 10.6052/1000-0879-17-237
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    STUDY OF PARAMETRIC VIBRATION OF GYROSCOPIC CONTINUA BASED ON NONLINEAR NORMAL MODES AND A NUMERICAL ITERATIVE APPROACH
    QI Hui, LIANG Feng
    2018, 40(1):  39-44.  DOI: 10.6052/1000-0879-17-252
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    The nonlinear normal mode technique and a numerical iterative approach are applied to study the nonlinear parametric vibrations of pipes conveying pulsating fluid as an example of gyroscopic continua. The nonlinear non-autonomous governing equations are transformed into a set of pseudo-autonomous ones by employing the harmonic balance method. The nonlinear normal modes are constructed by the invariant manifold method in the state space and a numerical iterative approach is adopted to obtain the modal coefficients, in which the modal solutions of the corresponding autonomous system are taken as the initial values. The results obtained see a fast convergence. The frequency-amplitude responses and the invariant manifolds are both obtained in the frequency-domain study, while the quadrature phase difference and the traveling waves are found in the time-domain complex modal analysis.
    A COMPLEX PARAMETER MODEL UPDATING METHOD FOR DAMPING CHARACTERISTICS OF FINITE ELEMENT MODELS
    LI Shuang, GANG Xianyue
    2018, 40(1):  45-50.  DOI: 10.6052/1000-0879-17-207
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    Damping plays an important role in structural dynamics. However,it is difficult to model the damping characteristics in the finite element analysis. Using the experimental and analytical frequency response functions (FRF), a complex parameter model updating method is developed to update the mass, stiffness and damping properties. Taking the complex proportional coefficients of the element matrices as the updating variables, the direct updating sensitivity equation system is deduced, and the relationship between the complex updating parameters and the typical damping types is revealed. At the end, the performance of the proposed method is evaluated with examples of a 6-DOF lumped system and a 25 truss structure.
    A DAMAGE CONSTITUTIVE MODEL OF ROCK WITH CONSIDERATION OF RESIDUAL STRENGTH
    ZHANG Huimei, LIU Xiaoning, PENG Chuan, YANG Gengshe, YE Wanjun, SHEN Yanjun, LIU Hui
    2018, 40(1):  51-55.  DOI: 10.6052/1000-0879-17-201
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    A rock damage constitutive model with consideration of residual strength is established,based on the strength of rock micro elements and the Weibull distribution law, and the damage variable correction factor is discussed.Using multivariate functions to obtain the extreme values,the theoretical expressions of model parameters \(m\) and \(F_0\) are derived with consideration of correction coefficients. The model consists of an addition of a linear term of correction coefficients; the correction factor \(\delta\) reflects the characteristics of the residual strength of the rock, to improve the accuracy of the modified constitutive model with an appropriate value of \(\delta\).
    MOTION OF THE ECCENTRIC ELLIPSOID: GYROSCOPIC BALANCE CONDITION AND STABILITY
    LI Luxian, ZHU Pancheng, LI Jinbin
    2018, 40(1):  56-60.  DOI: 10.6052/1000-0879-17-323
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    This paper studies the influence of the friction coefficient\(\mu\) and the eccentric distance \(\rho\) on the gyroscopic balance in the rotating process of the eccentric ellipsoid. The time evolution of the angle \(\theta=\theta(t)\) and two kinds of stationary solutions are obtained. Our numerical results show that the frictional force is an essential condition for spinning vertically, and can enhance it. That is, when \(\rho\) is constant, the time required for the ellipsoid to standing upright decreases with the increase of \(\mu\). The eccentric distance will delay the process of the standing upright of the rotator, and with the increase of \(\rho\), for a given frictional coefficient \(\mu\),it takes more time to reach the gyroscopic balance. When \(\rho\) keeps increasing, the ellipsoid will eventually take a position of a stabilized angle \(\theta_{\rm f}\) rather than an upright one, and \(\theta_{\rm f}\) is proportional to \(\rho\). The equivalent section curves are obtained corresponding to these values of eccentricity. When \(\rho\) continues to increase, a point will be reached where there will be no gyroscopic balance anymore.
    NODAL DISPLACEMENT ACCURACY OF ONE-DIMENSIONAL FINITE ELEMENTS
    XING Yufeng, HUANG Zhiwei
    2018, 40(1):  61-66.  DOI: 10.6052/1000-0879-17-213
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    One-dimensional (1D) components as rod, shaft and beam are widely used in engineering structures. This paper investigates the nodal displacement accuracy of 1D high-order rod element and beam elements subjected to arbitrary polynomial distributed loads. First, the exact solutions are derived for the uniform fixed-free rod and the Euler beam as well as the Timoshenko beam,then the free-end nodal displacements are obtained by using a second-order rod element, a fifth-order Euler beam element and a third-order Timoshenko beam element, respectively. By comparing the FEM results with the exact solutions, it is shown that accurate nodal displacements can be obtained by using linear or high-order rod elements, and cubic or high-order Euler and Timoshenko beam elements. Moreover, by taking the second-order rod element as an example, the present results and conclusions are validated by using the static condensation method.
    MOTION OF THE DAMPED FOUCAULT PENDULUM
    WU Yan
    2018, 40(1):  67-72.  DOI: 10.6052/1000-0879-14-316
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    We give the equation of motion, get the analytical solution to the damped Foucault pendulum, and do some exploration about properties of the solution in this thesis. The model built in this thesis is an ideal simple pendulum with Coriolis force and damping force that's proportional to velocity.
    Research on Education