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1.
The endochronic equations proposed by Valanis (1980) were extended to a finite deformation range. Jaumann's rate,Fu's rate and Wu's rate were incorporated into the endochronic equations to analyze simple shear finite deformation. Incremental equations and numerical solutions are deduced for three endochronic objective models. The results show that an oscillatory shear stress response to a monotonically increasing shear strain occurs when the Jaumann's rate objective model is employed for endochronic materials. The oscillatory response is dependent on the adopted objective rate. Compared with the Jaumann's rate, the Fu's rate and the Wu's rate satisfy the restrictions to elastic-plastic constitutive relations and are in agreement with the experimental results. 相似文献
2.
振动剪切作用下LDPE和HDPE熔体的非仿射网络结构模型 总被引：1，自引：0，他引：1
We propose molten polymer‘s entanglement network deformation to be nonaffine and use transient network structural theory with the revised Liu‘s kinetics rate equation and the revised upper convected Maxwell constitutive equation to establish a nonaffine network Structural constitutive model for studying the rheological behavior of molten Low-Density Polyethylene(LDPE)and High Density Polyethylene(HDPE)in oscillatory shear.As a result,when the strain amplitude or frequency increases,the shear stress amplitude increases.At the same time,the accuracy of the nonaffine network model is higher than that of affine network model.It is clear that there is a small amount of nonaffine network deformation for LDPE melts which have long-chain branches,and there is a larger amount of nonaffine network deformation in oscillatory shear for HDPE melts which has no long-chain branches.So we had better consider the network deformation nonaffine when we establish the constitutive equations of polymer melts in oscillatory shear. 相似文献
3.
The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated. Based on the first-order shear deformation theory （FSDT）, the nonlinear dynamic equations involving the transverse shear deformation and initial geometric imperfections were derived with the Hamilton philosophy. The axial shallow groove of the laminated composite cylindrical shell was treated as the initial geometric imperfections in the dynamic equations. A semi-analytical method of expanding displacements and loads along the circumferential direction and employing the finite difference method along the axial direction and in the time domain is used to solve the governing equations and obtain the dynamic response of the laminated shell. The B-R criterion was employed to determine the critical loads of dynamic buckling of the shell. The effects of the parameters of the shallow groove on the dynamic response and buckling were discussed in this paper and the results show that the axial shallow grooves greatly affect the dynamic response and buckling. 相似文献
4.
In this paper, a nonlinear mathematical model for analyzing dynamical response to the large deformation of piles with initial displacements is firstly established with the arc-coordinate, and it is a set of nonlinear integral-differential equations, in which, the Winkeler model is used to simulate the resistance of the soil to the pile. Secondly, a set of new auxiliary functions are introduced. The differential-integral equations are transformed into a set of nonlinear differential equations,and the differential quadrature method (DQM) and the finite difference method (FDM) are applied to discretize the set of nonlinear equations in the spatial and time domains, respectively. Then, the Newton-Raphson method is used to solve the set of discretization algebraic equations at each time step. Finally, numerical examples are presented, and the dynamical responses to the deformation of piles, including configuration, bending moment and shear force, are graphically illuminated. In calculation, two types of initial displacements and dynamical loads are applied, and the effects of parameters on the dynamical responses of piles are analyzed in detail. 相似文献
5.
硬盘系统一般采用气体润滑，以提高使用寿命和读写可靠性．本文讨论了多聚脂流体润滑的ＩＢＭ３３７０ 磁头／ 磁盘系统，以期提高磁记录密度．润滑模型中考虑了超薄流体润滑的剪薄效应，并用有限差分法对润滑方程进行求解．应用摄动理论建立了ＩＢＭ３３７０ 磁头／ 磁盘系统的动力学模型，分别对气体润滑和液体润滑的两自由度磁头的动力响应进行了仿真．仿真结果表明，在相同磁头倾角条件下，液膜润滑的磁头／ 磁盘的动力稳定性优于气体润滑的磁头／ 磁盘系统 相似文献
6.
Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is derived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be determined. 相似文献
7.
Zhiming Ye Ph. D. 《上海大学学报(英文版)》1997,1(1):28-35
In this paper, a new nonlinear formulation of plates, including shear and rotatory inertia and transverse normal stress effects,
is developed by means of general assumptions, of which the von Karman-type formulation and some thick plate theories are special cases. To keep the formulation fairly general, the problem addressed
in this paper simultaneously includes: the effects of shear deformation according to the geometric deformation similarity
of the cross-section, the rotatory inertia, and the transverse normal stress. The three-dimensional compatible equations are
applied to derive the basic equations. Numerical results are given for linear and non-linear analysis of plates.
This Work was supported by the Natural Science Fundation of Shanghai for Returning Scholars 相似文献
8.
Recently, the finite element method (FEM) has been commonly applied in the engineering analysis of rotor dynamics. Gyroscopic moments, rotary inertia, transverse shear deformation and gravity can be included in computational models of rotor-bearing systems. In this paper, a finite element model and its solution method are presented for the calculation of the dynamics of dual rotor systems. A typical structure with two rotor shafts is discussed and the procedure for obtaining the coupling motion equations of the subsystems is illustrated. A computer program is developed to solve critical speeds and to simulate the transient motion. The influence of gyroscopic moments on co-rotation and counter-rotation is analyzed, and the effect of the speed ratio on critical speed is studied. The dynamic characteristics under different conditions of increasing speed during start-up are demonstrated by comparison with transient nodal displacements. The presented model provides a complete foundation for further investigation of the dynamics of dual rotor systems. 相似文献
9.
考虑剪切效应有限变形粘弹性板的动力稳定性 总被引：4，自引：0，他引：4
Based on Reddy‘s theory of plates with higher-order shear deformations and the Boltzmann superposition principles,the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects,The Galerkin method was applied to simplify the set of equations.The numerical methods in nonlinear dynamics were used to solve the simplified system.It could e seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads.The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelatic plates were investigated. 相似文献
10.
LAU C.W.H. LIM C.W. LEUNG A.Y.T. 《浙江大学学报(A卷英文版)》2005,6(9):962-966
INTRODUCTION Piezoelectricity is an electromechanical phe- nomenon which couples elasticity and electricity through the existence of pressure induced electrical field or electric induced stress field. The piezoelectric materials are usually surface bonded in patches or fully embedded in the host structure, so that the structure becomes a laminated piezoelectric beam. Tzou and Gadre (1989), Lee (1990), Crawly and Lazarus (1991) developed laminated plate models incorporating the piezoelect… 相似文献
11.
Methane gas extraction by a deep well installed in methane hydrate bearing sediments (MHBS) found in deep subsea and permafrost regions is a coupled thermal–hydraulic–mechanical–chemical (THMC) process. The key processes include heat convection between layers, local deformation due to compaction, and stress relaxation caused by damage of the bonded structure. As improper production may induce formation compaction, sand production, and wellbore failures, a numerical code is needed to simulate the THMC processes during methane gas production so that geomechanics and production risks can be quantified. In this study, a nonlinear THMC model was implemented in the partial differential equations (PDE) and structural mechanics module of the COMSOL Multiphysics® finite element code. This paper describes the non-linear coupled governing equations of the mechanical behavior during hydrate dissociation. In particular, it introduces a new thermodynamics-based constitutive model to simulate the mechanical behavior of hydrate bearing sediments. The performance of the newly developed code was examined by comparing the computed results with test data and other simulation results. The differences between fully coupled and semi-coupled models were analyzed. For example, heterogeneous turbidite layers observed in the Nankai Trough were modeled, and behaviors such as heat convection between different layers, shear stress and strain concentration were examined. 相似文献
12.
Under tension and shear conditions related to unloading of rock mass, a jointed rock mass model of linear elastic fracture mechanics is established. According to the model, the equations of stresses, strains and displacements of the region influenced by the crack but relatively faraway the crack (the distance between the research point and the center of the crack is longer than the length of crack) are derived. They are important for evaluating the deformation of cracked rock. It is demonstrated by the comparison between computational results of these theoretical equations and the observed data from unloading test that they are applicable for actual engineering. 相似文献
13.
Yi-feng Wu Hao Wang Ai-qun Li Dong-ming Feng Ben Sha Yu-ping Zhang 《浙江大学学报(A卷英文版)》2017,18(5):363-376
Based on the explicit finite element (FE) software ANSYS/LS-DYNA, the FE model for a sliding lead rubber bearing (SLRB) is developed. The design parameters of the laminated steel, including thickness, density, and Young’s modulus, are modified to greatly enlarge the time step size of the model. Three types of contact relations in ANSYS/LS-DYNA are employed to analyze all the contact relations existing in the bearing. Then numerical simulations of the compression tests and a series of correlation tests on compression-shear properties for the bearing are conducted, and the numerical results are further verified by experimental and theoretical ones. Results show that the developed FE model is capable of reproducing the vertical stiffness and the particular hysteresis behavior of the bearing. The shear stresses of the intermediate rubber layer obtained from the numerical simulation agree well with the theoretical results. Moreover, it is observed from the numerical simulation that the lead cylinder undergoes plastic deformation even if no additional lateral load is applied, and an extremely large plastic deformation when a shear displacement of 115 mm is applied. Furthermore, compared with the implicit analysis, the computational cost of the explicit analysis is much more acceptable. Therefore, it can be concluded that the proposed modeling method for the SLRB is accurate and practical. 相似文献
14.
TANG Qian ZHU Cai-chao LIAO Xiao-yun LU Bo 《重庆大学学报(英文版)》2005,4(3):125-128
Traditional variation analysis methods are not applicable to non-rigid assemblies due to possible part deformation during the assembly process. This paper presents the use of finite element methods to simulate assembly deformation. The relationship between the parts＇ variation and the variation of the key points in final assembly for quality control is set up by calculating the spring back deformation after assembly. Moreover, the optimization method for non-rigid assembly variations based on finite element analysis is presented. The optimal objective is to reduce the manufacturing cost. The approach is implemented by using ANSYS and MATLAB. The test example shows that the proposed method is effective and applicable. 相似文献
15.
王芳 《雁北师范学院学报》2013,(4):4-6
讨论一类二阶非线性泛函微分方程（a（t）y′（t）σ）′＋q（t）F（y（t）,y（τ（t）））g（y′（t））=0在F（u,ν）=f（ν）∈C（R,R）这一特殊情形时方程解的振动性,得到此类方程的解振动性的充分判据,所获得的结果可应用于σ是分母为奇数时的情形,改进了一些文献中的相应结论。 相似文献
16.
研究了一类一阶非线性具偏差变元的微分方程解的性质，获得了其解的有关振动性质的一些新的结果，所用的方法也适用于时超微分方程，所得结果推广了文献中的相应结果． 相似文献
17.
The dynamic response of moored crane-ship is studied. Governing equations for the dynamic response of a crane-ship coupled with the pendulum motion of the payload are derived based on Lagrange＇s equations. The boom is modeled based on finite element method, while the payload is modeled as a planar pendulum of point mass. The dynamic response was studied using numerical method. The calculation results show that the large-amplitude responses occur at wave periods near the natural period of the payload. Load swing angle is smaller for crane-ship with flexible boom, in comparison with rigid boom. The ship surge motions have large vibrations for crane-ship with flexible boom, which were not observed for a rigid boom. The analysis identifies the significance of key parameters and reveals how the system design can be adjusted to avoid critical conditions. 相似文献
18.
INTRODUCTIONThemotionoftheflowinarotatingcurvedpipeisafundamentalproblem ,whosesolutionhaspotentialapplicationsingasturbines ,elec tricgenerators ,electricmotorsandsomeequip mentsusedinseparationprocesses.Itisimpor tanttoknowtheflowstructurecharacteristic… 相似文献
19.
本文讨论一类多滞量抛物型时滞偏微分方程解的振动性质 ,获得了其一切解振动的充要条件及一些充分条件 . 相似文献
20.
研究一类多滞量的非线性中立型抛物微分方程解的振动性，利用一阶泛函微分不等式的结果得到一些判断方程的解振动的务件．结果充分表明振动是由时滞引起的，并揭示了这类方程和普通的抛物型偏微分方程的本质差异。 相似文献