Dynamic crack growth under stress wave loading

The crack growth process has been analysed on the basis of a fracture criterion of a dynamic stress intensity factor when a crack in an infinite plate was subjected to a pulse type of stress wave. The crack velocity and the amount of crack extension were related to the constant amplitude and the duration of the stress pulse. The calculated amount of crack extension was well in agreement with the experimental one for the polymer material Acrylite (which is similar to polymethylmethacrylate) found by the authors, thus indicating the validity of the present approach.     

Dynamic analysis of underground composite structures under explosion loading

In selecting rational types of underground structures resisting explosion, in order to improve stress states of the structural section and make full use of material strength of each part of the section, the research method of composite structures is presented.Adopting the analysis method of micro-section free body, equilibrium equations, constraint equations and deformation coordination equations are given. Making use of the concept of generalized work and directly introducing Lagrange multiplier specific in physical meaning,the validity of the constructed generalized functional is proved by using variation method.The rational rigidity matching relationship of composite structure section is presentedthrough example calculations.     

Dynamic properties of automotive damper modules

This paper addresses the dynamic properties of automotive shock absorber modules. Analyzing an equivalent linear system, a set of characteristic dimensionless numbers are introduced in order to qualify the dynamic performance of the damper and the damper module. The dependency of these numbers on the main parameters of the module like the damping constant, the spring stiffness of the damper, the top mount stiffness and the piston rod mass is shown. These numbers may also serve as similarity coefficients for quite different dampers regarding their dynamic behavior. Furthermore, they can be used to adjust the stiffness of the different force elements of the damper module to achieve an optimal damping quality.     

Dynamic fracture analysis of adhesive bonded material under normal loading

Dynamic fracture behavior of a Griffith crack along the interface of an adhesive bonded material under normal loading is studied. The singular integral equations are obtained by employing integral transformation and introducing dislocation density functions. By adopting Gauss-Jacobi integration formula, the problem is reduced to the solution of algebraic equations, and by collocation dots method. their solutions can be obtained Based on the parametric discussions presented in the paper, the following conclusions can be drawn： （1） Mode I dynamic stress intensity factor （DSIF） increases with increasing initial crack length and decreasing visco-elastic layer thickness, revealing distinct size effect; （2） The influence of the visco-elastic adhesive relaxation time on the DSIF should not be ignored.     

Dynamic analysis of a disc brake under frictional and thermomechanical internal loading

The study of the vibratory response of a mechanical system as complex as a disc brake needs to consider the complexity of the problem induced by the coupling of tribological, thermomechanical and dynamical effects. Experimental consideration are discussed here for two set ups at the full scale of the disc brake and at a local scale focussed on the third body interface. A numerical model with thermomechanical and dynamical couplings is then presented, followed by a substantial discussion.     

Dynamic response of a pile embedded in elastic half space subjected to harmonic vertical loading

An analytical method is developed to investigate the dynamic response of a pile subjected to harmonic vertical loading.The pile is modeled as a one-dimensional(1D)elastic rod.The elastic soil is divided into a homogeneous half space underlying the base of pile and a series of infinitesimally thin layers along the vertical shaft of pile.The analytical solution for the soil-pile dynamic interaction problem is obtained by the method of Hankel transformation.The proposed solution is compared with the classical plane strain solution.Arithmetical examples are presented to demonstrate the sensitivity of the vertical impedance of the pile to relevant parameters.     

Dynamic analysis of an axially moving plate subjected to thermal loading

Dynamic analysis of axially moving thermally loaded two-dimensional system is presented in this paper. Using the Hamilton's principle, the differential equation of the transverse motion of the moving plate is derived. Using the extended Galerkin method the approximate solution is determined in this work. To verify the present approach, the calculation results of buckling thermal load for stationary plate are compared with the results published in literature. Dynamic analysis of axially moving aluminum plate subjected to thermal loading is presented. Besides the thermal critical loading the effects of transport speed and axial tension on dynamic behavior of axially moving aluminum plate are presented.     

Dynamic stress intensity factor for cracked functionally graded orthotropic medium under time-harmonic loading

Dynamic stress intensity factor for a Griffith crack in functionally graded orthotropic materials under time-harmonic loading is investigated in the present paper. By using the Fourier transform and defining the jumps of displacement components across the crack surface as the unknown functions, two pairs of dual integral equations are derived. To solve the dual integral equations, the jumps of the displacement components across the crack surface are expanded in a series of Jacobi polynomial. Numerical examples are provided to show the effects of material properties and the crack configuration on the dynamic stress intensity factors of the functionally graded orthotropic materials with a Griffith crack.     

Fatigue crack propagation life analysis of solder joints under thermal cyclic loading

Fatigue crack propagation life analysis of solder joints under thermal cyclic loadings was investigated by the strain energy release rate method using finite element analysis. A relationship between the crack-growth rate and the strain energy release rate was derived. Finite element simulations were carried out to investigate the effect of crack growth along the interface of solder and lead in a solder joint assembly. The crack propagation life of the solder joint with an interface crack was predicted from the derived relationship between crack growth rate and values of the strain energy release rate. It was found that crack propagation life is much higher than the crack initiation life.     

Dynamic analysis of rotating flexible disk subjected to double slider loading systems

Rotating disk subjected to stationary slider loading system is a very common mechanical structure. This paper investigates the multibody dynamics of a rotating flexible annular thin disk subjected to double slider loading systems. Along the rotating disk radial and circumferential directions, two stationary slider loading systems are distributed. System dynamic model is solved by Galerkin's method, and then natural frequency, dynamic stability and mode shape are determined with a quadratic eigenvalue problem. Effects of the distributing positions and interaction mechanism of the double slider loading systems on natural frequency, dynamic stability and mode shape are discussed and investigated.     

Dynamic analysis of a tethered satellite system for space debris capture

Herein we analyze the dynamic behavior of a tethered satellite system for space debris capture, considering the large deformation of a tether. The tethered satellite system is modeled as two point masses and a string, and the equations of motion of the tethered satellite system are derived by using the absolute nodal coordinate formulation. To calculate the net velocity after debris capture, equations are established describing the momentum exchange between the net and the space debris. By using this model, the dynamic responses of the tethered satellite system after debris capture are calculated for the variations of the capture angles and capture velocities of the debris. This allows analysis of the orbital response of the tethered satellite system and the large tensions arising from tether tumbling. Finally, we analyze the effects of varying system parameters of the tethered satellite system and the space debris upon the dynamic responses.     

梁的弯曲正应力的材料力学方法修正

从矩形截面梁的剪应力公式出发,推导了在横力弯曲情况下梁的弯曲正应力的近似公式．当梁上的分布荷载可用单一的多项式表示时,该公式在取泊松比v=0时与弹性力学的精确解一致,在其他情况下有些误差,但比传统的材料力学解精确很多．提供了简支梁部分受均布荷载作用的算例,给出了材料力学中梁的正应力公式、该近似公式的计算结果及精确解并做了比较．讨论了公式和方法的普适性．     

Electrostatic stress analysis of an anisotropic piezoelectric half-plane under surface electromechanical loading

The generalized stress components on an anisotropic piezoelectric half-plane boundary under surface electromechanical loading are investigated. It is found that the behaviors of generalized stress components are related to matrices Γ and Ω, which have the same form as those for the purely elastostatic problem. Matrices Γ and Ω contain all the electro-mechanical coupling phenomena of the generalized stress components. All elements of matrices Γ and Ω are expressed explicitly in terms of generalized elastic stiffness for monoclinic piezoelectric materials with the plane of symmetry at x₃ = 0 and for transversely isotropic piezoelectric materials in which the coupled effects between the mechanical (electrical) deformations induced by electrical (mechanical) loadings are studied analytically. A numerical example of the electro-mechanical coupling behavior for PZT-4 is also given.     

Prediction of fatigue crack growth life under variable-amplitude loading using finite element analysis

This article presents an elastic-plastic study aiming at predicting the fatigue crack growth (FCG) of 2024-T3 aluminum alloys under variable-amplitude loading. The proposed analysis needs the estimation of the residual stress distribution ahead of the crack tip during propagation. An elastic-plastic FE analysis has been implemented for modeling FCG using Chaboche's model. The FE study has been carried out through consideration of the loading history effect using the memory rules. Three different loading spectra have been applied in this work. The obtained results have been compared to the experimental ones and it has been proved that the suggested model has a better prediction of the FCG lives of cracked 2024-T3 aluminum alloy structures subjected to variable-amplitude loading.     

Dynamic loading of rigid-plastic cylindrical shells

The behaviour of an infinitely long, rigid-plastic cylindrical shell under impulsive loading by a ring of concentrated force and a band of uniform pressure is discussed. The loads are assumed to be greater than the statical collapse values and to act for a short period of time. Numerical results are obtained for rectangular and triangular pulse shapes for the ring of force and for a rectangular pulse shape for a band of uniform pressure. In the final section of the paper, the steady-state motion which would be produced by a constant load greater than the statical value moving along the shell with constant velocity is obtained for the particular cases of a ring of force and a band of uniform pressure.     

Dynamic stress analysis of the interface in a particle-reinforced composite

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大范围运动细长柔性空间结构动力学特性分析

自由-自由边界无约束状态的细长柔性空间结构大范围运动时的动力学特性对整体结构运动分析和运动控制系统设计具有极其重要的作用。通过浮动坐标系建立结构的运动学关系;借助假设模态法对结构变形进行变量分离;利用Lagrange’s方程建立了结构的刚柔耦合振动方程;再通过Rayleigh-Ritz法,以无大范围运动时的振型函数作为基本解组,得到了大范围运动影响下的结构振动特征方程,求解该方程得到了结构频率和振型。通过几组数值算例的对比分析,指出了非耦合模型和耦合模型下结构频率及振型之间的差异。     

一种新型的宽带随机谱下疲劳寿命计算模型的建立与分析

通过严密的数学推导和具体的数值分析，建立了一种新型的宽带随机载荷谱下疲劳寿命计算模型，数值计算表明，本模型较国际上已有的几种有代表性的近似计算模型有更大的适应范围和更高的精度。