AN EXPERIMENTAL STUDY ON POST-BUCKLING BEHAVIOR OF SLENDER COLUMN WITH FIBER REINFORCED COMPOSITE MATERIAL

Equilibrium paths of post-buckling are measured for large slenderness column specimensmade of the fiber reinforced composite material. The influence of the initial curvature is investigatedexperimentally and compared with the result of the initial post-buckling theory. Both the theoreticaland experimental results reveal that the column with the initial curvature has stable post-buckling be-haviors and is not sensitive to the imperfection in the form of initial curvature. The experimental re-sults show that when the lateral buckling displacement is less than 20 percent of the column length, theexperimental results agree with the results from the theory of initial post-buckling quite well, whilethey agree with the results from the large deflection theory in a quite large range.     

PERTURBATION ANALYSIS FOR WAVE EQUATION OF NONLINEAR ELASTIC ROD

The longitudinal oscillation of a nonlinear elastic rod with lateral inertia was studied. Based on the far field and simple wave theory, a nonlinear Schrodinger (NLS) equation was established under the assumption of small amplitude and long wavelength. It is found that there are NLS envelop solitons in this system. Finally the soliton solution of the NLS equation was presented.     

POST-BUCKLING AND IMPERFECTION SENSITIVITY OF A COLUMN WITH AN EQUILATERAL TRIANGULAR CROSS-SECTION IN THE PLASTIC RANGE

The asymmetric initial post-buckling corresponding to the lowest bifurcation load andthe imperfection sensitivity are analysed in detail for a compressed simply supported column with anequilateral triangular cross-section in the plastic range.The effect of elastic unloading is taken into ac-count in the analysis.The asymptotic relations,including high order terms,among the load,the am-plitude of imperfection and the amplitude of the bifurcation mode are realized.The results show thatthe maximum supported load is very sensitive to imperfection.     

带有初变形薄板的大位移和后屈曲分析

本文提出了一种适合于分析初弯曲板大挠度和后屈曲问题的有限元列式。基于总体的Ｌａｒｇｒａｎｇｅ描述，导出了计及初弯曲效应的非线性分析有关公式。计算表明，本有限元方法对于上述两类问题分析，结果精确，具有工程上的广泛应用价值。     

水平圆管中受压扭作用管桩屈曲后的解析解

首先建立了考虑自重、受水平圆管约束的管柱在压担组合作用下的屈曲方程：此方程为四阶强非线性常微分方程,难以直接精确求解;通过管柱的正弦屈由分析,找到了方程中的小参数;利用小参数摄动法求解了强非线性屈曲方程,得到了管柱螺旋屈曲后的实际屈曲构形解析解,由此可进一步得到管柱发生螺旋屈曲的临界载荷;所得解析结果与数值计算结果及本文结果退化后与文献中的相关结果比较都有良好的一致性．     

圆截面弹性细杆的平面振动

基于Kirchhoff理论讨论圆截面弹性细杆的平面振动．以杆中心线的Frenet坐标系为参考系建立动力学方程．杆作平面运动时,其扭转振动与弯曲振动解耦．讨论任意形状杆的扭转振动和轴向受压直杆在无扭转条件下的弯曲振动,证明直杆平衡的静态Lyapunov稳定性与欧拉稳定性条件为动态稳定性的必要条件．考虑轴向力和截面转动惯性效应的影响,导出弯曲振动的固有频率．     

非线性弹性杆中的应变孤波

本文对非线性弹性杆中的应变孤波进行了分析,着重讨论了杆的物理参数和几何参数对于波动的影响,阐明了孤波传播过程的主要特征。     

DYNAMIC BEHAVIOR OF THIN RECTANGULAR PLATE ATTACHED TO MOVING RIGID

A nonlinear dynamic model of a thin rectangular plate attached to a moving rigid was established by employing the general Hamilton's variational principle. Based on the new model, it is proved theoretically that both phenomena of dynamic stiffening and dynamic softening can occur in the plate when the rigid undergoes different large overall motions including overall translational and rotary motions. It was also proved that dynamic softening effect even can make the trivial equilibrium of the plate lose its stability through bifurcation. Assumed modes method was employed to validate the theoretical result and analyze the approximately critical bifurcation value and the post-buckling equilibria.     

ANALYTICAL SOLUTIONS FOR RESPONSE OF COLLISION OF PARTICLE WITH CONICAL ROD CAUSED BY LONGITUDINAL VIBRATION

The objective is to present exact analytical solutions of longitudinal impact analysis for slender conical rods struck by a particle and a new method is proposed for conical rod-particle impact analysis, in which the superposition method is used and the response of the rod is presented. These analytical results are exact and can be used to validate the numerical methods or other analytical results. The numerical example shows that one of the advantages of the present method is that the analytical form is very simple. The result is that mass ratio and some variables describing the geometrical shape of rods such as taper, length and radius play an important role in impact dynamic system.     

由基模态构造任意支撑杆的多项式型轴向刚度

给出了当杆的横截面积均匀而材料线密度为已知多项式时,由基模态构造任意支撑方式下杆的多项式型的轴向刚度系致的方法,证明了所得轴向刚度的正值性．     

超细长弹性杆动力学仿真的曲面处理算法

超细长弹性杆动力学研究在DNA的平衡、稳定性等问题的研究中有重要的应用。为了便于超细长弹性杆动力学研究中数值结果图形后处理以及研究表面接触等问题的需要,需要建立弹性杆的表面模型和相应算法。本文利用Kirchhoff弹性杆模型的动力学比拟技巧,建立了描述超细长弹性杆曲面的常微分/积分方程组,利用Adames方法和递推方法设计了方程的数值解法,并给出了超长弹性杆的数值仿真结果的图形处理的计算实例。     

INVESTIGATION OF ANTI-PLANE SHEAR BEHAVIOR OF TWO COLLINEAR CRACKS IN PIEZOELECTRIC MATERIALS BY A NEW METHOD

In this paper, the interaction between two collinear cracks in piezoelectric materials under anti-plane shear loading was investigated for the impermeable crack face conditions. By using the Fourier transform, the problem can be solved with two pairs of triple integral equations. These equations are solved using Schmidt's method. This process is quite different from that adopted previously. This study makes it possible to understand the two collinear cracks interaction in piezoelectric materials. The authors are grateful for financial support from the Post-Doctoral Science Foundation and the Natural Science Foundation of Heilongjiang Province.     

JUMPING INSTABILITIES IN THE POST-BUCKLING OF A BEAM ON A PARTIAL NONLINEAR FOUNDATION

Mode jumping is an instability phenomenon in the post-buckling region, which causes a sudden change in the equilibrium configuration and is thus harmful to structure. The con- figuration of a partial elastic foundation can directly induce mode coupling from the buckling stage and through the whole post-buckling region. The mode coupling effect due to the configuration of partial foundation on mode jumping is investigated and demonstrated to be an important factor of determining mode jumping. By properly choosing the partial elastic foundation configuration, mode jumping can be avoided.     

FRACTURE ANALYSIS OF A FUNCTIONALLY GRADED STRIP UNDER PLANE DEFORMATION

In this paper the plane elasticity problem for a functionally graded strip containing a crack is considered. It is assumed that the reciprocal of the shear modulus is a linear function of the thickness-coordinate, while the Possion's ratio keeps constant. By utilizing the Fourier transformation technique and the transfer matrix method, the mixed boundary problem is reduced to a system of singular integral equations that are solved numerically. The influences of the geometric parameters and the graded parameter on the stress intensity factors and the strain energy release rate are investigated. The numerical results show that the graded parameters, the thickness of the strip and the crack size have significant effects on the stress intensity factors and the strain energy release rate.     

平行于异材界面的三维椭圆平片裂纹分析

讨论了拉伸载荷作用下平行于两相材料界面的椭圆平片裂纹问题．首先,使用有限部积分概念和两相材料界面完全接合时的点力基本解导出了一组以裂纹表面位移差为未知函数的超奇异积分方程组．该组方程表明,此时三种裂纹模型同时存在;其次,在数值求解该组方程的过程中,未知函数裂纹表面位移差被近似为位移差的基本密度函数与多项式之积．基本密度函数反映了裂纹前沿应力奇性性态;最后,以拉伸载荷为例,讨论了椭圆平片裂纹与界面的距离、裂纹形状比和不同材料组合对应力强度因子的影响,并以图表形式给出。     

SMA短纤维增强复合材料在热载下的相交特性

在形状记忆合金（ＳＭＡ）复合材料研究中,相变特性的研究是一个主要的工作．基于Ｅｓｈｅｌｂｙ的等效夹杂模型和Ｍｏｒｉ和Ｔａｎａｋａ的场平均法,考虑到ＳＭＡ材料的强物理非线性,发展了增量型的等效夹杂模型（ＩｎｃｒｅｍｅｎｔａｌＥｑｕｉｖａｌｅｎｔＩｎｃｌｕｓｉｏｎＭｏｄｅｌ）．考虑在某一温度循环条件下讨论形状记忆合金短纤维增强的铝基复合材料在热载下的相变行为．特别研究了ＳＭＡ短纤维复合材料在变温过程中纤维几何尺寸、体积分数等参数对ＳＭＡ复合材料的相变行为和ＳＭＡ内残余应力等的影响．这些工作对于指导材料设计和了解ＳＭＡ复合材料热机械特性是颇有意义的．     

THE BEHAVIOR OF TWO COLLINEAR CRACKS IN MAGNETO-ELECTRO-ELASTIC COMPOSITES UNDER ANTI-PLANE SHEAR STRESS LOADING

In this paper, the behavior of two collinear cracks in magneto-electro-elastic composite material under anti-plane shear stress loading is studied by the Schmidt method for permeable electric boundary conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of displacements across the crack surfaces. In solving the triple integral equations, the unknown variable is expanded in a series of Jacobi polynomials. Numerical solutions are obtained. It is shown that the stress field is independent of the electric field and the magnetic flux.     

DYNAMIC BEHAVIOR OF TWO PARALLEL SYMMETRY CRACKS IN MAGNETO-ELECTRO-ELASTIC COMPOSITES UNDER HARMONIC ANTI-PLANE WAVES

The dynamic behavior of two parallel symmetry cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves is studied by Schmidt method. By using the Fourier transform, the problem can be solved with a pair of dual integral equations in which the unknown variable is the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the jumps of the displacements across the crack surface were expanded in a series of Jacobi polynomials. The relations among the electric filed, the magnetic flux and the stress field were obtained. From the results, it can be obtained that the singular stresses in piezoelectric/piezomagnetic materials carry the same forms as those in a general elastic material for the dynamic anti-plane shear fracture problem. The shielding effect of two parallel cracks was also discussed.     

双向应力状态下铝硅合金ZL105塑性行为的实验研究

本文对典型的拉、压性能不同的金属材料铝硅合金ZL105的塑性行为,屈服、强化、体积变化和流动特性,在双向应力状态下进行了全面和系统的实验研究,深入地探讨了影响材料塑性行为的主要因素,得出了新的结果和重要的结论。实验结果表明,平均应力直接影响材料的塑性行为,平均压应力使材料的韧性增强,而平均拉应力使材料的脆性增强。平均压应力不利于塑性变形的发生,相应平均压应力增大的应力状态,材料的屈服应力提高。与流行的塑性体积膨胀的观点不同,在平均应力是压应力的应力状态下,塑性体积收缩,因此,经典的正交准则不再适宜描述该材料的流动性质。材料的强化性质明显地依赖于应力状态。     

草地植物功能性状变异的程度和来源

分析了内蒙古草地植物的6个功能性状在种间、种内不同种群间和同一种群内不同个体间的变异.结果表明,除株高外其余5个功能性状的变异主要来自种间,但种内变异占总体变异的比例不能被忽视.不同功能性状的种内和种间变异的程度和来源不同,说明不同物种、不同性状对环境变化的响应不同.因此利用功能性状进行各种研究时,应该充分考虑种内变异的影响.