金属试件二维小接触问题的焦散线实验分析

本文是直接采用金属圆盘试件对二维小接触问题所作的光焦散线实验分析。所给出的接触面尺寸和面上的应力符合静力验证,也与理论分析较为一致。本文实验分析是焦散线法直接用于某些实际接触元件的探索。     

钢丝绳捻制成形接触问题的有限元分析

基于虚功原理建立了钢丝绳捻制成形过程中考虑接触摩擦时的刚度方程,将小球分裂算法用于接触搜索,Augmented Lagrange法用于计算接触力．以钢丝绳一次捻制成形过程为例,分析了摩擦系数和自扭转系数对接触应力和加工应力域变的影响．研究结果表明。摩擦系数对剪应力的影响比对等效应力和等效塑性应变的影响大;考虑摩擦时钢线表面的轴向残余应力计算结果比无摩擦条件下的计算结果更接近实验结果．     

混凝土材料冲击压缩试验中的一些问题

本文简要介绍了在大直径（φ74mm)直锥变截面式SHPB实验装置上进行混凝土试件冲击压缩实验方法。以及实验过程中出现的试件应力均匀性问题，对于由方波加载造成的试件内应力波反射次数不够，导致应力分布不均匀的问题，我们提出了波形整形的思想。将矩形波改造成三角波，增加试件破坏前的应力作用时间以获得应力均匀;对于由杆与试件接触不平引起的应力分布不均。我们设计了万向头加以消除，在此基础上进行了一系列试验并得出了一些结论。     

二维小接触问题的焦散线分析

本文是以一组聚碳酸脂园盘试件,用焦散线法对小接触问题所进行的一系列实验分析,其中包括一个滚柱轴承的模拟分析,定量地得到了接触面宽度和面上的应力。对小接触奇异应力场给出可靠的定量结果,这是其他实验力学手段目前难以解决的。此外,本文的实验分析结果也与理论计算相当一致。     

超声瑞利波测试材料表面载荷应力的实验研究

实验研究了利用超声瑞利波传播特性测试材料表面应力的方法.在测试过程中采用回振法测声速,以分辨应力作用引起声速的徽小变化;并设计夹具实现探头与试样之间的稳定耦合和弹性接触,精简了实验机构,提高了实验精度.研究结果表明,在应力作用下,平行和垂直于应力方向传播的瑞利波发生了相应的变化:应力较小时,声速随应力变化较快;随着应力...     

聚合物注塑残余应力的研究进展

综述了聚合物注塑残余应力的研究进展,详细介绍计算残余应力所用的理论模型及其基本概念．注塑制品残余应力由两部分组成,并且有不同的测试方法,这些应力是造成制品翘曲变形的原因．对于残余流动应力,重点分析本构模型的发展和注塑控制方程的建立;对于残余热应力,则讨论了冷却过程中的相交问题,以及热粘弹性模型在应力分析中的应用;最后介绍测量残余应力的几种实验方法．      

高应力比循环下微动疲劳裂纹萌生位置的预测分析

对于微动疲劳问题,循环应力比的大小会影响试件应力状态及分布,从而影响疲劳裂纹的萌生位置.本文通过对一类微动疲劳问题进行有限元法分析,模拟疲劳实验过程,并采用最大应力变化幅△σθmax作为指标预测了不同应力比下疲劳裂纹的萌生位置.数值分析显示,在应力比不是很大时,试件与微动接触头的边缘存在接触,并在此处产生较大的应力集中,容易萌生裂纹;而在应力比足够高时,微动接触头端部与试件呈恒张开状态,△σθmax及裂纹萌生发生在距初始接触区边缘一定距离处.疲劳裂纹萌生位置的理论预测结果与相关试验的疲劳裂纹发生位置比较一致.     

考虑摩擦三维弹塑性接触边界元法

边界元法与其它数值方法相比，由于具有应力和面力计算精度高的特点，非常适合于接触问题的分析，本文建立了考虑摩擦三维弹塑性接触问题的边界元法，采用此方法对板带轧制这一典型的弹塑性接触问题进行了分析，证明本文人出的方法是有效的。     

有限长圆柱体接触应力的光弹性解法

对两个有限长，外载荷又集中作用的圆拄体，在接触面上的应力分布是不均匀的．为了获得接触应力，本文应用弹性力学的理论、光弹性应力分析方法和有限元计算概念，提出了一种混合计算法．最后给出一个应用实例，讨论了某轧机轧辊的接触问题．     

有摩擦有间隙的三维接触问题有限元法及应用

介绍了一种求解三维弹性体间有摩擦、有间隙的接触问题有限元解法。文中推导出四种接触状态的接触条件。该方法通过赫兹问题验证，有限元解与精确解吻合较好。应用本方法对汽轮机汽缸法兰连接进行了应力计算，获得了法兰结合面上压应力分布规律并得出了一些重要结论。     

TSP问题的单元划分法

提出一种利用单元划分法求解ＴＳＰ问题的新求法，该法计算量小，且计算结果理想     

Analogy solutions of axisymmetrical twist problems by axisymmetrical finite element program

It used to be considered that an axisymmetrical problem and a twist problem of an axisymmetrical body cannot be simulated by each other, because the number of unknown variables in an axisymmetrical problem is greater than that in a twist problem, and the governing equations are not the same. This paper proposes a degenerated analogy method, by which the twist problems of axisymmetrical bodies can be simulated by axisymmetrical problems with finite element programs.An ordinary structural analysis method can be used to analyze an axisymmetrical problem, but a twist problem of axisymmetrical bodies is treated as a 3-dimensional problem usually. According to the method proposed in this paper, the analysis of a twist problem can be simulated by the analysis of an axisymmetrical body with a structural analysis problem. The example of analysis computation is also given. Thecomputed result is in agreement with the theoretical result.In this paper, the constitutive relation of the degenerated analogy problem is given.The authors suggest that a twist problem of a body made of any materials is simulated by an axisymmetrical problem of a body made of orthotropic material. If you have to use some program for the axisymmetrical problem to be limited to isotropic materials the penalty coefficient method can be used to solve the problem.     

Meshless methods for the inverse problem related to the determination of elastoplastic properties from the torsional experiment

The problem of determining the elastoplastic properties of a prismatic bar from the given experimental relation between the torsional moment M and the angle of twist per unit length of the rod’s length θ is investigated as an inverse problem. The proposed method to solve the inverse problem is based on the solution of some sequences of the direct problem by applying the Levenberg-Marquardt iteration method. In the direct problem, these properties are known, and the torsional moment is calculated as a function of the angle of twist from the solution of a non-linear boundary value problem. This non-linear problem results from the Saint-Venant displacement assumption, the Ramberg–Osgood constitutive equation, and the deformation theory of plasticity for the stress–strain relation. To solve the direct problem in each iteration step, the Kansa method is used for the circular cross section of the rod, or the method of fundamental solutions (MFS) and the method of particular solutions (MPS) are used for the prismatic cross section of the rod. The non-linear torsion problem in the plastic region is solved using the Picard iteration.     

热传导问题灵敏度分析的伴随法

在热传导灵敏度分析的直接法的研究基础上，进一步探讨了稳态和瞬态热传导问题灵敏度分析的伴随法.推导了伴随法的计算列式，对于瞬态热传导问题，研究了瞬态约束处理的关键点方法，并提出伴随方程的精细积分解法。算例表明，稳态问题灵敏度计算，伴随法与直接法的结果是一致的；瞬态问题灵敏度计算，两种方法的精度相当。     

轴对称体扭转问题的轴对称有限元模拟解

轴对称体的轴对称问题与扭转问题一向被认为是两个互相不能模拟的问题.前者的未知量与方程多于后者,形式也不相同.本文提出一种退化模拟方法.能够把扭转问题模拟为轴对称问题的一类特殊情况来解.一般的结构分析程序都能够分析轴对称问题,但轴对称体的扭转问题通常作为三维问题处理.按本文提出的方法,可用结构分析程序的轴对称分析功能模拟扭转分析.本文还给出模拟计算的算例.计算结果表明与理论解完全一致.本文对退化模拟的材料本构关系进行了研究,建议在数值计算时以各向异性材料的轴对称问题模拟任何材料的扭转问题.当限定用各向同性材料的轴对称问题来模拟时,采用了罚系数法.     

Stress analysis near the tips of a transverse crack in an elastic semi-strip

The plane elastic problem for a semi-strip with a transverse crack is investigated. The initial problem is reduced to a one-dimensional continuous problem by use of an integral transformation method with a generalized scheme. The one-dimensional problem is first formulated as a vector boundary problem, and then reduced to a system of three singular integral equations(SIEs). The system is solved by use of an orthogonal polynomial method and a special generalized method. The contribution of this work is the consideration of kernel fixed singularities in solving the system. The crack length and its location relative to the semi-strip's lateral sides are investigated to simplify the problem's statement. This simplification reduces the initial problem to a system of two SIEs.     

Numerical method for optimum motion of undulatory swimming plate in fluid flow

A numerical method for the optimum motion of an undulatory swimming plate is presented. The optimum problem is stated as minimizing the power input under the condition of fixed thrust. The problem is singular for the invisible modes, and therefore the commonly used Lagrange multiplier method cannot predict an optimum solution but just a saddle point. To eliminate the singularity, an additional amplitude inequality constraint is added to the problem. A numerical optimization code with a sequential quadratic programming method is used to solve the problem. The method is applied to several cases of the motion of two-dimensional and three-dimensional undulatory plates, and the optimum results are obtained.     

流体饱和多孔隙介质波动方程多尺度反演

基于多尺度的思想,将小波多分辨分析和多尺度方法相结合,应用于流体饱和多孔隙介质孔隙率的反演。利用小波变换,将原始反问题分解为不同尺度上的一系列子反问题,并按照尺度从粗到细的顺序依次求解。在每一个尺度上,都采用稳定、收敛快的正则化高斯牛顿法求解,次一级尺度上求出的“全局最优解”作为上一级的初始解,依此类推,直到求出原始问题的真正的全局最优解。通过与传统的正则化高斯牛顿法相比较,显示了小波多尺度法是一个大范围收敛、能够有效节省计算量的方法,数值模拟的结果也表明了方法的有效性。     

Difference inversion model of wave equation

A numerical iterative model was derived from the difference method and a perturbation assumption to calculate the coefficient function of a wave equation. The method was used to solve the disaccord problem of numerical precision between the direct problem model and inverse problem model, and its serial problems using the old method. Numerical simulation calculation shows that the method is feasible and effective.     

MHD Falkner-Skan flow of Maxwell fluid by rational Chebyshev collocation method

The magnetohydrodynamics （MHD） Falkner-Skan flow of the Maxwell fluid is studied. Suitable transform reduces the partial differential equation into a nonlinear three order boundary value problem over a semi-infinite interval. An efficient approach based on the rational Chebyshev collocation method is performed to find the solution to the proposed boundary value problem. The rational Chebyshev collocation method is equipped with the orthogonal rational Chebyshev function which solves the problem on the semi-infinite domain without truncating it to a finite domain. The obtained results are presented through the illustrative graphs and tables which demonstrate the affectivity, stability, and convergence of the rational Chebyshev collocation method. To check the accuracy of the obtained results, a numerical method is applied for solving the problem. The variations of various embedded parameters into the problem are examined.