改进的Z^2应力恢复过程与h型自适应有限元分析

建议了一种较为精确的边界应力求解方法，并用于改进Ｚｉｅｎｋｉｅｗｉｃｚ－Ｚｈｕ（Ｚ＾２）应力恢复过程。改进过程增加的计算量不大，但可有效地改善后验误估计精度。ｈ型自适应有限元分析结果表明，改进过程更有利于最优网格寻求工作。     

用动光弹性法研究材料引入的分配层对应力波传播的影响

本文用动态光弹性模拟试验分析方法，观察和分析研究了材料不同的分配层对应力波在结构中传播的影响，比较分析了冲击荷载产生的应力波在洞室结构顶部的传播及相互过程，得到指定点处的应力—时间关系曲线，为结构震塌机理的进一步的研究和防护结构的改进提供参考。     

采用改进的SHPB方法对泡沫铝动态力学性能的研究

本文改进了传统的分离式霍布金森压杆(SHPB)技术，采用夹在透射杆中的PVDF压电计直接测量透射杆中的应力时程．同时，采用输入波形整形技术，通过调整加载波形，使试样加载过程中保证均匀变形及应力平衡．利用此改进了的SHPB技术对泡沫铝进行了高应变率下的动态压缩实验．实验结果表明：泡沫铝的动态应力应变曲线具有泡沫材料的应力应变曲线的“三阶段”特征(elastic region，collapse region and densification region)，并且应变率对其力学性能影响明显．     

基于和声搜索遗传算法的桁架结构拓扑优化

为改善传统设计理念和遗传算法优化不足,促进桁架结构离散变量拓扑优化发展与创新,将遗传算法与和声搜索算法混合,同时对遗传交叉和变异分3种情况进行自适应改进,建立了用于桁架结构拓扑优化的新型混合遗传算法——和声搜索遗传算法,利用该方法分别对平面桁架和空间桁架结构进行拓扑优化分析,并与改进遗传算法、拟满应力遗传算法、相对差商法、复合形遗传算法和改进蚁群算法比较,证明了此方法是有效、可行的。     

单脉冲加载的Hopkinson扭杆装置

分析了反复加载现象及其对变形微结构的影响，介绍了对现有标准Ｈｏｐｋｉｎｓｏｎ扭杆的改进。改进后的新型Ｈｏｐｋｉｎｓｏｎ扭杆是具有特殊设计的加载头和传动器的四杆系统，它完全消除了应力波的反复加载效应，实现了过程的单脉冲加载。改进前后的实验波形和变形局部化微结构形态的比较证实了改进的有效性。     

一种SPH应力修正算法及自由表面流中的应用

提出了一种SPH应力修正算法,即模型中的拉应力和压应力分别采用不同的插值核函数和状态方程来处理,改善应力稳定性问题。介绍了一种改进的Quintic核函数,用于改善模型中压应力的稳定性。通过增加钟型核函数的光滑长度,改善模型中拉应力的稳定性。采用该应力修正算法模拟了无重力条件下方形液滴的震荡变形过程,对比分析了不同算法的模拟结果。此外,为进一步验证算法的适用性,模拟了溃坝算例。研究表明,改进的Quintic型核函数明显改善了粒子聚集现象,该SPH应力修正方法可以使液滴具有更均匀的粒子分布以及更光滑的自由表面,有效改善了SPH方法中的压应力不稳定作用以及自由表面流的模拟精度。     

利用形状记忆合金降低结构的应力集中研究

形状记忆合金（ＳＭＡ）由于具有形状记忆效应（ＳＭＥ），可以用于改善承载结构中受损伤部位的应力、应变分布，降低危险区域的应力集中。本文介绍了这项新技术，并以各向同性材料的带孔板的理论分析与实验说明它的可行性     

基于模糊卡尔曼滤波量测噪声自适应校正的方法研究

针对噪声的统计特性与实际不符时滤波器发散的现象，提出了一种适用于导航、制导以及其它控制系统的模糊自适应卡尔曼滤波器。基于模糊规则自适应改变测量噪声方差R，实现滤波器参数的在线改进，以缩小实际的滤波误差，提高滤波精度。     

铝合金筋板蠕变全过程的Graham改进模型研究

采用分离模型推导了铝合金筋板的循环弹塑性在蠕变全过程的应力-应变增量关系,并用塑性增量及蠕变理论分析了筋板在温度场及应力应变场作用下的热弹塑性-蠕变力学性质。将蠕变应变增量以初应变形式置入ANSYS隐式蠕变方程中,推导出包含初应力和初应变过程的Graham改进模型。用提出的Graham改进模型对四应力水平下的筋板蠕变实验数据进行拟合,并对比分析。结果表明,拟合结果能够较好地表征铝合金筋板在不同应力水平下不同蠕变阶段的蠕变特性,且对高应力水平的加速蠕变特性具有很好的适用性。同时,Graham改进模型和传统模型的有限元模拟预测结果进一步验证了在同一位置时改进模型的误差更小,拟合效果更好。     

三维粘弹性复合材料层合板固化残余应力研究

应用改进的有限元算法,综合考虑了碳纤维复合材料固化过程中树脂的化学收缩、应力松弛、材料的热收缩,建立了一个基于三维线性粘弹性的积分模型对复合材料层合板热压罐成型工艺过程中产生的残余应力进行了研究。结果表明:本文提出的方法能够完整地模拟树脂的固化过程并计算层合板的固化残余应力;对于文中的正交对称层合板而言,热收缩是影响残余应力大小的主要因素;固化完成后,0°铺层内的中面中心区域层间残余应力值接近于0,边缘区域会迅速增加,容易发生分层破坏;任意点处,轴向应力比其他两个方向的应力高出1~2个数量级;残余应力值沿厚度方向有较大变化;树脂的应力松弛行为会在一定程度上降低残余应力。     

LS—DYNA3D等非线性结构动力响应分析程序的局限性

通过理论分析和数值算例研究了采用LS－DYNA3D等非线性动力响应分析有限元程序于具有较大刚体转动的结构时,可能出现错误的应力和应变计算结果。主要原因是采用增量形式的应力修正时,其客观性被破坏。这是此类工程软件亟待改进的问题之一。     

一种有效的结构优化设计方法

基于非线性规划的对偶理论和函数的二阶台劳展开,得到了一种有效的结构优化设计方法,它具有通用性、可自动判别临界约束集合、计算效率高和适用于大型结构系统等优点,基于虚功原理,导出了性状参数的一阶和二阶导数计算式,利用圣维南原理,使性状参数二阶导数及相应的 Hessian 矩阵计算式大为简化,典型算例的计算结果表明本方法是相当有效的。     

Interface crack between two shear deformable elastic layers

An improved method based on the first-order shear deformable plate theory is developed to calculate the energy release rate and stress intensity factor for a crack at the interface of a bi-layer structure. By modeling the uncracked region of the structure as two separate Reissner-Mindlin plates bonded perfectly along the interface, this method is able not only to take into account the shear deformation in the cracked region, but also to capture the shear deformation in the uncracked region of the structure. A closed form solution of energy release rate and mode decomposition at the interface crack is obtained for a general loading condition, and it indicates that the energy release rate and stress intensity factor are determined by two independent loading parameters. Compared to the approach based on the classical plate theory, the proposed method provides a more accurate prediction of energy release rate as well as mode decomposition. The computational procedures introduced are relatively straightforward, and the closed form solution can be used to predict crack growth along the layered structures.     

Separation of dynamically induced low-frequency stresses in rods and pipes

Expressions are evaluated with which the separation of oppositely propagating axial-stress components in rods and pipes can be achieved from stress waveforms obtained at different locations on the rod or pipe. The corresponding measurement/processing procedures can produce either the power spectra or the waveforms of these components. Simplifications of basic procedures for waveform evaluation are formulated whenever possible.A few experiments are described which verify the analytical results obtained theoretically and which also demonstrate the applicability of the separation procedures.     

多重应力奇异性及其强度系数的数值分析方法

以具有两个应力奇异性次数的平面问题为例,提出了一种利用普通的数值分析结果确定奇异点附近多重应力奇异性的各阶次数以及相应的应力强度系数的数值分析方法,计算实例表明,本方法可以精确地求得各阶应力奇异性的次数,并且可以很方便地应用外插法确定出对应的应力强度系数。     

The computer-aided holophotoelastic method

The computer-aided holophotoelastic method (CAHPM) is presented and validated. With it complete experimental stress analyses of transparent structures subjected to two-dimensional states of stress can be conducted based solely on experimental data without resort to either a hybrid, iterative, or other numerical procedure. The stress analysis is determined from photoelastic and holographic data, i.e., isochromatic, isoclinic, and absolute retardation results. The experimental setup and procedures are discussed and the algorithms used for the data reduction are also presented. The method is validated using a disk in diametral loading.     

Local effects in plates - theoretical and practical consequences

The term “local effect” denotes local, pronounced, three-dimensional stress states which occur primarily at the boundaries of flat beams and stretched plates made of homogeneous or composite materials, particularly in the regions of notches, cracks, local mechanical and thermal loads, etc., but which may also occur in any other region. These effects are still ignored in common procedures of analytical mechanics and in traditional procedures of experimental stress analysis, despite the fact that they often increase drastically the maximal stress values occurring in critical regions of structures made of homogeneous and composite materials.The most consistent and rapid response to the needs of modern engineering design with respect to local effects has developed within the field of analytical mechanics. The emphasis has been placed on mathematically and physically admissible analytical solutions. The problem is that the developed analytical models and solutions must be tested experimentally and that this task cannot be reliably accomplished by using experimental procedures based on the concept of plane stress state.This paper presents three new analytical/experimental groups of methods developed by the author and his co-workers: isodyne methods, strain gradient methods and thermoelastic methods. The first two methods have been developed to analyze local effects: static and dynamic. The third method was developed to study dynamic strain/stress fields. The presented empirical evidence shows that the isodyne techniques and strain gradient techniques can be used to evaluate major stress components of three-dimensional stress states in plates and beams caused by local effects. This evidence can be used either directly in engineering design, or as a measure to test the predictive power of analytical models and solutions, and in particular, to quantify errors caused by the simplifying assumptions accepted in analytical solutions.     

用于高强度材料的SHPB实验添加垫块法

提出了用于高强度材料的改进的SHPB实验方法添加垫块法,运用数值模拟方法,利用有限元程序LS-DYNA3D分析了添加垫块实验方法的合理性和可行性。根据一维应力波理论,给出了数据处理的修正方法。作为应用实例,采用改进的实验方法对高强度的Al2O3陶瓷材料的动态力学性能进行了研究,得到了比常规方法较高的应变率及应力应变范围的动态应力应变曲线,表明Al2O3陶瓷为应变率相关的非线性弹脆性材料。结果表明,添加垫块实验方法可有效地防止实验中压杆端面的变形,提高试件的应力应变及应变率水平。添加垫块实验方法为在SHPB装置上实现高强度材料的动态实验提供了一种方便实用的途径。     

Three-dimensional crack analysis

A method is presented for the stress analysis of plane cracks of any shape in a stressed three-dimensional linear elastic space. The approach utilizes a system of integral equations which is defined over the crack area only. When these equations are solved for the unknown dislocations, all other quantities related to the crack and the space can then be found. The text contains sections concerning equation system derivation, numerical procedures, stress intensity factors, rectangular cracks, and earthquake control.     

Review of mass-flow hopper design with respect to stress fields and surcharge loads

Current procedures for mass-flow hopper design are based on the radial stress theory developed byJenike and involve the determination of the critical outlet dimensions for flow to be initiated. These procedures ignore the surcharge loads on the hopper and involve a study of the passive or arched stress field that exists under flow conditions. An alternative approach as applied to hopper wall load analysis is to employ the horizontal slice method. The arched stress field and horizontal slice methods of analysis are compared. The influence of surcharge loads in the determination of hopper geometry is investigated.