复合材料对称层合板单向拉伸与面内剪切下的三维应力分析

本文给出了单向拉伸与面向剪切载荷下复合材料对称层合板中心区域的应力和应变沿板厚的数值计算分布规律。计算结果表明，在斜交对称辅层的层合板中心区域层间界面附近存在着层间边界层效应。层间界面处纤维走向的突变导致局部的三维应力状态和很强的应力集中。     

横向剪变形对具有一小圆孔的浅壳应力集中系数的影响

本文导出了分析计及横向剪变形的浅壳小孔应力集中问题的简化方程.对浅球壳和圆柱壳带一小圆孔的情况,获得了方程的级数形式通解.对均匀内压作用下的圆柱壳,求得了小圆孔边上应力集中系数的近似显式解,并计算了数值结果.     

含分层复合材料层合梁弯曲问题的一般解法

基于一阶剪切梁理论,考虑分层边缘区域的变形特点,提出了含穿透分层复合材料梁模型．与传统分层模型不同,该文将未分层部分看作上下子梁,放弃了传统模型中分层前缘横截面始终保持平面的假设．通过分层前缘的位移连续条件和内力连续条件,建立了粘合段和分层段的控制方程．并且,应用该模型对不同边界条件下含不同分层尺寸对称和非对称分层的复合材料层合梁弯曲问题进行了求解,结果与三维有限元计算的结果一致,从而证明了模型的有效性和适用性．     

复合材料层合板三维线性理论的完整性

本文针对文献[1]所述复合材料层合板三维模型,在三维线性弹性理论基本方程和经典变分原理的基础上,通过分块矩阵运算和线性Lagrange乘子法,推导出比文献[1]更全面更系统的基本方程和变分原理,使复合材料层合板三维线性理论臻于完整。     

复合材料层合结构冲击损伤研究进展

分析总结了复合材料层合结构冲击损伤破坏形式及特征,以及冲击损伤产生和扩展机理;综述了国内外冲击损伤理论和冲击损伤检测的研究进展。探讨了复合材料层合结构冲击损伤研究的发展趋势。     

复合材料层合板低速冲击后压缩的损伤累积模型

为了分析复合材料层合板低速冲击后的压缩性能,首先用三维动态有限元素法对两种层合板进行了低速冲击损伤模拟计算,以此作为冲击后压缩（CAI）层合板的初始损伤,然后用三维静态有限元对含损伤的层合板进行压缩破坏模拟和剩余强度计算,从而实现了层合板从冲击损伤到压缩破坏损伤全过程的模拟．结果表明,损伤投影面积和CAI强度的计算值与试验结果有较好的一致性．     

外部压力作用下复合材料层合圆柱壳的脱层扩展分析

含脱层的层合圆柱壳在承受外部压力作用时,容易发生脱层扩展,进而引起结构失效．基于可动边界变分原理并考虑脱层间的接触效应对圆柱壳在外部压力作用下的脱层扩展进行了分析,同时应用Griffith准则,导出了脱层前缘各点处的能量释放率表达式,且以轴对称脱层层合圆柱壳为例进行了数值计算,讨论了脱层大小、脱层深度、几何尺寸、材料性质及纤维铺层方式等因素对脱层扩展的影响．     

基于混杂控制方法的生产库存策略的研究

研究了生产库存混杂动态模型的最优控制策略.首先,建立了生产库存系统的混杂动态模型,给出了其性能指标函数包含生产成本和库存成本的最优控制问题.基于参数化方法和古典的最优控制理论,给出了混杂动态最优控制问题的最优性必要条件.最后,利用该混杂最优性条件,得到了生产库存混杂动态控制问题的最优生产和库存策略,验证了结论的有效性.     

考虑横向剪切变形时通过层合复合材料圆柱壳的声音传输分析模型

由于复合材料结构具有较高的强度一重量比，经常在航空航天工业中广泛使用。在空中声音传输意义上研究声音的传输损耗，通过一个无限层合复合材料圆柱壳体向航行器内部传输。壳体浸泡在外部流体介质中，内部也包含有流体，气流在外部流体介质中以常速流动。根据层合复合材料壳体的一阶剪切变形理论（FSDT），同时求得其精确解和声波方程。求得其传输损耗的数值解并与其它作者的结果进行了比较。在一定数值范围内，研究了结构特性和飞行状态，特别是Mach数、层合的次序及其偏斜角度，对传输损耗值的影响。此外，使用经典薄壳理论（CST）和一阶剪切变形理论（FSDT），比较了层合各向同性复合材料圆柱壳的传输损耗。     

层合板壳脱层屈曲的有限元分析

通过建立一类新的参考面有限单元,得到适用于分析层合板壳脱层屈曲问题的有限元方法。指出了利用Mindlin假设意义下的变形协调条件,可以将大多数胜任层合板壳分析的一般板壳单元改造为相应的参考面单元。这一方法确保了位移场的合理性和协调条件的满足。为验证参考面单元的有效性,还对壳体脱层屈曲的几个算例作了数值分析。     

纤维复合材料中弹性波散射与动应力

基于弹性波动理论,对纤维增强复合材料结构中弹性波多重散射与动应力集中问题进行了分析研究,给出了介质各区域弹性波分析解的表达式.根据位移与应力在各区界面处的连续条件,确定了未知弹性波模式系数.采用Hankel函数的加法定理,将不同局部坐标系中散射波场的表达式变换到了同一个局部坐标系中,以给出弹性波模式系数和动应力集中因子的表达式.分析了多相纤维基体中两个散射体的间距、界层区材料性质以及界层区和纤维核区截面尺寸的变化,对各区界面动应力集中系数的影响.分析表明,两个散射体的间距、界层区材料性质和结构尺寸的变化对复合材料的力学特性具有显著影响.作为算例,给出了纤维增强复合材料结构中各区界面动应力集中系数的数值结果,并对其进行了分析讨论.     

应力偶对孔洞附近应力集中的影响

将求解无限弹性平面中孔洞附近应力集中问题的复变函数方法,推广到微极弹性介质的应力集中问题上去,在复平面上给出了二维微极弹性理论应力集中问题的一般解,它可由解析函数与“域函数”构造出来,并利用保角映射的方法来满足非圆孔洞的边界条件。在此基础上建立了求解微极弹性理论中应力集中问题的一般求解方法。最后,对圆形孔洞附近的应力集中系数作了数值计算,并给出了具体结果。     

Influence of Initial Stresses on Stress Intensity Factors at Crack Tips in a Composite Strip

The influence of initial tension or compression along cracks on the stress intensity factor (SIF) at crack tips under the action of additional normal forces on crack edges is studied for infinite bodies. A strip made of a composite material is considered. The strip ends are simply supported, and the strip contains a crack whose edges are parallel to its face planes. The strip is first stretched or compressed along crack edges, and then additional uniformly distributed normal forces are applied to the crack edges. The influence of the initial tension (compression) on the SIF caused by the additional normal forces is studied. The corresponding boundary-value problems are modelled with the use of the three-dimensional linearized theory of elasticity. All the investigations are carried out numerically by employing the finite-element method. The values of SIF are calculated by the energy release method.     

杂交元假设应力模式的变形刚度分析

通过本征变形模式提出识别杂交元零能变形模式和假设应力场中零能应力模式的新方法,同时给出了在假设应力场中增加应力模式时杂交元变形刚度的计算公式．从而从理论上阐明了在假设应力场中增加零能应力模式不仅不能抑制单元零能变形模式而且可能增加非零能变形模式的刚度,因此不宜用来假设应力场;同时进一步指出寄生应力模式将使单元产生虚假应变能而使单元显得过刚,因此即使它能够抑制单元零能变形模式也不宜用来假设应力场,从而为假设应力场提供了合理的建议．数值算例说明了包含零能应力模式和寄生应力模式时单元的性能．     

中日两国高校教师精神压力比较研究的统计分析

本文运用多元分析方法 ,给出中日两国高校教师精神压力的比较研究结果 ,分析了两国精神压力成因的异同、不同年龄段教师精神压力与健康的关系 ,以及中日高校教师精神压力性质和结构方面的差异     

Influence of the Interaction between Two Neighboring Periodically Curved Fibers on the Stress Distribution in a Composite Material

A method is developed for a stress analysis in an infinite elastic body containing two neighboring periodically cophasaly curved fibers located along two parallel lines. The stress distribution is studied when the body is loaded at infinity by uniformly distributed normal forces in the fiber direction. The investigation is carried out within the framework of a piecewise homogeneous body model with the use of exact three-dimensional equations of elasticity theory. Numerical results related to the stress distribution considered and the influence of interaction between the fibers on this distribution are given.     

Stress Intensity Factors near the Cracks on the Edges of Openings in Composite Plates

Based on the photoelasticity method, the behavior of stress intensity factors (SIFs) near cracks propagating from the edges of openings in plates made of elastic and linearly viscoelastic fibrous composite materials is studied. It is found that the relative value of the SIF, K ₁/K ₁ ⁰ (K ₁ ⁰=₀c), near the crack tips on the edges of openings in composite plates is a function of the ratio c/R, whose numerical values depend on the mechanical properties of materials of the plates. Using the quasi-elastic method for solving the viscoelastic problems, the effect of viscoelastic properties of the plate material on the value of K ₁/K ₁ ⁰ is estimated. It is shown that the values of the function K ₁(t)/>/K ₁ ⁰ near the cracks on the opening edges in plates made of linearly viscoelastic fibrous composites grow under creep.     

The Effect of Structural Curvings on the Stress Distribution in a Rigidly Fixed Composite Plate under Forced Vibration

Based on the exact three-dimensional equations of continuum mechanics and the Akbarov-Guz' continuum theory, the problem on forced vibrations of a rectangular plate made of a composite material with a periodically curved structure is formulated. The plate is rigidly fixed along the Ox ₁ axis. Using the semi-analytic method of finite elements, a numerical procedure is elaborated for investigating this problem. The numerical results on the effect of structural curvings on the stress distribution in the plate under forced vibrations are analyzed. It is shown that the disturbances of the stress ₂₂ in a hinge-supported plate are greater than in a rigidly fixed one. Also, it is found that the structural curvings considerably affect the stress distribution in plates both under static and dynamic loading.     

Stress distribution in an infinite elastic body containing two neighboring locally curved fibers

A method is developed for analyzing the stresses in an infinite elastic body containing two neighboring inphase locally curved fibers located along two parallel lines. The body is loaded at infinity by uniformly distributed nor mal forces in the direction of fibers. The investigation is carried out within the frame work of a piecewise homogeneous body model with the use of the three-dimensional ex act equations of the elasticity theory. Numerical results for stress distributions in the body and for the influence of interaction between fibers on these distributions are given. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 3, pp. 457-478, May-June, 2009.