有任意脱层复合材料梁的非线性动力稳定性

基于弹性理论建立了有脱层复合材料梁的基本方程式，研究了有任意脱层的考虑横向剪切变形的复合材料梁的非线性动力稳定性，对脱层梁进行分区处理，方便地描述了脱层长度，脱层位置，利用振型函数作为位移函数的形函数，采用增量谐波平衡法对基本方程式进行求解，考虑了不同脱层位置和不同脱层长度对脱层梁的非线性动力稳定性的影响，得出了各种情况下的动力不稳定性区域。     

复合材料梁的脱层识别

本文作者研究了具任意脱层复合材料梁的单参数振动反分析。基于弹性理论,建立了复合材料脱层梁的基本方程式。对脱层梁进行了分区处理,方便地描述了脱层长度、脱层位置。利用边界条件、区间位移连续性条件和弯矩剪力平衡条件建立了反分析的特征方程式。综合考虑系统的一阶固有频率和一阶振型,通过反分析特征方程式求出某一待定参数。为工程无损检测提供理论依据。     

脱层复合材料梁的多参数振动反分析

本文研究了具任意脱层复合材料梁的多参数振动反分析。基于弹性理论建立了考虑横向剪切变形时复合材料脱层梁的基本方程式。对脱层梁进行了分区处理，方便地描述了脱层长度、脱层位置。利用边界条件、区间位移连续性条件和弯矩剪力平衡条件建立了反分析的特征方程式。由系统的特征方程式求出主要参数的初值，采用逐步搜索的方法，利用一阶振型振幅比值之方差为最小，求出其余待定参数。为工程无损检测提供理论依据。     

复合材料层合板脱层诊断的实验研究

利用动态特性对复合材料层合板的脱层损伤进行无损检测,是一种方便、实用的方法.复合材料层合板发生脱层损伤时,其内部微观结构、应力分布以及材料性能参数都会发生变化,这些变化会引起材料的动态特性发生显著的变化.因此,分别研究层合板在健康状态下和损伤状态下的动态特性,就可以分析建立脱层损伤的诊断知识规则.     

预应力梁横向振动分析的模态摄动方法

以预应力简支梁为例,分析了预应力在梁的横向振动过程中的变化,建立了预应力梁横向弯曲振动的微分方程。采用模态摄动法,进一步推导出预应力梁模态特性的近似分析方法,把复杂的变系数微分方程的求解转化为线性代数方程组的求解,从而有效地简化了计算过程。最后通过算例,讨论了预应力对梁的横向振动特性的影响。计算结果表明:当施加预应力的位置有较大的偏心距时,预应力对梁的自振特性有较大的影响。     

带脱层的复合材料层板的屈曲分析

用基于Mindlin 板理论的有限元方法进行了带脱层损伤的复合材料层板的屈曲载荷分析。为了获得物理上可能的屈曲模态, 即避免上下脱层的相互贯穿, 在接触区域引入一些假想弹簧, 并给出了这些假想弹簧刚度系数的计算公式和接触计算的迭代格式, 通过这些弹簧对原始刚度矩阵进行修正可以有效地求解屈曲载荷特征值分析中的接触问题。数值计算结果表明了本算法的有效性和引入接触分析对这类屈曲分析的重要性。同时, 还对脱层的大小、形状、位置和脱层的纤维铺层方向对屈曲载荷的影响进行了研究。      

含单分层损伤复合材料层合梁的动力屈曲研究

采用有限差分（FDM）方法求解了含初始缺陷和单个分层损伤复合材料层合梁的轴向刚性质量块撞击的脉冲动力屈曲问题。基于Hamilton原理导出了考虑所有惯性影响以及一阶横向剪切变形（FSDT）影响时单个分层损伤复合材料梁的非线性动力屈曲控制方程；采用B—R准则判断梁动力屈曲时刻，同时确定刚性质量块的临界冲击速度。重点研究脱层、冲击速度、初始几何缺陷等因素对复合材料层合梁脉冲动力屈曲的影响。     

温度变化下复合材料层合板的试验模态分析

通过动力测试试验研究了环境条件变化对复合材料层合板振动特性的影响 , 这对于复合材料结构基于动力响应健康监测和振动控制系统设计使用的安全性具有重要意义。在不同温度条件下利用锤击以及激振器实验方法测定复合材料层合板的动力响应 , 采用随机子空间法 (SSI) 识别了其固有频率、 阻尼以及模态振型。研究结果表明 , 复合材料层合板结构固有频率及阻尼比与温度变化存在逆相关关系 , 而所识别的模态振型变化并没有非常清晰的相关关系。分析结果进一步表明 , 复合材料结构振动控制和健康监测系统设计过程中需要考虑上述影响。      

附加约束阻尼层的复合材料梁单元建模分析

复合材料空心圆截面梁是桁架和刚架结构中大量采用的常用构件，而实践证明约束阻尼层能有效改善复合材料空心圆截面梁的动力学特性，但传统的约束阻尼层结构有限元计算方法需要大量的单元，这给大型复杂结构的计算带来了巨大的困难。本文采用Timoshenko梁假定。建立了一类附加约束阻尼层复合材料空心圆截面梁弯曲的数学模型。应用Hamilton原理。采用三节点高次梁单元对构件进行离散化。建立了附加约束阻尼层复合材料空心圆截面梁的梁单元。同传统的锥壳单元相比，该方法极大地减少了计算时间。用实验验证了本文计算结果的正确性。同时也分析了约束层厚度对损耗因子的影响。     

Free Vibration Analysis of Generally Layered Composite Beams with Arbitrary Boundary Conditions

A hyperbolic shear deformation theory is used for the free vibration analysis of generally layered composite beams with arbitrary boundary conditions. The variationally consistent governing differential equations and boundary conditions are derived by employing Hamilton's principle. The dynamic stiffness method is applied to calculate the vibration frequencies of the laminated beams with the help of Wittrick–Williams algorithm. Examples of application of the hyperbolic shear deformation theory for the free vibration analysis of the laminated beams with a couple of different boundary conditions are presented. The present results are compared to the numerical solutions and experimental results available in the literature.     

Designation of Mode Mix in Orthotropic Composite Delamination Problems

In interfacial fracture modeling of composite delamination, mode mix is typically specified in terms of energy release rates. Other near-tip quantities can be used to designate mode mix, however. This paper considers the designation of mode mix in terms of energy release rates, stress intensity factors, stresses ahead of the crack tip and crack face displacements and the consequences of using different near-crack-tip quantities to designate mode mix in analyzing composite delamination. The problem addressed is two-dimensional debonding between plies or ply groups modeled as in-plane orthotropic materials; however, the conclusions discussed apply to general composite delamination problems. It is shown that use of different quantities to designate mode mix can give significantly different results in matching composite applications to mixed-mode toughness tests. For cases where measured interfacial toughness increases with increasing mode II deformation, it is demonstrated that use of a mode mix designation based on energy release rates could be non-conservative. Based on these findings, it is suggested that practitioners consider the differences in failure load predictions that would result if different near-tip quantities were used to relate composite applications to measured toughnesses. To this end, methods for converting mode mix designations in terms of energy release rates into designations in terms of other fracture quantities are outlined and applied. This revised version was published online in August 2006 with corrections to the Cover Date.     

高速机构用夹芯复合材料横板模态试验分析

针对高速机构用结构复合材料的动态性能问题,以高速织机用夹芯结构复合材料横板和碳铝横板为研究对象,在自由约束状态下,利用模态试验方法,分别沿设定的x和y方向激振,对其进行测试研究。结果表明:沿x和y方向激振时,与碳铝横板相比,夹芯结构复合材料横板对应阶数的固有频率测得值普遍较高,且沿x方向激振时,横板的固有频率测得值与其长度有很大关系。     

Flexural-Torsional Buckling and Vibration Analysis of Composite Beams

In this paper the general flexural-torsional buckling and vibration problems of composite Euler-Bernoulli beams of arbitrarily shaped cross section are solved using a boundary element method. The general character of the proposed method is verified from the formulation of all basic equations with respect to an arbitrary coordinate system, which is not restricted to the principal one. The composite beam consists of materials in contact each of which can surround a finite number of inclusions. It is subjected to a compressive centrally applied load together with arbitrarily transverse and/or torsional distributed or concentrated loading, while its edges are restrained by the most general linear boundary conditions. The resulting problems are (i) the flexural-torsional buckling problem, which is described by three coupled ordinary differential equations and (ii) the flexural-torsional vibration problem, which is described by three coupled partial differential equations. Both problems are solved employing a boundary integral equation approach. Besides the effectiveness and accuracy of the developed method, a significant advantage is that the method can treat composite beams of both thin and thick walled cross sections taking into account the warping along the thickness of the walls. The proposed method overcomes the shortcoming of possible thin tube theory (TTT) solution, which its utilization has been proven to be prohibitive even in thin walled homogeneous sections. Example problems of composite beams are analysed, subjected to compressive or vibratory loading, to illustrate the method and demonstrate its efficiency and wherever possible its accuracy. Moreover, useful conclusions are drawn from the buckling and dynamic response of the beam.     

含分层损伤缝合复合材料层板的剩余压缩强度

基于渐进损伤方法,研究了含单脱层缝合复合材料层板在压缩载荷下的剩余强度。通过商用软件ABAQUS建立了含单脱层缝合复合材料层板剩余压缩强度计算模型,考虑了子层屈曲和分层扩展对剩余强度的影响。通过UMAT子程序实现了层板失效、层间失效和缝线失效的模拟。通过嵌入式杆单元结构模拟了缝线桥联作用及失效。采用Hashin准则及刚度折减法对纤维拉压、基体拉压失效进行了模拟。通过渐进损伤分析,揭示了缝合情况下含单脱层复合材料层板的失效机理,讨论了缝合参数对剩余压缩强度的影响。所预测的破坏模式和剩余强度结果与实验能较好地吻合。分析表明缝合可以明显提高含分层损伤复合材料层板的子层屈曲载荷,抑制分层扩展,并提高层板的剩余压缩强度。     

主动杆系结构的模态性质分析

对主动杆系结构进行模态分析,指出主动杆系结构有左右模态振型之分,不同阶的左右模态振型关于结构系统加权正交;解释了左右模态振型不同的物理意义:右模态振型是主动结构系统真正意义上的振型;而左模态振型是主动结构系统的转置系统振型,它是外界因素对主动结构系统的影响程度,表征的是外界因素的模态分量。主动结构的模态是检验结构性能的主要指标,也是结构设计的目标函数,所以对主动杆系结构模态的分析研究有着很重要的理论和现实意义。最后,用数值算例进一步说明主动杆系结构的模态性质。