四步法三维编织复合材料杆件的刚度与阻尼分析

旨在预测四步法三维编织纤维增强复合材料矩形截面杆类构件的刚度和阻尼。基于层合板类推法和能量耗散原理,导出了此类构件的各种刚度系数和比阻尼容量计算公式。分析中该复合材料被视为四个单向纤维复合材料部分叠合形成,各单向纤维复合材料部分的单位能量耗散被分解为与σｘ′、σｙ′、σｚ′、τｙ′ｚ′、τｘ′ｚ′、τｘ′ｙ′对应的六个分量。     

基于ANSYS模态应变能法驱动轮过渡阻尼减振结构参数优化

为获得减振效果更加优异的驱动轮过渡阻尼减振结构设计参数,运用ANSYS参数化语言对两种驱动轮过渡阻尼减振结构进行建模。通过模态分析,计算前3阶模态驱动轮过渡阻尼减振结构的阻尼层耗能占总耗能的比率,并应用模态应变能法求取前3阶模态损耗因子,确定了该减振结构中阻尼层与过渡层相对最佳位置。在满足过渡层和阻尼层许用应力应变的条件下,建立了以结构前3阶多模态为优化目标,以基层、约束层、过渡层、阻尼层厚度,过渡层、阻尼层材料剪切模量和材料损耗因子为设计变量,利用了ANSYS 1阶优化对驱动轮过渡阻尼减振结构进行了优化设计。优化结果表明:优化后驱动轮过渡阻尼减振结构的基层、阻尼层厚度较优化前都略有增加,过渡层厚度则减少了0.004 89 m,占驱动轮过渡阻尼减振结构优化前过渡层厚度的48.9%;优化后减振结构中的阻尼层与过渡层的弹性模量相差约2个数量级,且阻尼层与基层(约束层)的弹性模量相差约5个数量级;阻尼层材料损耗因子则需大于过渡层材料损耗因子。本文理论和方法可为驱动轮过渡阻尼减振结构应用在工程机械上提供一定的参考,同时对于ANSYS优化在各种车辆结构设计中的运用具有一定的借鉴价值。     

形状记忆合金在结构阻尼性能优化中的应用

文中研究了通过嵌入NiTi-SMA丝提高自由阻尼层结构损耗性能的方法。首先描述了普通阻尼层材料的贮能模量及损耗因子随温度变化规律。基于一维SMA的Brinson模型给出了NiTi-SMA丝受限回复应力的计算公式,建立了含NiTi-SMA丝的自由阻尼处理梁结构损耗因子的计算公式。通过数值计算揭示了含NiTi-SMA丝的聚氨脂自由阻尼处理梁的耗散特性,分析了NiTi-SMA丝含量及阻尼层厚度对自由阻尼处理梁耗散特性的影响。结果表明,埋入NiTi-SMA丝之后,阻尼结构的损耗因子得到了显著提高。     

基于模态应变能的汽车地板自由阻尼材料布置

依据模态应变能理论确定了模态损耗因子与阻尼层厚度的直接关系,以及汽车地板结构模态应变能的分布情况。提出了一种基于模态应变能的阻尼材料不等厚布置方案,该方案与阻尼材料等厚布置方案相比,拥有较高的减振降噪效果,提高了阻尼材料的利用率。     

共固化双层阻尼薄膜复合材料结构的阻尼性能

为了获取共固化双层阻尼薄膜复合材料结构的阻尼特性,基于一阶剪切理论模型,利用Rayleigh-Ritz法计算共固化双层阻尼薄膜复合材料结构的固有频率和损耗因子,将计算结果同有限元法计算结果进行对比,验证该理论的正确性,同时分析结构固有频率和损耗因子随阻尼层位置和剪切模量变化的规律。结果表明:结构固有频率随着两阻尼层中面距离的增大先减小后增大,存在极小值;增大两阻尼层中面的距离,结构损耗因子先增大后减小,存在设计的最佳值;结构的固有频率随着结构剪切模量的增加而单调增加;随着剪切模量的增加,结构的损耗因子不再单调变化。     

基于Hoff夹层板理论计算约束阻尼结构的结构损耗因子

利用Hoff夹层板理论研究约束阻尼结构的固有频率和模态损耗因子的计算问题.计算结果表明,利用Hoff理论计算约束阻尼结构固有频率和模态损耗因子方法具有较高的计算精度,与Ansys计算结果较为接近,可用于约束阻尼结构固有频率和结构损耗因子计算.     

SIMP插值的约束层阻尼结构拓扑优化

针对约束层阻尼结构拓扑优化问题,采用SIMP插值模型和变密度方法,构建了以模态损耗因子为目标函数,约束阻尼材料用量为约束条件的拓扑优化模型。推导了模态损耗因子对设计变量的灵敏度表达式。采用优化准则法,计算了约束层阻尼的最优拓扑构型,给出了拓扑优化计算的流程。结果表明:采用该拓扑优化方法对约束层阻尼材料进行优化布局,能在减少阻尼材料用量的前提下,显著提高结构模态损耗因子,降低频率响应幅值。     

铺设角度对层合板结构声功率的影响分析*

针对层合板结构铺设角度对前二阶声辐射模态幅值和辐射声功率的影响进行分析。利用分层理论结合有限元模型求解层合板的铺设角度与振动速度信息之间关系。通过声辐射模态理论,以某12层层合板结构为例,研究固定边界条件下的层合板辐射模态数、对称铺设角度、单向铺设角度以及激励力位置对声辐射模态幅值和辐射总声功率的影响。计算结果表明,在相同角度下,对称铺设层合板结构最大声功率值要小于单向角度铺设层合板结构最大声功率值;另外在低频时,对层合板结构辐射声功率起主要贡献的是前两阶辐射模态。并以某16层零度铺设的固定边界条件下的层合板结构为例,对复合材料层合板结构的声辐射模态幅值及声功率进行试验分析。     

共固化缝合阻尼复合材料的动力学性能

为了研究共固化缝合阻尼复合材料（co?cured stitched damping composite,简称CSDC）动力学性能,建立了CSDC方形板的有限元模型,用有限元数值模拟方法研究了CSDC的动力学性能,通过试验与模拟数据的对比验证了模拟方法的有效性。在验证有限元模拟模型基础上,得出结论：随着针距或行距的增大CSDC方形板的1阶模态频率减小,一阶损耗因子增大;阻尼层厚度增加,CSDC方形板的1阶模态频率与模态损耗因子增大;CSDC方形板中的总阻尼层厚度相同,增加结构中的阻尼层数目,可以有效增大结构的模态损耗因子。该结果的实际意义在于可以通过改变共固化缝合阻尼复合材料结构的参数来避免共振现象,为CSDC广泛应用奠定基础。     

单向拼接复合材料层合板的抗拉强度研究

碳纤维增强树脂基复合材料层合板具有较高的抗拉强度,复合材料结构设计中会遇到含铺层拼接的层合板的问题,需要考虑拼接对层合板力学性能的影响。因此建立交错拼接单向层合板的力学模型,对其层间应力和承载能力进行分析,得到单向层合板拼接位置的层间应力分布和抗拉强度的解析解,并提出有效拼接长度的概念,可用于交错拼接层合板的设计。并建立不同拼接长度的交错拼接单向层合板模型,计算得到层间应力分布,并采用渐进损伤方法预测抗拉强度,解析解和有限元方法的强度预测结果均与试验结果具有较好的一致性。含交错拼接单向层合板拼接位置的层间切应力和抗拉强度决定于材料刚度、单层厚度、界面厚度和拼接长度。     

Vibration and stability of angle-ply laminated composite plates subjected to in-plane stresses

Natural frequencies and buckling stresses of angle-ply laminated composite plates are analyzed by taking into account the effects of shear deformation, thickness change and rotatory inertia. By using the method of power series expansion of displacement components, a set of fundamental dynamic equations of a two-dimensional higher-order theory for thick rectangular laminates subjected to in-plane stresses is derived through Hamilton's principle. Several sets of truncated approximate theories are applied to solve the eigenvalue problems of a simply supported thick laminated plate. In order to assure the accuracy of the present theory, convergence properties of the fundamental natural frequency are examined in detail. Numerical results are compared with those of the published existing theories. The modal displacement and stress distributions in the thickness direction are obtained and plotted in figures. The present global higher-order approximate theories can predict the natural frequencies, buckling stresses and modal stresses of thick multilayered angle-ply composite laminates accurately within small number of unknowns which is not dependent on the number of layers.     

Modal characteristics of symmetrically laminated composite plates flexibly restrained at different locations

A method for determining modal characteristics (natural frequencies and mode shapes) of symmetrically laminated composite plates restrained by elastic supports at different locations in the interior and on the edges of the plates is presented. The classical lamination theory together with an appropriate set of characteristic functions are used in the Rayleigh-Ritz method to formulate the eigenvalue problem for determining the modal characteristics of the flexibly supported laminated composite plates. Sweep-sine vibration testing of several laminated composite plates flexibly restrained at different locations on the plates is performed to measure their natural frequencies. The close agreement between the experimental and theoretical natural frequencies of the plates has verified the accuracy of the proposed method. The effects of elastic restraint locations on the modal characteristics of flexibly supported laminated composite plates with different lamination arrangements and aspect ratios are studied using the present method. The usefulness of the results obtained for predicting sound radiation behavior of flexibly supported laminated composite plates is discussed.     

约束阻尼板双线性材料插值法拓扑动力学优化

为减小阻尼板质量并提高减振性能,研究了结构动力学优化技术。构建了以移动常数与模态损耗因子差值为目标、阻尼层单元密度为拓扑变量、阻尼层体积用量及振动模态频率为约束的阻尼板优化模型。利用序列凸规划法构造目标函数的凸性逼近式,采用拉格朗日乘子法解算逼近函数,以获取全局优化的阻尼层布局。利用模态损耗因子与模态应变能的本构关系推导目标函数关于拓扑设计变量的灵敏度,基于K-T条件构造拓扑变量迭代式。引入双线性插值函数惩罚拓扑变量并使其值聚集于0或1,编写并实现了悬臂阻尼板优化程序。当阻尼层体积用量控制在50%时,1阶模态损耗因子增大52.29%,灰度单元占比1.78%。阻尼板谐响应分析表明优化构形具良好减振特性。双线性插值优化既能充分发挥阻尼层的耗能效力又可大幅减少灰度阻尼单元数。     

A Study on Determining Mode Components of Strain Energy Release Rate of Free-Edge Delaminations in Composite Laminates

A simplified method for determining the individual mode components of the strain energy release rate of free-edge delaminations in composite laminates is proposed. Interlaminar stresses are evaluated as an interface moment, as are interface shear forces that are obtained from equilibrium equation of stress resultants at the interface between the adjacent layers. The deformation of edge-delaminated laminate is calculated by using a generalised quasi-3D classical laminated plate theory developed by the authors. The analysis provides closed-form expressions for the Mode-I, Mode-II, and Mode-III components of the strain energy release rate by combining the deformation of the edge-delaminated laminate with the interface moment and the interface shear forces. Comparison of the results with a finite-element analysis using the virtual crack closure technique shows good agreement.     

基于HyperWorks 的不同铺层方式复合材料剪切强度有限元分析

剪切强度和剪切韧性是反映复合材料构件在复合受力状态下承载能力及耗能能力的重要指标,不同铺层方式的单向玻璃纤维与短切玻璃纤维混杂增强复合材料层合板的层间剪切性能有明显差异。文中基于HyperWorks 商用有限元软件建立了精确的复合材料层合板模型,通过数值模拟分析不同铺层方式复合材料层合板的层间剪切性能。研究结果表明,铺层材料对复合材料层合板的层间剪切性能影响较大,而铺层顺序对复合材料层合板的层间剪切性能影响较小。     

频率依赖性黏弹性复合板动力学特性计算方法

将涂覆黏弹性阻尼的压气机叶片简化为考虑频率依赖性的黏弹性复合板,基于经典模态应变能法推导了一种修正的模态应变能法,用于黏弹性复合板的损耗因子计算。设计了一种基于修正模态应变能法的迭代求解方法,通过算例分别使用该计算方法与复特征值迭代法计算考虑频率依赖性的黏弹性复合板动力学特性。结果表明:基于修正模态应变能法的迭代求解方法在提高运算效率的同时,能够准确地计算出频率依赖性黏弹性复合板的动力学特性。     

Free-edge stresses in general composite laminates

In the present study, by starting from the reduced form of elasticity displacement field for a long flat laminate, an analytical method is developed in order to accurately calculate the interlaminar stresses near the free edges of generally laminated composite plates under extension. The constant parameter appearing in the reduced displacement field, which describes the global rotational deformation of a laminate, is appropriately obtained by employing an improved first-order shear deformation theory. The accuracy and effectiveness of the proposed first-order theory are verified by means of comparison with the results of Reddy's layerwise theory as a three-dimensional benchmark. Reddy's layerwise theory is then utilized for analytical and numerical investigations of the boundary-layer stresses within arbitrarily laminated composite plates. Various numerical examples are presented for the interlaminar normal and shear stresses along the interfaces and through the thickness of laminates in the vicinity of the free edges. The effects of end conditions of laminates, fibers orientation angles as well as the stacking sequences of the layers within laminates, and geometric parameters on the boundary-layer stresses are presented and discussed.     

基于渐进法的约束阻尼结构拓扑多目标动力学优化

为实现阻尼结构减振优化,从阻尼材料的力学本构出发,基于虚功原理建立了约束阻尼板动力学平衡方程,从阻尼耗能角度推导出模态损耗因子解析计算式。构建了以模态损耗因子最大且模态频率变动最小为目标、以阻尼材料用量为约束的阻尼板多目标优化数学模型。在对模态损耗因子及模态频率灵敏度进行推导的基础上,构建了归一化复合灵敏度算式,并引入拓扑渐进法求解优化模型。编制出阻尼板渐近法优化程序,并对阻尼板进行了优化仿真。结果显示,采用多目标拓扑渐进优化,既能大幅提高阻尼材料的减振效能,又能保证阻尼板频率特性的稳定,且可较大幅度地降低阻尼材料用量。对阻尼板进行了谐响应分析,验证了优化结果的有效性。该优化法在对结构动力学特性有严格要求的减振设计中存在应用前景。     

Interlaminar stress analysis of general composite laminates

In this study, based on the reduced from of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates under the extension and bending. The constant parameters, which describe the global deformation of a laminate, are properly computed by means of the improved first-order shear deformation theory. Reddy's layerwise theory is subsequently utilized for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. A variety of numerical results are obtained for the interlaminar normal and shear stresses along the interfaces and through the thickness of laminates near the free edges. Finally the effects of end conditions of laminates on the boundary-layer stress are examined.     

Vibration analysis of rotating composite cantilever plates

A modeling method for the vibration analysis of rotating composite cantilever plates is presented in this paper. The coupling effects between inplane motions and the bending motion are considered and explicit mass and stiffness matrices are derived for the modal analysis. Numerical results are obtained and some of them are compared to those of a commercial program to confirm the accuracy of the present method. Numerical results show that the coupling effects become important only when laminates are stacked up unsymmetrically. Incidentally, natural frequencies loci veering, loci crossing, and associated mode shape variations are observed.