复合材料有效弹性性质分析方法eeeeee

建立复合材料的有效性质与微结构参数的关联,是复合材料优化设计的基础。本文具体针对有效弹性性质,重点介绍了建立有效性的基本思路 和主要分析方法。首先讨论了代表单元的概念,然后分别从复合材料有效性质的普适关系、界限理论和近似方法三个不同的视角较全面的介绍了建立非均质材料有效性质的方法、主要结果和最新进展。重点从构型的概念和微结构分布形式上分析了各种模型间及分析方法之间的联系与差别。最后还就建立非均质材料有效性质中存在的问题和研究热点做了简单的介绍。     

复合材料导向叶片的结构与材料一体化优化设计

将材料细观结构优化和宏观结构优化结合起来,从结构与材料两个尺度出发,发展复合材料导向叶片的结构与材料一体化优化设计方法。在建立平纹编织复合材料细观结构分析模型的基础上,采用细观力学有限元法进行材料刚度性能预测,热-固耦合分析方法进行涡轮导向叶片结构分析。同时以细观结构参数和宏观结构参数为设计变量,以叶片质量最小为优化目标,并要求满足应力和位移方面的约束,进行编织复合材料导向叶片的结构与材料一体化优化设计。     

复合材料周期性线弹性微结构的拓扑优化设计

提出复合材料周期性线弹性微结构拓扑优化设计的模型，模型1设计具有极值弹性特性的复合材料，模型2设计工况最刚微结构单胞。通过该模型和均匀化技术可以获得优化的微结构单胞，进而改善或者得到最优宏观特性的复合材料。为了便于制造和应用，用胞体材料而不是多相材料来得到复合材料的极值弹性特性和最大刚度。优化结果表明，该模型与数值方法相结合可以有效地实现微结构的拓扑优化设计。     

复合板件的等效非经典理论解

本文将组合板件、夹层板件、多层板件、复合材料板件等沿厚度构造或材料上非匀质的各种复合板件化为同一等效匀质各向异性板件用非经典理论求解,给出了基本方程与解和非经典理论效应系数以及各种复合板件的等效转换关系式,求得问题的解析解,从而为复合板件的工程计算提供一种较简便而实用的计算方法.     

复合材料组分性能随机性识别的克里金随机分析方法

建立非均匀材料宏观力学性能与微结构参数之间的定量关系一直是人们所关心的问题,利用材料微结构参数和组分性能预报复合材料宏观力学性能,已经取得了很大的进展,然而已知复合材料宏观性能,如何开展组分性能的随机识别,目前的研究工作还不多见.论文考虑了复合材料的随机性,在已知复合材料宏观有效性能的随机性条件下,采用克里金随机分析方法,对复合材料组分性能的随机性进行识别,通过单向纤维复合材料的宏观有效性能的随机性,计算得到了纤维弹性模量的均值与方差,证明了该方法的有效性.     

有应力史差非匀质截面轴心受压杆的性能研究

对有应力史差、非匀质、非线弹性的轴心受压构件进行了理论分析和试验研究，初步揭示了此类构件的受力特点．理论分析和试验表明：此类构件截面承载力不是各部分材料承载力的简单叠加；承载力和截面破坏控制点因截面上材料的本构关系的变化和应力史差而发生改变．     

非匀质材料弹塑性破裂过程的数值模拟研究

 阐述了岩土类材料的非匀质特性, 根据这种特性提出了对材料参 数进行随机赋值的方法. 为了对非匀质类材料的弹塑性破裂过程进行数 值模拟研究,必须在有限元计算中实现材料的参数随机赋值.还给出了实 例------平面应力状态下试样的弹塑性破裂过程的数值模拟分析.     

复合材料扭转轴截面微结构拓扑优化设计

提出复合材料扭转轴截面微结构拓扑优化设计新模型，模型的优化目标是获得具有最大宏观剪切特性加权和的单胞形式．通过模型和均匀化方法及优化技术可以获得优化的微结构单胞，进而改善或者得到最优宏观弹性特性的复合材料．为了便于制造和应用，胞体材料用来获得复合材料的极值剪切模量．最后的优化结果表明，该模型连同数值处理技巧可以非常有效地实现微结构的拓扑优化设计．     

非匀质复合矩形薄板内含Ⅲ型中心裂缝的问题

本文是文献[9]的继续,这次是采用福利叶(Fourier)变换的基本原理,对四种非匀质材料所组成的复合矩形无限大板在交界处存在Ⅲ型中心裂缝问题讨论,在此研究中,我们已证明了本问题的应力强度因子与复合材料的相异性毫无关系,即与同一非匀质材料所构成的矩形无限大板内含Ⅲ型中心裂缝问题的结果相同[1],当然,这个结论也和文献[9]一样,将会给设计工作者以及实验工作者带来很大的方便。     

非均质材料弹塑性破裂过程的数值模拟研究

阐述了岩土类材料的非均质特性，根据这种特性提出了对材料参数进行随机赋值的方法。为了对非匀质类材料的弹塑性破裂过程进行数值模拟研究，必须在有限元计算中实现材料的参数随机赋值。还给出了实例－－平面应力状态下试样的弹塑性破裂过程的数值模拟分析。     

含孔边非均匀材料圆环的无限大薄板的应力集中系数

对于含圆孔及孔边非均匀材料圆环的无限大薄板，假设非均匀材料的弹性模量沿径向按照指数函数变化，而泊松比为常数，分别导出了双轴拉伸和纯剪切作用时孔边及界面处的应力集中系数的解析解．通过数值算例详细分析了非均匀材料圆环的弹性模量的变化对无限大薄板的孔边及界面处的应力集中系数的影响．研究结果表明，合理选择孔边非均匀材料圆环的材料性能变化参数可有效地缓解薄板的孔边应力集中程度．本文的研究结果可为含圆孔的薄板的设计提供一定的参考．     

Thermal stress intensity factor for functionally gradient half space with an edge crack under thermal load

Summary The aim of this work is to investigate the thermal stress intensity factor of a functionally gradient half space with an edge crack under a steady heat flux. All material properties of the functionally gradient half space, except for the coefficient of linear thermal expansion, are exponentially dependent on the distance from the boundary of the plate. The coefficient of linear thermal expansion is assumed to be two-dimensionally dependent. The problem is reduced to a singular integral equation by using the Fourier transform. The thermal stress intensity factor versus the nonhomogeneous material parameters is calculated and represented in figures. The numerical results show that thermal stress intensity factor is dramatically decreased when the material nonhomogeneous parameters are appropriately selected.     

Viscoplastic parameter estimation by high strain-rate experiments and inverse modelling – Speckle measurements and high-speed photography

A methodology based on inverse modelling for estimating viscoplastic material parameters at high strain-rate conditions is presented. The methodology is demonstrated for a mild steel exposed for compression loading in a split Hopkinson pressure bar arrangement. By using dog-bone shaped specimens nonhomogeneous states of deformation are obtained throughout the entire deformation process. The resulting nonhomogeneous deformation of the specimens is evaluated using digital speckle photography (DSP) to give in-plane point-wise displacement and strain fields. The photographs are captured with a high-speed camera of image converter type, which acquire time resolved images during the impact loading. The experiments are simulated using finite element analysis (FEA), where the material model suggested by Johnson–Cook for high-strain rate conditions are utilised. Experimental and FE-calculated field information are compared in order to estimate the viscoplastic parameter in the Johnson–Cook material model. The estimation is performed by minimising least-square functions that contain the differences in displacements and strains, respectively. The quality of the estimated parameters is studied from statistical point of view.     

Quasi-static growth and dynamic extension of anti-plane shear crack in periodically nonhomogenous elastic material

The quasi-static growth of an anti-plane shear crack in a periodically nonhomogeneous elastic material is considered. An effective velocity dependent energy release rate is found for a semi-infinite crack. Approximate expressions of stress intensity factors for in-plane cracks in periodically nonhomogeneous material are also given.     

On Bone Mechanics,Modelling and Optimization

Analysis, evolution and layout in bone mechanics are described as seen from an optimal design and solid mechanics perspective. Anisotropic behaviour and three-dimensional modelling are necessary and focus is therefore put on the aspects of dealing with a large number of material parameters. The tools of homogenization, inverse homogenization and some basic results from optimal structural design are described.     

Mode III fracture problem of an arbitrarily oriented crack in a FGPM strip bonded to a FGPM half plane

This paper studies the mode III electro-elastic field of a cracked functionally graded piezoelectric strip bonded to a functionally graded piezoelectric half plane. The crack is oriented in arbitrary direction. The material properties along x-axis vary in exponential form. By using the Fourier transform, the problem can be formulated into a system of singular integral equations and solved by applying the Gauss–Chebyshev integration formula. The effects come from the edge, crack orientation and the nonhomogeneous material parameters on intensity factors are discussed graphically.     

Thermoelastic contact mechanics for a flat punch sliding over a graded coating/substrate system with frictional heat generation

The problem of thermoelastic contact mechanics for the coating/substrate system with functionally graded properties is investigated, where the rigid flat punch is assumed to slide over the surface of the coating involving frictional heat generation. With the coefficient of friction being constant, the inertia effects are neglected and the solution is obtained within the framework of steady-state plane thermoelasticity. The graded material exists as a nonhomogeneous interlayer between dissimilar, homogeneous phases of the coating/substrate system or as a nonhomogeneous coating deposited on the substrate. The material nonhomogeneity is represented by spatially varying thermoelastic moduli expressed in terms of exponential functions. The Fourier integral transform method is employed and the formulation of the current thermoelastic contact problem is reduced to a Cauchy-type singular integral equation of the second kind for the unknown contact pressure. Numerical results include the distributions of the contact pressure and the in-plane component of the surface stress under the prescribed thermoelastic environment for various combinations of geometric, loading, and material parameters of the coated medium. Moreover, in order to quantify and characterize the singular behavior of contact pressure distributions at the edges of the flat punch, the stress intensity factors are defined and evaluated in terms of the solution to the governing integral equation.     

An interaction energy integral method for nonhomogeneous materials with interfaces under thermal loading

A plane crack problem of nonhomogeneous materials with interfaces subjected to static thermal loading is investigated. A modified interaction energy integral method (IEIM) is developed to obtain the mixed-mode thermal stress intensity factors (TSIFs). Compared with the previous IEIM, the original point of this paper is: the domain-independence of the modified IEIM still stands in nonhomogeneous materials with interfaces under thermal loading. Therefore, the modified IEIM can still be applied to obtain the TSIFs of nonhomogeneous material even if the integral domain includes interfaces. The modified IEIM is combined with the extended finite element method (XFEM) to solve several thermal fracture problems of nonhomogeneous materials. Good agreement can be obtained compared with the analytic solutions and the domain-independence of the IEIM is verified. Therefore, the present method is effective to study the TSIFs of nonhomogeneous materials even when the materials contain interfaces. The influence of the discontinuity of the material properties (thermal expansion coefficient, thermal conductivity and Young’s modulus) on the TSIFs is investigated. The results show that the discontinuity of both thermal expansion coefficient and Young’s modulus affects the TSIFs greatly, while the discontinuity of thermal conductivity does not arouse obvious change of the TSIFs.     

Mode III crack problems of two bonded functionally graded strips with internal cracks

This paper deals with the anti-plane problem of two bonded functionally graded finite strips. Each strip contains an internal crack normal to the interface. The material properties of two strips are assumed to vary along the direction of the crack lines. A system of singular integral equations is derived and then solved numerically by using Gauss–Chebyshev integration formula. The influences of nonhomogeneous parameters, crack interactions and two edge conditions on the mode III stress intensity factors are investigated.     

非均匀介质有限元法

提出适合非均匀介质应力分析的有限元法．文中在有限单元内部采用等参变换方法模拟材料特性的变化，算例表明该法计算效率高，计算精度好．