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正交板材是由大量微小晶粒组成的正交多晶体材料,而多晶体中晶粒的取向分布(可通过取向分布函数中的织构系数来描述)影响着多晶体材料的力学性能,也必然影响着瑞利波的传播速度。将多晶体材料的织构系数引入到弹性张量中,通过特征值办法,采用线性化处理,推导出立方晶粒正交板材的瑞利波速与织构系数的关系式,在此基础上可通过正交板材瑞利波速的测量获得织构系数,并与通过超声横波纵波测得结果相比,吻合很好。 相似文献
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研究蠕变加载条件下线黏弹性材料接触界面端附近的奇异应力场问题.考虑接触界面的摩擦,假设界面端的滑移方向不改变,相对滑移量微小,且其与位移同量级,由此线性化局部边界条件,根据对应原理得到Laplace变换域中的界面端应力场,导出时域中奇异应力场的卷积积分表达式.对卷积积分核函数进行数值反演,考虑接触材料的两类组合,一是持久模量具有量级上的差异,另一是持久模量接近相同.算例结果证实核函数可以用准弹性法求得的解析式较准确地近似.在此基础上,利用积分中值定理,并引入各应力分量的修正系数,得到黏弹性奇异应力场的简化式.结合核函数的数值反演结果分析修正系数表达式的取值范围,得到如下结论,若两相接触材料的持久模量相差很大,可以采用准弹性解的解析式较准确地描述界面端的奇异应力场;一般情况下,应力场不存在统一的奇异值和应力强度系数,当采用类似于准弹性解的表达式近似给出黏弹性应力场时,可以估计此近似描述的误差限.文中最后采用有限元分析黏弹性板端部嵌入部位的应力场,算例包括了黏弹性板与弹性金属支承、黏弹性板与黏弹性垫层所形成的滑移接触界面端,利用黏弹性有限元的数值结果验证理论分析所得结论的有效性. 相似文献
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研究蠕变加载条件下线黏弹性材料接触界面端附近的奇异应力场问题.考虑接触界面的摩擦,假设界面端的滑移方向不改变,相对滑移量微小,且其与位移同量级,由此线性化局部边界条件,根据对应原理得到Laplace变换域中的界面端应力场,导出时域中奇异应力场的卷积积分表达式.对卷积积分核函数进行数值反演,考虑接触材料的两类组合,一是持久模量具有量级上的差异,另一是持久模量接近相同.算例结果证实核函数可以用准弹性法求得的解析式较准确地近似.在此基础上,利用积分中值定理,并引入各应力分量的修正系数,得到黏弹性奇异应力场的简化式.结合核函数的数值反演结果分析修正系数表达式的取值范围,得到如下结论,若两相接触材料的持久模量相差很大,可以采用准弹性解的解析式较准确地描述界面端的奇异应力场;一般情况下,应力场不存在统一的奇异值和应力强度系数,当采用类似于准弹性解的表达式近似给出黏弹性应力场时,可以估计此近似描述的误差限.文中最后采用有限元分析黏弹性板端部嵌入部位的应力场,算例包括了黏弹性板与弹性金属支承、黏弹性板与黏弹性垫层所形成的滑移接触界面端,利用黏弹性有限元的数值结果验证理论分析所得结论的有效性. 相似文献
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被动隔振体非线性振动的能量迭代解法 总被引:5,自引:0,他引:5
研究了由基础振动激励、弹性材料隔离的被动隔振体的强非线性动力响应。用变形的三次多项式函数表征隔振材料的非线性刚度特性,建立了被动隔振体的非线性动力学方程,得到有阻尼受迫振动Duffing方程。将求解强非线性自治系统的能量迭代方法加以改进,推广应用到强非线性非自治系统,求出周期响应的近似解析解表达式,以及幅频关系、相频关系和隔振系数的近似表达式。算例中应用本方法与Runge-Kutta方法进行了对照,结果表明求解精度较高。本文利用计算机进行了辅助推导。 相似文献
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非线性正交各向异性弹性材料的本构方程及其势函数 总被引:1,自引:0,他引:1
研究了非线性Green弹性材料弹性张量独立分量,归纳推导出各向异性Green弹性材料、具有一个对称面Green弹性材料、 正交各向异性非线性弹性材料独立的弹性常数个数.从张量函数出发,用含有高阶弹性张量的张量多项式,推导出三阶非线性正交各向异性Green弹性材料本构方程及其势函数.并将本构方程及其势函数用张量不变量,标量不变量表示.证明了方程是完备的,不可约的,满足张量函数表示定理.详细研究Green弹性材料势函数存在的充分和必要条件,给出并证明了具有普适性的势函数存在定理. 相似文献
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非线弹性平面杆系的应力应变分析 总被引:2,自引:0,他引:2
以指数函数近似表示非线弹性材料的应力-应交关系,推导出了非线弹性材料平面杆系结构应力应变计算的普遍表达式,编制了通用程序,使这一类问题有了一个通用的解题方法. 相似文献
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HuangMojia ZhengChaomei 《Acta Mechanica Solida Sinica》2004,17(4):337-346
A closed but approximate formula of Green‘s function for an arbitrary aggregate of cubic crystallites is given to derive the effective elastic stiffness tensor of the polycrystal. This formula, which includes three elastic constants of single cubic crystal and five texture coefficients,accounts for the effects of the orientation distribution function (ODF) up to terms linear in the texture coefficients. Thus it is expected that our formula would be applicable to arbitrary aggregates with weak texture or to materials such as aluminum whose single crystal has weak anisotropy.Three examples are presented to compare predictions from our formula with those from Nishioka and Lothe‘s formula and Synge‘s contour integral through numerical integration. As an application of Green‘s function, we briefly describe the procedure of deriving the effective elastic stiffness tensor for an orthorhombic aggregate of cubic crystallites. The comparison of the computational results given by the finite element method and our effective elastic stiffness tensor is made by an example. 相似文献
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Mojia Huang 《Journal of the mechanics and physics of solids》2004,52(8):1827-1853
Herein we obtain a formula for the effective elastic stiffness tensor Ceff of an orthorhombic aggregate of cubic crystallites by the perturbation method. The effective elastic stiffness tensor of the polycrystal gives the relationship between volume average stress and volume average strain. Under Voigt's model, Reuss’ model and Man's theory, the elastic constitutive relation accounts for the effect of the orientation distribution function (ODF) up to terms linear in the texture coefficients. However, the formula derived in this paper delineates the effect of crystallographic texture on elastic response and shows quadratic texture dependence. The formula is very simple. We also consider the influence of grain shape to elastic constitutive relations of polycrystals. Some examples are given to compare computational results of the formula with those given by Voigt's model, Reuss's model, the finite element method, and the self-consistent method. In Section 3, we also present an expression of the perturbation displacement field, in which Green's function for an orthorhombic aggregate of cubic crystallites is included. 相似文献
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Herein we consider polycrystalline aggregates of cubic crystallites with arbitrary texture symmetry. We present a theory in which we keep track of the effects of crystallographic texture on elastic response up to terms quadratic in the texture coefficients. Under this theory, the Lamé constants pertaining to the isotropic part of the effective elasticity tensor of the polycrystal will generally depend on the texture. We introduce also two simple models, which we call HM-V and HM-R, by which we derive an explicit expression for the effective stiffness tensor and one for the effective compliance tensor. Each of these expressions contains a term quadratic in the texture coefficients and, in addition to three parameters given in terms of the single-crystal elastic constants, each carries an undetermined material coefficient. These two remaining coefficients can be determined by imposing the requirement that the expressions from models HM-V and HM-R be compatible to within terms linear in the texture coefficients. 相似文献
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Mojia Huang 《Journal of Elasticity》2003,73(1-3):1-11
Herein a closed but approximate formula of the Green's function is obtained for orthorhombic aggregates of cubic crystallites. This formula, which includes three material constants and three texture coefficients, accounts for the effects of the orientation distribution function (ODF) up to terms linear in the texture coefficients. Thus it is expected that our formula would be applicable to aggregates with weak texture or to materials such as aluminum whose single crystal has weak anisotropy. The approximate formula remains valid and assumes a simpler form when the polycrystal reduces to a weakly anisotropic cubic crystal. Two examples are presented to compare predictions from our formula with those from Nishioka and Lothe's formula and from Synge's contour integral through numerical integration. 相似文献
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Surface Impedance Tensors of Textured Polycrystals 总被引:1,自引:0,他引:1
A formula for the surface impedance tensors of orthorhombic aggregates of cubic crystallites is given explicitly in terms
of the material constants and the texture coefficients. The surface impedance tensor is a Hermitian second-order tensor which,
for a homogeneous elastic half-space, maps the displacements given at the surface to the tractions needed to sustain them.
This tensor plays a fundamental role in Stroh's formalism for anisotropic elasticity. In this paper we account for the effects
of crystallographic texture only up to terms linear in the texture coefficients and give an explicit formula for the terms
in the surface impedance tensor up to those linear in the texture coefficients.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Roberto Paroni 《Archive for Rational Mechanics and Analysis》2000,151(4):311-337
The effective elastic properties of a polycrystalline material depend on the single crystal elastic constants of the crystallites
comprising the polycrystal and on the manner in which the crystallites are arranged. In this paper we apply the techniques
of homogenization to put the problem of determining effective elastic constants in a precise mathematical framework that permits
us to derive an expression for the effective elasticity tensor. We also study how the homogenized elasticity tensor changes
as the probability characterizing the ensemble changes. Under the assumption that the field of orientations of the crystallographic
axes of the crystallites is an independent random field, we show that our theory is compatible with the formulation used in
texture analysis. In particular, we are able to prove that the physical assumption made by [10] in his study of weakly-textured polycrystals holds true.
In addition, we establish some elementary bounds on the material constants that characterize the effective elasticity tensor
of weakly-textured orthorhombic aggregates of cubic crystallites.
Accepted: (June 15, 1999) 相似文献
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The Voigt-Reuss-Hill (VRH) average provides a simple way to estimate the elastic constants of a textured polycrystal in terms of its crystallographic texture and the elastic constants of the constituting crystallites. Empirically the VRH estimates were found in most cases to have an accuracy comparable to those obtained by more sophisticated techniques such as self-consistent schemes. In this paper we determine, in the space of fourth-order tensors with major and minor symmetries, a special set of irreducible basis tensors, with which we obtain a simple explicit formula for the VRH average for elastic polycrystals with arbitrary crystal and texture symmetries. Our formula is correct to first order in the texture coefficients. 相似文献
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Constitutive relation of weakly anisotropic polycrystal with microstructure and initial stress 总被引:2,自引:0,他引:2
Man (Nondestr Test Eval 15:191–214, 1999) derived the constitutive relation of a weakly-textured orthorhombic aggregate of cubic crystallites with effects of microstructure and initial stress. In this paper, a computational expression
on the integration is given. Then, by means of the computational expression, the general constitutive relation of a weakly-textured anisotropic polycrystal with the consideration of microstructure and initial stress is derived. As special cases of our general constitutive
relation, two constitutive relations are given for an isotropic polycrystal and a weakly-textured anisotropic aggregate of cubic crystallites. The acoustoelastic tensor of the reference cubic crystal is derived to determine the material
constants of the polycrystal. Two examples are given for understanding the physical meaning of the texture coefficients and
the constitutive relations.
The project supported by the National Natural Science Foundation of China (10562004, 10662004), the Natural Science Foundation
of Jiangxi of China (0512021), the Science Foundation of Jiangxi Educational Department of China([2006]3), and the Foundation
of Training Academic and Technical Header for Main Majors of Jiangxi of China. 相似文献
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《International Journal of Plasticity》2003,19(11):1867-1884
The main purpose of this work is to develop a phenomenological model, which accounts for the evolution of the elastic and plastic properties of fcc polycrystals due to a crystallographic texture development and predicts the axial effects in torsion experiments. The anisotropic portion of the effective elasticity tensor is modeled by a growth law. The flow rule depends on the anisotropic part of the elasticity tensor. The normalized anisotropic part of the effective elasticity tensor is equal to the 4th-order coefficient of a tensorial Fourier expansion of the crystal orientation distribution function. Hence, the evolution of elastic and viscoplastic properties is modeled by an evolution equation for the 4th-order moment tensor of the orientation distribution function of an aggregate of cubic crystals. It is shown that the model is able to predict the plastic anisotropy that leads to the monotonic and cyclic Swift effect. The predictions are compared to those of the Taylor–Lin polycrystal model and to experimental data. In contrast to other phenomenological models proposed in the literature, the present model predicts the axial effects even if the initial state of the material is isotropic. 相似文献