共查询到19条相似文献,搜索用时 78 毫秒
1.
建议了二维蠕变损伤问题的有效模量法,基于热动理论提出了一个损伤演化方程,给出有效模量法和有交应力法的有限元解,并对两种方法进行了数值比较。 相似文献
2.
蠕变损伤问题的有效模量法及差分解 总被引:2,自引:0,他引:2
本文在蠕变损伤问题中,以有效模量法将损伤变量引入本构方程,给出相应非线性问题的差分解;并将结果与一维实验数据及有效应力法的结果进行了比较。 相似文献
3.
损伤弹性材料的有效模量及本构关系 总被引:1,自引:0,他引:1
考虑了微裂纹之间的相互作用,利用随机熔断丝网络(Randomfusenetwork)作为模型,模拟了脆性材料在外载荷作用下,其有效模量随损伤的演变行为,并考察了系统含损伤的本构关系。发现在损伤初期,有效模量和损伤具有线性下降关系;而在后期,由于损伤局部化,有效模量迅速下降,提出了一个有效模量随损伤变化的非线性关系。讨论了利用网络模型来研究材料含损伤本构关系的可行性和优越性。 相似文献
4.
5.
6.
为了研究沥青路面结构在温度荷载作用下的疲劳损伤特性,运用通用有限元软件ABAQUS及其二次开发平台,建立了考虑路面材料非线性疲劳损伤的沥青路面结构数值计算模型。分析了沥青路面结构损伤、水平拉应力基于温度荷载重复作用,随空间与时间的变化规律,以及沥青路面裂纹形成寿命。结果表明:损伤主要分布在沥青面层;随着温变次数的增加,面层表面的损伤度呈线性增加;面层表面损伤度均随着面层模量与温变幅度的增加而增加;面层表面水平拉应力随着温度变化次数的增加,以线性特征逐步减小;面层表面水平拉应力随着面层模量与温变幅度的增加均是先增大后减小,有一个峰值点;沥青路面面层的温度型裂纹疲劳形成寿命与面层模量有关,模量越大,裂纹形成疲劳寿命越短,因此从温度疲劳寿命的角度来说,面层不宜选择模量过大的沥青混合料。 相似文献
7.
8.
基于等效特征应变原理,提出了一种新的复合材料有效模量细观力学分析方法。首先,在等效特征应变原理基础上提出平均等效特征应变原理,它可用于解决有限体下任意形状(无论是凸或凹形)的单个夹杂或多个夹杂的弹性变形问题。其次,将平均等效特征应变原理与细观力学直接均匀法相结合,来分析确定复合材料的有效模量。最后利用复合材料纤维与基体的力学性能参数及纤维的体分比,借助MATLAB编程方法,预测其有效模量。通过将理论预测值与已有的的试验值、其它理论预测值进行对比,验证了新分析方法的合理性和分析精度。 相似文献
9.
平行微裂纹损伤模型被用于构建各向异性损伤理论.当施加在代表性体积单元上的边界条件满足Hill条件时,基于平均场理论论证了由平行穿透裂纹损伤的弹性体仅有6个独立有效弹性常数.除了原各向同性基体的2个弹性常数外,与损伤相关的另外4个常数中,3个描述有效弹性常数的折减,1个描述损伤导致的拉剪耦合效应.结合单胞模型和有限元方法分析了双周期阵列平行裂纹问题,数值结果显示:裂纹呈一般双周期阵列时,拉剪耦合参数相比其它模量小很多;当裂纹密度一定时,改变裂纹的排列形式,面内剪切模量和面外剪切模量的折减呈现出不同的规律. 相似文献
10.
含微裂纹和椭球颗粒介质的强度及本构关系 总被引:8,自引:0,他引:8
针对含随机分布微裂纹及椭球颗粒的复合材料,通过考虑椭球颗粒内的本征应变及其与微裂纹的相互作用,利用等效夹杂方法研究了微裂纹损伤对材料有效模量和强度的影响,推导了复合材料的细观应力场及本构关系,并导出了材料破坏的临界条件. 相似文献
11.
疲劳损伤问题中有效应力的一种定义 总被引:3,自引:0,他引:3
有效应力是损伤力学中的一个重要概念,这个概念的提出为用无损状态下的本构方程描述有损伤材料的行为提供了有效手段.本文探讨损伤力学中有效应力的定义,通过对损伤演化规律的分析,指出有效应力的一般定义不适用于疲劳损伤问题.本文认为,疲劳问题中的有效应力应该以等效寿命为基础,并根据剩余寿命的概念引入了疲劳损伤问题中有效应力的一种定义. 相似文献
12.
13.
Yang Qingsheng 《Acta Mechanica Sinica》1998,14(2):171-178
The paper describes use of self-consistent finite element method (SCFEM) for predicting effective properties of fiber composite
with partially debonded interface. The effective longitudinal Young's modulus and shear modulus for unidirectional fiber reinforced
composites with fiber-end cracks are calculated. Numerical results show that the effective properties are considerably influenced
by the fiber-end cracks. The effects of microstructural parameters, such as fiber volume fraction, modulus ratio of the constituents
and fiber aspect, on the effective properties of the composites were discussed.
The project supported by the National Natural Science Foundation of China 相似文献
14.
《International Journal of Solids and Structures》2003,40(4):981-999
An analytical model for damaged woven fabric composites is developed using the theory of advanced mechanics of materials. The analysis is based on Castigliano’s second theorem and utilizes a damaged mosaic model laminate. Three damage modes (i.e., transverse yarn cracking, interface debonding, and sliding with friction at the interface) are considered. Only one independent interfacial parameter, the friction coefficient between warp and fill yarns, is introduced in the analysis. A closed-form formula is provided for estimating effective Young’s modulus of damaged woven laminates. A parametric study of some 192 sample cases of two different composite systems (i.e., glass fiber/epoxy and ceramic fiber/ceramic) is conducted to illustrate the application and significance of the newly derived analytical model. The numerical values of the effective Young’s modulus for the special case involving only transverse yarn cracking (the first damage mode) estimated by the present mechanics-of-materials model agree fairly well with those predicted by an elasticity-based model [Int. J. Solids Struct. 38 (2001) 855]. For the general case involving all three damage modes simultaneously, the present model reveals the complex nature of Young’s modulus reduction in a quantitative manner, which differs from existing models. 相似文献
15.
根据一维应变冲击波的基本关系,将Cochran 等定义的有效剪切模量与准弹性卸载过程的纵波和体波声速关联起来,并藉此研究了冲击波作用下铝的准弹性卸载特性. 利用VISAR高压声速测量技术获得了LY12铝在20$\sim$100\,GPa压力下沿着准弹性卸载过程的有效剪切模量,结果表明LY12铝的有效剪切模量随卸载应力的下降而迅速下降. 采用与卸载应力成线性关系的方程对有效剪切模量进行了近似描述,该方程的斜率随初始冲击压力的增加而增加,体现了准弹性卸载行为的压力相关性. 将有效剪切模量结果与准静态实验结果进行了比较,由此分析了冲击波作用下准弹性卸载过程的可能物理机制. 应用有效剪切模量方程对6061铝合金的准弹性行为进行了模拟,计算结果与实验结果符合很好. 相似文献
16.
An explicit expression of the effective moduli for composite materials filled with coated inclusions
The obvious shortcoming of the generalized self-consistent method (GSCM) is that the effective shear modulus of composite
materials estimated by the method can not be expressed in an explicit form. This is inconvenient in engineering applications.
In order to overcome that shortcoming of GSCM, a reformation of GSCM is made and a new micromechanical scheme is suggested
in this paper. By means of this new scheme, both the effective bulk and shear moduli of an inclusion-matrix composite material
can be obtained and be expressed in simple explicit forms. A comparison with the existing models and the rigorous Hashin-Shtrikman
bounds demonstrates that the present scheme is accurate. By a two-step homogenization technique from the present new scheme,
the effective moduli of the composite materials with coated spherical inclusions are obtained and can also be expressed in
an explicit form. The comparison with the existing theoretical and experimental results shows that the present solutions are
satisfactory. Moreover, a quantitative comparison of GSCM and the Mori-Tanaka method (MTM) is made based on a unified scheme.
The project supported by the National Natural Science Foundation of China under the Contract NO. 19632030 and 19572008, and
China Postdoctoral Science Foundation 相似文献
17.
The present paper studies the dynamic effective property of piezoelectric composites embedded with cylindrical piezoelectric fibers under anti-plane harmonic electro-elastic waves. By using the dynamic generalized self-consistent method (DGSM) of electro-elastic coupling wave, the problem of randomly distributed cylindrical fibers in a piezoelectric medium can be analyzed in terms of a representative volume element with a coated fiber embedded in an equivalent effective medium. The interfaces between the fibers and the matrix are assumed to be imperfect which are here modeled as spring- or membrane-type interfaces. Through wave function expansion method and an iterative method, the effective piezoelectrically stiffened shear modulus and the effective wave number are obtained. Examples are conducted to verify the present solutions and to illustrate the dependence of the effective piezoelectrically stiffened shear modulus on the wave number (frequency) as well as the interface properties. The special size effect related to interfacial imperfection is also discussed. 相似文献
18.
19.
A technique is proposed to estimate the energy density as fracture toughness for ductile bulk materials with an indentation system equipped with a Berkovich indenter based on the theory of plastic deformation energy transforming into the indentation energy of fracture. With progressive increase of penetration loads, the material damage is exhibited on the effective elastic modulus. A quadratic polynomial relationship between the plastic penetration depth and penetration load, and an approximate linear relationship between logarithmic plastic penetration depth and logarithmic effective elastic modulus are exhibited by indentation investigation with Berkovich indenter. The parameter of damage variable is proposed to determine the critical effective elastic modulus at the fracture point. And the strain energy density factor is calculated according to the equations of penetration load, plastic penetration depth and effective elastic modulus. The fracture toughness of aluminum alloy and stainless steel are evaluated by both indentation tests and KIC fracture toughness tests. The predicted Scr values of indentation tests are in good agreement with experimental results of CT tests. 相似文献