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为提高非均匀材料界面裂纹尖端断裂参数的求解精度,基于非均匀材料界面断裂力学、Cell-Based光滑有限元(Cell-SFEM)和非均匀材料的互交作用积分法,提出了求解非均匀材料界面裂纹尖端断裂参数的CellBased光滑有限元法,推导了基于Cell-Based光滑有限元法的非均匀材料的互交作用积分法,对非均匀材料间的界面裂纹尖端处正则应力强度因子进行了求解,并与参考解进行了比较,讨论了互交积分区域大小和光滑子元个数与正则应力强度因子的关系。数值算例结果表明:本方法具有很高的计算精度,对积分区域大小不敏感,可为设计、制造抗破坏非均匀材料提供依据。 相似文献
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梯度涂层材料中裂纹问题的非均匀元分析 总被引:4,自引:0,他引:4
本文采用非均匀等参有限元的方法研究了薄膜梯度涂层/均匀基材中的界面裂纹问题,并与双材料界面裂纹情况进行了对比计算。研究表明:在均匀基材上采用梯度涂层,与双材料相比可以有效地降低裂尖场应力强度因子;同时还分析了涂层厚度与梯度参数对界面应力强度因子的影响。结果表明:当薄膜厚度大于或等于裂纹长度时,应力强度因子(KI、KII)对其尺度的变化显得不敏感;对梯度参数的影响而言,当材料性能曲线的幂指数m大于1时,裂尖场的应力强度因子KII相对KI很小且基本不随m变化,因此裂尖场与均匀材料情况类似;当m小于1时,应力强度因子KII随m减小而急剧增大,裂尖场由KI及KII控制,断裂趋于混合型。 相似文献
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利用积分方程方法,本文研究了夹在两个均匀压电半空间的功能梯度压电带界面共线双裂纹的反平面问题。在电渗透型边界条件下,通过Fourier余弦变换将所考虑的问题化为一对偶积分方程,再用Copson方法将该对偶积分方程转化为Fredholm方程进行数值求解,从而给出了裂纹尖端的应力强度因子,电位移强度因子的表达式。分析了裂纹长度,功能梯度非均匀参数以及材料的几何尺寸等对应力强度因子的影响。 相似文献
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对称型陶瓷层状复合材料中的残余应力分析 总被引:9,自引:0,他引:9
针对由层间约束引起的层内残余应力,提出了用于描述层合材料应力应变状态的非均匀应变模型。利用非均匀应变模型推导出对称型层合材料由层间约束引起的层内残余应力的解析表达式,得到层内应力和界面应力沿长度方向分布的变化规律,指出轴向残余应力是层间界面剪应力造成的,是位置的函数;论证了由于表层材料受力的非对称性,界面必定存在正应力,且界面正应力须自平衡,界面正应力亦为长度方向上位置的函数,针对Si3N4-Si3N4/TiN-Si3N4三层及多层(2N+1)对称型陶瓷基层状复合材料,研究了残余应力对强界面结合的层合材料宏观力学性能和裂纹扩展行为的影响和作用。结果表明,材料的宏观性能随着残余应力的变化而变化,其变化规律与理论计算的结果吻合。 相似文献
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梯度复合材料应力强度因子计算的梯度扩展单元法 总被引:1,自引:0,他引:1
推导了一种适用于梯度复合材料断裂特性分析的梯度扩展单元, 采用细观力学方法描述材料变化的物理属性, 通过线性插值位移场给出了4节点梯度扩展元随空间位置变化的刚度矩阵, 并建立了结构的连续梯度有限元模型。通过将梯度单元的计算结果与均匀单元以及已有文献结果进行对比, 证明了梯度扩展有限元(XFEM)的优越性, 并进一步讨论了材料参数对裂纹尖端应力强度因子(SIF)的影响规律。研究结果表明: 随着网格密度的增加, 梯度单元的计算结果能够迅速收敛于准确解, 均匀单元的计算误差不会随着网格细化而消失, 且随着裂纹长度和属性梯度的增大而增大; 属性梯度和涂层基体厚度比的增大导致涂覆型梯度材料的SIF增大; 裂纹长度的增加和连接层基体厚度比的减小均导致连接型梯度材料的SIF增大。 相似文献
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推导了一种适用于梯度复合材料断裂特性分析的梯度扩展单元,采用细观力学方法描述材料变化的物理属性,通过线性插值位移场给出了4节点梯度扩展元随空间位置变化的刚度矩阵,并建立了结构的连续梯度有限元模型.通过将梯度单元的计算结果与均匀单元以及已有文献结果进行对比,证明了梯度扩展有限元(XFEM)的优越性,并进一步讨论了材料参数对裂纹尖端应力强度因子(SIF)的影响规律.研究结果表明:随着网格密度的增加,梯度单元的计算结果能够迅速收敛于准确解,均匀单元的计算误差不会随着网格细化而消失,且随着裂纹长度和属性梯度的增大而增大;属性梯度和涂层基体厚度比的增大导致涂覆型梯度材料的SIF增大;裂纹长度的增加和连接层基体厚度比的减小均导致连接型梯度材料的SIF增大. 相似文献
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《Thin solid films》1987,149(3):261-268
In this paper the influence of a spatially non-homogeneous trap distribution on the transient currents in insulating layers for high fields, weak injection and fast trapping is discussed. Two approximate solutions to the transport equations are obtained by including a non-homogeneous trap distribution in the previous formulation of Arnett (P. C. Arnett), J. Appl. Phys., 46 (1975) 5236); the discharge of the layer is also considered. The spatial behaviour of the trap density is assumed to be exponential and this is applied to the solutions obtained. Formulae relating the trap distribution parameters to electrically measurable quantities are proposed. 相似文献
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该文通过应用一种新的分层模型求解了剪切模量任意变化的非均匀土层受轴对称荷载时的表面位移沉降。根据任意曲线都可以用一系列连续的直线段来逼近,非均匀土层被分为若干个子层,在每个子层中,假设剪切模量沿厚度方向按线性变化,在子层的界面上剪切模量连续并且等于实际值。应用Hankel积分变换和传递矩阵方法,求解了剪切模量按照不同函数形式变化的表面沉降。 相似文献
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Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder 总被引:1,自引:0,他引:1
By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented. 相似文献
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The anti-plane vibration of a quartz plate having an additional partial non-uniform mass layer is solved by ignoring the effect of small c 56 in comparison with other elastic constants. This analysis is based on the trigonometric series solution, and the convergence is examined. Numerical simulation is conducted for several different types of layers of different thicknesses using linear, cosine, and quadratic functions. The frequency spectrums, in addition to the length and mass fraction of the layer, are discussed separately. Compared with the homogeneous mass layer, the non-homogeneous layer with greater inertia leads to earlier appearance of the higher modes and more modes trapped under the same condition. Especially, there is no energy trapping in the plate with a fully covered uniform mass layer. However, this kind of energy trapping can be obtained again when the surface is non-uniform for some cases. 相似文献
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A solution of a thermal-shock problem of generalized thermoelasticity of a non-homogeneous isotropic hollow cylinder using a finite-element method is developed. The formulation is applied to the generalized thermoelasticity based on the Green and Naghdi (GN) theory of type II and type III by an appropriate choice of parameters. The problem has been solved numerically using a finite-element method. Numerical results for the distributions of displacement, temperature, radial stress, and hoop stress are represented graphically. The results indicate that the effects of non-homogeneity are very pronounced. The effects of non-homogeneity are presented with the two types of the Green and Naghdi theory. 相似文献
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This paper deals with development of triangular finite element for buckling and vibration analysis of laminated composite stiffened shells. For the laminated shell, an equivalent layer shell theory is employed. The first-order shear deformation theory including extension of the normal line is used. In order to take into account a non-homogeneous distribution of the transverse shear stresses a correction of transverse shear stiffness is employed. Based on the equivalent layer theory with six degrees of freedom (three displacements and three rotations), a finite element that ensures C0 continuity of the displacement and rotation fields across inter-element boundaries has been developed. Numerical examples are presented to show the accuracy and convergence characteristics of the element. Results of vibration and buckling analysis of stiffened plates and shells are discussed. 相似文献
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Au/In等温凝固焊接失效模式研究 总被引:5,自引:0,他引:5
研究了Au/In等温凝固芯片焊接的失效模式,对每种失效模式的失效原因进行了讨论,并提出了相应的解决途径。结果表明:镀铟层过厚,会使焊层中产生Ni9In4相和大量空洞,导致焊层出现早期失效;焊接过程中芯片与衬底平行度不好,会使加载压力在焊区分布不均,并导致焊区局部区域发生Au/In不浸润;焊接温度过高,则焊层内会出现较大的热应力,可导致芯片或焊层开裂;在300℃高温下,由于过渡层Ni与Au/In相的反应,焊区内出现大量空洞,导致焊层剪切强度下降。对Au/In体系在未来高温电子器件芯片焊接中的应用,尚需寻找合适的过渡层材料。 相似文献
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Summary By means of introducing a new dependent variable and the separation of variables technique as well as the superposition method,
the axisymmetric plane strain dynamic problem of a special non-homogeneous magneto-electro-elastic hollow cylinder is finally
transformed to two Volterra integral equations of the second kind with respect to two functions of time. At each time subinterval,
a cubic Hermite polynomial is adopted to approximate the two undetermined functions, and the recursive formula is obtained.The
integral equation is then solved successfully. The transient responses of displacements, stresses, electric and magnetic potentials
are finally determined. Numerical results are presented at the end. 相似文献
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S. Simov 《Journal of Materials Science》1976,11(12):2319-2332
Published data on hollow crystals of II–VI compounds are reviewed. The experimental conditions for obtaining hollow crystals are discussed and presented systematically in tables. Some inferences concerning the effect of impurities, supersaturation, type of substrate and other factors on the growth of hollow crystals are made. Particular attention is paid to the structure, form and defects of hollow crystals and it is established that they can be classified in the following groups: hollow hexagonal columns and prisms, hollow pyramids, hollow crystals with spiral-like hexagonal form and hollow crystals with a more complex structure consisting of whisker-pyramid-prism. The mechanism and kinetics of the growth of hollow crystals as presented by different authors are discussed. 相似文献
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An asymptotic analysis of a layered structure with an imperfect interface subject to an anti-plane shear deformation and non-homogeneous Dirichlet end conditions is presented in this paper. Two layers of isotropic materials are bonded via a middle interface layer (adhesive joint), which is thin and soft; effectively, this can be described as a discontinuity surface for the displacement. Model fields are constructed to compensate for the error produced by the asymptotic solution for the case when the layered structure is subject to non-homogeneous Dirichlet end conditions. Numerical examples and analytical estimates are presented to illustrate the slow decay of the `boundary-layer' fields. 相似文献