共查询到19条相似文献,搜索用时 171 毫秒
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相较于传统有限元,数值流形方法(numerical manifold method, NMM) 的一个显著优点是在处理裂纹问题时网格无需与裂纹重合,这就方便了岩体破坏过程的模拟. 基于包含裂尖增强函数的NMM,采用Newmark 隐式动力学算法进行时间积分,重点研究了动力载荷条件下裂纹动态应力强度因子(dynamic stress intensity factor,DSIF) 的求解方法. 针对典型的线弹性动力裂纹问题,给出了NMM 的数值算例. 结果表明NMM 能够准确计算动载荷条件下裂纹的DSIF,并且具有较好的收敛性. 相似文献
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功能梯度夹层多个环形界面裂纹扭转冲击 总被引:1,自引:1,他引:0
研究位于功能梯度层和外部均匀材料之间多个环形界面裂纹的扭转冲击问题,功能梯度材料
(FGM)粘结在两种不同的弹性材料之间,功能梯度层和外部材料之间环形界面裂纹的数目是任意的.引进积分变换和位错密度函数将问题化为求解Laplace域里标准的Cauchy奇异积分方程,进而化为求解代数方程;应用Laplace数值反演技术,计算时域里的动应力强度因子(DSIF).考查了结构几何尺度和材料特性对裂尖动态断裂特性的影响.数值结果表明,DSIF存在一个主峰,到达主峰后,在其相应的静态值附近波动并最终趋于稳定;增加FGM的梯度能减小DSIF的峰值. 相似文献
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数值流形方法(numerucal manifold method,NMM)通过引入数学覆盖和物理覆盖两套系统来统一处理连续和非连续问题. 通过用移动最小二乘插值(moving least squares interpolation,MLS)中的节点影响域构造数学覆盖,得到了基于数值流形方法的无网格伽辽金法(element free Galerkin,EFG). 该方法在保证前处理简单的同时,又能方便处理如裂纹等不连续问题. 建立了适用于小变形和大变形的裂纹扩展计算格式,并通过对曲折裂纹(kinked crack)的处理,在不加密的情况下实现了任意小步长的裂纹扩展,大大提高了在固定网格中模拟裂纹扩展的实用性. 大小变形的结果对比表明,按照不考虑构型变化的小变形计算,结果可能偏于危险. 相似文献
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数值流形方法(numerucal manifold method,NMM)通过引入数学覆盖和物理覆盖两套系统来统一处理连续和非连续问题. 通过用移动最小二乘插值(moving least squares interpolation,MLS)中的节点影响域构造数学覆盖,得到了基于数值流形方法的无网格伽辽金法(element free Galerkin,EFG). 该方法在保证前处理简单的同时,又能方便处理如裂纹等不连续问题. 建立了适用于小变形和大变形的裂纹扩展计算格式,并通过对曲折裂纹(kinked crack)的处理,在不加密的情况下实现了任意小步长的裂纹扩展,大大提高了在固定网格中模拟裂纹扩展的实用性. 大小变形的结果对比表明,按照不考虑构型变化的小变形计算,结果可能偏于危险. 相似文献
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本文利用三维断裂力学的超奇异积分方程求解理论,对三维无限体中两平行平片裂纹在任意载荷作用下的相互干扰问题作了研究。首先导出了以裂纹面移间断(位借)为未知函数的超奇异积分方程组,然后为其建立了有限积分边界元法;在此基础上,讨论用了裂纹面位移间断计算应力强度因子的方法,最后用此计算了两平行平片裂纹的相对位置对裂前沿应力强度因子的影响,其数值结果令人满意。 相似文献
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基于弹性力学中平面问题的复势方法,应用保角映射技术,以Faber级数为工具,导出含任意多椭圆孔及裂纹群无限大板在任意载荷作用下其应力场和位移场的级数解,并在此基础上计算了任意多裂纹板的应力强度因子和M积分,数值结果表明,该方法具有计算精度高、收敛速度快、方便快捷等解析法特有的优点。通过算例分析了不同裂纹倾角时M积分值随载荷方向的变化关系,并讨论了裂纹长度、裂纹间距及裂纹倾角等参数对应力强度因子的影响规律,获得了一些重要结论. 相似文献
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横观各向同性材料的三维断裂力学问题 总被引:4,自引:0,他引:4
从三维横观各向同性材料弹性力学理论出发,
使用Hadamard有限部积分概念, 导出了三维状态下单位位移间断(位错)集度的基
本解. 在此基础上, 进一步运用极限理论, 将任意载荷作用下, 三维无限大横观各向
同性材料弹性体中, 含有一个位于弹性对称面内的任意形状的片状裂纹问题, 归结为求
解一组超奇异积分方程的问题. 通过二维超奇异积分的主部分析方法,
精确地求得了裂纹前沿光滑点附近的应力奇异指数和奇异应力场,
从而找到了以裂纹表面位移间断表示的应力强度因子表达式及裂纹局部扩展所提供
的能量释放率. 作为以上理论的实际应用,最后给出了一个圆形片状裂纹问题
的精确解例和一个正方形片状裂纹问题的数值解例.
对受轴对称法向均布载荷作用下圆形片状裂纹问题,
讨论了超奇异积分方程的精确求解方法, 并获得了位移间断和应力强度因子的封闭解,
此结果与现有理论解完全一致. 相似文献
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Dynamic fracture behavior of a Griffith crack along the interface of an adhesive bonded material under normal loading is studied. The singular integral equations are obtained by employing integral transformation and introducing dislocation density functions. By adopting Gauss-Jacobi integration formula, the problem is reduced to the solution of algebraic equations, and by collocation dots method. their solutions can be obtained Based on the parametric discussions presented in the paper, the following conclusions can be drawn: (1) Mode I dynamic stress intensity factor (DSIF) increases with increasing initial crack length and decreasing visco-elastic layer thickness, revealing distinct size effect; (2) The influence of the visco-elastic adhesive relaxation time on the DSIF should not be ignored. 相似文献
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用裂纹张开位移计算三点弯曲试样的动态应力强度因子 总被引:4,自引:0,他引:4
给出了一种由裂纹的动态张开位移计算三点弯曲试样的动态应力强度因子的简单方法。对于两种不同几何尺寸的试样,在三类不同载荷作用下给出了数植算例,并与完全的动态有限元方法的计算结果进行了比较。结果表明:两种方法的计算结果相当一致。最后,还给出了由测定三点弯曲试样的裂纹张开位移确定试样的动态应力强度因子,最终确定材料动态起裂韧性的方法。 相似文献
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This paper studies the dynamic stress intensity factor (DSIF) at the interface in an adhesive joint under shear loading. Material damage is considered. By introducing the dislocation density function and using the integral transform, the problem is reduced to algebraic equations and can be solved with the collocation dots method in the Laplace domain. Time response of DSIF is calculated with the inverse Laplace integral transform. The results show that the mode Ⅱ DSIF increases with the shear relaxation parameter, shear module and Poisson ratio, while decreases with the swell relaxation parameter. Damage shielding only occurs at the initial stage of crack propagation. The singular index of crack tip is -0.5 and independent on the material parameters, damage conditions of materials, and time. The oscillatory index is controlled by viscoelastic material parameters. 相似文献
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采用Green函数法研究界面上含圆孔边界径向有限长度裂纹的两半无限压电材料对SH波的散射和裂纹尖端动应力强度因子问题.首先构造出具有半圆型凹陷半空间的位移Green函数和电场Green函数,然后采用裂纹"切割"方法构造孔边裂纹,并根据契合思想和界面上的连接条件建立起求解问题的定解积分方程.最后作为算例,给出了孔边界面裂纹尖端动应力强度因子的计算结果图并进行了讨论. 相似文献
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Yong-Dong Li Kang Yong Lee Nan Zhang 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(2):175-187
A mechanical model was established for the antiplane dynamic fracture problem of a functionally graded coating–substrate structure
with a coating crack perpendicular to the weak-discontinuous interface. The problem was reduced to a Cauchy singular integral
equation by the methods of Laplace and Fourier integral transforms. Erdogan’s collocation method and the Laplace numerical
inversion proposed by Miller and Guy were used to calculate the dynamic stress intensity factors. Three conclusions were drawn
through parametric studies: (a) unlike the conclusion drawn for an interfacial crack, reducing the weak discontinuity of the
interface will not necessarily decrease the dynamic stress intensity factor (DSIF) of the coating crack perpendicular to the
interface; (b) increasing the stiffness of the substrate when that of the coating is fixed, or decreasing the stiffness of
coating when that of the substrate is fixed, will be beneficial for the reduction of the DSIF of a coating crack perpendicular
to the interface; and (c) the free surface has a greater influence on the DSIF than the interface does, and the effect of
the interface on the DSIF is greater than that of the material stiffness in the crack-tip region. 相似文献
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Scattering of SH-waves by an interacting interface linear crack and a circular cavity near bimaterial interface 总被引:1,自引:0,他引:1
An analytical method is developed for scattering of SH-waves and dynamic stress concentration by an interacting interface crack and a circular cavity near bimaterial interface. A suitable Green‘s function is contructed, which is the fundamental solution of the displacement field for an elastic half space with a circular cavity impacted by an out-plane harmonic line source loading at the horizontal surface. First, the bimaterial media is divided into two parts along the horizontal interface, one is an elastic half space with a circular cavity and the other is a complete half space. Then the problem is solved according to the procedure of combination and by the Green‘s function method. The horizontal surfaces of the two half spaces are loaded with undetermined anti-plane forces in order to satisfy continuity conditions at the linking section, or with some forces to recover cracks by means of crack-division technique. A series of Fredholm integral equations of first kind for determining the unknown forces can be set up through continuity conditions as expressed in terms of the Green‘s function. Moreover, some expressions are given in this paper, such as dynamic stress intensity factor (DSIF) at the tip of the interface crack and dynamic stress concentration factor (DSCF) around the circular cavity edge. Numerical examples are provided to show the influences of the wave numbers, the geometrical location of the interface crack and the circular cavity, and parameter combinations of different media upon DSIF and DSCF. 相似文献
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爆炸荷载下岩石破坏的数值流形方法模拟 总被引:1,自引:1,他引:1
为了更好地利用数值流形方法对动力学问题进行分析,在对原数值流形方法中的动力学问题求解思想进行分析的基础上,采用动力有限元方法中的Newmark法对该算法进行了改进。改进后的数值流形方法与原来相比具有三个明显的优势:(1)当选择合适的参数后,该方法能够保证解的无条件收敛;(2)可以采用比原算法大得多的时间步长;(3)充分考虑了动力学问题中的阻尼效应。最后通过一个算例说明了改进后的数值流形方法能够很好地模拟岩石在冲击载荷作用下破坏的全过程,克服了有限元法不能模拟岩石破坏后块体运动情况的不足。 相似文献
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Dynamic stress intensity factors of two collinear mode-III cracks perpendicular to and on the two sides of a bi-FGM weak-discontinuous interface 总被引:3,自引:0,他引:3
The mechanical model was established for the anti-plane dynamic fracture problem for two collinear cracks on the two sides of and perpendicular to a weak-discontinuous interface between two materials with smoothly graded elastic properties, as opposed to a sharp interface with discontinuously changing elastic properties. The problem was reduced as a system of Cauchy singular integral equations of the first kind by Laplace and Fourier integral transforms. The integral equations were solved by Erdogan's collocation method and the dynamic stress intensity factors in the time domain were obtained through Laplace numerical inversion proposed by Miller and Guy. The influences of geometrical and physical parameters on the dynamic stress intensity factors were illustrated and discussed, based on which some conclusions were drawn: (a) to increase the thickness of the FGM strip on either side of the interface will be beneficial to reducing the DSIF of a crack perpendicular to a bi-FGM interface and embedded at the center of one of the FGM strips; (b) To increase the rigidity of the FGM strip where the crack is located will increase the DSIF. However, when the material in one side of the interface is more rigid, the DSIF of the interface-perpendicular embedded crack in the other side will be reduced; (c) To decrease the weak-discontinuity of a bi-FGM interface will not necessarily reduce the stress intensity factor of a crack perpendicular to it, which is different from the case of interfacial crack; (d) For two collinear cracks with equal half-length, when the distance between the two inner tips is less than about three times of the half-length, the interaction of them is intensified, however, when the distance is greater than this the interaction becomes weak. 相似文献