共查询到19条相似文献,搜索用时 281 毫秒
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基于比例边界有限元法(SBFEM)和灰狼优化(GWO)算法,提出了一种裂纹尖端识别方法。首先,借助SBFEM解决断裂力学问题特有的优势,快速准确地计算出反演所需的测点位移,并验证了正问题求解的正确性。其次,建立与裂纹尖端位置有关的目标函数,将求解裂纹尖端位置转换为求解目标函数最小值的优化问题。最后,采用GWO算法对目标函数进行了优化,进而搜索裂纹尖端的最佳位置。数值算例结果表明:利用SBFEM的高精度、半解析的优点,在反演过程中采用其求解正问题是非常有效的;GWO算法具有良好的全局收敛性,且相比经典的粒子群算法,能够更快速准确地搜索出裂纹尖端的位置;GWO算法具有较好的抗噪性。 相似文献
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提出了一种新的弹性-粘塑性模型用于分析Ⅰ型动态扩展裂纹尖端的应力应变场.给出了适当的位移模式,推导了渐近方程并且给出了数值解.分析和计算表明:对于低粘性情况,裂纹尖端场具有对数奇异性;对于高粘性情况,渐近方程无解.分析比较表明该结果具有高玉臣提出的单参数解的所有优点,并且消除了粘性区随裂纹扩展而移动的不足. 相似文献
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在线弹性理论中,复合材料裂纹尖端具有多重应力奇异性,常规数值方法不易求解.该文建立的扩展边界元法(XBEM)对围绕尖端区域位移函数采用自尖端径向距离r的渐近级数展开式表达,其幅值系数作为基本未知量,而尖端外部区域采用常规边界元法离散方程.两方程联立求解可获得裂纹结构完整的位移和应力场.对两相材料裂纹结构尖端的两个材料域分别采用合理的应力特征对,然后对其进行计算,通过计算结果的对比分析,表明了扩展边界元法求解两相材料裂纹结构全域应力场的准确性和有效性. 相似文献
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本文在裂纹尖端场的应力分量仅仅是θ的函数的假设下,利用Hill屈服准则和平衡方程导出了正交异性理想塑性材料平面应力问题中裂纹尖端场的微分方程;在允许应力不连续线存在的情况下,把解析表达和数值计算法结合起来,得到了Ⅰ型和Ⅱ型裂纹尖端的应力场. 相似文献
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《数学的实践与认识》2013,(24)
将哈氏皮质骨看作纤维增强型复合材料,考虑了存在于哈氏皮质骨间质组织中的多条径向微裂纹问题.根据线弹性断裂理论,讨论了骨单位中骨密质和微裂纹群之间的相互影响.运用位错技术和奇异积分方程求解,得到了微裂纹尖端应力强度因子的数值结果.通过把此模型的数值结果与纤维陶瓷基底模型的结果比较,说明了哈氏管道的存在对微裂纹尖端应力强度因子的影响. 相似文献
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提出了一种新的弹性-粘塑性模型用于分析I型动态扩展裂纹尖端的应力应变场。给出了适当的位移模式,推导了渐近方程并且给出了数值解。分析和计算表明:对于低粘性情况,裂纹尖端场具有对数奇异性;对于高粘性情况,渐近方程无解。分析比较表明该结果具有高压臣提出的单参数解的所有优点,并且消除了粘性区随裂纹扩展而移动的不足。 相似文献
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利用复变函数理论中的解析延拓、奇性主部分析和推广的Liouville定理,求解了一维六方压电准晶双材料在集中载荷作用下界面共线裂纹反平面弹性问题.导出了含有一条和两条有限长界面裂纹的封闭解,同时给出了裂纹尖端场强度因子(包含声子场和相位子场应力强度因子和电位移强度因子)的表达式.数值算例分析了外荷载与耦合系数之比对裂纹尖端场强度因子变化规律的影响.从数值结果中可以看出,当裂纹长度增加时,裂纹尖端场强度因子随之增加;应力强度因子随双材料耦合系数之比的增大而增大,电位移强度因子几乎不变;不同载荷作用下,裂纹尖端场强度因子随着裂纹长度改变时的变化趋势也不尽相同.研究结果可为压电准晶双材料的设计和制备提供一定的理论参考. 相似文献
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In this paper, the three-dimensional automatic adaptive mesh refinement is presented in modeling the crack propagation based on the modified superconvergent patch recovery technique. The technique is developed for the mixed mode fracture analysis of different fracture specimens. The stress intensity factors are calculated at the crack tip region and the crack propagation is determined by applying a proper crack growth criterion. An automatic adaptive mesh refinement is employed on the basis of modified superconvergent patch recovery (MSPR) technique to simulate the crack growth by applying the asymptotic crack tip solution and using the collapsed quarter-point singular tetrahedral elements at the crack tip region. A-posteriori error estimator is used based on the Zienkiewicz–Zhu method to estimate the error of fracture parameters and predict the crack path pattern. Finally, the efficiency and accuracy of proposed computational algorithm is demonstrated by several numerical examples. 相似文献
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For a reliable prediction of crack paths, on the one hand the accurate calculation of crack tip loading quantities is inevitable, on the other hand orthotropic features of the fracture toughness need to be taken into account. The interplay of crack tip loading and material response due to fracture is still unclear and seems to have a crucial effect on crack path predictions. Numerical tools for the accurate calculation of crack tip loading quantities using path-invariant J-integrals and interaction integrals (I-integral) are presented. Here, global approaches are beneficial when considering crack tips approaching other crack faces or internal boundaries. Curved crack faces have to be taken into account and special treatment regarding crack face integrals is necessary. Experimental investigations are carried out at standard CT-specimens of rolled aluminum alloy Al-7075 exhibiting a directional orthotropy of the fracture toughness. Considering that property, the numerically predicted crack paths based on FE calculations show very good agreement with subcritically grown paths obtained from experiments. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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基于Westergaard应力函数裂纹尖端二阶弹性解,推导了裂纹尖端微裂区的轮廓线和特征尺寸的解析表达式;采用幂函数模型描述的拉应变软化模型,确定了在最大拉应力强度理论和最大拉应变强度理论下断裂过程区(FPZ)临界值的解析表达式;将基于Westergaard应力函数一阶弹性解及二阶弹性解、Muskhelishvili应力函数和Duan-Nakagawa模型确定的FPZ临界值进行了比较.结果表明裂纹尖端微裂区和FPZ临界值随着Poisson比的减小而增加并逐渐趋近于应用最大拉应力强度理论确定的结果;二阶弹性解确定的裂纹尖端微裂区和FPZ临界值大于一阶弹性解的值;FPZ临界值随着拉应变软化指数的增加而增加;二阶弹性解确定的FPZ临界值的精度远高于一阶弹性解确定的值. 相似文献
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Based on the work by Eshelby, the path-independent Jk-, M-, L- and interaction- or Ik-integrals were introduced and applied to cracks for the accurate calculation of crack tip loading quantities. Applying the FE-method to solve boundary value problems with cracks, numerically inaccurate values are observed within the crack tip region affecting the accuracy of local approaches. Simulating crack paths, local approaches face further problems as cracks are running towards interfaces, internal boundaries or other crack faces. Within global approaches, path-independent integrals are calculated along remote contours far from the crack tip, essentially exploiting numerically reliable data requiring special treatment only for the near-tip crack faces. To provide path-independence, additional integrals along interfaces, internal boundaries and crack faces are necessary. In this paper, new global approaches of path-independent integrals are presented and applied to the calculation of crack paths at two-cracks systems. A second focus is directed to the accurate loading analysis and crack path prediction considering anisotropic properties and material interfaces. The numerical model provides crack paths which are in good agreement with those obtained from crack growth experiments. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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This work presents numerical methods used for predicting crack paths in technical structures based on the theory of linear elastic fracture mechanics. The FE-method is used in combination with an efficient remeshing algorithm and a post processor to calculate crack tip loading. The interaction of cracks and internal boundaries and interfaces is investigated. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Using the nano-moiré method, we measure the near tip nanoscopic deformation on the [111] plane of single crystal silicon with
a loaded quasi-cleavage crack running in the [110] direction. The measured strain distribution ahead of the crack tip agrees
with the linear elastic fracture mechanics prediction up to 10 nm from the crack tip. Dislocations of Peierls type are detected
and they extend from the crack tip over a length of hundreds of Burgers vectors. 相似文献
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利用复变函数方法,通过构造广义保角映射,研究了一维正方准晶垂直于准周期方向具有不对称共线裂纹的圆形孔口问题,给出了各应力分量在象平面的复表示,并得到该裂纹尖端的应力强度因子.在极限情形下,给出一维正方准晶中具有对称共线裂纹的圆形孔口,带单裂纹的圆形孔口和Griffith裂纹在裂纹尖端的应力强度因子. 相似文献