共查询到19条相似文献,搜索用时 125 毫秒
1.
利用复变函数方法,通过构造保角映射,分析了不对称椭圆孔边裂纹问题,给出了裂纹尖端Ⅰ型与Ⅱ型问题应力强度因子的解析解.并由此模拟出了经典的Griffith裂纹、不对称十字裂纹,T型裂纹问题,所得结果与经典结果完全一致.这些解在科学及工程断裂中有着潜在的应用价值. 相似文献
2.
一维六方准晶中椭圆孔边裂纹的静态与动态分析 总被引:1,自引:0,他引:1
通过构造保角映射函数,借助复变函数方法,研究了一维六方准晶中椭圆孔边裂纹的反平面剪切问题,给出了Ⅲ型裂纹问题的应力强度因子的解析解.当椭圆的长、短半轴以及裂纹长度变化时,所得结果不仅可以还原为Griffith裂纹的情形,而且得到孔边裂纹问题、T型裂纹问题和半无限平面边界裂纹问题的应力强度因子的解析解.就声子场而言,这些解与经典弹性的结果完全一致.接着对椭圆孔边裂纹的动力学问题进行了研究,并得到了Ⅲ型动态应力强度因子的解析解.当裂纹速度V→0时,动力学解还原为静力学解.这些解在科学与工程断裂中有着潜在的应用价值. 相似文献
3.
带双裂纹的椭圆孔口问题的应力分析 总被引:5,自引:1,他引:5
利用复变方法,通过构造新的保角映射,研究了带双裂纹椭圆孔口的平面弹性问
题,得到了I型与II型裂纹问题应力强度因子的解析解.在极限情形下,
不仅可以还原经典的Griffith裂纹的结果,而且可模拟出十字裂纹和带双裂纹的圆
形孔口问题. 相似文献
4.
研究了材料中楔型向错偶极子与楔型裂纹的弹性干涉问题. 运用复变函数方法获得了复势函
数和应力场的封闭形式解答,导出了楔型裂纹尖端应力强度因子的解析表达式. 讨论了向错
偶极子的位置、方向和偶臂长度对楔型裂纹尖端应力强度因子的屏蔽和反屏蔽作用规律. 研
究结果表明,向错偶极子靠近裂纹尖端时,对应力强度因子的屏蔽或反屏蔽作用非常强烈.
在一定条件下,楔型向错偶极子能够延缓楔型裂纹的扩展;偶极子的方向也存在一个临界值
使其对应力强度因子的屏蔽或反屏蔽效应最大. 此外,楔型裂纹张开角以及偶极子臂长对应
力强度因子也有较大的影响. 相似文献
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7.
热机载荷共同作用下双材料和复合材料中的裂纹扩展往往发生在界面处,并且工程中实际遇到的裂纹大多数是三维裂纹.由于通用权函数仅仅与裂纹体的几何形状有关,与载荷、时间无关,因此在求解复杂冲击载荷下界面裂纹应力强度因子随时间的变化过程时,避免了反复的应力分析,计算效率得到提高.根据Betti互易原理,论文推导出三维界面裂纹问题通用权函数法的普遍表达式,并给出了热机载荷共同作用下三维界面Ⅰ型、Ⅱ型和Ⅲ型裂纹问题通用权函数法的有限元格式.通过与实例计算比较,表明此方法得到的结果可以达到满意的工程应用精度. 相似文献
8.
研究了多晶体材料中螺型位错偶极子和界面裂纹的弹性干涉作用.利用复变函数方法,得到了该问题复势函数的封闭形式解答.求出了由位错偶极子诱导的应力场和裂纹尖端应力强度应子,分析了偶极子的方向,偶臂和位置以及材料失配对应力强度因子的影响.推导了作用在螺型位错偶极子中心的像力和力偶矩,并讨论了界面裂纹几何条件和不同材料特征组合对位错偶极子平衡位置的影响规律.结果表明,裂纹尖端的螺型位错偶极子对应力强度因子会产生强烈的屏蔽或反屏蔽效应.同时,界面裂纹对螺型位错偶极子在材料中运动有很强的扰动作用. 相似文献
9.
扩展裂纹准静态渐近解中的矛盾 总被引:4,自引:2,他引:4
裂纹尖端附近的应力应变场是一个相当复杂的问题,对于不同的情况,这个场具有完全不同的渐近属性.具体说来,场的渐近属性取决于裂纹状态(静止还是扩展)、几何特征(平面应变还是平面应力)、加载速度(准静态还是动态)、裂纹型式(Ⅰ、Ⅱ、Ⅲ型)及材料性质(弹性、塑性、蠕变、……).其中,人们较为重视的一种情况是扩展裂纹尖端的塑性场.而且,为了使问题简化,通常采用准静态假定.对于理想塑性材料Ⅲ型扩展裂纹的渐近解由Chitaley和McClintock给出.对于Ⅰ型裂纹,Slepyan采用Tresca属服条件给出了渐近解,高玉臣和Rice采用Mises屈服条件得到了渐近解,但这些解只适用于 相似文献
10.
本文研究了有限宽、粘接的对称SANDW(?)CH型正交各向异性板条的静裂纹问题.在中间板条有内部裂纹和完全断裂的两种情形,解法和应力奇异性分析的过程都和板条为各向同性时相似;但在界面裂纹时,却归结为解一组与各向同性粘接板条不同的二类柯西型奇异积分方程.此时,各向同性粘接板条界面裂纹的应力强度因子的定义已不再适用.本文提出一种广义的应力强度因子定义,并给出上述三种裂纹问题的算例,计算裂纹长度、板条宽度或弹性常数对应力强度因子的影响. 相似文献
11.
By means of the complex variable function method and the technique of conformal mapping, the anti-plane shear problem of an elliptic hole with two straight cracks in one-dimensional hexagonal quasicrystals is investigated. The solution of the stress intensity factor (SIF) for mode III problem has been found. Under the condition of limitation, both the known results and the SIF solution at the crack tip of a circular hole with two straight cracks and cross crack in one-dimensional hexagonal quasicrystals can be obtained. 相似文献
12.
利用复变函数方法研究了一维六方准晶中星形静态裂纹和运动裂纹的反平面剪切问题,得到了星形裂纹尖端处应力强度因子和动应力强度因子的解析解.当裂纹条数给定时,由此可得到直线裂纹,Griffith裂纹,共点均匀分布三裂纹,对称十字形裂纹,米字型裂纹(对称八裂纹)静力学和动力学问题的解析解.当k=4时,用数值算例讨论了声子场-相位子场耦合系数和裂纹运动速度对动应力强度因子的影响.当速度趋于0时,运动裂纹的解可以退化为静态裂纹的解. 相似文献
13.
The Saint-Venant torsion problems of a cylinder with curvilinear cracks were considered and reduced to solving the boundary integral equations only on cracks. Using the interpolation models for both singular crack tip elements and other crack linear elements, the boundary element formulas of the torsion rigidity and stress intensity factors were given. Some typical torsion problems of a cylinder involving a straight, kinked or curvilinear crack were calculated. The obtained results for the case of straight crack agree well with those given by using the Gauss-Chebyshev integration formulas, which demonstrates the validity and applicability of the present boundary element method. 相似文献
14.
Mechanism of quasi-static crack branching in brittle solids has been analyzed by a modified displacement discontinuity method. It has been assumed that the pre-existing cracks in brittle solids may propagate at the crack tips due to the initiation and propagation of the kink (or wing) cracks. The originated wing cracks will act as new cracks and can be further propagated from their tips according to the linear elastic fracture mechanics (LEFM) theory. The kink displacement discontinuity formulations (considering the linear and quadratic interpolation functions) are specially developed to calculate the displacement discontinuities for the left and right sides of a kink point so that the first and second mode kink stress intensity factors can be estimated. The crack tips are also treated by boundary displacement collocation technique considering the singularity variation of the displacements and stresses near the crack tip. The propagating direction of the secondary cracks can be predicted by using the maximum tangential stress criterion. An iterative algorithm is used to predict the crack propagating path assuming an incremental increase of the crack length in the predicted direction (straight and curved cracks have been treated). The same approach has been used for estimating the crack propagating direction and path of the original and wing cracks considering the special crack tip elements. Some example problems are numerically solved assuming quasi-static conditions. These results are compared with the corresponding experimental and numerical results given in the literature. This comparison validates the accuracy and applicability of the proposed method. 相似文献
15.
S. E. Groves C. E. Harris A. L. Highsmith D. H. Allen R. G. Norvell 《Experimental Mechanics》1987,27(1):73-79
The development of damage in cross-ply Hercules AS4/3502 graphite/epoxy laminates has been investigated. Specific endeavors
were to identify the mechanisms for initiation and growth of matrix cracks and to determine the effect of matrix cracking
on the stiffness loss in cross-ply laminates. Two types of matrix cracks were identified. These include both straight and
curved cracks. The experimental study of matrix crack damage revealed that the curved cracks formed after the straight cracks
and followed a repeatable pattern of location and orientation relative to the straight cracks. Therefore, it was postulated
that the growth mechanism for curved cracks is driven by the stress state resulting from the formation of the straight cracks.
This phenomenon was analytically investigated by a finite-element model of straight cracks in a cross-ply laminate. The finite-element
results provide supporting evidence for the postulated growth mechanism. The experimental study also revealed that the number
of curved cracks increased with the number of consecutive 90-deg plies. Finally, experimental results show as much as 10-percent
degradation in axial stiffness due to matrix cracking in cross-ply graphite/epoxy laminates. 相似文献
16.
将梁中横向裂纹等效为无质量扭转弹簧,并忽略其对梁剪切变形的影响,得到的具有任意裂纹数目Timoshenko 梁自振模态的统一显示解析表达式.将裂纹梁的自振模态分为基本模态和裂纹附加模态,利用最小二乘拟合,建立了利用裂纹附加模态函数的梁裂纹损伤识别方法.通过数值模拟开展了简支单裂纹梁以及悬臂和固支双裂纹梁等的裂纹损伤识别,考察了测量误差对损伤识别的影响,数值结果表明本文所提出的裂纹损伤识别方法对裂纹位置的识别精度高于对裂纹损伤程度的识别精度;随着测量误差的增加,裂纹位置及裂纹损伤程度的识别误差增加,但仍在可接受的范围内,故该裂纹损伤识别方法在实际工程中具有一定的应用价值. 相似文献
17.
Infinitesimal plane deformations of ideal fiber-reinforced composites with elastic shearing stress response are considered. The fibers are straight and parallel, and there is a straight crack perpendicular to the fibers. A general expression for the energy release rate per unit length of crack advance is obtained. Explicit expressions in terms of the body geometry and loading are obtained for three special classes of body shapes: bodies symmetrical about a fiber, bodies bounded on the cracked side by a fiber, and bodies bounded on the opposite side by a fiber. The results also apply to cracks parallel to the fibers, and to cracks in compressible materials reinforced by two orthogonal families of inextensible fibers. 相似文献
18.
V. Lazarus 《Journal of the mechanics and physics of solids》2011,59(2):121-144
One current challenge of linear elastic fracture mechanics (LEFM) is to take into account the non-linearities induced by the crack front deformations. For this, a suitable approach is the crack front perturbation method initiated by Rice (1985). It allows to update the stress intensity factors (SIFs) when the crack front of a planar crack is perturbed in its plane. This approach and its later extensions to more complex cases are recalled in this review. Applications concerning the deformation of the crack front when it propagates quasistatically in a homogeneous or heterogeneous media have been considered in brittle fracture, fatigue or subcritical propagation. The crack shapes corresponding to uniform SIF have been derived: cracks with straight or circular fronts, but also when bifurcations exist, with wavy front. For an initial straight crack, it has been shown that, in homogeneous media, in the quasistatic case, perturbations of all lengthscales progressively disappear unless disordered fracture properties yields Family and Vicsek (1985) roughness of the crack front. Extension of those perturbation approaches to more realistic geometries and to coalescence of cracks is also envisaged. 相似文献
19.
A. N. Guz 《International Applied Mechanics》2011,47(2):121-168
Major results on the mechanics of crack propagation in materials with initial (residual) stresses are analyzed. The case of
straight cracks of constant width that propagate at a constant speed in a material with initial (residual) stresses acting
along the cracks is examined. The results were obtained, based on linearized solid mechanics, in a universal form for isotropic
and orthotropic, compressible and incompressible elastic materials with an arbitrary elastic potential in the cases of finite
(large) and small initial strains. The stresses and displacements in the linearized theory are expressed in terms of analytical
functions of complex variables when solving dynamic plane and antiplane problems. These complex variables depend on the crack
propagation rate and the material properties. The exact solutions analyzed were obtained for growing (mode I, II, III) cracks
and the case of wedging by using methods of complex variable theory, such as Riemann–Hilbert problem methods and the Keldysh–Sedov
formula. As the initial (residual) stresses tend to zero, these exact solutions of linearized solid mechanics transform into
the respective exact solutions of classical linear solid mechanics based on the Muskhelishvili, Lekhnitskii, and Galin complex
representations. New mechanical effects in the dynamic problems under consideration are analyzed. The influence of initial
(residual) stresses and crack propagation rate is established. In addition, the following two related problems are briefly
analyzed within the framework of linearized solid mechanics: growing cracks at the interface of two materials with initial
(residual) stresses and brittle fracture under compression along cracks 相似文献