共查询到20条相似文献,搜索用时 140 毫秒
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基于复变函数和格林函数的方法,探讨了SH波在具有圆孔的正交各向异性两相介质中的散射,分析了圆孔周围的动态响应规律。首先建立问题的二维解析模型,将全空间分为两个部分:均匀各向同性上半空间以及含圆柱形孔洞的正交各向异性下半空间。采用格林函数法推导出了两半空间界面处各点的格林函数表达式,并引入复变量,构造出了SH波入射下求解区域内位移和应力的表达式。考虑界面的连续性条件,将未定反平面力加载到两个半空间的水平界面上,推导出Fredholm定解积分方程组,用弱奇异积分方程的直接离散方法求解。最终通过算例分析,发现介质的正交各向异性参数、入射波波数、角度以及孔洞埋深等对下半空间圆孔周边的动应力集中系数(DSCF)影响显著。 相似文献
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从能量等效角度,提出了一种圆孔工字型截面蜂窝梁连续型模型,应用新的薄壁构件扭转理论:板-梁理论,建立了构件扭转模态自由振动能量泛函模型,明确了圆孔工字型截面蜂窝梁名义约束扭转惯性矩(翘曲常数)、自由扭转常数、转动惯量。通过变分运算,获得了平衡微分方程模型。基于扭转模态试函数,推导了圆孔工字型截面蜂窝梁自由振动扭转模态振动圆频率,并与有限元结果对比校验理论模型预测精度。开展了悬臂圆孔工字型蜂窝梁受集中扭矩作用的端部截面转角理论分析与有限元计算,进一步检验了基于板-梁理论建立的蜂窝梁连续模型的适用性。应用板-梁理论对圆孔工字型截面蜂窝梁自由振动扭转的分析过程及推导步骤,为其他开孔类型工字型蜂窝梁扭转模态自由振动研究提供了直接参考。 相似文献
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本文讨论孔边有加强环的球壳圆孔应力集中的轴对称问题。导出了径向弯矩、环向轴力、径向轴力的内力集中系数公式。文中对各种几何参数(孔洞尺寸,环梁截面尺寸,环梁与壳面的偏心距)下的内力分布作了详尽的讨论。就泊松比ν=0,壳面作用有法向面荷载q和孔边作用有线荷载p的情况,分别作了径向弯矩,环向轴力,径向轴力的内力集中系数表格。对于加强环内的弯矩,也给出了计算公式和表格。这些表格可供设计单位直接应用。①②③ 相似文献
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根据壳元的几何形状规定, 推导了壳元几何关系公式; 假设温度沿壳元厚度是二次多项式分布, 在给定边界条件下, 推导了壳元温度函数表达式; 根据传热定理和有限元离散原理, 推导了复合材料热传导系数从材料坐标系到有限元分析的等参元正则坐标系的变换关系, 建立了各向异性复合材料层合板的有限元热分析列式; 通过积分变换, 推导了三维退化热壳元公式。在此工作基础上, 编制了有限元计算程序, 将计算结果和ANSYS 计算结果进行了比较, 结果吻合较好。经证明, 三维退化热壳元可以节省内存和提高计算效率。 相似文献
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Mojtaba Hajimohamadi Rahmatollah Ghajar 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(3):743-751
An infinite quasi‐orthotropic plane with a cracked circular hole under tensile loading at infinity is studied analytically. To this end, complex variable theory of Muskhelishvili is used. In addition, to obtain analytical functions, a new conformal mapping is proposed and expanded to series expressions. Stress intensity factors (SIFs) for two unequal cracks emanating from a circular hole are obtained. To validate the analytical SIFs in a quasi‐orthotropic plane, the results are compared with FEM and the results of isotropic plane. The SIFs for small cracks in a quasi‐orthotropic and an isotropic plane are different, because of difference between stress concentrations in points which cracks emanate from the hole. However, the results of quasi‐orthotropic plane converge to isotropic plane for the large cracks. Therefore, the SIFs of the large cracks in a quasi‐orthotropic plane can be replaced by the results of the center crack with equivalent length in an isotropic plane. 相似文献
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正交各向异性孔板的材料参数识别 总被引:1,自引:0,他引:1
结合优化技术和边界元分析,针对正交各向异性孔板进行了材料参数的识别。材料参数识别的问题转化为极小化目标函数的问题,其中目标函数定义为测量位移与边界元计算相应的位移之差的平方和。采用Levenberg-Marquardt方法解极小化目标函数的问题,其中灵敏度的计算是基于离散的边界元代数矩阵方程对识别材料参数的求导。数值算例中,首先把边界元计算正交各向异性圆孔方板位移的结果与解析解进行比较,两者符合良好;然后采用本文提出的方法识别正交各向异性圆孔方板的材料参数。数值算例表明本文提出的方法是有效的。 相似文献
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Zheng Yang Chongdu Cho Chang‐Boo Kim Hyeon Gyu Beom 《International journal for numerical methods in engineering》2008,75(1):103-126
The elastic stress and strain fields of a finite thickness plate containing a circular hole subjected to a biaxial load are systematically investigated using the finite element method. It is found that the stress and strain concentration factors of the finite thickness plate are different even if the plate is in elasticity state. The maximum stress and strain concentration factors do not always occur on the mid plane of the plate. The maximum stress and strain concentration factors of the notch root increase from their plane stress value to their peak values, then decrease gradually with increasing thickness and tend to constant values related to the load biaxiality ratio, respectively. The stress and strain concentration factors at the notch root of free surface are the monotonic descent functions of thickness. Their values decrease rapidly and tend to lower the limit values related to the load biaxiality ratio with increasing plate thickness. The differences of stress and strain concentration factors between maximum and surface value increase rapidly and tend to constant values related to the load biaxiality ratio with increasing plate thickness. The smaller the load biaxiality ratio, the larger these differences. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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A three dimensional mixed-hybrid finite strip for composite structures is proposed. This finite strip method is developed for composite structures of uniform geometrical cross section, and is based on the Hellinger-Reissner variational principle. The method is employed for the first order approximation of the edge layer problem around a circular hole in composite laminated plate. Numerical results are presented to show the strips' behavior characteristics regarding to spectral accuracy, finite element convergence, accuracy of stress evaluation and the consumed CPU time. The improvement in accuracy in comparison with conventional methods is remarkable. 相似文献
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A finite element calculation of stress intensity factors by a modified crack closure integral 总被引:30,自引:0,他引:30
An efficient technique for evaluating stress intensity factors is presented. The method, based on the crack closure integral, can be used with a constant strain finite element stress analysis and a coarse grid. The technique also permits evaluation of both Mode I and Mode II stress intensity factors from the results of a single analysis. Example computations are performed for a double cantilever beam test specimen, a finite width strip with a central crack, and a pin loaded circular hole with radial cracks. Close agreement between numerical results given by this approach and reference solutions were found in all cases. 相似文献
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《Composites Part B》2003,34(2):127-134
Scale factors (SFs) are widely used in engineering applications to describe the stress concentration factor (SCF) of a finite width isotropic plate with a circular hole and under uniaxial loading. In this paper, these SFs were also found to be valid in an isotropic plate with biaxial loading and an isotropic cylinder with uniaxial loading or internal pressure, if a suitable hole to structure dimension ratio was chosen. The study was further expanded to consider orthotropic plates and cylinders with a center hole and under uniaxial loading. The applicable range of the SFs was given based on the orthotropic material parameters. The influence of the structural dimension on the SCF was also studied. An empirical calculation method for the stress concentrations for isotropic/orthotropic plates and cylinders with a circular hole was proposed and the results agreed well with the FEM simulations. This research work may provide structure engineers a simple and efficient way to estimate the hole effect on plate structures or pressure vessels made of isotropic or orthotropic materials. 相似文献
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Stress Concentration Factors for a Circular Hole in Curved Beams Under Bending Loads 总被引:1,自引:0,他引:1
Abstract: As a contribution to the field of stress concentration studies, the case of circular hole in curved bar elements under bending is hereby studied. Trend values of stress concentration factors (SCF) are presented based on selected variables of the problem for two critical hole locations. The results will help to identify an SCF law for practical use by applying the statistical method of regression analysis. Two approximations obtained by means of computational methods are compared with those obtained by photoelastic experimental method. 相似文献
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Xiangqiao Yan 《Engineering Fracture Mechanics》2006,73(12):1743-1754
A numerical analysis of cracks emanating from a circular hole (Fig. 1) or a square hole (Fig. 2) in rectangular plate in tension is performed by means of the displacement discontinuity method with crack-tip elements (a boundary element method) presented recently by the author. Detail solutions of the stress intensity factors (SIFs) of the two plane elastic crack problems are given, which can reveal the effect of geometric parameters of the cracked bodies on the SIFs. By comparing the SIFs of the two crack problems with those of the center crack in rectangular plate in tension (Fig. 3), in addition, an effect of the circular hole or the square hole on the SIFs of the center crack is discussed in detail. The numerical results reported here also illustrate that the boundary element method is simple, yet accurate for calculating the SIFs of complex crack problems in finite plate. 相似文献
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研究了压电复合材料中圆孔边4个非对称裂纹在远处受面内电载荷和面外力载荷共同作用下的断裂行为。利用复变函数方法和新映射函数将问题转化为Cauchy积分方程组。通过求解Cauchy积分方程组,得到了电非渗透型和电渗透型两种边界条件下裂纹尖端电弹性场和场强度因子的解析解。所得结果不仅可退化为已有解,而且可模拟出若干新的缺陷构型,如压电复合材料中圆孔边三裂纹、半无限压电复合材料中半圆孔边单裂纹及半无限压电体中边界裂纹。将所得结果与有限元结果进行比较,吻合很好,证实了文中方法的正确性和有效性。数值算例分析了缺陷的几何参数对场强度因子的影响规律。 相似文献
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T. N. WILLIAMS J. C. NEWMAN Jr P. M. GULLETT 《Fatigue & Fracture of Engineering Materials & Structures》2011,34(4):250-259
The purpose of this paper is to calculate and develop equations for crack–surface displacements for two‐symmetric cracks emanating from a circular hole in an infinite plate for use in strip‐yield crack‐closure models. In particular, the displacements were determined under two loading conditions: (1) remote applied stress and (2) uniform stress applied to a segment of the crack surface (partially loaded crack). The displacements were calculated by an integral‐equation method based on accurate stress–intensity factor equations for concentrated forces applied to the crack surfaces and those for remote applied stress or for a partially loaded crack surface. A boundary‐element code was also used to calculate crack–surface displacements for some selected cases. Comparisons made with crack–surface displacement equations previously developed for the same crack configuration and loading showed significant differences near the location where the crack intersected the hole surface. However, the previous equations were fairly accurate near the crack‐tip location. Herein an improved crack–surface displacement equation was developed for the case of remote applied stress. For the partially loaded crack case, only numerical comparisons were made between the previous equations and numerical integration. A rapid algorithm, based on the integral‐equation method, was developed to calculate these displacements. Because cracks emanating from a hole are quite common in the aerospace industry, accurate displacement solutions are crucial for improving life‐prediction methods based on the strip‐yield crack‐closure models. 相似文献