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基于数字散斑相关方法测定Ⅰ型裂纹应力强度因子 总被引:1,自引:0,他引:1
提出了一种通过数字散斑相关方法测定金属材料Ⅰ型裂纹尖端位置和应力强度因子的实验方法.实验采用疲劳试验机对含Ⅰ型缺口的Cr12MoV钢试件预制裂纹,通过数字散斑相关方法测试试件在三点弯曲加载条件下裂纹的扩展过程及裂尖区域的位移场.将位移场数据代入裂尖位移场方程组,采用牛顿-拉普森方法求解含未知参量的裂尖非线性位移场方程组,计算裂尖位置和应力强度因子.实验结果表明,采用该方法可以准确地测定金属材料Ⅰ型裂纹应力强度因子、裂尖位置及裂纹扩展长度,解决了以往研究中因不能准确测定裂纹尖端位置,而无法准确计算Ⅰ型裂纹裂尖断裂参数的难题,揭示了金属材料裂纹扩展过程中应力强度因子演化特征. 相似文献
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双轴载荷作用下源于椭圆孔的分支裂纹的一种边界元分析 总被引:2,自引:1,他引:1
利用一种边界元方法来研究双轴载荷作用下无限大板中源于椭圆孔的分支裂纹.该边界元方法由Crouch与Starfied建立的常位移不连续单元和笔者提出的裂尖位移不连续单元构成.在该边界元方法的实施过程中,左、右裂尖位移不连续单元分别置于裂纹的左、右裂尖处,而常位移不连续单元则分布于除了裂尖位移不连续单元占据的位置之外的整个裂纹面及其它边界,文中算例说明本数值方法对计算平面弹性裂纹的应力强度因子是非常有效的。该文对双轴载荷作用下无限大板中源于椭圆孔的分支裂纹的数值结果进一步证实本数值方法对计算复杂裂纹的应力强度因子的有效性,同时该数值结果可以揭示双轴载荷及裂纹体几何对应力强度因子的影响。 相似文献
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三点弯曲试样动态应力强度因子计算研究 总被引:2,自引:0,他引:2
利用Hopkinson压杆对三点弯曲试样进行冲击加载,采集了垂直裂纹面距裂尖2mm和与裂纹面成60°距裂尖5mm处的应变信号。根据裂尖附近测试的应变信号计算试样的动态应力强度因子,并与有限元计算结果进行比较,结果表明由于裂尖有一段疲劳裂纹区,通过裂尖附近应变信号来计算动态应力强度因子时,如果裂尖位置确定不准及粘贴应变片位置不够准确对计算结果将带来很大影响。因此利用应变片法计算动态应力强度因子时,为了获得更准确的计算结果,在实验后应对试件裂纹面进行分析测量,重新确定裂尖位置,必要时需对应变片至裂尖距离进行修正后再计算动态应力强度因子值。 相似文献
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为研究叶片裂纹尖端的应力奇异性,以某型航空发动机压气机叶片为例,利用有限元方法研究了叶片裂纹尖端应力强度因子的计算方法,并研究了旋转叶片振动状态下裂尖应力强度因子随裂纹长度的变化规律。建立计算模型时,在裂纹尖端划分了三维奇异单元,在裂尖外围划分了过渡单元。计算结果表明:研究旋转叶片振动状态下的裂尖应力奇异性,仅利用I型应力强度因子就具有足够的精度;对于同一裂纹,绝大多数情况下叶盆面应力强度因子大于叶背面应力强度因子,故研究叶片应力强度因子时只需研究叶盆应力强度因子即可;随着裂纹扩展,叶盆面I型应力强度因子不断增大。本文的研究方法及结论为进一步研究叶片的裂纹扩展规律及损伤容限奠定了基础。 相似文献
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基于新型裂尖杂交元的压电材料断裂力学研究 总被引:2,自引:1,他引:2
提出了一种裂尖邻域杂交元模型,将其与标准杂交应力元结合来求解压电材料裂纹尖
端的奇性电弹场和断裂参数的数值解.裂纹尖端杂交元的建立步骤为:1)
利用高次内插有限元特征法求解特征问题,得到反映裂尖奇异性电弹场状况的特
征值和特征角分布函数;2)
利用广义Hellinger-Reissner变分泛函以及特征问题的解来建立裂尖邻域杂交元模型.该
方法求解电弹场时,摒弃了传统有限元方法中裂尖奇异性场需要借助解析解的做法,也避免
了单纯有限元方法中需要在裂尖端部进行高密度单元划分.采用PZT5板中心裂纹问题
作为考核例,数值结果显示了良好的精确性.作为进一步应用,求解了含中心界面裂纹
的PZT4-PZT5两相压电材料的应力强度因子和电位移强度因子.所有的算例都考虑
了3种裂纹面电边界条件. 相似文献
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内部压力作用下矩形板中源于椭圆孔的分支裂纹应力强度因子的一种数值分析 总被引:1,自引:0,他引:1
应用一种边界元方法来研究内部压力作用下矩形板中源于椭圆孔的分支裂纹。该边界元方法由Crouch与Starfied建立的常位移不连续单元和笔者最近提出的裂尖位移不连续单元构成。在该边界元方法的实施过程中,左、右裂尖位移不连续单元分别置于裂纹的左、右裂尖处,而常位移不连续单元则分布于除了裂尖位移不连续单元占据的位置之外的整个裂纹面及其它边界。本数值结果进一步证实这种数值方法对计算有限大板中复杂裂纹的应力强度因子的有效性,同时该数值结果可以揭示裂纹体几何对应力强度因子的影响。 相似文献
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Ravitej Kommana Venkitanarayanan Parameswaran 《International Journal of Solids and Structures》2009,46(11-12):2420-2428
The variation of stress intensity factor along the thickness in a cracked transversely graded plate subjected to in plane bending is investigated in this study. A transversely graded plate having elastic modulus varying continuously along the thickness was prepared by embedding glass beads in epoxy resin. An edge crack in this plate was subjected to in plane bending and the crack tip displacement field on the surfaces of the plate was measured using digital image correlation (DIC). Using the recently reported asymptotic displacement fields for cracked transversely graded plates (Wadgaonkar, S.C., Parameswaran, V., 2009. Structure of near tip stress field and variation of stress intensity factor for a crack in a transversely graded material, Journal of Applied Mechanics 76 (1), 011014), the stress intensity factor (SIF) on the surfaces of the plate was calculated from the experimental data. The results of this part of the study indicated that the extent of variation of the SIF across the plate thickness is nearly the same as that of the elastic modulus. An expression to calculate the variation of the SIF through the plate thickness was developed assuming simple bending of the plate. The predicted variation of SIF was verified through finite element calculations. Further, the behavior of the SIF near the intersection of the crack front and the plate surfaces, the extent of dominance of the corner singular field and the exponent of the corner singularity were also investigated in detail. Finally, the effect of gradation strength and gradation type on the SIF was also studied. 相似文献
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Based on Chun-Tu Liu's result for Reissner's plate, an equation of caustics in cracked plate under symmetric bending was obtained. The shape and the distribution of light intensity of the caustic curve were discussed in detail. The relation between the stress intensity factor (SIF) and the size of the caustic curve was found by numerical method, and a simple and accurate experimental method for evaluating SIF in plate under bending was proposed. 相似文献
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王元汉 《应用数学和力学(英文版)》1990,11(8):723-732
In this paper, Muskhelishvili complex function theory and boundary collocation method are used to calculate the stress intensity factors (SIF) of a plate with two cracks emanating from an arbitrary hole. The calculated examples include a circular, elliptical, rectangular, or rhombic hole in a plate. The principle and procedure by the method is not only rather simple, but also has good accuracy. The SIF values calculated compare very favorably with the existing solutions. At the same time,the method can be used for different finite plate with two cracks emanating from a hole with more complex geometrical and loading conditions. It is an effective unified approach for this kind of fracture problems. 相似文献
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有限厚度板穿透裂纹前缘附近三维弹性应力场分析 总被引:7,自引:1,他引:7
通过三维有限元计算来研究有限宽度、有限厚度含有穿透裂纹板的裂纹前缘应力场,从中找出应力强度因子与板的厚度、裂纹长度之间的关系,同时还分析了裂尖的三维约束程度和三维约束区的大小。分析结果表明:应力强度因子沿厚度的分布是不均匀的,应力强度因子的最大值及其位置与厚度有关;有限厚度板中面应力强度因子(KI)m-p及最大应力强度因子(KI)max均大于平面应力或平面应变的应力强度因子。对有限厚度裂纹问题,按平面应力或平面应变来考虑是不安全的;板中面的应力强度因子(KI)m-p及最大应力强度因子(KI)max是厚度B/a的函数;板的中面离面约束系数Tx最大,自由面(z=B)Tx=0。沿厚度方向裂尖附近的离面约束系数Tx也是z/B和B/a的函数,随着厚度的增加离面约束系数Tx增大,离中面越近离面约束系数Tx越大。Tx随着x的增大急剧减小,三维约束影响区域大小大约为板厚的一半,且裂纹长度a/W对应力强度因子沿厚度变化规律及Tx影响区域大小影响较小。 相似文献
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Cracking analysis of fracture mechanics by the finite element method of lines (FEMOL) 总被引:1,自引:0,他引:1
The Finite Element Method of Lines (FEMOL) is a semi-analytic approach and takes a position between FEM and analytic methods.
First, FEMOL in Fracture Mechanics is presented in detail. Then, the method is applied to a set of examples such as edge-crack
plate, the central-crack plate, the plate with cracks emanating from a hole under tensile or under combination loads of tensile
and bending. Their dimensionless stress distribution, the stress intensify factor (SIF) and crack opening displacement (COD)
are obtained, and comparison with known solutions by other methods are reported. It is found that a good accuracy is achieved
by FEMOL. The method is successfully modified to remarkably increase the accuracy and reduce convergence difficulties. So
it is a very useful and new tool in studying fracture mechanics problems.
The English text was polished by Yunming Chen. 相似文献
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This work presents a semi-analytical model to explore the effects of cooling rate on the thermal shock resistance behavior of a functionally graded ceramic (FGC) plate with a periodic array of edge cracks. The FGC is assumed to be a thermally heterogeneous material with constant elastic modulus and Poisson's ratio. The cooling rate applied at the FGC surface is modeled using a linear ramp function. An integral equation method and a closed form asymptotic temperature solution are employed to compute the thermal stress intensity factor (TSIF). The thermal shock residual strength and critical thermal shock of the FGC plate are obtained using the SIF criterion. Thermal shock simulations for an Al2O3/Si3N4 FGC indicate that a finite cooling rate leads to a significantly higher critical thermal shock than that under the sudden cooling condition. The residual strength, however, is relatively insensitive to the cooling rate. 相似文献
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THE EVALUATION OF STRESS INTENSITY FACTORS OF PLANE CRACK FOR ORTHOTROPIC PLATE WITH EQUAL PARAMETER BY F2LFEM 总被引:1,自引:0,他引:1
In this paper, the evaluation of stress intensity factor of plane crack problems for orthotropic plate of equal-parameter is investigated using a fractal two-level finite element method (F2LFEM). The general solution of an orthotropic crack problem is obtained by assimilating the problem with isotropic crack problem, and is employed as the global interpolation function in F2LFEM. In the neighborhood of crack tip of the crack plate, the fractal geometry concept is introduced to achieve the similar meshes having similarity ratio less than one and generate an infinitesimal mesh so that the relationship between the stiffness matrices of two adjacent layers is equal. A large number of degrees of freedom around the crack tip are transformed to a small set of generalized coordinates. Numerical examples show that this method is efficient and accurate in evaluating the stress intensity factor (SIF). 相似文献
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估算裂纹应力强度因子的新方法 总被引:1,自引:0,他引:1
根据裂纹形状与裂纹尖端应力强度因子分布之间的固有关系,在线弹性断
裂力学条件下,提出了一种按已知I型裂纹应力强度因子分布规律求裂纹形状及相应应力强
度因子的无梯度迭代法. 通过有限厚度、有限宽度板穿透裂纹和表面裂纹的数值模拟实例验
证了所提出方法的有效性和实用性,并对不同应力强度因子分布规律对裂纹形状以及相应的
应力强度因子大小的影响进行了分析和讨论. 所提出的方法有助于提高实际扩展裂纹应
力强度因子的估算精度以及更合理地预测疲劳裂纹形状演化. 相似文献
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The problem of two unequal collinear straight cracks weakening a poled transversely isotropic piezoelectric ceramic is addressed under semi-permeable electric boundary conditions on the crack faces. The plate has been subjected to combined in-plane normal(to the faces of the cracks) mechanical and electric loads. Problem is formulated employing Stroh formalism and solved using complex variable technique. The elastic field, electric field and energy release rate are obtained in closed analytic form. A case study is presented for poled PZT-5H cracked plate to study the effect of prescribed mechanical load, electric load, inter-crack distance and crack lengths on crack arrest parameters stress intensity factor (SIF), electric displacement intensity factor (EDIF) and mechanical and total energy release rates (ERR). Moreover a comparative study is done of impermeable and semi-permeable crack face boundary conditions on SIF, EDIF and ERR, and results obtained is presented graphically. It is observed that the effect of dielectric medium in the crack gap cannot be ignored. 相似文献