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991.
????????????????????????????о? 总被引:2,自引:1,他引:2
基于射孔完井水平裂缝中支撑剂均匀充填,考虑充填层强度、油层和流体
物性以及裂缝的渗流条件,研究了地应力及渗流引起的附加应力联合作用的支撑剂充填层渗
流模型和力学模型,并进行现场应用. 研究表明,所建立的模型对压裂油井支撑剂回采出砂
状况分析具有较高的符合率,油井总体符合率、不出砂井符合率和出砂井符合率分
别为84.66\%, 84.18\%和88.10\%, 为大庆油田压裂油井防砂措施实施方案制定提
供了决策支持,有利于提高措施有效率. 相似文献
992.
本文对含裂纹焊接接头的简化模型——软夹硬不均匀裂纹体和硬夹软不均匀裂纹体——进行了弹塑性有限元分析,研究了材质力学性能不均匀性对OOD的影响规律.还研究了在静载和疲劳载荷下材质不均匀性对软夹硬不均匀体裂纹扩展行为的影响. 相似文献
993.
In this paper, the classical solution of the opening mode crack in the 90° layer of 0/90/0 laminates has been determined by
means of Fourier transformations and the procedure of Copson for a pair of dual integral equations. The fracture behavior
and the in situ transverse strength of the 90° layer have been quantitatively studied in graphite/epoxy laminates, based on
the solution obtained above.
The results show that the stress intensity factor of this kind of laminates, which is different from that of a single unidirectional
90° layer, decreases with the increase in thicknessb, or modulusE
L orG
LT of the 0° layer and also decreases with the decrease in the thickness of the 90° layer. So the lamination effect manifests
itself and thein situ transverse strength of the 90° layer is thereby enchanced. The theoretical calculations agree with the experimental data
presented by D.L. Flaggs.
Supported by National Natural Science Fundation of China. 相似文献
994.
焊接热影响区断裂性能试验研究 总被引:4,自引:0,他引:4
钢框架梁柱节点在最近几次地震中经历了大量断裂破坏现象。可以采用杆端非线性弹簧模型对这种破坏模式进行数值模拟。为了确定断裂分析模型的参数,本文进行了结构钢(Q235c,Q345c)焊接热影响区断裂性能试验研究,获得了两种材料在焊接热影响区的JR阻力曲线。通过比较不同的断裂准则,考虑了裂纹失稳扩展前的稳态裂纹累计,根据J积分撕裂模量法建立了裂纹失稳的失效评定图。采用两种材料分别制作了一组外形尺寸一致,初始裂纹尺寸不同的单边裂纹焊接板,测出相应的极限拉伸应力,并和理论曲线进行了对比。最后,对于本文研究结果的适用范围做了说明。 相似文献
995.
Ductile fracture occurs due to micro-void nucleation, growth and finally coalescence into micro-crack. In this study a new ductile fracture condition that based on the microscopic phenomena of void nucleation, growth and coalescence was proposed. Using this condition and combining with finite element model to predict the fracture locations in bulk metal forming, the results show that it is in close accordance with observations of some experimental specimens. However, in order to obtaining the high trustiness many experiments have to be carried out. 相似文献
996.
This paper is concerned with dynamic problems in fracture mechanics for elastic solids having cracks with contacting faces.
The contact problem for a penny-shaped crack with a nonzero initial opening under normally incident harmonic wave is solved
by the method of boundary integral equations. The solutions are compared with those that neglect the contact interaction of
the crack faces. Results are presented for different values of the initial crack opening
Presented at the 6th International Conference on Modern Practice in Stress and Vibration Analysis (Bath, United Kingdom, September
5–7, 2006).
Published in Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 125–131, July 2007. 相似文献
997.
A process has been developed recently to fabricate a structure comprising, from top to bottom, a SiGe thin film, a glass layer,
and a Si wafer. The SiGe film is a perfect crystal, and is under biaxial compression. The SiGe film is patterned into islands.
On annealing, the glass flows and the islands relax. The resulting strain-free islands are used as substrates, to grow epitaxial
optoelectronic devices. This article describes a series of studies on the annealing process, combining experiment and theory.
A small island relaxes by expansion, starting at the edges and diffusing to the center. A large island wrinkles before the
expansion reaches the center. After some time, the wrinkles either disappear, or cause the island to fracture. We model the
island as an elastic plate, and the glass layer as a viscous liquid. The strains in the islands are measured by X-ray diffraction
and Raman spectroscopy, and the wrinkle amplitudes by atomic force microscope. The data are compared with the theoretical
predictions. We determine the conditions under which the islands relax by expansion without significant wrinking, and demonstrate
that a cap layer suppresses wrinkles, relaxing a large island crack-free.
The project supported by NSF (CMS-9820713), DARPA (N66001-00-1-8957), ARO (DAA655-98-1-0270), and New Jersey Science and Technology
Commission 相似文献
998.
999.
ANTI-PLANE FRACTURE ANALYSIS OF FUNCTIONALLY GRADIENT MATERIAL INFINITE STRIP WITH FINITE WIDTH 总被引:3,自引:0,他引:3
The special case of a crack under mode III conditions was treated, lying parallel to the edges of an infinite strip with finite width and with the shear modulus varying exponentially perpendicular to the edges. By using Fourier transforms the problem was formulated in terms of a singular integral equation. It was numerically solved by representing the unknown dislocation density by a truncated series of Chebyshev polynomials leading to a linear system of equations. The stress intensity factor (SIF) results were discussed with respect to the influences of different geometric parameters and the strength of the non-homogeneity. It was indicated that the SIF increases with the increase of the crack length and decreases with the increase of the rigidity of the material in the vicinity of crack. The SIF of narrow strip is very sensitive to the change of the non-homogeneity parameter and its variation is complicated. With the increase of the non-homogeneity parameter, the stress intensity factor may increase, decrease or keep constant, which is mainly determined by the strip width and the relative crack location. If the crack is located at the midline of the strip or if the strip is wide, the stress intensity factor is not sensitive to the material non-homogeneity parameter. 相似文献
1000.
A. I. Khromov A. A. Bukhan'ko O. V. Kozlova S. L. Stepanov 《Journal of Applied Mechanics and Technical Physics》2006,47(2):274-281
Based on the theory of an ideal rigid-plastic body, an approach is formulated for determining fracture constants on the basis
of standard mechanical tests on uniaxial extension of plane and cylindrical samples. Instead of the experimentally determined
characteristics of fracture of materials (dimensionless elongation and constriction of the sample during its fracture), two
invariant tensor characteristics of the degree of sample deformation are introduced, which correspond to the moment of origination
of a macrocrack and critical strain at the crack tip determining the process of crack propagation.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 147–155, March–April, 2006. 相似文献