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41.
针对弹塑性材料裂纹管道的J积分计算建立了等效穿透裂纹和表面半椭圆裂纹2种有限元模型。在等效穿透裂纹模型中应用了1/4节点单元,在表面裂纹模型中采用了线弹簧单元。用这2种模型计算J积分,分别对3个实际含裂纹管段建立了失效评定曲线。比较了2种模型的失效评定曲线和R6通用曲线的差别,指出穿透裂纹模型偏于保守,建议在油气管道断裂的工程评定中采用半椭圆表面裂纹模型。 相似文献
42.
动基座自校零压电陀螺 总被引:2,自引:2,他引:0
研制的一种压电陀螺能在动基座条件下自动消除由于温度和时间变化造成的零位漂移。典型的产品可使零位变化小于0.05°/s。零位的温度系数小于0.0005°/s/℃。 相似文献
43.
The coupled system of three partial differential equations governing a flexible shallow shell dynamics is analysed. No any prior assumptions about the temperature distribution through the shell thickness are applied. The efficiency of the method used here when applied to the solution of integral-differential equations with different dimensions (three-dimensional equations related to the Kirchhoff-Love model) and of different type (heat transfer equations and the hyperbolic equations of shell theory) is demonstrated. Many computational results are reported and discussed. 相似文献
44.
We propose an asymmetric integral imaging method to adjust the resolution and depth of a three‐dimensional image. Our method is obtained by use of two lenticular sheets with different pitches fabricated under the same F/#. The asymmetric integral imaging is the generalized version of integral imaging, including both conventional integral imaging and one‐dimensional integral imaging. We present experimental results to test and verify the performance of our method computationally. 相似文献
45.
A new interaction integral formulation is developed for evaluating the elastic T-stress for mixed-mode crack problems with
arbitrarily oriented straight or curved cracks in orthotropic nonhomogeneous materials. The development includes both the
Lekhnitskii and Stroh formalisms. The former is physical and relatively simple, and the latter is mathematically elegant.
The gradation of orthotropic material properties is integrated into the element stiffness matrix using a “generalized isoparametric
formulation” and (special) graded elements. The specific types of material gradation considered include exponential and hyperbolic-tangent
functions, but micromechanics models can also be considered within the scope of the present formulation. This paper investigates
several fracture problems to validate the proposed method and also provides numerical solutions, which can be used as benchmark
results (e.g. investigation of fracture specimens). The accuracy of results is verified by comparison with analytical solutions. 相似文献
46.
H. Wolf F. Wagner Th Wichert R. Grill E. Belas Isolde Collaboration 《Journal of Electronic Materials》2006,35(6):1350-1353
Anomalous diffusion profiles of Ag in single crystalline CdTe were observed using the radiotracer 111Ag. The diffusion anneals were performed at 800 K under Cd or Te vapor and in vacuum with low Ag concentrations. The measured
Ag profiles directly reflect the distribution of the self-interstitials and vacancies of the Cd sublattice and are the result
of chemical self-diffusion which describes the variation of the deviation from stoichiometry of the binary crystal as a function
of depth and time. It turned out that the spread of the Ag dopant essentially is determined by the drift of the charged defects
within the electric field caused by the distribution of the extrinsic and intrinsic defects. 相似文献
47.
本文考虑受控系统为Banach空间中一类G0紧半群的非线性脉冲积微分方程的最优反馈控制问题。首先证明容许控制对的存在性,进一步对Lagrange问题给出了一个新的存在性定理。 相似文献
48.
Rafael Gallego Lucia Comino Alberto Ruiz‐Cabello 《International journal for numerical methods in engineering》2006,66(12):1913-1933
In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
49.
Periklis E. Ergatis Panagiotis G. Massouros Georgia C. Athanasouli George P. Massouros 《国际能源研究杂志》2003,27(9):795-811
A time‐dependent coefficient of heat transfer is proposed for the computation of thermal power required, so that a room temperature reaches a desired value within a given time. A mathematical formulation of the room heating transient phenomenon is constructed in a dimensionless form. Using an integral approximate solution an analytical expression for this coefficient is provided and it is verified by diagrams adopted by DIN 4701. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
50.
Masashi Kashiwagi 《Journal of Engineering Mathematics》2007,58(1-4):51-66
Based on the momentum and energy conservation principles, a compact calculation formula is analytically derived for the wave-drift
force on a 2-D body floating in a two-layer fluid of finite depth. In a two-layer fluid, two different wave modes (the surface-wave
mode with longer wavelength and the internal-wave mode with shorter wavelength) exist not only in the incident wave but also
in the body-scattered wave, and these wave characteristics are properly incorporated in the obtained formula. It is noted
that, unlike the single-layer case, the wave-drift force can be negative in the incident wave of surface-wave mode, if the
transmitted wave with internal-wave mode is large. Numerical computations are implemented for a Lewis-form body by means of
the boundary-integral-equation method with Green’s function for the two-layer fluid problem. The effects of density ratio,
interface position, and body motions on the wave-drift force are studied, and some important features are found for two-layer
fluids. 相似文献