Stress intensity factor analysis of friction sliding at discontinuity interfaces and junctions

A stress intensity factor (SIF) analysis for two-dimensional fractures with frictional contact (crack friction) is presented. This analysis is carried out using the symmetric-Galerkin boundary element method, and a modified quarter-point crack tip element. As in case of non-contact fracture, it is shown that highly accurate SIFs can be obtained, even with the simple Displacement Correlation SIF technique. Moreover, with the modified crack tip element, the mesh on the crack does not need to be excessively refined in order to achieve high accuracy. This meshing advantage is especially important in the context of the nonlinear frictional contact problem, as the computing time for the iterative process strongly depends on the number of elements used. Several numerical examples are presented and the SIF results are compared with available analytical or reference solutions. This research was supported in part by the University of South Alabama Research Council, and by the Applied Mathematical Sciences Research Program of the Office of Mathematical, Information, and Computational Sciences, U.S. Department of Energy under contract DE-AC05-00OR22725 with UT-Battelle, LLC.     

InGaAlP LED发光特性分析

InGaAlP LED发光效率高，性能稳定，应用相当广泛。在InGaAlP LED的应用中，发光特性是相当重要的参数，而发光强度和半强度角是LED发光特性的两个主要参数。介绍了不同的InGaAlP LED芯片结构．分析了其发光特点及封装后的发光特性，讨论了不同的反射式支架结构对其发光特性产生的不同影响。     

5MW低功率堆主屏蔽设计与安全分析

本文介绍了5MW 低功率堆(5MW LPR)主屏蔽辐射场和温场的计算模型、方法和程序,给出了修改设计的主要计算结果。混凝土屏蔽层内表面的入射中子通量和γ通量均满足设计标准规定。最高温度、最大温升及最大温度梯度亦均符合规定要求。为证明温场程序的可靠性,将HFETR 混凝土屏蔽层内温度计算值与实测值作了比较,结果符合得很好。     

角锥棱镜阵列式反射镜反光性能及其评价的研究

角锥棱镜阵列式反射镜由角锥棱镜列阵构成，是用光学塑料注塑制造的。本文论述了这种反向镜反射光发散角的形成和反射光有效通光口径与入射角的系统等理论，提出了应从制造和使用角度考虑分别用新单项参数和综合参数来评定其反光性能，同时还提出了对各项参数的测量方法。     

Modeling and experimental verification of radiative transfer of a flat‐plate photoreactor with immobilized photocatalyst

A cost‐effective design of photocatalytic reactor needs efficient contact of the polluted substance with the solid catalyst while uniformly irradiating the solid catalyst with light. In the present paper, an immobilized photocatalyst comprising TiO₂ coated on Pyrex‐glass‐coils (abbreviated hereafter as TGC) was developed, and a flat‐plate photocatalytic reactor packed with TGC was designed. The reactor has some advantages such as low pressure drop, intensification of mass transfer; relatively uniform distribution of light radiation; high ratio of illuminated catalyst surface area to volume, and is flexible enough for large‐scale application. The radiation intensity distribution and the two‐flux model parameters were measured, and the two‐flux model was solved numerically. The experimental values were compared with the theoretical predictions. Good agreement was obtained with a maximum deviation about 10%. Finally, the two‐flux model described the radiation intensity distribution and local volumetric rate of energy absorption in the flat‐plate reactor packed with TGC. © 2002 Society of Chemical Industry     

Analysis of a mode III crack problem in a functionally graded coating-substrate system with finite thickness

This paper presents an analysis of the static problem of model III crack of a functionally graded coating-substrate system with an internal crack perpendicular to the interface under antiplane shear loading when the coating layer and substrate have finite thickness. After the Fourier transform method is employed, the expressions of the displacement components can be obtained. Integral transforms are employed to reduce the problem to a singular integral equation that can be solved numerically. The influences of the nonhomogeneity constant, relative crack length and thickness ratio are quantitatively studied.     

Anti-plane transient fracture analysis of the functionally gradient elastic bi-material weak/infinitesimal-discontinuous interface

The mechanical model was established for the Dirac-type anti-plane transient fracture problem of the weak-discontinuous interface between two FGMs half-planes. Integral transform was adopted to derive Cauchy singular integral equation and Erdogan’s allocation method was used to calculate transient stress intensity factors numerically. The numerical solutions of the weak-discontinuous case were contrasted with those of the infinitesimal-discontinuous one. Two possible effective methods to diminish the peak values of transient stress intensity factors are discussed. One is to reduce the weak-discontinuity of the interface, i.e., to make the ratio of the two non-homogeneity parameters be close to 1.0 and to avoid the case that the signs of the two non-homogeneity parameters are different. Another is to make a compromise between the weak-discontinuity and the all-continuity, i.e., to make FGMs interface infinitesimal-discontinuous. Simple method was suggested for the realization of the infinitesimal-discontinuity of FGMs interface. From the strong-discontinuous interface to the weak- discontinuous one, and then to the infinitesimal-discontinuous one, this is a law and trend of the development of composite interfaces. To design and manufacture infinitesimal-discontinuous interfaces may be a brand-new effective approach to enhance the reliability of composite structures, and the first rank infinitesimal-discontinuity is enough to improve the mechanical performances of composites notably.     

秭归水田坝等三条断裂关系及孕震强度评价

鄂西种秭归盆地是长江三峡地区重要的构造单元之一，盆地东侧水田坝断裂与其南部龙王冲断裂、北部新华断裂，经分析不属同一基底构造体系。尽管各断裂近期活动不甚明显，按活动断裂评价标准，均不属工程活动断裂，但不能排除发生中强地震的危险性。用经验公式法估算的最大构造地辱震级，水田坝断裂为５．５级、龙王冲断裂为６．０级、新会断裂为６．５级。     

挟沙水流几个运动特性的探讨

 引用大气边界层的混掺长度表达式作为挟沙水流近壁区的混掺长度,从挟沙水流总切应力平衡方程导出了近壁区的流速分布公式，通过比较验证后推广到整个水深范围，进而使用该公式导出了挟沙水流主流区以上的混掺长度、动量交换系数和整个水深的垂向紊动强度公式 前两者与水槽资料点绘的结果吻合良好，由后者得到了垂向紊动强度增减的临界条件。     

Reduction of free-edge stress intensities in anisotropic bimaterials

We investigate the free-edge stresses in anisotropic bimaterials through the use of the free-edge stress intensity factor, Kf. This requires a determination of the singularity order at the free-surface as well as a calculation of the near-field stresses. We determine the order of the singularity for arbitrary free-surface orientation of the upper material using an eigenvalue analysis for anisotropic bimaterials. The interfacial stresses are determined using a boundary element calculation based on anisotropic, bimaterial Green's functions. The variation of Kf with free-surface orientation is determined. We find that the free-edge singularity vanishes for certain angles dependent on the anisotropic elastic constants. This revised version was published online in August 2006 with corrections to the Cover Date.