Effects of the Change in Average Permittivity and Conductivity of Grating on Diffraction Efficiency

A model describing the propagation of optical waves in a hologram volume grating is studied. Then the effects of the change in the average permittivity and conductivity of a grating on diffraction efficiency are discussed. Finally a comparision of the results of this model with those by Solymar is made. The authors come to a conclusion that the effects of the change can be compensated.     

Nonlinear Elastic Constitutive Model of Soil-Structure Interfaces Under Relatively High Normal Stress

The shear characteristics of soil-structure interfaces with different roughness are studied systematically by using the DRS-1 high normal stress and residual shear apparatus. The experimental results indicate that, under a relatively high normal stress, normal stress and the coefficient of structural roughness are the most important factors affecting the mechanical interface characteristics. The relationship between shear stress and shear displacement of the soil-structure interface is a hyperbolic curve with high regression accuracy. Based on our experimental results, a nonlinear elastic constitutive model of the soil-structure interface under relatively high normal stress is established with a definite physical meaning for its parameters. The model can predict the strain hardening behavior of the soil during the shearing process. The results show an encouraging agreement with experimental data from direct shear tests.     

Comparative Evaluation of the Implant Made of Yttrium-partially Stabilized Zirconia and Pure Titanium on Stress Distribution by Anisotropic Finite Element Method

The purpose of this research is to analyze and compare stress distribution patterns around dental implant made of pure titanium and yttrium-partial stabilized zirconia （YPSZ） in anisotropic versus isotropic finite element method under vertical and oblique loads. Although the properties of implant and crown were changed, similar stress distribution and close stress level were observed in two different implant finite element models. The stress values were a little lower in the YPSZ model. In the bone, anisotropy increased the stress values by 30%- 70% in the isotropic cases. The YPSZ implant could be more valuable choice for implant because of esthetic requirement. Anisotropy had subtle, yet significant effects on the stress level.     

Comparative Evaluation of the Implant Made of Yttrium-partially Stabilized Zirconia and Pure Titanium on Stress Distribution by Anisotropic Finite Element Method

1Introduction Implantplacementindentistry[1]andorthopedics[2]isapredicabletreatmentmodality.Thematerialsforden talimplantsandjointsaremetalandpolyethylene.These materialshavebeenusedfordecades;however,thein creasingproblemssuchasthewearofthepolyethylene,t…     

Dynamic experiment and numerical simulation of solute transmission in heap leaching processing

Solute transmission in saturated ore heap was studied numerically and experimentally. The convection-diffusion equation (CDE) used to describe the mass transportation in porous media was solved by characteristic difference method to give the distribution of the concentration of ferrous ion in the ore column. To calibrate the computational model, a column test was performed using infiltration of sulfide ferrous solution (the initial concentration is c0=0.04 mol/L) on a 100 cm high column composed of ore particles smaller than 10 mm for 2.5 h. The numerical analysis shows that the results obtained from numerical modeling under the same operating conditions as used for column test are in good agreement with those from experimental procedure on the whole trend, which indicates that the model, the numerical method, and the parameters chosen can reflect the rule of ferrous ion transmission in ore heap.     

Stress Distribution and Plastic Spherodization Effect in the Integral Hydro-Forming of Spherical Vessels

This paper introduces the principle and procedure of integral hydro-forming technology for spherical vessels and the elastoplastic stress fields near weld seams. It also presents mechanical models of the angular distortion area, which explains the circularization bending moment and the effect of spherodization in the angular distortion area during the process of hydro-bulging.     

Separating Performance of Fly Ash in Water Media

The stress state and floating-sinking reqularity of various particles in fly ash in water were analyzed. The formula for calculating the floating-sinking rate was given. And the formula for calculating the magnetic force needed to separate magnetic beads from magnetic separator was also obtained.     

Reflection and Transmission of the Level Step to the Waves in a Linear and Continuous Layer Liquid

1 Introduction Owing to the hot radiation of the sun, the den- sity distribution of water is usually perpendicular in actual oceans and river bayoux. The source of the disturbance will not only produce water waves of a surface mode, but also of an internal mode[1–2]. In layered liquids the internal mode will induce some dynamic water phenomena which are different from those in the single layer liquid[3]. Considering the propagation of waves in deep upheaval terrain, the problem can be simplif…     

An Estimation Method of Stress in Soft Rock Based on In-situ Measured Stress in Hard Rock

The law of variation of deep rock stress in gravitational and tectonic stress fields is analyzed based on the Hoek-Brown strength criterion. In the gravitational stress field, the rocks in the shallow area are in an elastic state and the deep, relatively soft rock may be in a plastic state. However, in the tectonic stress field, the relatively soft rock in the shallow area is in a plastic state and the deep rock in an elastic state. A method is proposed to estimate stress values in coal and soft rock based on in-situ measurements of hard rock. Our estimation method relates to the type of stress field and stress state. The equations of rock stress in various stress states are presented for the elastic, plastic and critical states. The critical state is a special stress state, which indicates the conversion of the elastic to the plastic state in the gravitational stress field and the conversion of the plastic to the elastic state in the tectonic stress field. Two cases studies show that the estimation method is feasible.     

Dynamic Control and Simulation of Space Flexible Manipulator

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双圆孔的动应力集中

关于双圆孔的静应力集中问题,林致平教授早在1948年就进行过研究[1],但其动态问题的理论于1991年才由作者在另一篇论文中完成[2]. 从文献[2]的理论出发,本文研究了孔边受余弦分布动载作用下含双圆孔无限介质的动应力集中问题,目的在于模拟孔边紧固件的压力分布,为处理钉孔动态接触问题打下基础.问题的几何形状和坐标系     

BEM for Diffraction of Elastic Wave and Dynamic Stress Concentrations in Thin Plate with a Circular Hole

oroThinplateS.arewidelyusedinengineering.DifferentholesaresomthesInadeinplatestosatisfyvariousneeds,therebycausingrvtricaldiscontinuahon.Dy-nndcstressconcentIationoccursamundtheholeinaplateonload.TheloadbearingcaPaityoftheplateisthereforeloweredanditSservicelifeisshortened-ThisisthereasonwhymanyexpeItShathhomeandabtalnmthcoreticalanalysis,calculationandexperiInntalreserehonthisasPectinrecentyere['-'].ForstalcsbessconcentIationamundaholeinaplateonbendingload,muchstudyhasbeenunderwayforyear…     

SH波在压电材料中的散射和动应力集中

利用复变函数和波函数展开法，对稳态SH波在含有圆形孔洞的无限弹性压电介质中的散射与动应力集中问题进行研究。获得压电材料圆形缺陷对入射波强度和外加电场的依赖关系，及圆孔周边动应力的表达式，并对具有不同特征参数和不同波数情况下的孔边动应力集中系数进行了数值计算。为压电材料断裂动力学问题的研究提供了一种行之有效的分析方法。计算结果表明，对含圆形缺陷的压电材料进行低频和大特征参数λ情况下的动力分析是非常重要的。     

用边界元法对弹性体进行动力分析

本文对解瞬态动力问题的Nardini-Brebbia边界元法作了简要介绍,并扩充到解稳态问题.对瞬态和稳态问题各计算了一例,与解析解相比较,结果是满意的.最后对带圆孔的板条的动应力集中系数进行计算和实验测定,两者符合得较好     

平板弯曲粘弹性波散射问题的研究

基于薄板粘弹性弯曲波动方程,采用复变函数方法对平板开孔弹性波的散射问题进行了研究,得到了传播稳态波时此种平板弯曲波动问题的分析解。分析了材料粘性阻尼及入射波距离对开孔弹性波散射结果的影响。作为算例,给出了平板圆形开孔的动应力集中系数的数值结果,并对计算结果进行了分析讨论。     

弹性各向异性损伤

采用损伤影响张量,研究了弹性各向异性损伤时的有效应力,按照Lemaitre应变等价性假设,建立了弹性各向异性损伤应力应变关系,并引入了材料的有效柔度张量.由于应变应该具有对称性,因此要求有效柔度张量具有对称性.本文采用Sidoroff的弹性能等值假设和弹性余能等值假设构造了材料的有效柔度张量.推导出损伤应变能释放率张量.     

航空透明件应力集中的声弹检测

在应力与超声传播方向垂直情况下，建立了单向应力状态时双探头测量声速的表面波实用公式，研制了用于航空透明件表面检测的表面波超声换能器，运用表面波传播速度与表面应力之间的依赖关系，对有中心圆孔的ＹＢ－３航空透明件典型试件进行了局部应力集中状态的声弹检测实验，同时借助应变计测量方法做了对比实验。实验结果表明，构件表面局部应力声弹检测方法可靠、有效。     

均匀各向异性媒质的简化波函数理论

基于电磁波的角谱展开法，均匀各向异性媒质的第一、第二、第三、第四类球波函数已由第一作者十多年前定义并已用于解决各种工程问题。该文给出一种均匀各向异性媒质的简化波函数理论。简化的含义是在原来的角谱积分表达式的基础上导出有限和表达式。因而最终波函数的级数表达式不再含数值积分。从应用角度看就是最终线性方程组每一元素均为显式表达，没有数值积分。这一理论的数值计算和验证已在二维情况下完成，则给出适用于三维情况的，在圆柱、圆球坐标系下的简化矢量波函数的表达式。     

建基面弹性波检测数据处理系统的研制

应用Ｃ语言和ＡｕｔｏＬｉｓｐ语言相互结合编制软件，对弹性波检测数据进行处理，在ＡｕｔｏＣＡＤ软件平台中绘制出地震波等值线图和灰度图及声波曲线图实现了弹性波数据处理计算机化，利用参数化绘图及时提供检测结果，满足工程需要     

各向异性板应力集中问题最小二乘虚边界元解法

针对各向异性板的应力集中问题,依据虚边界元法的求解思路,以复变函数表达的基本解作为权函数,建立了相应最小二乘虚边界元的数学模式;其可求解正交各向异性或一般各向异性材料的平面问题.文中给出了含圆孔的各向异性板应力集中问题的数值算例;通过与边界元直接法、有限元法的数值比较可知,本文方法的数值结果具有较高的计算精度.此外,相对其它数值方法本文方法对于各向异性板应力集中问题的求解,具有较好的适用性和数值计算的稳定性.