Investigation of the Rheological Properties of Dense Clayey Soils

Results of experimental investigations are presented for rheological state equations of clayey soils in an axisymmetric stress state induced by two loading regimes. An approximation of rheological equations for shear and dilatational strains is given.     

Near surface stress analysis strategies for axisymmetric fretting

Fretting is essentially a surface phenomenon, but bulk stresses and material properties contribute to subsequent failure. This feature of fretting demands a thorough understanding of near surface stresses under the joint action of normal, shear and thermal loading. Axisymmetric fretting is of great concern in piping and coupling design. In this paper, we develop design tools for Near Surface Analysis (NSA) for understanding axisymmetric fretting. Axisymmetric Fretting Analysis (AFA) becomes formidable owing to localised tractions that call for Fourier transform techniques. We develop two different NSA strategies based on two-dimensional plane strain models: 2D strip model (2DS) and half-plane Flamant model (2DF). We compare the results of 2DS and 2DF with the exact results for AFA obtained using Love’s stress function in conjunction with Fourier transform. There is a good correspondence between stress components obtained from 2D-models.     

The mode III axisymmetric crack problem in a non-homogeneous interfacial region between homogeneous half-spaces

In this study, the mode III axisymmetric crack problem in a non-homogeneous interfacial region between two homogeneous half-spaces is considered. The shear modulus of the interfacial layer is assumed to be μ₂(z)=μ₀ e_mz. It is also assumed that this shear modulus varies continuously between that of the two half-spaces. By using the Hankel transform technique the problem is reduced to a singular integral equation. The problem is solved for various material combinations, crack geometries and for three different sets of crack surface tractions, and the corresponding stress intensity factors are tabulated. This revised version was published online in August 2006 with corrections to the Cover Date.     

子午线轮胎强度性能的有限元分析

根据子午线轮胎的实际结构,建立了一种轮胎轴对称非线性有限元模型,考虑轮胎橡胶材料非线性、帘线-橡胶复合材料的各向异性以及大变形等力学特性,分析了轮胎在充气压力及离心载荷下的变形和应力-应变场,分析结果与试验结果较吻合。     

有限元分析中轴对称问题研究与应用

简要介绍了轴对称问题的概念和特征,列举了其基本方程和优点,将三维问题转化为二维问题,并且用一个正方形轴对称模型利用ANSYS软件建立四分之一模型,施加约束和载荷进行了有限元分析。通过与理论解的对比,发现随着网格的加密,有限元结果不断趋近于理论解,但在网格加密到一定程度1000×1000时,程序内存不够会导致崩溃,若充分利用模型的轴对称性能则可大大减少有限元分析的计算量。     

轴对称非球面轨迹包络磨削中砂轮对刀误差分析

硬脆材料的轴对称非球面光学零件所具有的回转曲面,既需要达到很低的表面粗糙度值又要有很高的几何形状精度,采用轨迹包络磨削加工是达到其精度要求的重要工艺方法。轨迹包络磨削过程中,砂轮的对刀误差是影响轴对称非球面形状精度的关键因素之一。通过建立砂轮的对刀误差数学模型,推导出轨迹包络磨削轴对称回转非球面过程中出现对刀误差时的磨削轨迹曲线方程,并分析了x方向存在、y方向存在、x和y方向同时存在对刀误差对轴对称回转非球面的曲面形状精度的影响。分析结果表明:砂轮的对刀误差将影响轴对称回转非球面的母线的形状和位置。     

Simulation of thermophysical flow in axisymmetric nozzle with expansion chamber

Axisymmetric nozzle flows with a free‐jet expansion are simulated considering several substances and several flow conditions, and the thermophysical properties in the nozzle and the free‐jet region are predicted. The present numerical method is based on the preconditioning method developed by Yamamoto and the mathematical models of thermophysical properties of the substances. As numerical examples show, gas flows of carbon dioxide, water, and nitrogen under a subcritical pressure condition are first calculated. Calculated distances to the Mach disk are compared with the experimental results, and also the density distributions are compared among these three substances. Second, carbon dioxide flows while changing the pressure from subcritical to supercritical values are calculated and the effect of pressure on the flow field is investigated. Third, flows of water vapor with and without nonequilibrium condensation are calculated and the effect of condensation on the flow field is investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Application of upper bound method to the powder‐forging of cup‐shaped axisymmetric preforms for estimating punch load

This paper is concerned with the analytic derivation of the punch load required to forge cup‐shaped axisymmetric porous preforms. Splitting the two‐dimensional preform domain into three rectangular regions, we assumed the kinematically admissible velocity fields to apply the upper bound method. According to the resulting formulas, we developed an incremental numerical algorithm for computing time‐discretized step‐wise punch loads and preform volumes. In order to illustrate the validity of the proposed estimate, we compared the numerical results obtained by the present analysis with those by the finite element simulation. From the comparison made through different preform dimensions, we observed that the present analysis expects the reliable upper bounds of process step‐wise punch loads. Copyright © 2001 John Wiley & Sons, Ltd.     

High-temperature effects in hypersonic flows

The hypersonic (M=25) flow past a 10° right circular cone at 0° angle of attack has been computed using an implicit, noniterative, finite-difference scheme for the Parabolized Navier-Stokes (PNS) equations. Three different gas models have been considered in the study — (1) ideal gas (γ = constant), (2) equilibrium air, and (3) five species (N₂, O₂, NO, N, O) chemical nonequilibrium air. For the nonequilibrium air case, three different models have been considered — (a) one in which the constituent species have no internal structure (i.e., species are ideal gases), (b) one in which the constituent species have internal structure (i.e., species are thermally perfect gases), and (c) one in which the species have internal structure and their thermodynamic properties have been obtained from quantum mechanical and spectroscopic calculations.     

Hydromagnetic boundary layer flow with heat transfer past a rotating disc embedded in a porous medium

In this study, the effect of Coriolis force along with the Darcy parameter has been analyzed on time-dependent forced convective boundary layer flow of conducting fluids over a rotating disc embedded in a porous medium. The modeled system is solved by power series approximations in the Mathematica environment shooted values. The significant impact of the rheological properties, such as Darcy parameter $\beta$ and Prandtl number $\mathit{Pr}$, of water, hydrocarbon, and kerosene-based conducting fluids for the deviation of parameter $\xi$ (Karman) has been noted and then analyzed qualitatively and quantitatively with graphs and tables.