Flange earing and its control on deepdrawing of anisotropy circular sheets

The Hill's quadric anisotropy yield function and the Barlat-Lian anisotropy yield function describing well anisotropy sheet metal with stronger texture are introduced into a quadric-flow corner constitutive theory of elastic-plastic finite deformation suitable for deformation localization analysis. And then, the elastic-plastic large deformation finite element formulation based on the virtual power principle and the discrete Kirchhoff shell element model including the yield functions and the constitutive theory are established. The focus of the present research is on the numerical simulation of the flange earing of the deep-drawing of anisotropy circular sheets, based on the investigated results, the schemes for controlling the flange earing are proposed. Supported by NSFC(No. 19832020) and National Automobile Dynamic Simulation Laboratory of China.     

MULTIAXIAL BEHAVIOR OF NANOPOROUS SINGLE CRYSTAL COPPER： A MOLECULAR DYNAMICS STUDY

The stress-strain behavior and copper are studied by the molecular dynamics incipient yield surface of nanoporous single crystal （MD） method. The problem is modeled by a periodic unit cell subject to multi-axial loading. The loading induced defect evolution is explored. The incipient yield surfaces are found to be tension-compression asymmetric. For a given void volume fraction, apparent size effects in the yield surface are predicted： the smaller behaves stronger. The evolution pattern of defects （i.e., dislocation and stacking faults） is insensitive to the model size and void volume fraction. However, it is loading path dependent. Squared prismatic dislocation loops dominate the incipient yielding under hydrostatic tension while stacking-faults are the primary defects for hydrostatic compression and uniaxial tension/compression.     

Damage in fiber bundle models

We introduce a continuous damage fiber bundle model and compare its behavior with that of dry fiber bundles. Several interesting constitutive behaviors, such as plasticity, are found in this model depending on the value of the damage parameter and on the form of the disorder distribution. We compare the constitutive behavior of global load transfer models, obtained analytically, with local load transfer models numerical simulations. The evolution of the damage is studied analyzing the cluster statistics for dry and continous damage fiber bundles. Finally, it is shown that quenched random thresholds enhance damage localization. Received 27 March 2000     

含偶氮苯类星型液晶化合物的光致变色

研究了一种以Si为中心外围含4个丁氧基偶氮苯液晶基元的星型液晶化合物Si(AZO)4的光致变色规律,利用紫外-可见吸收光谱研究了在氯仿和四氢呋喃溶液中的量子产率、光致变色和光回复反应.实验结果表明样品在各溶液的光致变色和光回复反应均为一级动力学反应,并求算了光致变色反应的正、逆反应速率常数均为10-1s-1数量级,是偶氮类侧链液晶高分子的速率常数的107倍,表明Si(AZO)4的星型结构对末端偶氮基团的吸收光谱没有明显影响,产物具有类似小分子的光致变色性,并且Si(AZO)4的正、逆反应速率常数比值小于液晶基元的比值,表明具有更好的光可逆性,有望作为光控开关和新型信息功能材料.     

Supplier diversification under binomial yield

We consider supplier diversification in an EOQ type inventory setting with multiple suppliers and binomial yields. We characterize the optimal policy for the model and show that, in this case, it does not pay to diversify, in contrast to previous results in the random yield literature.     

激光场的空间非均匀性对阈上离化的影响

本文在基本态模型中计及激光场的空间非均匀性,得到了与实验相吻合的结果.     

Anisotropic energy distribution of sputtered atoms induced by low energy heavy ion bombardment

The theory of anisotropic sputtering published in Phys. Rev. B 71(2), 026101 (2005) and Radiat. Effects Defects Solids 159(5), 301 (2004) has been modified and used to calculate the sputtering yield energy distributions for copper, tungsten, and aluminum targets bombarded by low-energy argon ion. As usual, the electronic stopping is ignored in the analysis. The present theory (modified Sigmund’s theory) has been shown to fit the corresponding experimental results of sputtering yield energy distributions well, except for the cases where the larger ion incident angle and larger sputtering emission angles were considered. The larger discrepancy between the present theory and the experimental result in the latter cases is probably due to the influence of direct recoil atoms on the energy spectrum. Compared with Falcone’s analytical theory, the present theory can reproduce much better experimental results of sputtering phenomena. The fact clearly demonstrates the intrinsic relation between the ion–energy dependence of the total sputtering yield and the sputtering yield energy distribution and suggests the great importance of momentum deposited on the target surface in the physical sputtering     

Determination of charge states of single swift heavy projectiles by high-energy delta-electrons

The effective charge state is an important particle parameter which is required for the calculation of many effects concerning the interaction between radiation and matter such as an estimate of the radial dose of swift heavy projectiles, stopping power and so on. A new method for the determination of effective charge states of heavy ions is based on the measurement of the number of high-energy delta-electrons which are ejected from a target by the penetrating ion. These electrons are detectable with a CCD-detector and their number can be correlated to the effective charge state of the projectile for known particle velocities. This method is even applicable to operation with single swift heavy ions within statistical bounds.     

Matrix Effect of Alkali and Alkaline Earth Metal Halides on Fluorescence Quantum Yield of Indium in Laser‐Induced Fluorescence Flame Spectrometry

As interfered with by alkali and alkaline earth metal halides added as the matrix in an acetylene/air flame, the fluorescence quantum yield of In as the analyte in a laser‐induced fluorescence (LIF) flame spectrometry has been thoroughly characterized. The fluorescence quantum yield is determined by a ratio of F to A, where F is the measured fluorescence of In and A is the difference between the absorption signals recorded for the analyte and the blank solutions. The normalized fluorescence signal is treated to prevent deviations due to variations of the atomization efficiency under the conditions with and without the matrix added. The fluorescence quantum yield is measured to be almost independent of the matrix concentration up to 500 ppm (μg/mL) studied, under conditions of either optical unsaturation or saturation. By considering a quenching effect induced by electron‐atom collisions, the calculated fluorescence quantum yields are consistent with our observations.     

Confining effect on the bearing capacity of circular footings on a purely cohesive soilEffet du confinement sur la capacité portante d'une fondation circulaire sur un sol purement cohérent

The bearing capacity of axially symmetrical footings acting on a purely cohesive soil foundation contained by a rigid wall at a finite distance is investigated within the framework of the Yield design theory. Following the same tracks as in a preceding paper devoted to strip footings, the analysis is performed by referring to already existing results concerning the bearing capacity of a circular footing on a soil layer with limited thickness. It comes out that the bearing capacity factor determined by Eason and Shield for a rough circular footing on an unlimited soil foundation is increased by a correction factor that increases when the diameter of the container decreases. Comparison with the results obtained for strip footings acting on a purely cohesive soil in the same conditions shows that the confining effect is significantly lower for a circular footing than for a strip footing. To cite this article: J. Salençon, C. R. Mecanique 330 (2002) 521–525.