Grain statistics effect on deformation behavior in asymmetric rolling of pure copper foil by crystal plasticity finite element model

The grain statistics effect was investigated through asymmetric rolling of pure copper foil by a realistic polycrystalline aggregates model and crystal plasticity element finite model.A polycrystalline aggregate model was generated and a crystal plasticity-based finite element model was developed for each grain and the specimen as a whole.The crystal plasticity model itself is rate dependent and accounts for local dissipative hardening effects and the original orientation of each grain was generated based on the orientation distribution function（ODF）.The deformation behaviors,including inhomogeneous material flow,decrease of contact press and roll force with the increase of grain size for the constant size of specimens,were studied.It is revealed that when the specimens are composed of only a few grains across thickness,the grains with different sizes,shapes and orientations are unevenly distributed in the specimen and each grain plays a significant role in micro-scale plastic deformation and leads to inhomogeneous deformation and the scatter of experimental and simulation results.The slip system activity was examined and the predicted results are consistent with the surface layer model.The slip band is strictly influenced by the misorientation of neighbor grain with consideration of slip system activity.Furthermore,it is found that the decrease of roll force and the most active of slip system in surface grains are caused by the increase of free surface grain effect when the grain size is increased.The results of the physical experiment and simulation provide a basic understanding of micro-scaled plastic deformation behavior in asymmetric foil rolling.

运用激励手段 调动职工积极性

“激励”一词,早见于我国汉朝司马迁所著的《史记》,范睢、蔡泽列传中,有“欲以激励应候”之语,意思是激发使其振作。但作为心理学的一个术语,它译自英文“motivation”,是指激发人的动机,使人有一股内在的动力,朝向所期望的目标前进的心理活动过程。它是促使人的心理动机发生转化的外在因素,其基本特征是:能产生自觉性行为,使趋向性行为持续,皮避向性行为逆转或萎缩。运用到组织管理中,就是充分挖掘人的潜力,调动人的积极性的问题。

艺术的自然性与自然主义的艺术

艺术的“表现力”或艺术的概念性主题等以往被视为艺术的生命力、艺术内在的灵魂的东西,已变成了一种不可捉摸的、含混或模棱两可的东西。艺术丧失了其自身的规定性。人们已很难在什么是艺术品,什么是非艺术品之间做出判断。的确,当艺术家、博物馆或其它艺术组织第一次承认或认为物品的装置是艺术以后,这一点似乎已变得不可逆转:在简单的人工制品、物体、事物和刻意的创造之间已不再存在艺术与非艺术的差别。但是,无论我们是用“先锋派”、“后现代性”或“后传统”的名号来称谓自杜尚以来不断变化的艺术,都可以从中看到这样一种令人惊叹的现象:艺术正向自然回归,它正在不断清除原本存在于它对对象自然之间的界限。但艺术并没有因此丧失其本质的规定性。相反,这种自我否定的反向性行为,却似乎把这作为一种创制活动的本性更加清晰地展露了出来。因此,不能根据艺术所表现出来的那种看似是自我否定的行为倾向而仓促地认为,艺术是一种没有自己固定的领域的创制活动,因为这等于说,艺术已丧失了属于它自身的表意的功能。这种看法显然违背了艺术的自然本性,并因此会阻碍我们对艺术活动与非艺术活动做出正确的判断。实际上。

以激励焕发活力——浅谈激励手段在企业管理中的运用

一、激励的概念和激励的基本特征什么是激励?一般地说,激励就是利用外部诱因,调动人的积极性和创造性。企业管理中的激励,就是通过一定的方法,激励职工的内在动力,开发职工为实现企业的经营目标而奋斗。激励的基本特征是:能产生自觉性行为,使趋向性行为持续,使背向性行为逆转或萎缩。现代心理学研究表明,经过激发与未经激发的工作热情存在约60%的差距。在国内外市场竞争如此激烈的情况下,企业要生存和发展,就要不断地提高自己的竞争能力,为此,就必须最大限度地激励全体职工充分挖掘其内在潜力。二、管理者的激励能力现代企业管理的核心是人的管理。

Calibration of anisotropic yield function by introducing plane strain test instead of equi-biaxial tensile test

The equi-biaxial tensile test is often required for parameter identification of anisotropic yield function and it demands thespecial testing technique or device. Instead of the equi-biaxial tensile test, the plane strain test carried out with the traditional uniaxialtesting machine is suggested to provide the experimental data for calibration of anisotropic yield function. This simplified method byusing plane strain test was adopted to identify the parameters of Yld2000-2d yield function for 5xxx aluminum alloy and AlMgSialloy sheets. The predicted results of yield stresses, anisotropic coefficients and yield loci by the proposed method were very similarwith the experimental data and those by the equi-biaxial tensile test. It is validated that the plane strain test is effective to provideexperimental data instead of equi-biaxial tensile test for calibration of Yld2000-2d yield function.

High temperature plastic deformation behavior of non-oriented electrical steel

High temperature plastic deformation behavior of non-orientated electrical steel was investigated by Gleeble 1500 thermo-mechanical simulator at strain rate of 0.01-10 s^-1 and high temperature of 500-1 200 ℃. The stress level factor （a）, stress exponent （n）, structural factor （A） and activation energy （Q） of high temperature plastic deformation process of non-orientated electrical steel in different temperature ranges were calculated by the Arrhenius model. The results show that, with dynamic elevation of deformation temperature, phase transformation from α-Fe to γ-Fe takes place simultaneously during plastic deformation, dynamic recovery and dynamic recrystallization process, leading to an irregular change of the steady flow stress. For high temperature plastic deformation between 500 and 800 ℃, the calculated values of a, n, A, and Q are 0.039 0 MPa 1, 7.93, 1.9× 10^18 s^-1, and 334.8 kJ/mol, respectively, and for high temperature plastic deformation between 1 050 and 1 200 ℃, the calculated values of a, n, A, and Q are 0.125 8 MPa1, 5.29, 1.0 × 10^28 s^-1, and 769.9 kJ/mol, respectively.

Phase Transitions in a Mixture of Hard-Sphere Dipoles and Neutral Hard Spheres

Using the reference hypernetted chain （RHNC） integral equation theory and a rigorous stability analysis method, we investigate the phase behavior of a mixture of hard-sphere dipoles and neutral hard spheres based on the correlations of the homogeneous isotropic phase. Lowering the temperature down to the points where the RHNC equations fail to have a solution, several ttuctuations strongly increase. At low densities our results indicate the onset of ／ chain formation, which is similar with the pure DHS system. At high densities, the results indicate the appearance of isotropic-to-ferroelectric transitions （small neutral hard spheres concentrations） and demixing transitions （large neutral hard spheres concentrations）.

The effects of Haversian fluid pressure and harmonic axial loading on the poroelastic behaviors of a single osteon

In order to well understand the mechanism of the mechanotransduction in bone, we propose a new model of transverse iso- tropic and poroelastic osteon cylinder considering Haversian fluid pressure. The analytical pore pressure and velocity solutions are obtained to examine the fluid transport behavior and pressure distribution in a loaded osteon on two different exterior sur- face cases. Case I is stress free and fully permeable and case I1 is impermeable. The following are the results obtained. （i） The Haversian fluid may not be ignored because it can enlarge the whole osteonal fluid pressure field, and it bears the external loads together with the solid skeleton. （ii） The increase of both axial strain amplitude and frequency can result in the increase of fluid pressure and velocity amplitudes, while in case II, the frequency has little effect on the fluid pressure amplitude. （iii） Under the same loading conditions, the pressure amplitude in case II is larger than that in case I, while the velocity amplitude is smaller than that in case I. This model permits the linking of the external loads to the osteonal fluid pressure and velocity, which may be a stimulus to the mechanotransduction of bone remodeling signals.

An unconventional phase field modeling of domains formation and evolution in tetragonal ferroelectrics

Based on characteristic functions of variants, we developed an unconventional phase field modeling for investigating domains formation and evolution in tetragonal ferroelectrics. In order to develop this computational approach, we constructed the anisotropy energy of tetragonal variants, which is used instead of Landau-Devonshire potential in the conventional phase field method, resulting in that much fewer parameters are needed for simulations. This approach is advantageous in simulations of emerging ferroelectric materials. We employ it to study the formation and evolution of domains in tetragonal barium titanate single crystal, as well as the nonlinear behaviors under cyclical stress and electric field loading. A multi-rank laminated ferroelectric domain pattern, 90° domain switching accompanied by polarization rotation, and 180° domain switching accompanied by move of domain wall are predicted. It is found that the speed of 90° domain switching is slower than that of 180° domain switching, due to both polarization and transformation strain changed in 90° domain switching. It also suggests that large strain actuation can be generated in single crystal ferroelectrics via combined electromechanical loading inducing 90° domain switching. The good agreement between simulation results and experimental measurements is observed.

Undrained anisotropy and non-coaxial behavior of clayey soil under principal stress rotation

In this study, a series of undrained tests were conducted on both intact and reconstituted clay using an automatic hollow cylinder apparatus. Monotonic shearing tests with fixed principal stress directions were carried out, pure and cyclic prin- cipal stress rotation tests were also performed. The non-coaxiality, defined as the non-coincidence of the principal plastic strain increment direction and the corresponding principal stress direction, of clayey soil was studied experimentally. The effects of the intermediate principal stress, shear stress level, and inherent anisotropy were highlighted. Clear non-coaxiality was observed during pure principal stress rotation, in both intact and reconstituted clay. The influence of the intermediate principal stress pa- rameter, shear stress level, and inherent anisotropy on the non-coaxial behavior of the clayey soil was found to be insignificant when compared with the sand. The non-coaxial behavior of the clayey soil depended more on the stress paths. Under undrained conditions, the contribution of elastic strain to the direction of the total principal strain increment cannot be ignored.

Unified analytical solutions for a circular opening based on non-linear unified failure criterion

Unified analytical solutions are presented for the predictions of the stresses and displacements around a circular opening based on nonqinear unified failure criterion and the elastic-brittle-plastic softening model. Unified analytical solutions not only involve generally traditional solutions which are based on the Hock-Brown （H-B） failure criterion or the non-linear twin-shear failure criterion, but also involve other new results. The results of the radius of plastic zone, radial displacements and stresses are obviously different using three rock masses when different values of the unified failure criterion parameter or different material behavior models are used. For a given condition, the radius of plastic zone and radial displacements are reduced by increasing the unified failure criterion parameter. The latent potentialities of rock mass result from considering the effect of intermediate principal stress. It is shown that proper choices of the failure criterion and the material behavior model for rock mass are significant in the tunnel design.

Loading direction dependent mechanical behavior of graphene under shear strain

The mechanical behavior of graphene under in-plane shear is studied using molecular dynamics simulations.We show that the shear behavior of chiral graphene is dependent on the loading direction due to its structural asymmetry.The maximum shear failure strain of graphene in one direction may be 1.7 times higher than that in the opposite direction.We discuss also the influence of the cut-off parameters on the calculations.Our findings are useful for the understanding of mechanical behavior of graphene and the potential applications of graphene in nanodevices.

A single-site anisotropic soft-core model for the study of phase behavior of soft rodlike particles

A novel mesoscopic simulation model is proposed to study the liquid crystal phase behavior of the anisotropic rodlike particles with a soft repulsive interaction,which possesses a modified anisotropic conservative force type used in dissipative particle dynamics.The influences of the repulsion strength and the particle shape on the phase behavior of soft rodlike particles are examined.In the simulations,we observe the formation of the nematic phase and smectic-A phase from the initially isotropic phase.Moreover,we find that shorter soft rodlike particles with anisotropic repulsive interactions can form a stable smectic-B phase.Our results demonstrate that the soft anisotropic purely-repulsive potential between the rodlike particles can reflect the interaction nature between soft rodlike particles in a simple way and is sufficient to produce a range of ordered LC-like mesophases.

A physical mechanism based investigation on the elasto-plastic-damage behavior of anisotropic aluminum alloys under finite deformation

The elasto-plastic-damage behavior of anisotropic aluminum alloys is investigated under finite deformation using a physical mechanism based constitutive model.With an application to the structural calculation,the present model is used to describe and analyze the mechanical response of anisotropic 6260-T6 aluminum alloy extrusions.For the tensile specimens extracted along three different material orientations from the extruded aluminum profile,twelve simulations are carried out covering four different specimen geometries.The simulation results in force-displacement response and central logarithmic axial strain evolution are compared with experimental results.From the comparisons,it can be concluded that the present model has the capacity to describe the behavior of anisotropic material.From the force-displacement curves,the anisotropy is observed in different material orientations,and the physical mechanism of anisotropy is analyzed.