Elasticity solution of laminated beams with temperature-dependent material properties under a combination of uniform thermo-load and mechanical loads

An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.

Thermoelastic topology optimization for structures with temperature-dependent material properties

A thermoelastic topology optimization is proposed for structures with temperature-dependent material properties.Different from the common assumption of constant material properties in traditional thermoelastic topology optimization,the temperaturedependent material properties related to mechanical and thermal fields are taken into account.The non-uniform temperature distribution of the structure is a design dependent field that may vary during the optimization,and the nonlinear heat transfer analysis is considered according to the large temperature gradient.Based on these,a thermoelastic topology optimization model considering temperature-dependent material properties is formulated.The sensitivities with respect to the design variables are derived and the Method of Moving Asymptotes(MMA)algorithm is used to update the topological design variables.A cooperation platform based on MATLAB and ABAQUS is developed for the proposed thermoelastic topology optimization method to deal with problems with arbitrary domains for the design of complex engineering structures.Several typical numerical examples are given to illustrate the effectiveness of the proposed method and show the important influence of the temperaturedependent material properties.

INFLUENCE OF TEMPERATURE-DEPENDENT PROPERTIES ON TEMPERATURE RESPONSE AND OPTIMUM DESIGN OF C/M FGMS UNDER THERMAL CYCLIC LOADING

The influence of temperature-dependent properties on temperature response and optimum design of newly developed ceramic-metal functionally graded materials under cyclic thermal loading and high temperature gradient environment is studied. The thermal conductivity of the material is considered to be dependent on the temperature. In this paper, the temperature response of the material is calculated using a nonlinear finite element method. Emphasis is placed on the influence of temperatue-dependent properties on the thermal response and insulation property of the material render the different graded compositional distributions and different heat flux magnitudes. Through the analysis, it is suggested that the influence of temperature-dependent properties can not be neglected in the temperature response analysis and the optimum design process of the material must be based on the temperature-dependent temperature analysis theory.

INFLUENCE OF TEMPERATURE-DEPENDENT PROPERTIES ON THERMAL STRESSES RESPONSE AND OPTIMUM DESIGN OF C/M FGMS UNDER THERMAL CYCLIC LOADING

The influence of temperature-dependent properties on thermal stresses response and optimum design of newly developed ceramic-metal functionally graded materials under cyclic thermal loaning and high temperature gradient environment is studied. The thermal conductivity of material is considered to be dependent on the temperature. In this paper, the thermal stresses response of the material is calculated rising a nonlinear finite element method. Emphasis is placed on the influence of temperature-dependent properties on the thermal stresses response characteristics, the thermal stresses relaxation property and the thermal stresses history under the different graded compositional distributions and different heat flux magnitudes. Through tile analysis. it is suggested that the influence of temperature-dependent properties can not be neglected In the thermal stresses response analysis and the optimum design process of the material must be based on the temperature-dependent thermo-elastic-plastic theory.

不同壁材组合对三丁酸甘油酯微胶囊性质的影响

为拓宽三丁酸甘油酯的应用范围,以三丁酸甘油酯为芯材,抗性糊精-明胶-海藻酸钠(RGS)、抗性糊精-明胶-海藻酸钠-月桂酸单甘酯(RGSG)、抗性糊精-明胶-壳聚糖(RGC)、抗性糊精-明胶-壳聚糖-月桂酸单甘酯(RGCG)为壁材,采用喷雾干燥法制备4种微胶囊,对微胶囊包埋率及产率、粒径分布、基本理化性质、颜色、结构特征及外观形貌进行分析,探究不同壁材对三丁酸甘油酯微胶囊性质的影响。结果表明:RGSG微胶囊包埋率(91.05%)及产率(90.46%)较高;与RGC、RGS微胶囊相比,RGSG、RGCG微胶囊的水分活度、粒径分布、流动性、吸湿性、亮度均有一定的改善;红外光谱及扫描电镜结果表明三丁酸甘油酯被壁材有效包埋起来,其中RGSG、RGCG微胶囊形成了更强的氢键。综上,RGSG制备的微胶囊综合性质优于其他3种壁材。

A Two-Dimensional Thermoelastic Analysis of a Cylindrical Shell Made of FGM with Temperature-Dependent Physical Properties

This paper numerically and analytically investigates a non-linear static,twodimensional thermoelastic analysis in the radial and tangential directions of a cylindrical shell made of functionally graded materials.The dependence of material properties on temperature makes the heat governing equations non-linear.To obtain the temperature field analytically,the heat conduction equation is linearized and exactly solved using a linearizing transformation,then this exact solution is substituted in the Lamme-Navier equations,and the elasticity equations are numerically solved using a second-order central finite difference method,and displacement and stress distributions are obtained.Finally,the temperature field,stress,and displacement distributions are presented,and the effect of inhomogeneous parameters on them is examined and discussed.The correctness and accuracy of the exact analytical solution of the temperature field are illustrated by a comparison with the numerical solution.The results show a good agreement.

透水铺装材料湿物理性质测定

为获取典型透水铺装材料的湿物理性质,以用于进行透水铺装热湿传递计算,进而科学评价其蒸发降温效果。以中国居住区广泛使用的3种透水铺装材料:烧结陶瓷透水砖(TC)、再生骨料混凝土透水砖(ZS)和普通透水砖(PT)为研究对象,参考相关标准,采用真空饱和实验测试了透水铺装材料的表观密度ρ、开放孔隙率及真空饱和含湿量wvac;采用单面浸泡实验测试了毛细饱和含湿量wcap及吸水系数A;采用渗透实验测试了其渗透系数kT。通过对测试结果进行误差分析,建立了透水铺装材料与液态水相关的湿物理性质数据库。通过对比3种材料测试数据发现:保水性能方面,ZS最优、PT次之、TC最差;吸水性能方面,TC最优、PT次之、ZS最低,表明材料保水与吸水性能并非正相关;渗透性能方面,TC性能最优、PT次之、ZS最弱,在满足渗透性能的前提下,PT最有利于吸水后的蒸发降温。

化学结合磷酸盐胶凝材料对Pb(Ⅱ)滞留性的研究

研究化学结合磷酸盐胶凝材料（CBPC）固化体对Pb^2＋滞留性的影响。在不同Pb^2＋加入量和养护龄期下,测定固化体力学性能,以及浸出溶液的pH值、电导率和Pb^2＋质量浓度,分析CBPC固化体对Pb^2＋的稳定效果。结果表明,不同Pb^2＋加入量下,CBPC固化体均具有较好的早期力学性能,养护1 d的抗压强度超过30 MPa;1 d和3 d龄期的固化体浸出液的pH值约为7.5-8.0、电导率为1.95-3.04ms/cm;浸出液中Pb^2＋质量浓度较小。当Pb^2＋加入量为5%（Pb^2＋加入质量占固体总质量的比例）时,1 d龄期的CBPC固化体浸出液中Pb^2＋质量浓度仅为0.45 mg/L,远低于国标中危险废物的鉴别标准,此时Pb^2＋固化效率超过99.9%。研究表明,CBPC是一种非常有效且稳定的固铅材料。

不同变形状态下变物性梯度功能材料板瞬态热应力

用非线性有限元法分析了由ZrO2和Ti-6Al-4V组成的变物性梯度功能材料板的对流换热瞬态热应力问题,与已有文献比较检验了方法的正确性,给出了该材料板在不同变形状态下的瞬态热应力分布,并与常物性时的结果进行了比较。结果表明:无限自由长板内的热应力最小;当无限长板只能伸长、不能弯曲时,板内瞬态拉应力最大;当无限长板伸长、弯曲受限时,板内的瞬态压应力最大;考虑变物性时的最大拉应力比常物性减小48.9%,最大压应力减小39.6%;此外,对流换热系数的变化对不同变形状态下该变物性材料板瞬态热应力场的影响显著。此结果为该材料的设计和应用提供了准确的理论计算依据。

蓄热调温袜设计与生产

针对夏季运动和冬季运动对袜子的性能要求,以蓄热调温混纺纱为原料,使用计算机辅助设计系统设计出适合于夏季运动穿着的网眼船袜和冬季运动穿着的毛圈中统袜,并在全电脑织袜机上编织生产,测试了蓄热调温袜的保温性能和调温性能,结果表明调温袜具有优良的保暖性能和调温性能。

改性纳米SiO_2/环氧-丙烯酸酯复合材料的制备与性能研究

通过溶胶-凝胶法自制纳米二氧化硅(SiO_2),并采用油酸对其进行改性,改性纳米SiO_2与环氧树脂充分混合,加入丙烯酸单体,制得改性纳米SiO_2/环氧-丙烯酸酯复合材料。复合材料经透射电子显微镜(TEM)、扫描电子显微镜(SEM)等表征和分析。实验结果表明,改性后的纳米SiO_2/环氧-丙烯酸酯复合材料的拉伸强度、冲击强度、拉伸模量等力学性能得以明显提高,当纳米SiO_2与环氧-丙烯酸酯复合材料的摩尔配比为3∶100时,改性纳米SiO_2/环氧-丙烯酸酯复合材料具有最佳的力学性能:冲击强度达到15.63kJ/m2,拉伸强度达到55.68MPa,拉伸模量达到3.67GPa;铅笔硬度达到2H、黏度明显提高达到125MPa·s;耐盐雾、耐水指标都有明显改善。

2,4,6,8-四硝基-2,4,6,8-四氮杂三环[3.3.0.0^(3,7)]辛烷的理论研究

为了研发新型高能量密度化合物,设计了一种笼型奥克托金——2,4,6,8-四硝基-2,4,6,8-四氮杂三环[3.3.0.0^(3,7)]辛烷(cage-HMX)。基于密度泛函理论(DFT)的B3LYP方法,在6-31G**基组水平上,研究了cageHMX-I^cage-HMX-IV的几何构型、张力能、静电势分布、密度、生成焓、氧平衡、爆速、爆压、单元比冲以及撞击感度。结果表明,cage-HMX-I是4种构型中较为稳定的构型;cage-HMX的张力能大于CL-20;与HMX相比,cageHMX具有较高的密度(1.92~1.93g/cm^3)、爆速(9.341~9.478km/s)、爆压(40.97~42.30GPa)、单元比冲(277.1~281.4s)和撞击感度(4.3~5.0J),是一种潜在的高能量密度材料。

基于生物质制备活化三维多孔碳及其在微生物燃料电池中的应用

微生物燃料电池是一种能把污水中有机物蕴含的化学能直接转换成电能的装置。目前,相对低的输出功率密度限制了它的应用。开发高性能的阳极材料是解决途径之一。基于生物质秸秆利用Hummers氧化法结合抗坏血酸还原法制备了活化三维多孔碳阳极,用扫描电子显微镜观察了所制备的材料的形貌、发现活化过程可以产生许多大小不一的孔结构,可有效帮助传质扩散。交流阻抗谱、循环伏安测试表明,活化可以大大提高三维多孔碳的电化学性能,基于活化三维多孔碳3DPC阳极所制备的微生物燃料电池(MFCs),最大功率密度可达到1184.5W/m^3,远远高于改性前(774.8W/m^3)。此研究为构筑新型三维碳基阳极提供了新思路和新方法。

Preparation and Properties of Smart Thermal Control and Radiation Protection Materials for Multi-functional Structure of Small Spacecraft

Considering the unique properties of small spacecraft, such as light weight, low power-consumption and high heat flux density, a new kind of lightweight boron carbide （B4C） radiation-protection coating material was proposed. New techniques for preparing LSMO thermal control coating and B4C radiation-protection coating were developed. The sample piece of multi-functional structure was manufactured by using the proposed materials, and a series of performance tests, such as thermal control and radiation-protection behaviors were evaluated. Test results show that： the emissivity of the multi-functional structure varies from 0.42 to 0.86 at 240 K to 353 K and the phase transition temperature is about 260 K. The electron radiation-protection ability of the multi-functional structure is 3.3 times better than that of Al material. The performance index of this multi-functional structure can meet the requirements for space application in on-board electronic equipment.

Stresses of orthotropic laminated beams subjected to high temperature and mechanical load

Thermo-elastic analysis of simply-supported orthotropic laminated beams subjected to high temperature and mechanical load is presented on the basis of the exact two-dimensional thermoelasticity theory.The beam is composed of several orthotropic layers,each with temperaturedependent material properties.The governing equation for each layer is analytically solved using the state space method.The displacement and stress solutions of the beam are obtained using the transfer-matrix method.A numerical example is included to study the effects of temperature on the mechanical responses of a sandwich beam.The results reveal two main effects of temperature:(i)inducing deformations and stresses by itself;(ii)affecting the deformations and stresses induced by the mechanical load.

A comprehensive testing method for global stability analysis of high arch dams

Hydropower projects are rapidly developing in China at present, and a number of high daras and large reservoirs are currently under construction or will soon be built. These large projects are mainly located on the great rivers in West China with complicated topographical and geological conditions. Evaluation of stability and safety of these high dam projects is an important topic. Geomechanical model test is one of the main methods to study the global stability of high dam and foundation. In this paper, a comprehensive testing method that combines overloading and strength reduction in a model is proposed. In this method, both the influence of excessive flooding and the effects of strength reduction of rock masses and weak structural planes on dam stability are considered. Thus, the comprehensive testing method can accurately incorporate multiple factors that affect the global stability of high dam and its foundation. Based on the failure testing principle and model similarity theory, a similarity relation formula for safety evaluation through comprehensive test is established. A new model material, temperature-dependent analogous material, is also developed. By rising the temperature and reducing the strength of the mod,~l material, the mechanical behaviors resulting from gradual strength reduction can be simulated. Thus, the comprehensive testing method is realized in a single model. For case studies, the comprehensive geomechanical model test is conducted for Jinpinlg I and Xiaowan high arch dam projects.

宽温域阻尼材料用嵌段溶聚丁苯橡胶的合成与性能

以苯乙烯和丁二烯为单体、正丁基锂为引发剂、2,2-二(四氢呋喃)丙烷为调节剂、环己烷为溶剂,采用活性负离子聚合技术设计并合成出两段组成及比例不同的嵌段型溶聚丁苯橡胶(SSBR),使用核磁共振波谱仪和凝胶渗透色谱仪表征其微观结构、化学组成和分子量及其分布,并采用橡胶拉力机和动态机械分析仪分别对嵌段SSBR硫化胶的力学性能和动态力学性能进行测试。结果表明,嵌段SSBR分子结构满足设计要求;嵌段SSBR硫化胶具有较好的力学性能和动态力学性能;嵌段SSBR的软段与硬段的质量比越高,有效阻尼温域越宽;当软段为结合苯乙烯含量更低的链段,嵌段SSBR有效阻尼温域进一步拓宽;当嵌段SSBR两段结合苯乙烯结构单元质量分数分别为15%和50%且二者质量比为7/3时,损耗因子不小于0.3时的温域超过53℃。

Thermal stress and fracture temperature prediction for flexible pavement

Analytical solutions of thermal stresses in multilayered elastic system whose materials characteristics are dependent on temperature are derived by a transfer matrix and integral transformation method.The resulting formulation is used to calculate thermal stresses in the low temperature cracking problem of asphalt pavement.Numerical simulations and analyses are performed using different structural combinations and material characteristics of base course.And fracture temperatures are predicted for a given flexible pavement constructed with three types of asphalt mixtures based on the calculated results and experimental data.This approach serves as a better model for real pavement structure as it takes into account the relationships between the material characteristics and temperature in the pavement system.

论QQ号码的法律性质

QQ号码的使用随着互联网的飞速发展而普及,其法律性质尚未明确,用户权利得不到有效保护。本文通过对虚拟财产、网络财产的分析揭示QQ号码的物权属性。针对这一属性,对由于侵权责任人的原因造成的对原用户的损害,笔者认为可采取恢复原状和损害赔偿的保护方法。

Effects of mechanical boundary conditions on thermal shock resistance of ultra-high temperature ceramics

The effects of mechanical boundary conditions, often encountered in thermalstructural engineering, on the thermal shock resistance（TSR） of ultra-high temperature ceramics（UHTCs） are studied by investigating the TSR of a UHTC plate with various types of constraints under the first, second, and third type of thermal boundary conditions. The TSR of UHTCs is strongly dependent on the heat transfer modes and severity of the thermal environments. Constraining the displacement of the lower surface in the thickness direction can significantly decrease the TSR of the UHTC plate, which is subject to the thermal shock at the upper surface. In contrast, the TSR of the UHTC plate with simply supported edges or clamped edges around the lower surface is much better.