MgO/Ni系FGM的热应力缓和特性设计

对于MgO/Ni系FGM材料,分别用实验和微观力学模型测定和计算了用于热应力缓和设计的各物性参数。结合烧结体的显微结构,讨论了二种结果之间存在差异的原因。用有限元方法计算了FGM的热应力,得到MgO/Ni系FGM的综合设计准则。     

Finite Element Analysis of Thermal Stresses in Ceramic/Metal Gradient Thermal Barrier Coatings

This paper studied the thermal stresses of ceramicl metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating （TBC） and functionally gradient material （FGM）. Thermal stresses and residual thermal stresses were calculated by an ANSYS finite element analysis software. Negative thermal expansion coefficient method was proposed and element birth and death method was applied to analyze the residual thermal stresses which have non-uniform initial temperature field. The numerical results show a good agreement with the analytical results and the experimental results.     

对称型梯度功能材料的瞬态热应力强度因子

采用摄动法推导出无限大对称型梯度功能材料平板的一维非定常温度场及非定常热应力场的解析表达式 ,并采用权函数法计算了受热冲击的含双边裂纹的对称型梯度功能材料平板的瞬态热应力强度因子 .通过两种Al2 O3 TiC系梯度功能陶瓷平板表面冷却条件下的计算实例并与均质陶瓷材料对比 ,分析了材料的热 物理性能分布规律对瞬态热应力强度因子的影响 ,并提出高抗热震性梯度功能陶瓷的设计原则     

Fabrication and Microstructure of W/Cu Functionally Graded Material

W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM combines the advantages of tungsten such as high melting point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat corrosion and thermal shock resistance and will be a promising candidate as divertor component in thermonuclear de-vice. Owing to the dramatic difference of melting point between tungsten and copper, conventional processes meet great difficulties in fabricating this kind of FGMs. A new approach termed graded sintering under ultra-high pressure (GSUHP) is proposed, with which a near 96% relative density of WICu FGM that contains a full distribution spectrum (0-100%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zirconium, vanadium) is employed as additives to activate tungsten's sintering, enhance phase wettability and bonding strength between W and Cu. Densification effects of different layer of FGM were investigated. Microstructure morphology and interface elements distribution were observed and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.     

梯度陶瓷水煤浆喷嘴的残余热应力有限元分析

根据陶瓷水煤浆喷嘴出口破损和脱落的主要原因, 提出了梯度功能陶瓷喷嘴的设计思想,目的是人为的在喷嘴的制备过程中在喷嘴的出口处形成有利的残余压应力,缓和喷嘴在使用中的拉应力. 通过合理地设计梯度功能陶瓷喷嘴不同部位材料组分的分布,设计了两种模型：轴向梯度陶瓷喷嘴FGM-Z, 径向梯度陶瓷喷嘴FGM-R. 利用有限元法对两种模型进行了分析,得出：两种梯度喷嘴模型在出口处均形成了有利的压应力,特别是FGM-R喷嘴在喷嘴的整个内壁都形成了有利的压应力. 通过比较,初步确定最佳模型为FGM-R陶瓷水煤浆喷嘴.     

Design and development of SiC/(W,Ti)C gradient ceramic nozzle

The idea of functionally gradient material (FGM) theory was used to design ceramic nozzle based on the erosion wear behaviors of the ceramic nozzles and the outstanding properties of FGM. The purpose is to reduce the tensile stress at the entry region of the nozzle during sand blasting processes. The design theory and methods of gradient ceramic nozzle were proposed. The physical, micromechanical, and composition distribution models of gradient ceramic nozzle were established. The optimum composition distribution of the gradient ceramic nozzle material was determined from the solution of the multi-objective optimization calculation by constructing the models of the composition distribution versus the structural integrity of the compact in fabricating process. Results showed that compressive residual stresses appeared at the entry area of the gradient ceramic nozzle. The optimized component distribution exponent p is 0.5. An SiC/(W,Ti)C gradient ceramic nozzle material was synthesized by hot-pressing according to the design result. Results showed that the surface Vickers hardness of the FGM-1 gradient ceramic nozzle materials was greatly improved in comparison with that of the other layers. Supported by the Specialized Research Fund for Doctoral Program of Higher Education (Grant No. 20030422105), the Natural Science Foundation of Shandong Province (Grant Nos. Y2004F08, Z2003F01) and the Program for New Century Excellent Talents in University (Grant No. NCET-04-0622)     

金属－陶瓷梯度材料的弹性和弹塑性设计

系统研究了金属－陶瓷梯度材料在不同组成分布情况下的制备热应力分布规律和特征，提出了优化梯度材料组成和控制梯度材料破坏的方法，考虑了弹性和弹塑性二种设计方法，讨论了二种设计方法的特点和不同，结果表明，对于由韧性金属和陶瓷合成的梯度材料，弹塑性设计比弹性设计更为合理。     

金属－陶瓷梯度材料的热应力分析

分析了金属－陶瓷梯度材料的微观结构特征，并用Ｅｓｈｅｌｂｙ等效原理和Ｍｏｒｉ－Ｔａｎａｋａ平均场理论导出了梯度材料性能预测的三相理论公式．在对性能预测的基础上，用有限元法计算了ＭｇＯ／Ｎｉ梯度材料体系的制备热应力；得到了一些有意义的结论．     

金属/陶瓷梯度热障涂层的研究进展

综述了金属／陶瓷梯度涂层材料的作用机理、研究工作及应用领域、金属／陶瓷梯度热障层的制备工艺。     

Kinetics of Combustion Synthesis in Ti-C-3Ni-Al System

The Kinetics and mechanisms of the combustion reaction in theTi-C-3Ni-Al system were studied. Samples were prepared by igniting compacts of elemental Ti, C, Ni and Al powders with a heating tungsten coil under an inert argon atmosphere. The activation energies of Ti+C+50wt%(3Ni+Al)→TiC+50%Ni3Al and Ti+C+80wt%(3Ni+Al) →TiC+80%Ni3Al exothermic reactions were determined by measuring the combustion wave velocity and the combustion temperature, which are 129kJ.mol-1 and 79kJ*mol-1, respectively. The mechanism of formation of products for Ti-C-3Ni-Al system was found:metal phases (Ti-3Ni-Al) are melted in combustion process,and carbon dissolves into the liquid metal and TiC is subsequently precipitated out of solution, and Ni3Al is crystallized during the cooling process. The mechanism is fairly similar with that of Ti+C→TiC and Ti+C+Ni→TiC+Ni. There are two reactions (Ti+C→TiC, 3Ni+Al→Ni3Al) in the Ti+C+3Ni+Al system, and the wave velocity is mainly controlled by the velocity of Ti + C→TiC, but the velosity of 3Ni+Al→Ni3Al may play a significant role when Ni3Al contents are higher than 70wt%.     

THERMO-ELASTIC-PLASTIC RESPONSE AND OPTIMUM DESIGN OF CERAMIC-METAL FGMS-CYCLIC THERML LOADING PROBLEM

The materials are made with a graded composition and microstructure in the thickness direction from the ceramic side to the metal side. The cyclic thermal loading and high temperasure gradient environment are simulated by heating the ceramic surface with a cyclic heat flux input and cooling the metal surface with a flawing liquid niterogen. The thermal and thermo-elastic-plastic response of the materials is calculated using the isotropic hardening model and kinetic hardening model. Emphasis is     

TiC陶瓷滤片的制备及其性能研究

在对TiC陶瓷的性能及其制备工艺进行分析研究的基础上,利用SHS/PHIP技术制备了致密的TiC-TiB2复相陶瓷材料,并对材料进行切割加工成型和清洗,得到和所需滤片形状相同的TiC-TiB2复相陶瓷片,然后再根据TiC和TiB2化学性能的差异,用王水的强腐蚀性溶解其中的TiB2陶瓷相从而得到孔隙大小均匀的、性能优异的TiC陶瓷滤片.用该方法制备的TiC陶瓷滤片,孔隙的直径范围在2~3μm,分布均匀,可以在任何性质的液体中使用,也可用于熔融金属液的过滤.     

Vibration of functionally graded sandwich doubly curved shells using improved shear deformation theory

Nonlinear forced vibrations and natural frequency of sandwich functionally graded material doubly curved shallow shell with a rectangular base are investigated. The sandwich functionally graded material (FGM) doubly curved shell is subjected to a harmonic point load at centre. The sandwich doubly curved shell with homogeneous face sheets and FGM face sheets is considered respectively when the natural frequencies are studied. Reddy’s third order shear deformation theory is expanded in which stretching effects in thickness are considered by introducing the secant function. Hamilton’s principle and von-Karman type nonlinear geometric equation are applied to obtain partial differential equation of the FGM sandwich doubly curved shell. Comparative studies with other shear deformation theories are carried out to validate the present formulation. Navier method is used to discuss the natural vibration frequencies of the FGM sandwich doubly curved shell. Numerical simulation is applied to demonstrate the nonlinear dynamic responses of the FGM sandwich doubly curved shell. Multiple periods, quasi-period and chaos are detected for the dynamic system for different core thickness.     

微分求积法求解功能梯度材料梁的弯曲问题

基于Reddy三阶剪切变形理论,研究了功能梯度材料梁的线性弯曲问题,假设功能梯度材料性质只沿梁厚度方向变化,且服从幂函数规律,推导了问题的控制方程,考虑固支边界条件,并选用合适的计算结构,用微分求积法对其进行数值求解.利用数值结果考察了材料的梯度性质,载荷条件、细长比等对梁弯曲行为的影响.结果表明:相同条件下,FGM梁...     

Al—Ti系金属间化合物梯度功能材料抗热冲击性的研究

基于脆性材料临界应力理论推导出梯度材料抗热冲击阻抗的数值表达式，利用非线性有限元程序对Ａｌ－Ｔｉ系金属间化合物梯度材料耐热冲击性进行了数值模拟，采用激光加热，声发射试验手段对其梯度材料的抗热冲击性进行试验研究。     

陶瓷／金属梯度材料瞬态传热的有限差分分析

利用有限差分法对陶瓷/金属梯度材料的瞬态传热问题进行数值计算,得出了线性梯度材料在不同瞬时的温度分布以及不同梯度结构的梯度材料在不同时刻的温度分布。     

梯度热障涂层服役条件下的蠕变响应分析

利用数值方法研究了陶瓷/金属梯度功能热障涂层在服役条件下的热-力响应,同时考虑了梯度功能热障涂层各层的蠕变现象,数值研究表明在对梯度功能热障涂层进行热-力响应分析过程中,材料的蠕变现象是不能够忽略的,即使该层材料是富陶瓷材料。     

Thermoelectric properties of p-type (Bi_(0.15)Sb_(0.85))_2Te_3-PbTe graded thermoelectric materials with different barriers

The p-type (Bi0.15Sb0.85)2Te3 and PbTe are typical thermoelectric materials used for low and middle temperature range and functional graded materials (FGM) is an inevitable way to widen the working temperature range. Here two segments graded thermoelectric materials (GTM) consisting of (Bi0.15Sb0.85)2Te3, PbTe and different barriers were fabricated by the common hot pressure method. Metals Fe, Mg and Ni were used as barriers between the two segments. The diffusion of different barriers between the barriers and bases were analyzed by electron microprobe analysis (EMA). The phase and crystal structures were determined by X-ray diffraction analysis (XRD). The thermoelectric properties were measured at 303 K along the direction parallel to the pressing direction. The results show that the compositional diffusion occurs when there is no barrier at the interface of the two segments, and the diffusion of Pb is most obvious; as the barrier material, the diffusion of metals Fe, Mg and Ni between different bases is not very obvious, and the thermoelectric properties of GTM is much better than that of the original segment.     

Ti-C-Al-Fe2O3体系原位合成钢基复合材料组织与形貌研究

采用Ti-C-Al-Fe2O3反应体系,结合铸造和自蔓延高温合成（SHS）两种工艺,在湿砂型中浇注高温熔融的钢水,引燃SHS压块,从而发生自蔓延高温合成反应,生成了高硬度的陶瓷相TiC、Al2O3.通过改变Ti-C-Al-Fe2O3体系组分配比,探讨了体系在金属液内SHS反应对原位内生TiC、Al2O3尺寸与分布的影响.结果表明,随着过量Al元素的增加,陶瓷增强颗粒尺寸逐渐减小且分布更均匀;稀土CeO2加入量的增加,增强区更加致密,稀土CeO2添加剂含量为0.8%时制备的复合材料中原位形成的Al2O3、TiC颗粒尺寸较小,分布均匀.     

功能梯度材料的研究现状及应用

为了对功能梯度材料的发展趋势进行探讨，从功能梯度材料的概念、性质、开发背景、研究现状（包括材料设计、材料制备、材料性能评价）以及在航天、核领域、生物医学、化学、电磁、民用建筑等方面的广泛应用．对功能梯度材料以后的发展趋势进行了简单的预测．同时指出，功能梯度材料的研究应将基础理论研究同工艺制造及性能评价结合起来，以促进梯度材料技术更快发展．