梯度功能材料特性评价技术的研究现状

本文对具有热应力缓和特性的梯度功能材料(functionally Gradient Materials,FGM)的隔热性能、热疲劳特性、耐热冲击特性、热应力缓和性能以及梯度层的力学性质的评价原理、方法以及评价装备的现状进行了阐述;对梯度功能材料特性评价技术其发展方向及在我国的发展趋势也进行了简要论述。     

W-Mo-Ti功能梯度材料的断口形貌研究

目前，金属-金属功能梯度材料的研究开发是材料科学领域的一大热点，但对采用共沉降法制备的金属-金属功能梯度材料微观组织的研究还很少，因而对此种功能梯度材料进行显微分析显得尤为重要．采用扫描电子显微镜(SEM)和能谱仪(EDS)，对共沉降法制备的W—Mo—Ti系功能梯度材料的显微组织、断口形貌进行了较详细的研究．     

梯度功能材料热应力缓和优化设计

在研究梯度功能材料效应力缓和优化问题时,提出了一个分析梯度功能材料中间层体积组分规律的关系式．并运用这个关系式．结合优化理论,对效应力缓和梯度功能材料进行了计算,并得出一些对梯度功能材料设计有价值的结论。     

功能梯度材料的进展

功能梯度材料是一种新型复合材料，介绍了功能梯度材料的概念，制备工艺，应用领域，设计方法及其特征评价，并讨论了功能梯度材料研究的主要方面。     

一次铸造成型功能梯度材料

爱尔兰都柏林大学（UCD）的研究人员开发出一种廉价的一次铸造成型功能梯度材料的方法。功能梯度材料在同一部件中，可根据部件不同部位的性能要求形成不同的材料性能。这种称为“铸造转移铸造”（CastDecantCast）（CDC）的工艺，可在一道铸造工序中生产功能梯度材料。     

梯度功能材料的性能评价研究

梯度功能材料(FGM)是组成和性能呈连续变化的先进材料。FGM的性能评价是设计和制备优质FGM的重要内容。在此详细叙述了当前FGM的力学性能、热震性能、压缩性能和热处理性能的评价方法及实验手段，提出了FGM性能评价的发展方向。     

先进材料及其应用研究进展

论述了极限材料、智能材料、复合材料及梯度功能材料等先进材料的开发与应用研究进展。超微粒子和纳米材料等极限材料具有巨大的表面积,因而具有特殊的磁、光、电、热特性,已成为新材料 的基本组元;非晶材料则具有很高的强度,良好的电磁特性和耐腐蚀特性。形状记忆材料、压电材料、电（磁）流变体、光纤、储氢金属等智能材料具有特殊的热、力、电、磁、光效应,是智能元件和智能结构的重要组分。定向凝固复合材料属平衡反应型复合材料,晶界少,具有良好的稳定性和抗疲劳性,是理想的高温材料。梯度功能材料的成分、组织及化学、力学、热学性能也呈梯度变化,可缓和应力集中,延长使用寿命,成分的梯度变化,也赋予材料一些特殊性质,材料制作与性能评价方法将是梯度功能材料今后研究的重点。     

梯度功能材料热弹性应力的分析方法

本文介绍了近年来国外有关梯度功能材料热弹性应力问题的最新研究方法，并对其方法特点进行了评述．     

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．     

梯度功能材料的制造方法及应用

梯度功能材料是组分和结构呈连续变化的先进材料，由于它具有优异的性能和特殊的功能，使其填补了合金化材料和复合材料应用领域的空白，具有广阔的应用前景。本文详细叙述了梯度功能材料的设计思想和制造方法，论述了梯度功能材料的应用领域及其研究现状。     

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。     

非卤直接法制备硅氧烷材料的研究进展

评介了非卤直接法一步合成硅氧烷技术的研究状况,指出了今后的研究方向。硅粉与醇类、醚类等直接反应,非卤直接法制备硅氧烷材料,是解决传统制备技术低效率与高污染弊端,并降低制造成本的绿色换代技术手段,其发展潜力和应用前景巨大。     

热压烧结法制备钨铜复合材料的工艺研究

铜钨复合材料是以铜、钨元素为主的一种两相结构假合金,广泛应用于电接触材料,电子封装和热沉材料.作者研究了采用轴向热压烧结来制备纳米W-15%Cu复合材料的方法,分析了工艺参数对该复合材料性能的影响及其影响机理.实验为获得超细晶粒显微组织和优异均匀性纳米W-15%Cu复合材料提供了重要的实验基础和依据.     

Dynamic characteristics analysis for the random FGM beam

The uncertainty in effective physical properties is inherent since the manufacturing and fabrication processes of FGM (Functionally Graded Materials) are extremely complex. Based on the high-order shear deformation theory, the finite element model is developed for the FGM beam with material properties varying in the axial direction, taking into account the shear deformation. Using the moment method of the random function, the statistics of dynamic characteristics for the FGM beam is calculated, and the effect of random constituent material properties on the dynamic characteristics for the FGM beam is systemically investigated in the case of different volume fraction indexes. The Monte-Carlo method is used to verify the presented method. Numerical results show the dominant effect of the constituent volume fraction index on the dispersion in dynamic characteristics, and the dispersion in modal frequencies becomes higher when more material properties are considered random, and the dispersion in mode shapes depends mainly on the randomness of constituent material mass densities, while the volume fraction index and random elastic modulus of constituent materials have little influence on mode shapes.     

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.     

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.     

Influence of Inclusion Shape on Thermoelasto-Plastic Optimun Design of Ceramic Metal Functionally Graded Materials

A nonlinear finite element method is applied to observe how inclusion shape influence the thermal response of a ceramic-metal functionally graded material (FGM). The elastic and plastic behaviors of the layers which are two-phase isotropic composites consisting of randomly oriented elastic spheroidal inclusions and a ductile matrix are predicted by a mean field method. The prediction results show that inclusion shape has remarkable influence on the overall behavior of the composite. The consequences of the thermal response analysis of the FGM are that the response is dependent on inclusion shape and its composition profile cooperatively and that the plastic behavior of each layer should be taken into account in optimum design of a ceramic-metal FGM.     

Hardness Measurement of (TiB_2-TiAl)/TiAl Symmetrically Function Gradient Materials

( TiB2-TiAl)/TiAl symmetrically function gradient materials ( FGM) were prepared by spark plasma sintering ( SPS). Owing to the difference, of the thermal expansion coefficients between TiB2 and TiAl, a compressive surface stress was introduced to the FGM fry the thermal expansion mismatch. The hardness values of the uniform materials and the FGM were tested, respectively. For the FGM with a compressive surface stress, hardness is obviously superior to that of the uniform material. When the FGM was subjected to heat treatment, the hardness decreased due to a partial relaxation of the compressive surface stress.     

Genetic Algorithm for the Thermal Stresses Optimum Design of Functionally Gradient Material Plate

Based on the thermal stress distribution for functionally gradient material (FGM) plates, a Genetic Algorithm (GA) method for the thermal stresses optimum design of FGM plate with computer technologies is given. The minimum thermal stresses combination distribution for FGM is obtained.     

功能梯度材料零件快速成型方法

针对现有快速成型技术难以成型具有复杂材料属性的多维功能梯度材料零件问题,以功能梯度材料零件为研究对象,研究了一维、二维及多维功能梯度材料零件的快速成型方法,并应用该方法选取一维、二维功能梯度材料零件进行了实验验证。