An inverse method for determining elastic material properties and a material interface

A numerical procedure which integrates optimization, finite element analysis and automatic finite element mesh generation is developed for solving a two-dimensional inverse/parameter estimation problem in solid mechanics. The problem consists of determining the location and size of a circular inclusion in a finite matrix and the elastic material properties of the inclusion and the matrix. Traction and displacement boundary conditions sufficient for solving a direct problem are applied to the boundary of the domain. In addition, displacements are measured at discrete points on the part of the boundary where the tractions are prescribed. The inverse problem is solved using a modified Levenberg-Marquardt method to match the measured displacements to a finite element model solution which depends on the unknown parameters. Numerical experiments are presented to show how different factors in the problem and the solution procedure influence the accuracy of the estimated parameters.     

The aesthetic and functional properties of enamel coatings on steel

In this work, the aesthetic and functional properties of enamelled steel panels were investigated.     

Application of the method of integral cross-sections for estimating the effective elastic properties of composite materials

We substantiate estimates of the upper and lower bounds of the effective elasticity modulus of piecewise homogeneous bodies. Using the method of integral cross-sections, we solve the elastic problem concerning the bending of a Kirchhoff inhomogeneous square plate and find the effective cylindrical stiffness of this inhomogeneous plate for various geometric parameters of inclusion, as well as determine the upper and lower bounds of the effective stiffness for the set of problems considered. Odessa State Polytechnic University, Odessa, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 5, pp. 807–813, September-October, 1997.     

周期性单胞复合材料有效弹性性能的边界力方法

均匀化方法是一种适应于周期性构造复合材料有效性能预测的有效方法。然而均匀化方程数学表达形式复杂, 均匀化方法很难直接应用通用有限元软件进行计算, 因此本文中提出一种便于求解均匀化方程的边界力方法, 利用高斯定理将原均匀化问题转化为普通的三维应力问题, 给出了单胞中不同材料交界面上作用的面分布力形式。运用有限元软件求解了均匀化系数, 预报了单向复合材料和三维四向编织复合材料的有效性能, 计算结果与实验吻合很好。      

Determination of elastic properties of triax composite materials

Triax composite materials are textile composites made of tows that are woven along three in-plane directions. For satellite applications, the structure is made of only one single layer of the triax fabric. As such, the structure has open holes within its boundaries. The challenge of the problem is how to determine the properties of a material/structure with open holes. This paper presents methods developed for the determination of elastic constants for this triax material. Both the equivalent energy approach and the experimental method are used to determine the elastic constants.     

Structure and properties of laser-cladded Ni-based amorphous composite coatings

A (N_i0.6Fe_0.4)₆₅B₁₈Si₁₀Nb₄C₃ amorphous composite coating has been fabricated on a mild steel substrate by a laser cladding process under different heat inputs. Observation of the structure and phase showed that the thickness of the coating decreased and the amorphous fraction increased when the laser cladding heat input was lower. The cooling rate increases when the heat input decreases, which favours the formation of amorphous phase. Microhardness and wear resistance test results indicated that a lower heat input led to higher microhardness and better wear resistance of the coating. An average microhardness of 1187.0 HV0.2 was obtained with a heat input of 69?J?mm^–1.     

A combined numerical method for determining the conductance of composite bodies

We propose a new numerical method (a combination of the method of grids with Rayleigh's method) which is very promising for the calculation of potential fields, fluxes, and conductance of composite bodies, especially in the case of components with sharply differing properties.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 2, pp. 284–291, February, 1977.     

Express method for determining the presence of defects of the surface of oxide-ceramic coatings

Using a multiresolution relevance function for the localization and subsequent segmentation of surface objects of oxide-ceramic coatings, we propose an express method for determining their number and sizes.     

A method for determining the residual stresses in fibrous composite materials

A method for determing the original residual stresses in a composite material is suggested, in which the stress/strain curves for the matrix and composite are compared. The changing residual stresses in the components of a model composite, which are dependent upon the amount of prestraining, were analysed; the model composite consisted of elastic fibres and an elastic-plastic matrix, having linear work hardening. Formulae are presented for determining the amount of prestraining needed to give rise to compressive residual stresses in the matrix equal to the compressive yield stress, and for determining the volume fraction of fibres in the composite when, after prestraining, the compressive residual stress equals the compressive yield stress. An experimental examination of the theoretical conclusions has been conducted using an aluminium alloy/steel wire composite.     

面外波纹对复合材料层合板弹性性能的影响

基于经典层合板理论（CLT）,提出一个多参数解析模型,定量研究了面外波纹缺陷对含波纹缺陷的复合材料层合板弹性模量、剪切模量和泊松比等弹性性能的影响。 结果表明:面外波纹对主弹性模量、Z向弹性模量、X - Z平面剪切模量和面内泊松比都产生了显著影响;对于碳纤维/环氧树脂材料体系算例,在特定波纹比和波纹区域范围内,面内泊松比出现了负值。该建模方法为研究波纹缺陷对复合材料层合板弹性性能影响提供了参考。      

甲基硅酸盐/硅酸盐复合膜的组成和性能研究

采用两步法制备甲基硅酸盐/硅酸盐复合膜,通过扫描电子显微镜(SEM)及EDS分析、红外光谱(FT-IR)分析、接触角测试、中性盐雾实验和极化曲线等对膜层的微观形貌、化学组成、疏水性及耐腐蚀性能进行了研究,并与单独的硅酸盐膜、甲基硅酸盐膜进行对比.利用电化学阻抗谱和等效电路拟合分析甲基硅酸盐/硅酸盐复合膜的防腐蚀机理.结果表明:甲基硅酸盐/硅酸盐复合膜层的外层与单独甲基硅酸钠膜的成分含量基本一致,但其微观形貌与单独甲基硅酸盐膜表面布满裂纹不同,复合膜层的表面均匀平整、没有开裂,膜层附着性好.单独硅酸盐膜为亲水性膜层,甲基硅酸盐/硅酸盐复合膜表现出疏水性,与单独硅酸盐膜相比,复合膜对腐蚀的阴极过程的抑制明显增强,极化阻抗增加至单独硅酸盐膜的5倍以上,复合膜的总阻抗值超过100 kΩ·cm2,复合膜的腐蚀电流密度比单独硅酸盐膜的降低了60％.     

Structure and properties of composite iron-based coatings obtained by the electromechanical technique

The influence of the electrolyte temperature and current density on the content of inclusions of powder particles in composite coatings obtained by the electrochemical technique has been investigated. It has been found that the wear resistance of iron coatings with inclusions of powder particles of aluminum, kaolin, and calcium silicate increases from 5 to 10 times compared to coating without inclusions of disperse particles, and the friction coefficient therewith decreases from 0.097 to 0.026. It has been shown that the mechanical properties of iron obtained by the method of electrochemical deposition depend on their fine structure. The regimes of deposition of iron-based coatings have been optimized. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 23–27, September–October, 2007.     

铝合金基体上等离子喷涂复相陶瓷涂层力学性能研究

针对铝活塞表面容易划伤的实际,利用机械球磨法和PVA造粒技术制备复合陶瓷粉末,采用等离子喷涂法在XGFH-3铝合金表面制备复合陶瓷涂层,涂层制备过程采用氧气送粉,不喷过渡层,测试了涂层结合强度、显微硬度、耐磨性等性能。结果表明,粉末球磨96h制备的涂层结合强度最高,达到了19.07MPa,复相陶瓷涂层的显微硬度最大值达到了HV0.11105,是基体的16倍,基体单位面积磨损量远高于喷涂试样,大约为涂层磨损量的8.5倍以上,最大达到了13.6倍。