A multiresolution homogenization of modal analysis with application to layered media

We apply multiresolution techniques to study the effective properties of boundary value problems. Conditions under which boundary values are preserved in the effective (‘homogenized') formulation are developed and discussed. Relations between the eigenfunctions and eigenvalues of the generic formulation and those of the effective formulation are explored. Applications to the construction of effective Green function in a complex lamination are discussed. The analytic results are demonstrated via numerical computations.     

Prediction of Austenitization and Homogenization of Q235 Plain Carbon Steel during Reheating Process

In this paper,the austenitization and homogenization process of Q235 plain carbon steel during reheating is predicted using a two-dimensional model which has been developed for the prediction of diffusive phase transformation(e,g.αto γ).The diffusion equations are solved within each phase(αand γ) and an explicit finite volume technique formulated for a regular hexagonal grid are used.The discrete interface is represented by special volume elements α/γ,an volume element α undergoes a transition to an interface state before it becomes γ.The procedure allows us to handle the displacement of theinterface while respecting the flux condition at the interface.The simulated microstructure shows the dissolution of ferrite particles in the austenite matrix is presented at different stages of the phase transflrmation.Specifically,the influence of the microstructure scale and the hwating rate on the phase transformation kinetics has been investigated.The experimental results agree well with the simulated ones.     

Homogenization of Carbides in Ni60/WC Composite Coatings Made by Fiber Laser Remelting

In the current study, the effect of laser remelting on homogenization of carbides in WC-reinforced Ni60 composite coatings was investigated. Ni60 + 50 wt% WC composite coatings were fabricated on the surface of Q550 steel by LDF4000-100 fiber laser device. First cladding layer was made by rectangle laser spot and then circular laser spot was utilized to remelt the coatings. Microstructure characteristics were investigated by optical microscope and scanning electron microscopy. Elemental distribution and phase constitution were analyzed by energy disperse spectroscopy and X-ray diffraction. The results showed that accumulation of residual WC particles was sufficiently eliminated under the effect of laser remelting. The irregularly shaped carbides in first cladding layer were transformed into well-distributed polygonal carbides by laser remelting. Statistical analysis indicated median size of reinforcement particles decreased from 35.40 to 5.62 µm. Microhardness of remelted region had a smooth profile and decreased by ?50 HV_0.1 than that of first cladding region. Homogenization of carbides in nickel composite coating was well realized by laser remelting.     

Variability response functions for effective material properties

The variability response function (VRF) is a well-established concept for efficient evaluation of the variance and sensitivity of the response of stochastic systems where properties are modeled by random fields that circumvents the need for computationally expensive Monte Carlo (MC) simulations. Homogenization of material properties is an important procedure in the analysis of structural mechanics problems in which the material properties fluctuate randomly, yet no method other than MC simulation exists for evaluating the variability of the effective material properties. The concept of a VRF for effective material properties is introduced in this paper based on the equivalence of elastic strain energy in the heterogeneous and equivalent homogeneous bodies. It is shown that such a VRF exists for the effective material properties of statically determinate structures. The VRF for effective material properties can be calculated exactly or by Fast MC simulation and depends on extending the classical displacement VRF to consider the covariance of the response displacement at two points in a statically determinate beam with randomly fluctuating material properties modeled using random fields. Two numerical examples are presented that demonstrate the character of the VRF for effective material properties, the method of calculation, and results that can be obtained from it.     

A two scale anisotropic damage model accounting for initial stresses in microcracked materials

In a recent study [15], we proposed a class of isotropic damage models which account for initial stresses. The present paper extends this approach to anisotropic damage due to growth of an arbitrarily penny-shaped microcracks system. The basic principle of the upscaling technique in the presence of initial stress is first recalled. Then, we derive a closed-form expression of the elastic energy potential corresponding to a system of arbitrarily oriented microcracks. It is shown that the coupling between initial stresses and damage is strongly dependent of the microcracks density and orientation. Predictions of the proposed model are illustrated through the investigation of the influence of initial stresses on the material response under non monotonous loading paths. Finally, by considering a particular distribution of microcracks orientation, described by a second order damage tensor, it is shown that the model is a generalization of the macroscopic damage model of Halm and Dragon [9], for which a physically-based interpretation is then proposed.     

Homogenization of metamaterials using full-wave simulations

We present a full-wave homogenization method to determine the effective material parameters of metamaterials by considering a spherical piece of metamaterial. We use a T-matrix approach that is accelerated by a multilevel fast multipole method that is stable at low frequencies. To determine the T-matrix of one inclusion in the metamaterial a Method of Moments surface integral equation is used that is also accelerated using another multilevel fast multipole method that is stable at low frequencies. We also derive a new closed-form expression to extract the effective material parameters from the T-matrix of the spherical piece of material. Examples verify the accuracy and limitations of the method. We show results for metamaterials comprising more than 40,000 particles.     

组件均匀化常数计算

扼要地介绍了先进均匀化理论的发展和由来，然后应用先进均匀化理论计算轻水堆中的组件均匀化常数，并对影响组件均匀化常数计算的各种因素作了较为详尽的分析、研究。计算实例表明，只要通过传统的组件计算，就可以计算出组件的等效均匀化常数，而不需要作全堆非均匀计算。     

泸州古隆起嘉陵江组油气成藏期的确定

通过流体包裹体分析及其均一温度的研究，并结合烃源岩演化史、储层地温史、岩心薄片镜下沥青的观察，按照油气分段捕获原理，确定四川盆地泸州古隆起嘉陵江组油气共存在4次成藏期，即中三叠世、中侏罗世前后、晚白垩世前后和喜山运动中晚期, 分别对应古油藏的形成与破坏期、志留系注气为主期、二叠系注气为主期和油气再分配期。同时，根据储层沥青在镜下的光学特征和在各类孔隙中的分布形态的观察，可定性确定泸州古隆起嘉陵江组油气存在多期注入和叠加的历史，并证实泸州古隆起核部曾经存在一个来自志留系烃源的印支期古油气藏。结果表明，综合考虑多种因素,应用流体包裹体确定油气成藏期的方法行之有效。     

5MW低功率堆主屏蔽设计与安全分析

本文介绍了5MW 低功率堆(5MW LPR)主屏蔽辐射场和温场的计算模型、方法和程序,给出了修改设计的主要计算结果。混凝土屏蔽层内表面的入射中子通量和γ通量均满足设计标准规定。最高温度、最大温升及最大温度梯度亦均符合规定要求。为证明温场程序的可靠性,将HFETR 混凝土屏蔽层内温度计算值与实测值作了比较,结果符合得很好。     

Homogenization technique of discrete atoms into smeared continuum

A homogenization technique was developed and presented to replace a discrete atomic domain by an equivalent continuum domain that could be discretized into finite elements. Equivalent material properties of the smeared continuum domain were computed from the atomic model. Using the developed technique, a computationally efficient analysis could be performed for a large size of domain by proper mixture of a discrete atomic region and a smeared continuum region. In addition, this technique provided a means for multi-scale analysis. Examples for static and dynamic analyses were provided to demonstrate the technique.