Earticle

The purpose of this study is to analyze plates with Composite materials. so as to achieve this aim, in this study, homogenization method is adopted and supplement calculation program(H-Gen) is coded to easy access this method's results. Using the result, finite element analysis for plate's eigenvalues is performed and then it is compared to full 3d analysis. The results of this study are as follows; homogenization method is good choice to modelling composite material's properties and developed program is useful of analysing plates with composite materials. but the result has restriction because mixing process of composite materials is various. so succeeding study on this point of view is demanded.

Topology optimization is begun with layout optimization that is attributed to Rozvany and Prager of the 1960's. They claimed that structure was transformed into truss connecting all the nodes of finite element and optimized by control of its sectional modulus. But, this method is partial topology optimization. General layout optimal design appliable to continum structure was proposed by Bendsoe and Kikuchi in 1988. Topology optimization expresses material stiffness of structure into function of arbitrary variable. If this variable is 1, material exists but if this variable is 0, material doesn't exist. Therefore, topology optimization searches the distribution function of material stiffness for structure. There are a few researchs for simple engineering problem such as topology optimization of square plane structure or truss structure. So, This study applied to topology optimization of table liner for vertical roller mill that is the largest scale in the world. After table liner decreased by 20% of original weight, the structure analysis for first optimized model was performed.

The purpose of this study was to execute structural-acoustic coupling analysis for plates with composite materials using Homogenization method. Nowadays, many kinds of composite materials are used to protect noises through floor. but its dynamic characteristics are very complicate, From among noise factors, resonance sound is main reason for floor's solid noise. therefore, In this study, structural-acoustic coupling analysis for floor resonance sounds with Composite materials is established and that a case study is suggested with it.

구조물의 진동으로부터 구조음장을 예측하는 수치해석법에는 유한차분법(Finite Difference Method), 유한요소법(Finite Element Method), 경계요소법(Boundary Element Method) 등이 있다. 이러한 기법은 기본적으로 해석대상 구조물의 전 주파수 해석 범위에서의 진동모드와 진폭의 산정을 필요로 한다. 이 경우 진동모드는 주파수가 증가함에 따라 기하급수적으로 늘어나기 때문에 많은 계산 시간을 필요로 함으로 층간소음 예측에 적용하기에는 많은 어려움이 있었다. 따라서 본 연구에서는 복합재료 개별 소재 조합에 따른 복합재의 구조성능 예측 및 설계를 위한 기초 연구로서 수치해석을 위한 복합재료의 등가 물성치를 Rank적층 복합기법을 사용하여 제시하고, 이를 이용하여 복합재료의 특성을 예측하는 방안을 제시하도록 한다.

The aim of this research is to investigate computation method for composite material with Homogenization method. Nowadays, Noise Isolation techniques using composite material plate are studied in the various fields of industry. In this paper, Structural-Acoustic Coupling analysis is performed and characteristics of result is reviewed first. after that, Using computer program with arbitrary rank microstructure, Variation on composite material properties is considered.

Critical imperfections such as Debond, voids and cracks decrease performance of composite structure. Accurate evaluation of properties of composites with above imperfections prevents the catastrophic failure of designing components. In this study, finite element analysis is performed to determine the effective elastic properties of debonded unidirectional composites with Micro and Macro-mechanics approaches. Intensity of fully debonded fibers on the behavior of total composite material is studied. The applicability of the present work is explored for conventional fiber of boron with homogenized nano fullerene particle mixed polymer matrix. The effect of debonding of boron fiber reinforcement on the effective Young’s modulus and Poisson’s ratio of the composite is demonstrated. The study revealed that transverse Young’s modulus (E2) is extensively affected than longitudinal Young’s modulus due to debond.

This study significantly reduced the seismic analysis time of PCSG assembly by introducing a reduced model using homogenization and sub-structuring methods. The homogenization method was applied to the primary and secondary micro-channel sheets, and the sub-structuring method was applied to the PCSG module sets. Modal analysis and frequency response analysis were then performed to validate the accuracy of the reduced model. The analysis results were compared with the full model and it was confirmed that the reduced model provided almost the same analysis results as the full model. To verify the computational efficiency of the reduced model, the computational time was then compared with the full model, and it was confirmed that the modal analysis time was reduced by 3.42 times and the frequency response analysis time was reduced by 4.59 times.

In this paper, a procedure for evaluating the structural integrity of the PCSG (Printed Circuit Steam Generator) unit block is presented with a simplified FE (finite element) analysis technique by applying the homogenization method. The homogenization method converts an inhomogeneous elastic body into a homogeneous elastic body with same mechanical behaviour. This method is effective when the inhomogeneous elastic body has repetitive microstructures, and thus the method was applied to the sheet assembly among the PCSG unit block components. From the method, the homogenized equivalent elastic constants of the sheet assembly were derived. The validity of the determined material properties was verified by comparing the mechanical behaviour with the reference model. Thermo-mechanical analysis was then performed to evaluate the structural integrity of the PCSG unit block, and it was found that the contact region between the steam header and the sheet assembly is a critical point where large bending stress occurs due to the temperature difference.

To compute a permeability coefficient along a rough fracture that takes into account the fracture geometry, this study performed detailed measurements of fracture roughness using a confocal laser scanning microscope, a quantitative analysis of roughness using a spectral analysis, and a homogenization analysis to calculate the permeability coefficient on the microand macro-scale. The homogenization analysis is a type of perturbation theory that characterizes the behavior of microscopically inhomogeneous material with a periodic boundary condition in the microstructure. Therefore, it is possible to analyze accurate permeability characteristics that are represented by the local effect of the facture geometry. The Cpermeability coefficients that are calculated using the homogenization analysis for each rough fracture model exhibit an irregular distribution and do not follow the relationship of the cubic law. This distribution suggests that the permeability characteristics strongly depend on the geometric conditions of the fractures, such as the roughness and the aperture variation. The homogenization analysis may allow us to produce more accurate results than are possible with the preexisting equations for calculating permeability.

The frontal crash optimization of S-shaped closed-hat section member using the homogenization method, design of experiment (DOE) and response surface method (RSM) was studied. The optimization to effectively absorb more crash energy was studied to introduce the reinforcement design. The main focus of design was to decide the optimum size and thickness of reinforcement. In this study, the location of reinforcement was decided by homogenization method. Also, the effective size and thickness of reinforcements was studied by design of experiments and response surface method. The effects of various impact velocity for reinforcement design were researched. The high impact velocity reinforcement design showed to absorb the more crash energy than low velocities design. The effect of size and thickness of reinforcement was studied and the sensitivity of size and thickness was different according to base thickness of model. The optimum size and thickness of the reinforcement has shown a direct proportion to the thickness of base model. Also, the thicker the base model was, the effect of optimization using reinforcement was the bigger. The trend curve for effective size and thickness of reinforcement using response surface method was obtained. The predicted size and thickness of reinforcement by RSM were compared with results of DOE. The results of a specific dynamic mean crushing loads for the predicted design by RSM were shown the small difference with the predicted results by RSM and DOE. These trend curves can be used as a basic guideline to find the optimum reinforcement design for S-shaped member.

The development of fast reactors with complex designs and operation status requires more accurate and effective simulation. The Monte-Carlo method can generate multi-group cross-sections in arbitrary geometry without approximation on resonances treatment and leads to good results in combination with diffusion codes. However, in previous studies, the coupling of Monte-Carlo generated multi-group cross-sections (MC-MGXS) and transport solvers has shown relatively large biases in fast reactor problems. In this paper, the main contribution to the biases is proved to be the neglect of the angle-dependence of the total cross-sections. The flux-moment homogenization technique (MHT) is proposed to take into account this dependence. In this method, the angular dependence is attributed to the transfer cross-sections, keeping an independent form for the total sections. For the MET-1000 benchmark, the multi-group transport simulation results with MC-MGXS generated with MHT are improved by 700 pcm and an additional 120 pcm with higher order scattering. The factors that cause the residual bias are discussed. The core power distribution bias is also significantly reduced when MHT is used. It proves that the MCMGXS with MHT can be applicable with transport solvers in fast reactor analysis.

The homogenization method is applied to maximize crash energy absorption for a given volume. Tow simple example problems, one straight-type frame and the other S-type frame, have been analyzed using the method. The results show that the crash energy absorption of a new design with holes is increased and that the method is more effective for straight-type frame. Optimization study under european 35mph 40% offset impact condition is conducted, and the original design and a new design with holes for an offset problem are compared for crash energy absorption.

본 연구에서는 RVE(Representative Volume Element) 기반의 2단계 멀티스케일 균질화 기법을 정립하여 평직 탄소섬유 복합재료의 기계적 강성을 예측하였다. 미시적 구조를 모사하기 위해 해석 범위를 Micro-mesoscale로 구분하여 단계적 균질화 과정을 수행하였다. 먼저 1차 균질화를 통해 T300 탄소섬유와 K51 에폭시 수지 간의 상호작용이 반영된 섬유 다발(Yarn)의 이방성 유효 물성을 도출하였으며, 이를 평직 구조 모델에 적용하여 최종적인 유효 강성을 산출하였다. 제안된 프레임워크의 검증을 위해 ASTM D3039 표준 인장 시험을 수행한 결과, 실험값(68.3 GPa)과 해석값(73.94 GPa) 사이에서 약 8.25%의 오차를 확인하였다. 이는 주기적 경계 조건(PBC)에 따른 연속체 가정 및 실제 공정 결함의 배제에 기인한 것으로 판단된다. 본 연구를 통해 확립된 해석 기법은 복잡한 직조 구조 복합재의 초기 설계 단계에서 물성 예측 기술로서의 유효성을 입증하였다.

This study numerically predicted the mechanical stiffness of plain weave CFRP by establishing a two-step multiscale homogenization technique based on Representative Volume Elements (RVE). To simulate the complex woven structure, a stepwise homogenization process was performed across micro and mesoscales. First, the anisotropic effective properties of the yarn, reflecting the interaction between T300 fiber and K51 resin, were derived. These were then applied to a mesoscale RVE model to calculate the final effective stiffness. To verify the framework, tensile tests were conducted per ASTM D3039. The experimental Young's modulus (68.3 GPa) and the FEA result (73.94 GPa) showed a relative error of approximately 8.25%. This difference is attributed to the infinite continuum assumption of periodic boundary conditions (PBC) and the exclusion of manufacturing defects. The established multiscale technique demonstrated excellent effectiveness in predicting the behavior of woven composites during the initial design phase.

The demand for electric vehicles has increased because of environmental regulations. The lithium-ion battery, the most widely used type of battery in electric vehicles, is composed of a cathode, an anode, and an electrolyte. It is manufactured according to the pole plate, assembly, and formation processes. To improve battery performance and increase manufacturing efficiency, the manufacturing process must be optimized. To do so, simulation can be used to reduce wasted resources and time, and a finite-element method can be utilized. For high simulation quality, it is essential to reflect the material properties of the electrode by considering the pores. However, the material properties of electrodes are difficult to derive through measurement. In this study, the representative volume element method, which is a homogenization method, was applied to estimate the representative material properties of the electrode considering the pores. The representative volume element method assumes that the strain energy before and after the conversion into a representative volume is conserved. The method can be converted into one representative property, even when nonhomogeneous materials are mixed in a unit volume. In this study, the material properties of the electrode considering the pores were derived. The results should be helpful in optimizing the electrode manufacturing process and related element technologies.

In this study, homogenization method combined with the effective interface model for the characterization of properties of the nanoparticulate composites is developed. In order to characterize particle size effect of nanocomposites, effective interface model has been developed. The application range of analytical micromechanics approach is limited because a simple analytical approach is valid only for simple and uniform geometry of fiber particles. Therefore this study focuses on the analysis of mechanical properties of the effect interface through the continuum homogenization method instead of using analytical micromechanics approach. Using the homogenization method, elastic stiffness properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. The suggested homogenization method is expected to be applied to optimization problems for nanocomposite design.

기존의 멀티스케일 유한요소법(Multiscale finite element, FE² )은 거시 스케일의 모든 적분점에서 대표 체적요소(representative volume element, RVE)의 미시 경계치 문제를 반복적으로 계산하기 때문에 긴 해석 시간과 많은 데이터 저장 공간을 필요로 한다. 이를 해결하기 위해 본 연구에서 평균장 균질화 데이터 기반 멀티스케일 해석 기법을 개발하였다. 데이터 기반 전산역학(data-driven computational mechanics, DDCM) 해석은 변형률-응력 데이터 셋을 직접적으로 사용하는 모델-프리(model-free)접근 방식이다. 멀티스케일 해석을 수행하기 위해, 평균장 균질화(mean-field homogenization)를 활용하여 복합재의 미세구조에 대한 변형률-응력 데이터베이스(database)를 효율적으로 구축하고, 이를 기반으로 데이터 기반 전산역학 시뮬레이션을 수행하였다. 본 논문에서는 개발한 멀티 스케일 해석 프레임워크(framework)를 예제에 적용하여, 초탄성(hyperelasticity) 복합재의 미세 구조를 고려한 데이터 기반 전산역학 시뮬레이션 결과를 확인하였다. 따라서, 데이터 기반 전산역학 접근 방식을 활용한 멀티스케일 해석기법은 다양한 재료 및 구조에 적용될 수 있으며, 멀티스케일 해석 연구 및 응용 가능성을 열어줄 것으로 기대된다.

The classical multiscale finite element (FE² ) method involves iterative calculations of micro-boundary value problems for representative volume elements at every integration point in macro scale, making it a computationally time and data storage space. To overcome this, we developed the data-driven multiscale analysis method based on the mean-field homogenization (MFH). Data-driven computational mechanics (DDCM) analysis is a model-free approach that directly utilizes strain-stress datasets. For performing multiscale analysis, we efficiently construct a strain-stress database for the microstructure of composite materials using mean-field homogenization and conduct data-driven computational mechanics simulations based on this database. In this paper, we apply the developed multiscale analysis framework to an example, confirming the results of data-driven computational mechanics simulations considering the microstructure of a hyperelastic composite material. Therefore, the application of data-driven computational mechanics approach in multiscale analysis can be applied to various materials and structures, opening up new possibilities for multiscale analysis research and applications.

To study numerically the mechanical behaviors of advanced composite materials considering the microscopic phenomena as well as the macroscopic properties and behaviors, a multi-scale modeling and analysis by the mathematical homogenization method with the help of the finite element method(FEM) are reviewed. The hierarchical modeling strategy and the formulation are briefly described first to give some idea of the multi-scale framework. The latter half of this article focuses on the verification of the multi-scale analysis by the homogenization method in its applications to real advanced materials. The first example is the verification of the predicted macroscopic(homogenized) properties based on the microstructure of porous ceramics. In spite of the complexity of the random microstructure, the error between the predicted and the measured values was only 1%. Next, two applications to the process simulation of fiber reinforced polymer matrix composites are presented. The permeability characteristics are evaluated for sheared weave fabrics for resin transfer molding(RTM) simulation, and the thermoforming of FRTP sheet is analyzed considering the large deformation of the knit structure during the deep-draw forming was verified by comparison with the experimental results.

This study proposes a computational approach to accurately predict the deformation behavior of polycrystalline stainless steel (STS 316L) considering the effects of microstructure and texture evolution under cryogenic temperature (-196°C). While single crystal plasticity models effectively describe deformation response of single crystals, their accuracy and computational efficiency diminish when applied to polycrystalline materials due to the complexity of grain interactions and texture evolution. To overcome these limitations, we developed a dislocation-densitybased crystal plasticity model integrated with a computational homogenization framework. A representative volume element (RVE) and periodic boundary conditions (PBC) were employed to accurately capture complex microstructural features such as grain morphology, grain boundary effects, and texture evolution. The proposed model was implemented in a commercial finite-element software (Abaqus) using a user-defined material subroutine (UMAT), and its predictive capabilities were verified against experimental tensile test results performed at -196°C. The results demonstrate that the model effectively predicts the hardening behavior observed experimentally and qualitatively captures the characteristic serration phenomena. However, further improvements are needed to achieve quantitative accuracy regarding the amplitude and frequency of the serrations.