Equivalent material properties of perforated metamaterials based on relative density concept

Mohammad Reza Barati,Hossein Shahverdi 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.5

In this paper, the equivalent material properties of cellular metamaterials with different types of perforations have been presented using finite element (FE) simulation of tensile test in Abaqus commercial software. To this end, a Representative Volume Element (RVE) has been considered for each type of cellular metamaterial with regular array of circular, square, oval and rectangular perforations. Furthermore, both straight and perpendicular patterns of oval and rectangular perforations have been studied. By applying Periodic Boundary conditions (PBC) on the RVE, the actual behavior of cellular material under uniaxial tension has been simulated. Finally, the effective Young’s modulus, Poisson’s ratio and mass density of various metamaterials have been presented as functions of relative density of the RVE.

Study of the Effectiveness of the RVEs for Random Short Fiber Reinforced Elastomer Composites

Lili Chen,Boqin Gu,Jianfeng Zhou,Jiahui Tao 한국섬유공학회 2019 Fibers and polymers Vol.20 No.7

The effectiveness of the representative volume elements (RVEs) established by a modified random sequentialadsorption method for random short fiber reinforced elastomer composites (SFECs) was studied. The RVE is considered tobe effective when the RVE’s fiber orientation is isotropic. And the effectiveness of the RVEs was verified by evaluating themechanical properties in different loading directions based on the finite element method. The results show that the fibernumber N=4000 can be regarded as a steady threshold for the isotropy of the fiber orientation in RVEs with various fiberaspect ratios and dilute volume fraction.

Improvement of the Representative Volume Element Method for 3-D Scaffold Simulation

Cheng Lv-Sha,Kang Hyun-Wook,Cho Dong-Woo The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

Predicting the mechanical properties of the 3-D scaffold using finite element method (FEM) simulation is important to the practical application of tissue engineering. However, the porous structure of the scaffold complicates computer simulations, and calculating scaffold models at the pore level is time-consuming. In some cases, the demands of the procedure are too high for a computer to run the standard code. To address this problem, the representative volume element (RVE) theory was introduced, but studies on RVE modeling applied to the 3-D scaffold model have not been focused. In this paper, we propose an improved FEM-based RVE modeling strategy to better predict the mechanical properties of the scaffold prior to fabrication. To improve the precision of RVE modeling, we evaluated various RVE models of newly designed 3-D scaffolds using FEM simulation. The scaffolds were then constructed using microstereolithography technology, and their mechanical properties were measured for comparison.

Improvement of the Representative Volume Element Method for 3-D Scaffold Simulation

Lv-Sha Cheng,Hyun-Wook Kang,Dong-Woo Cho 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

Predicting the mechanical properties of the 3-D scaffold using finite element method (FEM) simulation is important to the practical application of tissue engineering. However, the porous structure of the scaffold complicates computer simulations, and calculating scaffold models at the pore level is time-consuming. In some cases, the demands of the procedure are too high for a computer to run the standard code. To address this problem, the representative volume element (RVE) theory was introduced, but studies on RVE modeling applied to the 3-D scaffold model have not been focused. In this paper, we propose an improved FEM-based RVE modeling strategy to better predict the mechanical properties of the scaffold prior to fabrication. To improve the precision of RVE modeling, we evaluated various RVE models of newly designed 3-D scaffolds using FEM simulation. The scaffolds were then constructed using microstereolithography technology, and their mechanical properties were measured for comparison.

머신 러닝을 사용한 열전도 문제에 대한 기능적 등급구조 설계

문윤호,김철웅,박순옥,유정훈,Moon, Yunho,Kim, Cheolwoong,Park, Soonok,Yoo, Jeonghoon 한국전산구조공학회 2021 한국전산구조공학회논문집 Vol.34 No.3

본 연구는 효과적인 열전도를위한 거시적 구조 구성과 단위 구조 변화의 동시 설계를 위한 위상 최적화 방법을 제시한다. 거시적 규모의 구조 내에서 위치에 따른 단위 구조의 형태 변화는 거시적 규모뿐만 아니라 미시적 단위의 설계도 가능하며 등방성 단위 구조를 사용하는 것보다 더 나은 성능을 제공할 수 있다. 이 결과로 두 구성을 결합한 기능적으로 등급의 복합 구조가 생성된다. 대표 체적 요소 (RVE) 방법은 형태 변화에 따른 다중 재료 기반 단위 구조의 다양한 열전도 특성을 얻기 위해 적용된다. RVE 분석 결과를 바탕으로 머신 러닝 기법을 이용하여 특정 형태의 단위 구조물의 물성치를 도출할 수 있다. 거시적 위상 최적화는 기존의 SIMP 방법을 사용하여 수행되며, 거시 구조를 구성하는 단위 구조는 동시 최적화 과정에 따라 열전도 성능을 향상시키기 위한 다양한 형태를 가질 수 있다. 제안된 방법의 효과를 확인하기 위해 열 컴플라이언스 최소화 문제의 수치예가 제공된다. This study introduces a topology optimization method for the simultaneous design of macro-scale structural configuration and unit structure variation to ensure effective heat conduction. Shape changes in the unit structure depending on its location within the macro-scale structure result in micro- as well as macro-scale design and enable better performance than using isotropic unit structures. They result in functionally graded composite structures combining both configurations. The representative volume element (RVE) method is applied to obtain various thermal conductivity properties of the multi-material based unit structure according to its shape change. Based on the RVE analysis results, the material properties of the unit structure having a certain shape can be derived using machine learning. Macro-scale topology optimization is performed using the traditional solid isotropic material with penalization method, while the unit structures composing the macro-structure can have various shapes to improve the heat conduction performance according to the simultaneous optimization process. Numerical examples of the thermal compliance minimization issue are provided to verify the effectiveness of the proposed method.

Efficient generator of random fiber distribution with diverse volume fractions by random fiber removal

Park, Shin-Mu,Lim, Jae Hyuk,Seong, Myeong Ryun,Sohn, Dongwoo Elsevier 2019 Composites Part B, Engineering Vol.167 No.-

<P><B>Abstract</B></P> <P>In this paper, we propose a simple and efficient generator of random fiber distribution with diverse fiber volume fractions ( <SUB> V f </SUB> ) for unidirectional composites by a random fiber removal technique. From the representative volume element (RVE) consisting of 100 fibers that have a maximum <SUB> V f </SUB> of about 65% in this work, also termed the master model, we randomly eliminate fibers to match the predefined <SUB> V f </SUB> ranging from 60%, 55%, 45%, 35%, 25%, 15%, and 5%, which are lower than that of the master model. Accordingly, 100 RVE samples for each <SUB> V f </SUB> can be constructed in a straightforward manner.</P> <P>To demonstrate the performance of the proposed algorithm, its fiber locations are verified in terms of statistical spatial metrics, such as the nearest neighbor orientation, Ripley's K function, and pair distribution function. Furthermore, the elastic properties and the anisotropic ratios of the generated RVEs are investigated and compared to those of other random fiber generation algorithms.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Efficient and powerful RVE generation with diverse volume fractions is achieved by random fiber removal technique. </LI> <LI> Once the finite element (FE) model of the master model is created, no further finite element (FE) model generation is required. </LI> <LI> By simply reassigning the material properties of the FE models for the fiber to those for the matrix, a new RVE can be generated. </LI> <LI> Through statistical spatial and physical metric evaluation, the performance of random removal technique proposed is verified. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Study on Anisotropic Characteristics of Representative Elementary Volumes of Rock Mass

( Jianping Chen ),( Ying Liu ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Asymmetric, anisotropy, irregular, discontinuity is the basic properties of rock mass due to the fractures extensive universal developed, that gives rise to complicated physical and mechanical behavior of rock mass, strength of rock mass is influenced by size effect, representative elementary volumes (RVE) has a very close relationship with the size effect of the rock mass, RVE value is calculated in different direction, the result shows that the RVE also has the anisotropic characteristics. Field observation value of fractures is obtained by the method of sampling windows during the field geological survey, then, the statistical homogenous zones is demarcated based on Miller’s method, the bias of observed trace length, orientation and spacing of fractures is corrected in each homogenous unit, and then a three dimensional fracture network models for different homogenous unit are established by using Monte-Carlo method. The REV of rock mass is calculated based on the three-dimensional fracture network. Based on the 3D fracture network model, the volume fracture intensity index (P32) and multisampling non-parametric statistical test method are used to analyze the REV characteristics in different sampling directions. With the increase of the number of fracture groups, the anisotropic characteristics of REV become more obvious. Acknowledgments This work was supported by the State key program of National Natural Science Fund of China-Yunnan Joint Fund (Grant No. U1702241).

Simulation and Parameter Design of the Groove Structure on the Metal/GFRP Bonding Joint Using the RVE Model

Zhenhang Kang,Yongpeng Lei,Zhonghua Shi,Quanwei Song,Jifeng Zhang 한국섬유공학회 2022 Fibers and polymers Vol.23 No.12

Co-cured metal/GFRP joints with groove structures can maintain the integrity of GFRP and the continuity of glassfibres. To improve the performance of the groove structure, it is necessary to design groove parameters (groove depth, width,etc.). Due to the repetitive structure of the groove morphology, the representative volume element (RVE) was used to buildthe model. Then, shearing and pulling-out simulations of the groove structures were carried out, and the simulated resultswere compared with the experimental results. In addition, the influence of groove depth and width on the bondingperformance of the structures was studied, and the optimal result was obtained (width: 1.00 mm, depth: 0.75 mm). Finally, the±45 ° groove structure (width: 1.414 mm, depth: 1.00 mm) was equivalent to a 0-thickness cohesive element layer throughthe stiffness equivalent method, and the results were compared with the previous test (DCB and shear test) results, and similarresults were obtained. The equivalent analysis not only verifies the applicability of the stiffness equivalent method but alsoverifies the practicability of the groove structure obtained by the RVE model.

Probabilistic multiscale modeling of 3D randomly oriented and aligned wavy CNT nanocomposites and RVE size determination

Zhu, Fei-Yan,Jeong, Sungwoo,Lim, Hyoung Jun,Yun, Gun Jin Elsevier 2018 Composite structures Vol.195 No.-

<P><B>Abstract</B></P> <P>This paper presents a probabilistic multiscale approach to model the random spatial distribution of local elastic properties arising from the heterogeneous waviness and orientation of CNT fillers within a 3D microscale continuum representative volume element (RVE) of a CNT-reinforced polymer matrix. The proposed direction-sensitive 3D Karhunen-Loève expansion (KLE) provides the basis to simulate stochastic variations in the CNT orientations rather than assuming a perfect alignment. Computational homogenization analyses are carried out to investigate the effects of the statistical parameters of random CNT waviness on the microscale continuum RVE size. The proposed probabilistic multiscale modelling framework allows to consider the uncertainty associated with the use of CNT nanocomposites for various applications.</P>

Elastic properties of CNT- and graphene-reinforced nanocomposites using RVE

Dinesh Kumar,Ashish Srivastava 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.5

The present paper is aimed to evaluate and compare the effective elastic properties of CNT- and graphene-based nanocomposites using 3-D nanoscale representative volume element (RVE) based on continuum mechanics using finite element method (FEM). Different periodic displacement boundary conditions are applied to the FEM model of the RVE to evaluate various elastic constants. The effects of the matrix material, the volume fraction and the length of reinforcements on the elastic properties are also studied. Results predicted are validated with the analytical and/or semiempirical results and the available results in the literature. Although all elastic stiffness properties of CNT- and graphene-based nanocomposites are found to be improved compared to the matrix material, but out-of-plane and in-plane stiffness properties are better improved in CNT- and graphene-based nanocomposites, respectively. It is also concluded that long nanofillers (graphene as well as CNT) are more effective in increasing the normal elastic moduli of the resulting nanocomposites as compared to the short length, but the values of shear moduli, except G23 of CNT nanocomposite, of nanocomposites are slightly improved in the case of short length nanofillers (i.e., CNT and graphene).