• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.4
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• pp.319-326
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• 2008

In this study, we investigate the deformation behavior of F.C.C. single crystals containing micro- or submicron-sized voids by using three dimensional finite element methods. The locally homogeneous constitutive model for the rate-dependent crystal plasticity is integrated based on the backward Euler method and implemented into a finite element program (ABAQUS) by means of user-defined subroutine (UMAT). The unit cell analysis has been investigated to study the effect of stress triaxiality and crystallographic orientations on the growth and coalescence of voids in F.C.C. single crystals.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.487-494
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• 2018

The purpose of the present paper is to study the bending and free vibration of Functionally Graded Material (FGM) plate using user-defined material subroutine on the finite element software ABAQUS. The FGM plate is simply supported and subjected to sinusoidal and uniform load. The Poisson's ratio is kept constant. The results obtained compared to those available in the literature show the convergence, the exactitude and the efficiency of the method used with various power index of the materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.596-599
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• 1997

In this study, the flow control system with shape memory alloy in jet engine inlet was suggested to adjust the shock boundary layer interact~on for supersonic flight system. It consisted of the flap with shape memory alloy, spar with steel, and fixing device with aluminum alloy. The advantages of itself are a simple configuration, a passive air circulation by using the flap deflection due to pressure difference, and no need to be required the auxiliary devices. Finite element analysis was conducted to predict the thenno-mechanical behavlor of the flap system with shape memory alloy. The user-defined subroutine UMAT was implemented with ABAQUS to accon~modate the thermo-mechanical constitutive relation of shape memory alloy.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.778-783
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• 2006

This study investigates the ultimate behavior of reinforced concrete beams by means of practical nonlinear finite element (FE) analyses. Uniaxial constitutive models for the concrete and steel material are selected in this study. The adopted material model is integrated into the ABAQUS fiber beam elements through a user-defined material subroutine (UMAT). Within a developed nonlinear finite element framework, the FE results have been compared to experimental results reported by other researchers. It has been found that the proposed finite element model is capable of predicting the initial cracking load level, the yield load, the ultimate load, and the crack distribution with acceptable accuracy.

• Structural Engineering and Mechanics
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• v.67 no.6
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• pp.643-658
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• 2018

In this paper, we introduce a new framework for running the finite element (FE) packages inside an online Loop together with MATLAB. Contrary to the Hardware-in-the-Loop techniques (HiL), in the proposed Software-in-the-Loop framework (SiL), the FE package represents a simulation platform replicating the real system which can be out of access due to several strategic reasons, e.g., costs and accessibility. Practically, SiL for sophisticated structural design and multi-physical simulations provides a platform for preliminary tests before prototyping and mass production. This feature may reduce the new product's costs significantly and may add several flexibilities in implementing different instruments with the goal of shortlisting the most cost-effective ones before moving to real-time experiments for the civil and mechanical systems. The proposed SiL interconnection is not limited to ABAQUS as long as the host FE package is capable of executing user-defined commands in FORTRAN language. The focal point of this research is on using the compiled FORTRAN subroutine as a messenger between ABAQUS/CAE kernel and MATLAB Engine. In order to show the generality of the proposed scheme, the limitations of the available SiL schemes in the literature are addressed in this paper. Additionally, all technical details for establishing the connection between FEM and MATLAB are provided for the interested reader. Finally, two numerical sub-problems are defined for offline and online post-processing, i.e., offline optimization and closed-loop system performance analysis in control theory.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.663-670
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• 2020

A study on mechanical property characterization and modeling technique was carried out to approximate the behaviour of structures with 2.5D C/SiC material. Several tensile tests were performed to analyze the behaviour characteristics of the 2.5D C/SiC material and elastic property was characterized by applying a mathematical homogenization and a modified rule of mixture. SiC matrix representing the elasto-plastic behavior approximates as a bilinear function. Then the equivalent yield strength and equivalent plastic stiffness were calculated by minimizing errors in experiment and approximation. RVE(Representative Volume Element)was defined from the fiber and matrix configuration of 2.5D C/SiC and a process of calculating the effective stiffness matrix by applying the modified rule of mixture to RVE was implemented in the ABAQUS User-defined subroutine. Finite element analysis was performed by applying the mechanical properties of fiber and matrix calculated based on the proposed process, and the results were in good agreement with the experimental results.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.713-722
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• 2019

Micromechanics is a technique for the analysis of composites or heterogeneous materials which focuses on the components of the intended structure. Each one of the components can exhibit isotropic behavior, but the microstructure characteristics of the heterogeneous material result in the anisotropic behavior of the structure. In this research, the general mechanical properties of a 3D anisotropic and heterogeneous Representative Volume Element (RVE), have been determined by applying periodic boundary conditions (PBCs), using the Asymptotic Homogenization Theory (AHT) and strain energy. In order to use the homogenization theory and apply the periodic boundary conditions, the ABAQUS scripting interface (ASI) has been used along with the Python programming language. The results have been compared with those of the Homogeneous Boundary Conditions method, which leads to an overestimation of the effective mechanical properties. According to the results, applying homogenous boundary conditions results in a 33% and 13% increase in the shear moduli G₂₃ and G₁₂, respectively. In polymeric composites, the fibers have linear and brittle behavior, while the resin exhibits a non-linear behavior. Therefore, the nonlinear effects of resin on the mechanical properties of the composite material is studied using a user-defined subroutine in Fortran (USDFLD). The non-linear shear stress-strain behavior of unidirectional composite laminates has been obtained. Results indicate that at arbitrary constant stress as 80 MPa in-plane shear modulus, G₁₂, experienced a 47%, 41% and 31% reduction at the fiber volume fraction of 30%, 50% and 70%, compared to the linear assumption. The results of this study are in good agreement with the analytical and experimental results available in the literature.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.265-271
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• 2014

304L stainless steel sheets are used as a primary barrier for the insulation of membrane-type liquefied natural gas(LNG) carrier cargo containment system. 304L stainless steel is a transformation-induced-plasticity(TRIP) steel that exhibits complex material behavior, because it undergoes phase transformation during plastic deformation. Since the TRIP behavior is very important mechanical characteristics in a low-temperature environment, significant amounts of data are available in the literature. In the present study, a uniaxial tensile test for 304L stainless steel was performed to investigate nonlinear mechanical characteristics. In addition, a viscoplastic model and damage model is proposed to predict material fractures under arbitrary loads. The verification was conducted not only by a material-based comparative study involving experimental investigations, but also by a structural application to the LNG membrane of a Mark-III-type cargo containment system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.253-261
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• 2005

In decades, a substantial body of work on a unified viscoplastic model which considers the mechanism of plastic deformation and creep deformation has developed. The systematic scheme for numerical analysis of unified model is necessary because the dominant failure mechanism is the defect growth and coalescence in materials. In the present study, the unified viscoplastic model for materials with defects suggested by Suquet and Michel was employed for numerical analysis. The constitutive equations are integrated based on the generalized mid-point rule and implemented into a finite element program (ABAQUS) by means of user-defined subroutine (UMAT). To evaluate the validity of the developed UMAT code and the assessment of the adopted viscoplastic model, the results obtained from the UMAT code was compared with the numerical reference solution and experimental data. The unit cell analysis also has been investigated to study the effect of strain rate, temperature, stress triaxiality and initial defect volume fraction on the growth and coalescence of the defect.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.543-551
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• 2015

Polyurethane Foam(PUF), a outstanding thermal insulation material, is used for various structures as being composed with other materials. These days, PUF composed with glass fiber, Reinforced PUF(R-PUF), is used for a insulation system of LNG Carrier and performs function of not only the thermal insulation but also a structural member for compressive loads like a sloshing load. As PUF is a porous material made by mixing and foaming, mechanical properties depend on volume fraction of voids which is a dominant parameter on density. Thus, In this study, density is considered as the effect parameter on mechanical properties of Polyurethane Foam, and mechanical behavior for compression of the material is described by using modified Gurson damage model.