• Proceedings of the KSME Conference
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.745-750
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• 2000

A warpage analysis program has been developed for fiber-reinforced injection molded parts. The warpage is Predicted from the residual stress and anisotropic thermo-mechanical properties coupled with fiber orientation in the integrated injection molding simulation. A simple elastic model is used for the calculation of thermally and pressure-induced residual stresses which are employed as the initial conditions in the structural analysis. To improve the reliability of warpage analysis, a new triangular flat shell element superimposing well-known efficient plate bending and membrane element is presented. The numerical examples address the neccesity to use anisotropic models for fiber-reinforced materials and show that predicted warpage is in good agreement with experimentally measured one.

• Coupled systems mechanics
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• 제13권1호
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• pp.61-72
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• 2024

This study seeks to develop analytical solutions for the biothermoelastic model without accounting for energy dissipation. These solutions are then applied to estimate the temperature changes induced by external heating sources by integrating relevant empirical data characterizing the biological tissue of interest. The distributions of temperature, displacement, and strain were obtained by utilizing the eigenvalues approach with the Laplace transforms and numerical inverse transforms method. The impacts of the rate of blood perfusion and the metabolic activity parameter on thermoelastic behaviors were discussed specifically. The temperature, displacement, and thermal strain results are visually represented through graphical representations.

• Tunnel and Underground Space
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• 제30권1호
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• pp.39-62
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• 2020

In this study, Barcelona Basic Model (BBM) was implemented into TOUGH2-MP/FLAC3D for the numerical analysis of coupled thermo-hydro-mechanical (THM) behavior of unsaturated soils and the prediction of long-term behaviors. Similar to the methodology described in a previous study for the implementation of BBM into TOUGH-FLAC, the User Defined Model (UDM) of FLAC based on the Modified Cam Clay Model (MCCM) and the FISH function of FLAC3D were used to extend the existing MCCM module in FLAC3D for the implementation of BBM into TOUGH2-MP/FLAC3D. In the developed BBM module in TOUGH2-MP/FLAC3D, the plastic strains due to change in suction increase (SI) in addition to mean effective stress are calculated. In addition to loading-collapse (LC) yield surface, suction increase (SI) yield surface is changed by hardening rules in the developed BBM module. Several numerical simulations were conducted to verify and validate the implementation of BBM: using an example presented in the FLAC3D manual for the standard MCCM, simulation results using COMSOL, and experimental data presented in SKB Reports. In addition, the developed BBM analysis module was validated by simultaneously performing a series of modeling tests that were performed for the validation of the Quick tools developed for the purpose of effectively deriving BBM parameters, and by comparing the Quick tools and Code_Bright results reported in a previous study.

• Tunnel and Underground Space
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• 제32권6호
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• pp.568-585
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• 2022

In the present study, we proposed a numerical method for simulating thermally induced fracture slip using a grain-based distinct element model (GBDEM). As a part of DECOVALEX-2023, the thermo-mechanical loading test on a saw-cut rock fracture conducted at the Korea Institute of Civil Engineering and Building Technology was simulated. In the numerical model, the rock sample including a saw-cut fracture was represented as a group of random Voronoi polyhedra. Then, the coupled thermo-mechanical behavior of grains and their interfaces was calculated using 3DEC. The key concerns focused on the temperature evolution, thermally induced principal stress increment, and fracture normal and shear displacements under thermo-mechanical loading. The comparisons between laboratory experimental results and the numerical results revealed that the numerical model reasonably captured the heat transfer and heat loss characteristics of the rock specimen, the horizontal stress increment due to constrained displacement, and the progressive shear failure of the fracture. However, the onset of the fracture slip and the magnitudes of stress increment and fracture displacement showed discrepancies between the numerical and experimental results. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study.

• Structural Engineering and Mechanics
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• 제22권5호
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• pp.517-539
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• 2006

Friction problems involving rubber components are frequently encountered in industrial applications. Their treatment within the framework of numerical simulations by means of the Finite Element Method (FEM) is the main issue of this paper. Special emphasis is placed on the choice of a suitable material model and the formulation of a contact model specially designed for the particular characteristics of rubber friction. A coupled thermomechanical approach allows for consideration of the influence of temperature on the frictional behavior. The developed tools are implemented in the commercial FE code ABAQUS. They are validated taking the sliding motion of a rubber tread block as example. Such simulations are frequently encountered in tire design and development. The simulations are carried out with different formulations for the material and the frictional behavior. Comparison of the obtained results with experimental observations enables to judge the suitability of the applied formulations on a structural scale.

• Coupled systems mechanics
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• 제10권1호
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• pp.39-60
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• 2021

The present paper is concerned with the study of nonlinear ultrasonic waves in a magneto thermo (MT) elastic armchair single-walled carbon nanotube (ASWCNT) resting on polymer matrix. The analytical formulation is developed based on Eringen's nonlocal elasticity theory to account small scale effect. After developing the formal solution of the mathematical model consisting of partial differential equations, the frequency equations have been analyzed numerically by using the nonlinear foundations supported by Winkler-Pasternak model. The solution is obtained by ultrasonic wave dispersion relations. Parametric work is carried out to scrutinize the influence of the non local scaling, magneto-mechanical loadings, foundation parameters, various boundary condition and length on the dimensionless frequency of nanotube. It is noticed that the boundary conditions, nonlocal parameter, and tube geometrical parameters have significant effects on dimensionless frequency of nano tubes. The results presented in this study can provide mechanism for the study and design of the nano devices like component of nano oscillators, micro wave absorbing, nano-electron technology and nano-electro- magneto-mechanical systems (NEMMS) that make use of the wave propagation properties of armchair single-walled carbon nanotubes embedded on polymer matrix.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.39-52
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• 2009

Theory-based models and high performance simulations are briefly reviewed starting with atomistic methods, such as Electronic Structure calculations, Molecular Dynamics, and Monte Carlo, continuing with meso-scale methods, such as Dislocation Dynamics and Phase Field, and ending with continuum methods that include Finite Element and Finite Volume. Special attention is paid to relating thermo-mechanical and chemical properties of the fuel to reactor parameters. By inserting atomistic models of point defects into continuum thermo-chemical calculations, a model of oxygen diffusivity in $UO_{2+x}$ is developed and used to predict point defect concentrations, oxygen diffusivity, and fuel stoichiometry at various temperatures and oxygen pressures. The simulations of coupled heat transfer and species diffusion demonstrate that including the dependence of thermal conductivity and density on composition can lead to changes in the calculated centerline temperature and thermal expansion displacements that exceed 5%. A review of advanced nuclear fuel performance codes reveals that the many codes are too dedicated to specific fuel forms and make excessive use of empirical correlations in describing properties of materials. The paper ends with a review of international collaborations and a list of lessons learned that includes the importance of education in creating a large pool of experts to cover all necessary theoretical, experimental, and computational tasks.

• Advances in nano research
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• 제9권3호
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• pp.133-145
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• 2020

In this study, nonlinear vibrations and dynamic instabilities of a smart embedded micro shell conveying varied fluid flow and subjected to the combined electro-thermo-mechanical loadings are investigated. With the aim of designing new hydraulic sensors and actuators, the piezoelectric materials are employed for the body and the effects of applying electric field on the stability of the system as well as the induced voltage due to the dynamic behavior of the system are studied. The nonlocal piezoelasticity theory and the nonlinear cylindrical shell model in conjunction with the energy approach are utilized to mathematically modeling of the structure. The fluid flow is assumed to be isentropic, incompressible and fully develop, and for more generality of the problem both steady and time dependent flow regimes are considered. The mathematical modeling of fluid flow is also carried out based on a scalar potential function, time mean Navier-Stokes equations and the theory of slip boundary condition. Employing the modified Lagrange equations for open systems, the nonlinear coupled governing equations of motion are achieved and solved via the state space problem; forth order numerical integration and Bolotin's method. In the numerical results, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence, flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or vibration amplitude controller in the micro electro mechanical systems.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.199-213
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• 2017

Chloride penetration is among the main causes of corrosion initiation in reinforced concrete (RC) structures producing premature degradations. Weather and exposure conditions directly affect chloride ingress mechanisms and therefore the operational service life and safety of RC structures. Consequently, comprehensive chloride ingress models are useful tools to estimate corrosion initiation risks and minimize maintenance costs for RC structures placed under chloride-contaminated environments. This paper first presents a coupled thermo-hydro-chemical model for predicting chloride penetration into concrete that accounts for realistic weather conditions. This complete numerical model takes into account multiple factors affecting chloride ingress such as diffusion, convection, chloride binding, ionic interaction, and concrete aging. Since the complete model could be computationally expensive for long-term assessment, this study also proposes model simplifications in order to reduce the computational cost. Long-term chloride assessments of complete and reduced models are compared for three locations in France (Brest, Strasbourg and Nice) characterized by different weather and exposure conditions (tidal zone, de-icing salts and salt spray). The comparative study indicates that the reduced model is computationally efficient and accurate for long-term chloride ingress modeling in comparison to the complete one. Given that long-term assessment requires larger climate databases, this research also studies how climate models may affect chloride ingress assessment. The results indicate that the selection of climate models as well as the considered training periods introduce significant errors for mid- and long- term chloride ingress assessment.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제32권8호
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• pp.693-700
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• 2008

The primary mirror system in a satellite camera is an opto-mechanically coupled system for a reason that optical and mechanical behaviors are intricately interactive. In order to enhance the opto-mechanical performance of the primary mirror system, opto-mechanical behaviors should be thoroughly investigated by using various analysis procedures such as elastic, thermo-elastic, optical and eigenvalue analysis. In this paper, optimal design of the bipod flexure mounts for high opto-mechanical performance is performed. Optomechanical performances considered in this paper are RMS wavefront error under the gravity and thermal loading conditions and 1st natural frequency of the mirror system. The procedures of the flexure mounts design based on design of experiments and statistics is as follows. The experiments for opto-mechanical analysis are constructed based on the tables of orthogonal arrays and analysis of each experiment is carried out. In order to deal with the multiple opto-mechanical properties, MADM (Multiple-attribute decision making) is employed. From the analysis results, the critical design variables of the flexure mounts which have dominant influences on opto-mechanical performance are determined through analysis of variance and F-test. The regression model in terms of the critical design variables is constructed based on the response surfaceanalysis. Then the critical design variables are optimized from the regression model by using SQP algorithm. Opto-mechanical performance of the optimal bipod flexure mounts is verified through analysis.