• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1653-1665
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• 2002

One of the most significant problems in the processing of composite materials is residual stresses. The residual stresses may be high enough to cause cracking in the matrix even before external loads are applied and can degrade the integrity of composite structures. In this study, thermo-viscoelastic residual stresses occurred in the polymeric composite cylinder are investigated. This type of structure is used for the launch vehicle fuselage. The time and degree of cure dependent thermo-viscoelastic constitutive equations are developed and coupled with a thermo-chemical process model. These equations are solved with the finite element method to predict the residual stresses in the composite structures during cure. A launch vehicle experiences high thermal loads during flight and re-entry due to aerodynamic heating or propulsion heat, and the thermal loads may cause thermal buckling on the structure. In this study the thermal buckling analysis of composite cylinders are performed. Two boundary conditions such as all clamped and all simply supported are used for the analysis. The effects of laminates stacking sequences, shapes and residual stresses on the critical buckling temperatures of composite cylinders are investigated. The thermal buckling analysis is performed using ABAQUS.

• Tunnel and Underground Space
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• v.29 no.1
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• pp.38-51
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• 2019

Barcelona Basic Model (BBM) can describe not only swelling owing to decrease in effective stress, but also wetting-induced swelling due to decrease in suction. And the BBM can also consider increase in cohesion and apparent preconsolidation stress with suction, and decrease in the apparent preconsolidation stress with temperature. Therefore, the BBM is widely used all over the world to predict and to analyze coupled thermo-hydro-mechanical behavior of bentonite which is considered as buffer materials at the engineered barrier system in the high-level radioactive waste disposal system. However, the BBM is not well known in Korea, so this paper introduce the BBM to Korean rock engineers and geotechnical engineers. In this study, Modified Cam Clay (MCC) model is introduced before all, because the BBM was first developed as an extension of the MCC model to unsaturated soil conditions. Then, the thermo-elasto-plastic version of the BBM is described in detail.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.1-15
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• 1998

In this paper, thermo-viscoplastic finite element analysis of the effect of tool edge radius on cutting process are performed. The thermo-viscoplastic cutting model is capable of dealing with free chip geometry and chip-tool contact length. The coupling with thermal effects is also considered. Orthogonal cutting experiments are performed for 0.2% carbon steel with tools having 3 different edge radii and the tool forces are measured. The experimental results are discussed in comparison with the results of the FEM analysis. From the study, we confirm that this cutting model can well be applied to the cutting process considered the tool edge radius and that a major causes of the "size effect" is the tool edge radius. With numerical analysis, the effects of the tool edge radius on the stress distributions in workpiece, the temperature distributions in workpiece and tool, and the chip shape are investigated.estigated.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.1063-1077
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• 2016

Components manufactured from composite materials are frequently subjected to superimposed mechanical and thermal loadings during their operating service. Both types of loadings may cause fracture and failure of composite structures. When composite cross-ply laminates of type [$0_m/90_n]_s$ are subjected to uni-axial tensile loading, different types of damage are set-up and developed such as matrix cracking: transverse and longitudinal cracks, delamination between disoriented layers and broken fibers. The development of these modes of damage can be detrimental for the stiffness of the laminates. From the experimental point of view, transverse cracking is known as the first mode of damage. In this regard, the objective of the present paper is to investigate the effect of transverse cracking in cross-ply laminate under thermo-mechanical degradation. A Finite Element (FE) simulation of damage evolution in composite crossply laminates of type [$0_m/90_n]_s$ subjected to uni-axial tensile loading is carried out. The effect of transverse cracking on the cross-ply laminate strength under thermo-mechanical degradation is investigated numerically. The results obtained by prediction of the numerical model developed in this investigation demonstrate the influence of the transverse cracking on the bearing capacity and resistance to damage as well as its effects on the variation of the mechanical properties such as Young's modulus, Poisson's ratio and coefficient of thermal expansion. The results obtained are in good agreement with those predicted by the Shear-lag analytical model as well as with the obtained experimental results available in the literature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1609-1618
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• 1997

Thermo-mechanical behaviors of polymer matrix composite(PMC) with continuous TiNi fiber are studied using theoretical analysis with 1-D analytical model and numerical analysis with 2-D multi-fiber finite element(FE) model. It is found that both compressive stress in matrix and tensile stress in TiNi fiber are the source of strengthening mechanisms and thermo-mechanical coupling. Thermal expansion of continuous TiNi fiber reinforced PMC has been compared with various mechanical behaviors as a function of fiber volume fraction, degree of pre-strain and modulus ratio between TiNi fiber and polymer matrix. Based on the concept of so-called shape memory composite(SMC) with a permanent shape memory effect, the critical modulus ratio is determined to obtain a smart composite with no or minimum thermal deformation. The critical modulus ratio should be a major factor for design and manufacturing of SMC.

• Tribology and Lubricants
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• v.18 no.3
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• pp.194-203
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• 2002

This paper is the first step fur thermo-mechanical stress analyses of part with coated layer under contact load. A lot of coated material is applied in many structures to endure severe situation, like thermal stresses, high temperature gradients, irradiation, impacts by microscopic meteorites, and so on. In this part we are going to apply the FEM to analyze space parts with a coated layer subjected to a contact load thermo-mechanically. Coating layer is very thin in comparision with the structure, therefore it should take more times and behaviors to analyze whole model. In these reason we develop the FEM method of analyzing part with coated layer under contact load using partial model. Steady state temperature distribution of the part is obtained first, and then we apply quasi-static external load on the part. To obtain the final stage of solution, we compute the total solution, and by subtracting the thermal strain from the total ones we get the mechanical strains to compute stresses of the parts. In using the FEM, one has to discretize the model into many sub-domain, finite elements. The method is consisited of two steps. First step is to analyze the whole model with rather coarse meshes. Second step we cut a small region near the loading point, and analyze with very fine meshes. This method is allowable by the Saint-Venant's principle. And then, we finally shall check the therma1 load on the stresses of the space part with coating layer with or without substrate cracks. Then, we predict the actual behaviors of the part used in space.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.45-52
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• 2011

To improve fire-resistance of a high strength concrete against spalling under elevated temperature, fibers can be mixed to provide flow paths of evaporated water to the surface of concrete when heated. In this study, the experiment of a column under fire and mechanical loads is conducted and the material model for predicting temperature of reinforcement steel bar and mechanical behavior of fiber-mixed high strength concrete is suggested. The material model in previous studies is modified by incorporating physical behavior of internal concrete and thermal characteristics of concrete at the elevated temperature. Thermo-mechanical analysis of the fiber-mixed high strength concrete column is conducted using the calibrated material model. The performance of the proposed material model is confirmed by comparing thermo-mechanical analysis results with the experiment of a column under fire and mechanical loads.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.426-431
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• 2000

A decoupled thermo-piezoelectric-mechanical model of composite laminates with surface bonded piezoelectric actuators, subjected to externally applied load, temperature change load, electric field load is developed. The governing differential equations are obtained by applying the principle of free energy and variational techniques. A higher order zigzag theory displacement field is employed to accurately capture the transverse shear and normal effects in laminated composite plates of arbitrary thickness.

• Transactions of Materials Processing
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• v.6 no.2
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• pp.161-175
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• 1997

The effects of various process paramenters on the detailed aspects of the thermo-mechanical behavior of work roll and on the roll life are investigated via a series of process simulation, using a mathematical model presented previously. The process conditions are discussed that are favorable or optimal in terms of reducing roll wear in the front finishing stands.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2173-2187
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• 2022

A 3D thermo-elasto-hydrodynamic model is developed to analyze the sealing performance of a notched mechanical seal applied in the reactor coolant pump. In the model, the generalized Reynolds equation, the energy equation coupled with notch heat balance equation, the heat conduction equations, and the deformation equations of the sealing rings are iteratively solved by the finite element method. The film pressure and temperature distribution are obtained, and the deformation of the sealing rings is revealed to study the mechanism of the notched mechanical seals. A parameterized study is conducted to analyze the sealing performance under different operating conditions. As a comparison, the sealing performance of non-notched seals is also studied. The results show that the hydrostatic effect is dominant in the load-carrying capacity of the fluid film due to the radial mechanical and thermal deformations. The notch can cool the fluid film and influence the thermal deformation of seal rings. The sealing performance is sensitive to the pressure difference, ambient temperature, and rotational speed. It is suggested to set the notches on the softer sealing rings to acquire the greater hydrodynamic effect. Compared with the non-notched, the notched end face holds a better lubrication performance, especially under lower rotational speed.