Wyniki wyszukiwania - Biblioteka Nauki

1

Thermo-viscoelastic-plastic deformation of huge products in thermal process

100%

Cho C. , Kwahk S.-Y. , Kim W.-J. , Choi J.-K.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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tom Vol. 17, nr 1-2

233--236

EN

Purpose: This paper is to numerically predict thermo-elastic-plastic deformation during thermal process. Decreasing material strength in thermal processes causes severer deformation at elevated temperature even under self-weight of huge and heavy products. Design/methodology/approach: A hybrid method is proposed and applied, in this study, to analyse thermomechanically coupled problems such as heat treatment. The finite difference method (FDM) and the finite element method (FEM) are prefered. In general, FDM is favored for heat/fluid flow, FEM for structure analysis. Findings: The solution of heat treatment processing is conducted by using the proposed hybrid method that we developed the numerical program for calculating the deflection induced due to its own weight and the creep. The code is verified by the analytic solution of a simple plate model. Research limitations/implications: There have been developed peculiar computational methods fitted in each single field problem. Recent problems necessitate total solutions not only in a major relating science but also in adjacent engineering parts. To keep the efficiency of respective methods even in coupled field problems, it is very desirable to combine advantages of respective methods as hybrid technique. This study suggests and applies a hybrid method of FEM and FDM for simulating heat treatments. Further improvement to convert different types of computational models to each other is one of important issues. Practical implications: In the past half century, there have been developed numerous computational techniques in various fields in separate ways. Hybrid method of combining existing computational techniques rather than further extending the techniques may have significant implication whenever practical problems necessitate total solutions coupled over multiple physics. Originality/value: The concept of a hybrid technique between FEM and FDM was implemented in this study and applied to simulate a heat treatment case as a multiphysical problem.

2

Normal fertility in male mice lacking ADAM32 with testis-specific expression

100%

Lee S. , Hong S. H. , Cho C.

Reproductive Biology

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2020

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tom 20

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nr 4

3

A management on mesh modelling for finite element analysis in casting simulation

88%

Cho C. , Kim W. , Choi B. , Kwak S. , Pan Q.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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tom Vol. 20, nr 1-2

335-338

EN

Purpose: In this paper we present a finite element mesh management technique applied to analyze thermal stress distribution of mushy region including molten materials and solidifying shell. Design/methodology/approach: In this study we terminated and eliminated the finite elements representing molten materials on the element list. When they became cooler than the liquidus temperature, the deleted elements were recreated. Findings: We considered temperature-dependent material properties during simulation and adopted hybrid FDM/FEM method for enhancing accuracy: We validated the proposed technique by comparing with other methods. As results, the proposed method is found to effectively simulate real-time casting process. Research limitations/implications: The resulting simulation of conventional methods should induce errors on estimating residual stress of the cast subjected to non-uniform cooling. For the stress analysis study of casting process before complete solidification, we introduce a special technique to treat molten parts in the numerical procedure. This study proposes a method reducing by several orders the elastic modulus of molten material through employing a reduction factor. Practical implications: Conventional casting process simulations don't consider stress due to complex rheological behavior of molten metals until the cast completely solidifies. Achieving uniform cooling rate in a whole cast body while solidifying must be an ideal casting process to avoid undesirable thermal distortion and stress in product which may induce hot tear and crack. Conventionally many prototyping tests should be conducted to this end and necessitate expensive costs. Originality/value: In this study we propose a new technique of "Element Creation and Termination" which terminates (or removes) molten elements and creates them just after they cool down to lower than liquidus temperature. Notice that the previous methods do not remove but deactivate molten elements.