• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.283-286
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• 2005

Because CV Joint which is one of the component of automobile power train system communicates high power and performs power steering function, it requires high qualities such as high strength, high toughness and high fatigue resistance. This component undergoes a series of production processes such as forging, machining and heat treatment and required properties for this component depends on plastic deformation and heat treatment heavily. Therefore in this study, in order to these effects on mechanical properties due to plastic deformation and heat treatment we performed heat treatment following plastic deformation and then tensile test.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.129-134
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• 2001

It is essential to predict the welding deformation at assembly stage, to increase productivity through mechanization and automation effectively. A practical analysis method appled for production engineering was proposed to simulate the deformation of arc welding, with an analytical model using finite element method solving thermal-elastic-plastic behavior. In this research, for accurate assembling, 3-D thermal-elastic-plastic finite element model is used to simulate the out-of-plane deformation caused by arc welding. Efforts have been made to find out the efficient method to improve the reliability and accuracy of the numerical calculation. Each of theories of small and large deformation is applied in solving 3-D thermal-elastic-plastic problem to compare with their efficiency about calculation imes and solution accuracy. When solid elements are used in a bending problem of a plate, phenomenon that the predictive deformation is more than that of actual survey is observed. To prevent this phenomenon, reduced integration method for element is employed instead of full integration that is generally used in 3-D thermal-elastic-plastic analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.260-263
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• 2004

Since Outerrace is one of the components of driving shaft for power train of automobile and transmits high torque, high strength and high toughness are necessary so forging process is adopted to manufacture such parts. Therefore, in order to improve strength and toughness, heat treatment is accomplished after plastic deformation(forging). Because Each component of driving shaft is mounted to automobile after a series of forging, machining and heat treatment, in order to evaluate mechanical properties of such components in use, plastic deformation and heat treatment must be considered. So, in this paper, tensile tests are performed with tensile specimens which have passed through a series of upsetting, machining and heat treatment to evaluate mechanical properties of such components.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1344-1352
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• 2005

Densification behavior of iron powder under cold stepped plastic deformation was studied. Experimental data were also obtained for iron powder under cold stepped plastic deformation. The elastoplastic constitutive equation based on yield function of Shima and Oyane was implemented into a finite element program (ABAQUS) to simulate compaction responses of i.on powder during cold stepped plastic deformation. Finite element calculations were compared with experimental data for densification, deformed geometry and density distribution. The agreement between finite element results and experimental data was good for iron powder.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.33-40
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• 1994

Welding of structure produces welding residual stresses which influence buckling strength, brittle fracture strength and cold crack on the weld parts. Therefore, it is very important to accurately analyze the residual stress before welding in order to guarantee the safety of weldment. If the weld length is long enough compared to the thickness and the breadth of plate, thermal and mechanical behaviors in the middle portion of the plate are assumed to be uniform along the thickness direction(z-axis). Thus, the following conditions(so-called plane deformation) can be assumed for the plate except near its end;1) distributions of stress and strain are independent on the z-axis;2) plane normal to z-axis before deformation remains plane during and after deformation. In this paper, plane-deformation thermal elasto-plastic problem is formulated by being based on the finite element method. Moreover special regards and paid to the fact that material properties in elastic and plastic region are temperature-dependence. And the method to solve the plane-deformation thermal elasto-plastic problem is shown by using the incremental technique. From the results of analysis, the characterisics of distribution of welding residual stress and plastic strain with the production mechanism are clarified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1672-1679
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• 2002

This paper provides an engineering J estimation equation for cylinders with finite internal axial surfacecracks under internal pressure. The proposed equation is the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practically interesting ranges of the mean radius-to-thickness ratio, the crack depth-to-length ratio, the crack depth-to-thickness ratio. the strain hardening index for the R-O material, and the location along the semi-elliptical crack front. Based on tabilated plastic influence functions, the J estimation equation along the crack front is proposed and validated for R-O materials. Good agreements between the FE results and the proposed J estimation provide confidence in the use of the proposed method to elastic-plastic fracture mechanics of pressurized piping.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.25-26
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• 2007

At the time when nanostructured materials (NSMs) are becoming a major focus of materials research, the attention of researchers is turning more to their mechanical performance. In contrast with conventional coarse grained materials, which are either strong or ductile, but rarely both at the same time, it is expected that with NSMs both high strength and ductility can be achieved and confirmed by several experimental studies. In spite of the significant interest and efforts in the mechanical properties of NSMs, deformation mechanisms during plastic deformation as well as elastic deformation are not well established yet. In this talk, the deformation mechanisms of NSMs under various grain sizes, temperatures and strain rates were investigated. It is based on recent modelling that appears to provide a conclusive description of the phenomenology and the mechanisms underlying the mechanical properties of NSMs. Based on the theoretical model that provides an adequate description of the grain size dependence of elasticity and plasticity covering all grain size range from coarse down to the nanoscale, the tensile deformation response of NSMs, especially focusing on the deformation mechanisms was investigated.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.163-172
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• 1995

A simple numerical method is applied to calculate the large deflection of a cantilever beam under an elastic-plastic deformation by dividing the deformed axis into a number of small segments. Assuming that each segment can be approximated as a circular arc, the method allows large deflections and plastic deformation to be analyzed. The main interests are the load-deflection relationship, curvature distribution along the beam and the length of the plastic region. The method is proved to be easy and particularly versatile. Comparisons with other studies are given.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.420-425
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• 2004

Lee and Kang measured side-necking deformation near a crack-tip for CT specimen using Stereoscopic Digital Speckle Photography and Digital Image Correlation. In this work the same technique was applied to SENB specimen. We happened to find that the deformation shape of the side-necking is similar to the one of plastic region estimated by McClictock using slip line theory. Based on volume constancy of plastic deformation as well as this finding, it is expected that a linear relationship holds between the volume of plastic deformation region and the one of side-necking upon the lateral surface of a specimen. To prove the idea, a preliminary study has been performed using 3-D finite element method on a model with modified boundary layer formulation. As the result, it is shown that the idea works well with acceptable error.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1314-1321
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• 1992

In analyzing the plastic flow of axisymmetric tube extrusion a new method of formulation using the stream function approach and upper-bound theorem is proposed which permits the prediction of plastically deformed zone in analytic expression as well as metal flow. It is shown that the formulation proposed in this work covers the solid extrusion and tube extrusion in axisymmetric case. The effect of some process parameters such as area reduction, the ratio of radii(inner radius to outer radius) and friction factor on extrusion pressure, deformation zone and plastic flow through stream-lined dies has been studied. The presented theoretical analysis can be effectively used for the prediction of deformation zone and plastic flow.