• Magazine of the Korean Society of Agricultural Engineers
• /
• v.35 no.4
• /
• pp.106-118
• /
• 1993

The purpose of this study is to develop a multireservoir water balance model which may be used to evaluate rural water demands such as agricultural water, domestic water, industrial water and livestock water and to determine effective storage of reservoir. The model was verified to compare the observed reservoir release data with the simulated reservoir release data of the existing Munsan and Dongbu reservoirs located in the Gisan rural district for 3 years('87~'89). For model application, the effective storages of existing reservoirs(Munsan & Dongbu) were evaluated for 10-year frequency drought and that of newly planned reservoirs(Kumbok & Kudong) were determined for 10-year frequency drought. In addition, the behavior of effective storages for existing reservoirs were analyzed in the case of introducing new reservoirs in the existing system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.103-108
• /
• 2001

Wear test has been performed to evaluate the wear mechanism of Inconel alloys against ferritic stainless steels in room temperature water. By means of scanning electron microscopy (SEM), the worn surface and microstructure of subsurface layer have been examined. The wear at steady state conditions result in the formation of 5∼7${\mu}$m thick layers with fragmented microstructure. The thickness of these layers seems to depend on the ability of work hardening and deformation accommodation at the contact areas during wear. Therefore, in room temperature water, the wear rate is closely related with the wear resistance of these fragment microstructure which are generated after severe subsurface deformation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.326-329
• /
• 2005

Since the required strength of forged part is achieved by work hardening with the accumulation of plastic strain during the cold working, severe load can be exerted on die system. So, dies are liable to the early fracture for the non-heat treated steel forging in comparison with the conventional mild steels. Therefore, it is necessary to lower the flow stress of steels as much as possible during forging steps. Bauschinger effect can be utilized to lower flow stress during forging steps by giving the tensile prestrain on the forging billet during wire drawing step. In the present study, the prestrain effect on Bauschinger phenomenon is studied to avoid difficulties with application of non-heat treated cold forging steels in practice.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.336-339
• /
• 2005

API steel is used for line-pipe to transport the oil and natural gas. As the recent trends in the development of API steel are towards the use of larger diameter and thicker plate, many researches have been studied to achieve higher strength, higher toughness and lower yield ratio in API steel. However, the strength of API steel after pipe forming is changed depend on the competition of the Bauschinger effect and work hardening. So, the purpose of this study is to investigate the influence on the Bauschinger effect for API steel by addition of V and Cu which are formed the precipitations for higher strength in API steel. The results are that the addition of V considered as a ferrite stabilizer and Cu considered as a austenite stabilizer decreases and increases the Bauschinger effect for API steel respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2002.05a
• /
• pp.184-186
• /
• 2002

The evolution of texture and microstructure during warm rolling and subsequent annealing in aluminium 3004 alloy sheet was investigated by X-ray texture measurements and microstructure observations. Warm rolling at 250$^{\circ}C$ led to the development of strong through thickness texture gradients with shear textures at the surface layer and a regular rolling texture in the center of the sheets. FEM simulations indicated that these texture gradients are caused by pronounced strain gradients throughout the sheet thickness. Upon recrystallization annealing, in the sheet center the characteristic cube-recrystallization texture developed, while in the surface layers with a pronounced shear texture continuous recrystallization took place which led to the formation of a very fine grained microstructure. It is concluded that the very complex strain history in the near-surface layers together with the resulting high work-hardening rate gave rise to the formation of the ultra-fine grains with an average size smaller than 2$\mu\textrm{m}$.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.287-290
• /
• 2002

Stainless steel used widely in various fields of industry have the characteristics of difficulty-to-cut. This difficulty comes from its peculiarity, for example work hardening, vibration, etc. And these peculiarity on the cutting process have an effect on tool wear or life shortness of tools. To solve these problems several method have been developed. Hot-machining is one way of these method. when a material is heated, organization of material is soften. So cutting process becomes easy. When such a hot-machining method applies on drilling process and then heated material is processed, cutting force is less than usual drilling process cutting force. In this paper, cutting force is compared heated SUS 304 with usual SUS 304. And shape of chips is also compared.

• Journal of Welding and Joining
• /
• v.22 no.4
• /
• pp.65-72
• /
• 2004

The aim of this study is to investigate the optimum drawing parameter for BAS111 welded tubes. The BAS111 aluminium alloy tubes with 25.4mm in external diameter and 1.5mm in thickness for heat-exchangers were manufactured by high frequency induction welding with the V shaped convergence angle 6.8$^{\circ}$ and power input 50㎾. With increasing the reduction of area (1.6, 5.8, 11.5, 14.2, 18.5, 22.5%) by drawing, tensile strength was increased and elongation was decreased. With increasing the reduction of area by drawing, hardness in weld metal increased rapidly, while that of base metal increased slowly. In the specimen with the outer diameter smaller than 22mm, hardness of weld metal was higher than that of base metal. The optimum drawing parameter of area reduction was estimated about 15% because of the work hardening of welds.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.37 no.2
• /
• pp.73-85
• /
• 1995

This study aimes at investigating the applicability of single surface work - hardening model(7, 8) to clayey soils through FEM analysis. The comparison was carried out for the results between numericaL analysis and cubical triaxial tests in which confined stress was applied differently and 3-directional principal stress can be controlled. Furthermore, the results of the numerical analysis were compared with observed values of load test on the 2-dimensional model foundation composed of clayey soils. The agreement between nu- merical and observed values proved to be of high accuracy, which indicates that numeri- cal techniques developed during this study using the model can be used for the prediction of settlement, leteral displacement and pore water pressure of actual soft foundation of clayey soils.

• Coupled systems mechanics
• /
• v.4 no.3
• /
• pp.211-235
• /
• 2015

In this work we present a one-dimensional damage model capable of representing the dynamic fracture for elastodamage bar with combined hardening in fracture process zone - FPZ and softening with embedded strong discontinuities. This model is compared with another one we recently introduced (Do et al. 2015) and it shows a good agreement between two models. Namely, it is indicated that strain-softening leads to a sensitivity of results on the mesh discretization. Strain tends to localization in a single element which is the smallest possible area in the finite element simulations. The strain-softening element in the middle of the bar undergoes intense deformation. Strain increases with increasing mesh refinement. Strain in elements outside the strain-softening element gradually decreases to zero.

• Transactions of Materials Processing
• /
• v.12 no.4
• /
• pp.328-333
• /
• 2003

Ball indentation tests have been used to estimate the mechanical properties of materials by several investigators. In this study, load-depth curves from ball indentation tests were analyzed using the geometric conditions of the contact between ball and specimen. A series of numerical calculations and experimental results showed that the contact load-depth curves could be simplified by linear functions. Once we obtained the contact indentation depth from linearizing the experimental indentation curves, the estimation process of the flow properties became straight-forward and the scatter of results could be drastically reduced.