• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1335-1342
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• 1988

In this paper, mechanical properties of mild steel plate which was pretreated by prestress and prestrain loading conditions were studied. The variation of the mechanical properties of the test materials is evaluated in the light of Taylor's work hardening theory. Through this experimental study, it is recognized that material showed unstable phenomena after cyclic loading and it will recover its stability after a certain period of time accompaning the increment of hardness and the yield strength of the material. Also, the strength of smooth specimen, the notch strength of notch specimen and propagation behavior of fatigue specimen which were subjected to prestress and prestrain reveal that the optimal conditions may occur in the first, the middle and the later half of stage II of Taylor's work hardening theory, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.3
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• pp.39-44
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• 1991

The purpose of this investigation is to examine the effects of spraying conditions on the mechanical properties of flame-sprayed titania ceramic coating layer. Titania ceramic was sprayed onto the mild steel substrate under the various spraying conditions. Spraying distances were 100, 150, 200, 250mm respectively and pinch air pressures were 0.2 0.3, 0.4 MPa at each spraying distance. The mechanical properties such as microhardness, adhesive strength and erosion wear resistance were tested for the specimens sprayed under the various spraying conditions above mentioned. The optimum operational conditions obtained through the experimental results were 150mm of spraying distance and 0.3 MPa of pinch air pressure.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.13 no.3
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• pp.203-215
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• 2009

In this article, we study the existence and uniqueness of mild and classical solutions for a nonlinear impulsive differential equation with nonlocal conditions u'(t) = Au(t) + f(t, u(t); Tu(t); Su(t)), $0{\leq}t{\leq}T_0$, $t{\neq}t_i$, u(0) + g(u) = $u_0$, ${\Delta}u(t_i)=I_i(u(t_i))$, i = 1,2,${\ldots}$p, 0<$t_1$<$t_2$<$\cdots$<$t_p$<$T_0$, in a Banach space X, where A is the infinitesimal generator of a $C_0$ semigroup, g constitutes a nonlocal conditions, and ${\Delta}u(t_i)=u(t_i^+)-u(t_i^-)$ represents an impulsive conditions.

• Journal of Welding and Joining
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• v.18 no.1
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• pp.52-58
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• 2000

Spot welding, namely a kind of electric resisting welding has been used widely in field of automobile and aircraft industries because of easiness to apply. Specimens used in this study was a mild steel of 1.2mm thickness and the electrode was a Cu-Cr alloy of 6mm diameter. The surface sheared of specimens after testing of tensile shear was observed by SEM(scanning electron microscope) after ultrasonic cleaning for 10min., and microstructures and grain size of all specimens were measured with using of O.M.(Optical microscope). By the means of measurement and observations of tensile shear load, fatigue strength and share surface, the weldability of spot welding was evaluated. When tensile shearing testing, fracture starting point in all specimens was took place at the bond between HAZ(Heat affected zone) and nugget. With increasing in number of layers, fatigue strength was decreased. With increasing in electric current, grain size in the HAZ became more fine.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.429-429
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• 2009

Nanoporous anodic alumina membranes (NAAM) with high-density through-hole pores fabricated by hard anodization of aluminum in 0.3 M oxalic acid under the applied voltage of 40 (mild anodization), 80, 100, 120 and 140 V were investigated. The current-time responses monitored using a PC-controlled anodization cell and the corresponding pore structures attainable from field-enhanced scanning electron microscopy (FE-SEM) were analyzed in order to establish the optimum fabrication process. The nanoporous structure can be produced for all the voltage conditions, while the stabilized through-hole pore formation seems to occur at 40, 80 and 140 V. The growth rate under 140 V hard anodization was over 30 times higher than under 40 V mild anodization (1.5 um/hr).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.181-188
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• 1994

Generally, the structural material shows rate dependent behaviors, which require to constitute different strain-stress relations according to strain rates. Conventional rate- independent constitutive equations used in general purpose finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate dependent constitutive equation for elastic-plastic material was developed. The plastic stretch rate was modeled based on slip model with dislocation velocity and density so that there is no yielding condition, and no loading conditions. Non-linear hardening rule was also introduced for finite strain. Material constants of present constitutive equation were determined by experimental data of mild steel. The constitutive equation was applied to uniaxile tension. It was appeared that the present constitutive equation well simulates rate dependent behaviors of mild steel.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.117-121
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• 2001

For the effective development or preservation of Tokdo, the natural environments in the ambient sea area should be well investigated. The wave deformations and wave breaking in the vicinity have much affected the bottom morphology of Tokdo as well as its ecological environment. The present study investigates the wave deformations and wave breaking through a numerical model. The final goal is to provide the fundamental wave data for the effective development or preservation of Tokdo in future. The extended mild slope equation was applied to Tokdo sea area for three different deep water wave conditions (S, SSE, NNE directions). The results showed that for the S and SSE directions the wave heights in the area between the east island and the west island were very low with the level of 1~2m, but for the NNE direction they appeared pretty high with 3~4m, In the sea area near the northwest of west island, the wave heights were low to be 1~3m for all three directions of deep water wave.

• Journal of Institute of Convergence Technology
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• v.5 no.1
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• pp.23-26
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• 2015

The purpose of present study is to analysis the Characteristics of fuel economy and Green house gases due to the driving mode conditions of The hybrid electric vehicle(HEV). HEVs are divided into mild and power types according to the their functions. mild type HEVs are inexpensive because they do not need to implement a pure electric mode. Power type HEVs are more expensive but has also better fuel efficiency. In the present paper, the test results for the gasoline vehicle using FTP-75 mode and HWFET are present.

• Journal of Welding and Joining
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• v.8 no.2
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• pp.70-79
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• 1990

Stainless clad steels were made through hot rolling process. Backing plates employed in this study were HSLA steel and mild steel. The shear bond strength increased with an increase of the soaking temperature and time. It was also found that the shear bond strength increased with an increase of the reduction ratio. The threshold deformation was observed to be 20% and 10% respectively when the soaking conditions of 15 min. at 900.deg. C and 30 min. at 1000.deg. C were applied. Either the rolling or the transverse direction did not give any significant difference in the shear bond strength. Stainless steel-HSLA steel was superior to stainless steel-mild steel in the same range of magnitude. Because the above experimental results were in contrary to the existing mechanisms, the new model was proposed to describe the bonding mechanism and the void formation.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.784-787
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• 2008

Nanoscale $YVO_4:Eu^{3+}$ phosphor has been synthesized by a mild hydrothermal reaction at various experimental conditions. The particle and luminescent properties of nanophosphors were characterized with X-ray diffraction, electron microscopy and photoluminescence. It has been found that pH value play a key factor both controlling particle size and luminous efficiency.