• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1995.04a
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• pp.27-27
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• 1995

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 1995.06a
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• pp.336-343
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• 1995

• Proceedings of the KWS Conference
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• 1999.05a
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• pp.6-9
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• 1999

• Composites Research
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• v.31 no.5
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• pp.215-220
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• 2018

In this study, finite element analysis of Carbon-Steel Laminates with different layup pattern was conducted to verify similarity to the results of previous studies and to develop the effective model for low-velocity impact analysis. As in the experiment, Finite element analysis of the Fiber metal laminates (FMLs) with five different lamination patterns was carried out, and the impact resistance of the FMLs was confirmed by comparing the energy absorption ratio. The FMLs showed the higher energy absorption ratio than the mild steel having the same thickness, and it was confirmed that all the FMLs had the high energy absorption ratio over than 96%. In addition, the low-velocity impact analysis model proposed in this study can be effectively used to study composite forms and automotive structures.

• Corrosion Science and Technology
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• v.7 no.4
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• pp.224-232
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• 2008

During the hot rolling process, steels develop an oxide scale on their surface. This scale can affect the mechanical properties of the rolled steel and its surface aspect. The main problem comes from the mechanical integrity of the oxide scales which could delaminate or crack, leading eventually to later oxide incrustation within the steel. The objective of the present work is to qualify the mechanical integrity of the iron oxide scales during the hot rolling process. The laboratory experiments use a four point bending test to simulate the mechanical solicitation which takes place during the rolling sequence of the steel slabs. The oxide scales grow on a mild steel at $900^{\circ}C$ under wet or dry atmosphere and the oxidized steel is then mecahnically tested at $900^{\circ}C$ or $700^{\circ}C$. The high temperature four point bending tests are completed with microstructural observations and with the record of acoustic emission to follow in-situ the mechanical damages of the oxide scales. The results show the role of water vapor which promotes the scale adherence, and the role of the temperature as the oxide are more damaged at $700^{\circ}C$ than at $900^{\circ}C$.

• Corrosion Science and Technology
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• v.10 no.1
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• pp.1-5
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• 2011

The major purpose of the present study is to evaluate the performance of various galvanized (GI) or galvannealed (GA) mild steels and AHSS in stamping applications. Finite Element Analysis (FEA) of selected stamping operations was conducted to estimate the critical pressure boundary conditions that exist in practice. Using this information, laboratory tribotests, e.g. Twist Compression (TCT), Deep Drawing (DDT) and Strip Drawing (SDT) Tests, were developed to evaluate the performance of selected lubricants and die materials/coatings in forming galvanized steels of interest. The sheet materials investigated included mild steels and AHSS (e.g. DP600 GI/GA, DP780 GI/GA, TRIP780 GA and DP980 GI/GA). Experimental results showed that galvanized material resulted in more galling, while galvannealed material showed more powdering and flaking. The surface roughness and chemical composition of galvanized sheet materials affected the severity of galling under the same testing conditions, i.e. lubricants and die materials/coatings. The results of this study helped to determine the critical interface pressure that initiates lubricant failure and galling in stamping selected galvanized sheet materials. Thus, to prevent or postpone the critical interface conditions, the results of this study can be used to select the optimum combination of galvanized sheet, die material, die coating and lubricant for forming structural automotive components.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.1-7
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• 2014

In this study, for the evaluation of the static and fatigue joining strength of the joint, the geometry of the cross-tension specimen was adopted. The specimens were produced with optimal joining force and fatigue life of the clinch joint specimens was evaluated. The material selected for use in this study was cold rolled mild steel (SPCC) with a thickness of 0.8 mm. The maximum tensile load was 708 N for the specimen with single point. The fatigue endurance limit (=42.6 N) per point approached to 6% of the maximum tensile strength at a load ratio of 0.1, suggesting that the joints are vulnerable to cross-tension loading during fatigue. Compared to equivalent stress and maximum principal stress, the SWT fatigue parameter and equivalent strain can properly predict the current experimental fatigue life. The SWT parameter can be expressed as $SWT=2497.5N^{-0.552)_f$.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.334-344
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• 1998

Yew coating pmccss t.o form a surface layer ol CrN phasc on mild steel (A81 1020!, AlSI Hi3, 1Cr-0.5Mo steel (ASTM A213 and Nickrl-base superalloy (Inconel 718) was developed. Surlaces of various alloys t,n.ateii by chromizing for the formation ol Cr diffusion layer was subsequently trcaled by plasma nitriding in order t.o form the hard CrS coating layer on the surfaces. This duplex plasma surface tri-atments of chromizing and plasma nitriding have induced a lormation of a duplex-lrcated surfacr hyer of approximat~ls 70-80 $\mu\textrm{m}$thickncss with a iargcly improved microiiardnrss up to approxiniateW 1500Hv(50gf). The main cause for the lage improvment in the surface hardncss is altribilted to [.he fact that CrN and $Fe_xN$ phases are created successfully by ccliromizins and plasma nilriding treatment. High tenipera1,urc wear resislance of the duplex-treated mild steel and HI3 steels at $600^{\circ}C$ was examined. Comparing the duplex-treated specimens with the specimens treated only by chromizing, the rcsults shovmi that, thc wear volume of the duplex-treated mild skcl and 1113 stcel aSt.er a wear test, at $600^{\circ}C$ were reduced hy a Iactor of 8 and 3, respectively. Characteristics of the CrS phase by duplrx treatment were compared with $CrN_x$,/TEX> film by ion plating and the wear behaviors of CrN film lormed by two different nroccsses arc nea.riy identical.

• Analytical Science and Technology
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• v.8 no.1
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• pp.85-90
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• 1995

Corrosion characteristics of 4 kinds of the Fe-Al damping alloys has been studied in the 3.5% NaCl solution and compared with a cold rolled mild steel and pure Ti, No passivation, besides Ti, was observed in the Fe-Al damping alloys and a cold rolled mild steel. Corrosion rate was decreased with lower carbon concentration. In the case of Mn addition for improving damping capacity, corrosion rate was decreased in scrap iron but was not decreased in electrolytic iron. It has been shown that corrosion rate of Fe-Al damping alloys lays between that of the pure Ti and that of a cold rolled mild steel.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.5-10
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• 2000

In the present work, corrosion rate W and corrosion potential tow were simultaneously measured as a function of relative humidity RH employing the electrochemical wet and dry method as an accelelated atmospheric corrosion method. The W versus (vs.) RH curve is classified into .three regions, namely, the first W plateau region, the second region of the linear relationship between logarithmic W and RH, finally, followed by an abrupt decay region. Based upon the atmospheric corrosion mechanism of mild steel, we introduced another diagram of $\varepsilon_{corr}$ vs. RH which is divided into three regions. In the first region, the corrosion scales are composed of single lepidocrocite-phase $(\gamma-FeOOH)$; in the second region, $\gamma-FeOOH$-phase coexists with magnetite-phase $(Fe_3O_4)$ in the scales and finally the oxide scales change into a single Fe304-phase in the third region. The three distinct regions of both representations share almost each other, which is validated by FT-IR (Fourier transform infra-red) analysis and surface observation. Both representations prove to be convenient and complementary for surveying the spectrum of the atmospheric corrosion of mild steel.