• Corrosion Science and Technology
• /
• v.9 no.6
• /
• pp.247-253
• /
• 2010

The characteristics of selective oxidation prior to hot-dip galvanizing with the annealing atmosphere dew point and chemical composition in dual-phase steels and their effect on the inhibition layer formation relevant to coating adhesion have been studied using a combination of electron microscopic and surface analytical techniques. The annealed and also galvanized samples of 3 kinds of Si/Mn ratios with varied amounts of Si addition were prepared by galvanizing simulator. The dew point was controlled at soaking temperature $800^{\circ}C$ in 15%$H_2$ -85%$N_2$ atmosphere. It was shown that good adhesion factors were mainly uniformity of oxide particle distribution of low number density and low Si/Mn ratio prior to hot-dip galvanizing. Their effect was the greatly reduced coating bare spots and the formation of uniform inhibition layer leading to good adhesion of Zn overlay. The mechanism of good adhesion is suggested by two processes: the formation of inhibition layer on the oxide free surface uncovered with no $SiO_2$-containing particles in particular, and the inhibition layer bridging of oxide particles. The growth of inhibition layer was enhanced markedly by the delayed reaction of Fe and Al with the increase of Si/Mn ratio.

• Journal of the Korean Society of Industry Convergence
• /
• v.21 no.6
• /
• pp.419-427
• /
• 2018

In case high strength steels are applied for press-formed automotive parts, it is very difficult to secure forming accuracy due to large springback compared to moderate strength steels. In this study, a repetitive step-wise forming analyses based on secant method was proposed as the die design method for mandrel(bending tool) for the 2-axis bending equipments. A bending die with circular mandrel was designed for the DP780 blow motor case of which diameter and thickness are 70.8mm and 2.0mm respectively. Forming tests were performed to verify the validity of established die design and the results were compared with that of conventional HGI(Hot galvanized iron steel) blow motor case. For additional improvement in forming accuracy, an elliptical mandrel was proposed and its validity was verified using forming analyses based on secant method.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 1996.06c
• /
• pp.937-946
• /
• 1996

A Far Infrared Ray (FIR) dryer was designed , constructed and tested for red pepper , lycium chinese, and mushroom (Cortiellus shiitake ) drying , and the results were compared to the heated air dryer at the same condition. In the FIR dryer, three different panel materials , galvanized, copper and stainless steel, were used and no ceramic coating and those with ceramic coating (three panels) were 58% , 56%, 64%, and 88% , respectively. The drying times of lycium chinese and mushroom were shortened in FIR dryer by 6 hrs and 4 hrs compared to the heated air drying, respectively. while to remarkable difference in the drying times was found in the red pepper drying . The quality of products was better in FIR dryer where more red color value for red pepper and lycium chinese and more brightness for mushroom . The drying performance of a FIR dryer was superior in terms of total cost of 80,800 WON /100kg of lycium chinese , reduced by 25% compared to the heated air drying.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.4
• /
• pp.405-412
• /
• 2012

In the past, a very popular way to reduce the corrosion rate of zinc was the use of chemical conversion layers based on $Cr^{+6}$. However, the use of chromium salts is now restricted because of environmental protection legislation. Previous research investigated the optimum corrosion resistance of galvanized steel treated with an organic/inorganic solution containing Si. The result showed that the optimum corrosion resistance occurred by heat treatment of $190^{\circ}C$ in 5 min. In this study, one organic and three hybrid organic/inorganic coating solutions were applied to cold-rolled (CR) carbon steel. The coatings were then evaluated for corrosion resistance under a salt spray test. The coating solutions examined in this study consisted of urethane-only, urethane-Si, urethane-Si-Ti, and urethane-Si-Ti-epoxy. The results of the 7 h salt spray test showed that the urethane-Si-Ti and urethane-Si-Ti-epoxy coating solutions had superior corrosion resistance on CR steel.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.9
• /
• pp.1062-1069
• /
• 2011

In electro-galvanizing line to manufacture the electro-galvanized steel sheet, polishing system is required to maintain clean surface of conductor roll and to secure the quality of the steel sheet. At the same time, prediction and decision of the replacement cycle for felt material and its brush installed in the polishing system is also important because the brush is directly contacted on the conductor roll surface. In this study, the polishing system has been designed which the brush is repetitive translating according to the longitudinal direction of the conductor roll. Furthermore, the prediction on the wear-life of the felt material used for the brush is performed using the contact pressure extracted by finite element analysis. And to verify the predicted wear-life of the felt material, the experimental study is also carried out. From the comparison result between the predicted and the measured wear-life of the felt material, it is presented that the wear-life and the replacement cycle of the felt material are well predicted by considering a wear compensation factor, and the wear compensation factor is useful and reasonable.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.2
• /
• pp.535-541
• /
• 2013

The present study was carried out to investigate the effects of welding parameters such as current, voltage and shielding gases on the bead shape, microstructures and hardness. It was confirmed that bead height was lowered and bead depth was increased with increasing voltages while height, depth and width of beads increased with welding currents. The hardness of weld metals with Ar+10% $O_2$ and Ar+20% $CO_2$ was low due to the formation of grain boundary and polygonal ferrites while that of weld metals with Ar+2% $O_2$ was high due to the presence of acicular, bainitic and sideplate ferrites.

• Journal of Biosystems Engineering
• /
• v.33 no.3
• /
• pp.173-178
• /
• 2008

Some physical properties of rapeseed were measured at five moisture levels of 10.03, 14.91, 20.07, 25.06 and 30.12% (w.b.), which include frictional properties (coefficient of static friction, emptying and filling angle of repose) and aerodynamic properties (terminal velocity and drag coefficient). The physical properties of rapeseed were evaluated as a function of seed moisture content. In the moisture content range, the coefficients of static friction, emptying and filling angle of repose increased linearly with increase of moisture content. The maximum values of coefficients of static friction were on the acrylic surface, varied from 0.34 to 0.43; the next is on the galvanized steel, varied from 0.30 to 0.38; and the minimum were on stainless steel surface, varied from 0.27 to 0.35. Emptying and filling angle of repose varied from 26.12 to 29.62 and 23.83 to 27.05 degrees, respectively. Terminal velocity increased linearly from 3.47 to 3.91 m/s with increase of moisture content. Drag coefficient varied from 1.84 to 1.64 as the moisture content increased. The relationship between drag coefficient and moisture content were expressed by non-linear equation.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.28 no.2
• /
• pp.63-73
• /
• 1986

The model was developed by applying the principles of Bacot and Vidal to measure the behavior of deformation of the reinforced earth wall, and various tasts were performed by using the plastic fabric filter and the galvanized steel plate as a strip. The results obtained are as follows; 1. When the reinforced earth wall is deformed by the load, the strip is completely reinforced by the backfill materials and changed to the rigid block state, under the state of failure which permits sliding only, the next theoretical equation is formed. (H/L) . tan$\theta$ [cosO-sinOtanO] =2sinO[tan($\theta$ +0) +tanO] 2.The degree of the mutual reinforcement of the backfill material and the strip depend on the physical characteristics of the each material especially the angle of shearing resistance of the backfill material is desirable over 20$^{\circ}$ and, if it is over 400, its function could be a maximum. 3.The distribution of the maximum tensile strain of the reinforcement is changing with the height of reinforced earth wall, and when the height from bottom of the reinforced earth wall is 1.85 to 3. 35m, the maximum tensile strain appears at 2m from the skin element. The maximum tensile strain is increased by the depth of the reinforced earth wall from surface, and increased with the lapse of time after construction. 4.The failure surface of the reinforced earth wall by the concrete skin was about 60$^{\circ}$and the failure behavior of the reinforced earth wall in which the fabric filter was buried was slow, and so the pore pressure could be decreased. 5.It is possible to construct the fabric retained earth wall by the plastic fabric filter only. And the reinforcing effect between the steel plate and the plastic fabric filter is not largely different. however, in the aspect of the economic durability, the plastic fabric filter is more advantageous. 6.The reinforcing action mainly depends on the width and the length of the reinforcing materials, if possible, the full width is advantageous to enlarge the contact area with backfill. but considering the economic aspect, it is neccessary to develop the method controlling the space of the strip.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.68-68
• /
• 2009

Recently, resistance spot welding using Inverter DC is applied to improve the weldability of high strength steel for the auto-body fabrication. In this study, inverter DC spot welding machine, which is developed in the domestic, was evaluated weldability of the galvanized and cold rolled dual-phase steel(tensile strength : 590MPa). The welding conditions (welding time, current and force) were decided by tensile-shear test, and welding strength and nugget size were analyzed by statistical analysis methods which involved dynamic resistance and indentation. The results of the statistical analysis was utilized for real-time estimation of the invisible nugget size and tensile strength. Moreover, it can be achieved without the conventional destructive testing of welds.

• Journal of Biosystems Engineering
• /
• v.40 no.3
• /
• pp.201-211
• /
• 2015

Purpose: Designing equipment for processing, sorting, and other post-harvest operations of agricultural products requires information about their physical properties. This study was conducted to investigate some of the mechanical and physical properties of Moringa oleifera L. pods and seeds. Methods: Properties such as the length, width, thickness, bulk density, porosity, mass, static coefficient of friction, and angle of repose were determined as a function of moisture content. Statistical data and force-deformation curves obtained at each loading orientation and moisture level were analyzed for bioyield point, bioyield strength, yield force, rupture point, and rupture strength using a testrometric machine. Result: The basic dimensions (length, width, and thickness) of moringa pods and seeds were found to increase linearly from 311.15 to 371.45 mm, 22.79 to 31.22 mm, and 22.24 to 29.88 mm, respectively, in the moisture range of 12 to 49.5% d.b. The coefficient of friction for both pods and seeds increased linearly with an increase in moisture content on all the surfaces used. The highest value was recorded on mild steel, with 0.581 for pods and 0.3533 for seeds, and the lowest on glass for pods, with a value of 0.501, and of 0.2933 for seeds on galvanized steel. The bioyield and rupture forces, bioyield and rupture energies, and deformation of the pods decreased with an increase in moisture content to a minimum value, then increased with further decrease within the moisture content range, while the yield force increased to a maximum value and then decreased as the moisture content increased. Conclusion: These results will help to determine the most suitable conditions for processing, transporting, and storing moringa pods, and to provide relevant data useful in designing handling and processing equipment for the crop.