• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.134-135
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• 2003

The dental implant materials required good mechanical properties, such as fatigue strength, combined with a high resistance to corrosion. For increasing fatigue resistance and delaying onset of stress corrosion cracking, shot peening has been used for > 50 years to extend service life of metal components. However, there is no information on the electrochemical behavior of shot peened and hydroxyapatite(HA) coated Ti-6Al-4V alloys. To increase fatigue strength, good corrosion resistance, and biocompatibility, the electrochemical characteristics of Ti/TiN/HA coated and shot peened Ti-6Al-4V alloys by electron beam physical vapor deposition(EB-PVD) have been researched by various electrochemical method in 0.9%NaCl. Ti-6Al-4V alloys were prepared under the condition of hydrogen and vacuum arc furnace. The produced materials were quenched at 1000$^{\circ}C$ under high purity dried Ar atmosphere and were hold at 500$^{\circ}C$ for 2 hrs to achieve the fatigue strength(1140㎫) of materials. Ti-6Al-4V alloys were prepared under the condition of hydrogen and vacuum arc furnace. Shot peening(SP) and sand blasting treatment was carried out for 1, 5, and 10min. On the surface of Ti-6Al-4V alloys using the steel balls of 0.5mm and alumina sand of 40$\mu\textrm{m}$ size. Ti/TiN/HA multilayer coatings were carried out by using electron-beam deposition method(EB-PVD) as shown Fig. 1. Bulk Ti, powder TiN and hydroxyapatite were used as the source of the deposition materials. Electrons were accelerated by high voltage of 4.2kV with 80 - 120mA on the deposition materials at 350$^{\circ}C$ in 2.0 X 10-6 torr vacuum. Ti/TiN/HA multilayer coated surfaces and layers were investigated by SEM and XRD. A saturated calomel electrode as a reference electrode, and high density carbon electrode as a counter electrode, were set according to ASTM GS-87. The potentials were controlled at a scan rate of 100 mV/min. by a potentiostat (EG&G Co.273A) connected to a computer system. Electrochemical tests were used to investigate the electrochemical characteristics of Ti/TiN/HA coated and shot peened materials in 0.9% NaCl solution at 36.5$^{\circ}C$. After each electrochemical measurement, the corrosion surface of each sample was investigated by SEM.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.217-220
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• 2001

In the shearing process the burr or rollover must be minimized in order to improve the quality of product. The burr size can be minimized by control of several process parameters. But removal of all burrs are impossible. Most mechanical type deburring methods (vibrating bowls, rotating barrels, shot blasting, for example.) will remove large burrs, other methods use chemical (electro-chemical deburring) or heat (thermal energy deburring). The electro-chemical deburring process removes burrs by the deplating method. Electro-chemical deburring equipment is requires a small capital investment than other methods(mechanical or thermal methods). Electro-chemical deburring method need to many parameters for control such as a time, voltage and concentration of electrolyte. In this paper shows relations of these parameters by experiment.

• Journal of the Semiconductor & Display Technology
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• v.10 no.3
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• pp.35-42
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• 2011

This paper describes the characteristics of high speed grinding and the influence of wheel surface speed V and a grindability of the grinding materials. The various fine ceramics pieces was ground by metal and vitrified bonded diamond wheel. The surface roughness of fine ceramics(Zirconia($ZrO_2$), Silicon Carbide(SiC), Silicon Nitride($Si_3N_4$), Alumina($Al_2O_3$)) decreases from $0.05{\mu}m(R_{max})$ to $0.025{\mu}m(R_{max})$ when the wheel speed at grinding point increases the wheel speed. Relation between the temperature at grinding point and surface roughness was linear. Abrasive jet machining(AJM), a specialized from of shot blasting, is considered one of the most helpful micro machining methods for hard and brittle materials such as glasses and ceramics by constant pressure grinding.

• Explosives and Blasting
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• v.27 no.1
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• pp.7-20
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• 2009

In this study, 5 steps of different delay intervals are applied to a plasma rock-breaking machine that is driven by electric shocks in order to improve the workability of the traditional single-shot type plasma rock-breaking operation. The sequential steps use the electrolyte volume per delay of 1, 2, 3, 4, 5 kg and it has been analyzed to measure the delay time and level of the ground vibration and noise according to exploding. The delay time of the rock-breaking machine by an electric shock of 5 steps has used about 40~50ms at the electrolyte connected from 1 to 3 holes, about 70~80ms at the electrolyte connected from 4 to 5 holes. It is identified that the extents of the ground vibration is low to 1 over 3~6 compared with that of the emulsion explosives.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.621-626
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• 1998

An experimental investigation on the reinforcing bar corrosion and relationshid of reinforcing bar and concrete bond strength has been conducted to establish the allowable limit of rust in the construction field. The reinforcing bars used in this study were rusted before embedding in concrete. The first component of this experiment is to make rust of reinforcing bar rust artificially based on Faraday's theory at certain rates such as 2, 4, 6, 8 and 10% of reinforcing bar weight. For estimation of the amount of rust by weight, Clarke's solution and Shot blasting were adopted and compared. Parameters include 240 and 450kg/㎠ of compressive strengths and diameter of reinforcing bar (16, 19 and 25mm) corresponding development length for pull-ort test. And, pull-out tests were carried. out according to KSF 2441 and ASTMC 234 to investigate the effect of the corrosion rate on reinforcing bar-concrete bond behavior. It is found from the test results that the test techniques for corrosion of bar used in this study is relatively effective and correct test method. Results shows that up to 2% of rust increases the bond strength regardless of concrete strength and diameter of reinforcing bar like the existing data. It might be because of the roughness from rust. As expected, the bond strength increases as compressive strength of concrete increases and the diameter of bar decreases.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.478-481
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• 2004

An experimental investigation on the relationship between corrosion of reinforcement and bond strength in pull-out test specimen has been conducted to establish the allowable limit of rust of reinforcement in the construction field. The reinforcing bars used in this study were rusted before embedded in pull-out test specimen. The first component of this experiment is to make reinforcing bar rust electrically based on Faraday's theory to be 2, 4, 6, 8 and $10\%$ of reinforcing bar weight. For estimation of the amount of rust by weight, Clarke's solution and shot blasting were adopted and compared. Parameters also include 24 and 45MPa of concrete compressive strengths and diameter of reinforcing bar (16, 19 and 25mm). Pull-out tests were carried out according to KS F 2441 and ASTM C 234. Results show that up to $2\%$ of rust increases the bond strength regardless of concrete strength and diameter of reinforcing bar. As expected, the bond strength increases as compressive strength of concrete increases and the diameter of bar decreases.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.562-567
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• 2006

Micro-alloyed steel or heat-treatment-free used in clean technology have been replacing for conventional quenched-and-tempered structural steels since the micro-alloyed forging steel was developed in early 1970s in Germany for saving money of heat treatment, simplified process, short delivery and good productivity. In this paper, ball stud assembled in steering system for automobile was selected to compare conventional process making heat treatment with new process using high strength micro-alloyed steel without heat treatment. The conventional process for ball stud was composed of a total of 6 steps including upsetting, forward extrusion, machining, burnishing and tread rolling with heat treatment and shot blasting. As opposed to conventional process, newly proposed process for ball stud using the clean technology without heat treatment is simplified such as forward extrusion, heading, upsetting, forming having a flange shape and tread rolling. Also net shape forming process to achieve specified process not to include machined step fur manufacturing the ball stud was applied to newly simplified process since micro-alloyed steel is difficult to be formed.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.206-214
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• 2004

Residual wall thicknesses, corrosion rates, and residual life of thirty four samples of cast iron pipes(CIPs) and ductile cast iron pipes(DCIPs) collected from water mains of B city were studied to estimate their remaining service life or optimum time of rehabilitation. The internal maximum corrosion depths of samples measured using a dial gauge after shot blasting were twice higher than the external in most cases. Therefore corrosion of water pipes was much more affected by internal water quality than soil. Residual wall thicknesses of DCIPs were higher than those of CIPs. That reason was thought to be that DCIPs have been protected from internal corrosion by lining cement mortar. Residual life calculated by maximum corrosion rate was ranged up to 44 years with 12.40 years average. Since most CIPs were much deteriorated, rehabilitation plan should be established soon in B city. Residual life of DCIP was 33.52 years average. When cement mortar lining is used up by neutralization of DCIPs. DCIP also should be rehabilitated.