• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.5 no.2
• /
• pp.46-56
• /
• 1996

Drilling tests were carried out austempered ductile castiron(ADI) to clarify the factors influencing the drilling characteristics of ADI material. The machinability of material was evaluated using high speed steel drill and cobalt contained drill of 6mm diameter. The spheroidal graphite cast iron materials were austenized at 90$0^{\circ}C$ for 1 hour and then wear was kept at 375$^{\circ}C$ for 2 hours. Austempered ductile cast iron contains a great deal of retaine austenite which contributes to an improvement of impact strength, In this paper, machinability of ADI was investigated by drilling experimentation. The results obtained are as follows: a)Flank wear increases logarithmically with the increases of cutting time. b) Relation of flank wear and cutting force can be appiled to $F_z$ = 925VB + 820 for the cutting suggested condition. c) Drilling hole number of about 2 times can be reduced more step feed than ordinary feed due to the high hardness of ADI material and hardness increasing ascribed to the martensite of retained austenite.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.6
• /
• pp.142-149
• /
• 2002

The frictional properties of nylon can be improved by the impregnation of lubricants like wax, oil or graphite. The inclusion of these lubricants, on the other hand, decreases the mechanical properties of nylon, such as tensile strength, hardness and impact strength. As an attempt to maximize frictional properties, while minimizing a decrease in the mechanical properties, various kinds of nylon containing 3 wt% wax and varying contents of oil or graphite were prepared. It was found that the synergy effects to improve both friction and anti-wear properties is evidenced by impregnating a combination of wax/oil or wax/graphite. The wear rate of a nylon containing 3 wt% of wax and 1.5 wt% of oil turned out to be 1/4 of that of nylon impregnated with 8 wt% wax or 8 wt% oil. The latter showed the lowest wear rate among the nylons prepared with a single lubricant. In addition, the friction coefficient of the developed nylon was found to be very similar to the nylon with 8 wt% wax only.

• The Journal of Korean Academy of Prosthodontics
• /
• v.39 no.1
• /
• pp.84-95
• /
• 2001

Titanium is widely used in dentistry for its low density, high strength, fatigue resistance, corrosion resistance, and biocompatibility. But it has a tendency of surface damage under circumstance of friction and impact for its low hardness of the surface. Coating is one of methods fir increasing surface hardness. Its effect is to improve surface physical characteristics without change of titanium. Diamond-like carbon and titanium nitride are known for its high hardness of the surface. So that this study was aimed at the wear test and the cytotoxicity test of the commercially pure titanium and Ti-6Al-4V alloy which were deposited by diamond-like carbon film or titanium nitride film to acertain improvement of the surface hardness and the biocompatibility. A disk (25mm diameter, 2mm thickness) was made of commercially pure titanium and Ti-6Al-4V alloy and these substrates were deposited by diamond-like carbon film or titanium nitride film. Diamond-like carbon film was deposited by the method of radiofrequency plasma assisted chemical vapor deposition and titanium nitride film was deposited by the method of reactive arc ion plating. Then these substrates were tested about wear characteristics by the pin-on-disk type wear tester in which ruby ball was used as a wear causer under the load of 32N, The fracture cycles were measured by rotating the substrates until their films were fractured. The wear volume was measured after 150 cycles and 3,000 cycles using surface profiler. The cytotoxicity test was peformed by the method of the MTT assay. The results were as follows : 1. In the results of the wear volume test, commercially pure titanium and titanium alloy which were coated by diamond-like carbon film or titanium nitride aim had higher resistance against wear than the substrates which were not coated by any films (P<0.05). 2. In the results of the fracture cycle test and the wear volume test, diamond-like carbon film had higher resistance against wear than titanium nitride film (P<0.05). 3. In both coatings of diamond-like carbon aim and titanium nitride film, Ti-6Al-4V alloy had higher resistance against wear than commercially pure titanium (P<0.05) 4. In the results of the cytotoxicity test, diamond-like carbon film and titanium nitride film had little cytotoxicity as like commercially pure titanium or Ti-6Al-4V alloy (P>0.05).

• Journal of the Korean Society of Safety
• /
• v.30 no.3
• /
• pp.7-12
• /
• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.45 no.3
• /
• pp.188-193
• /
• 2009

The present study was undertaken to evaluate the effect of temperature on the results of Charpy impact test for glass fiber reinforced polyurethane(GF/PUR) composites. The Charpy impact test were conducted in the temperature range from -50$^{\circ}$ to 50$^{\circ}$. The impact fracture toughness of GF/PUR composites was considerably affected by temperature and it was shown that the maximum value was appeared at room temperature. It is believed that sensitivity of notch on impact fracture energy were increased with decrease in temperature of specimen. As the GF/PUR composites exposed in low temperature, impact fracture toughness of composites decreased gradually owing to the decrease of interface bonding strength caused by difference of thermal expansion coefficient between the glass fiber/polyurethane resin. And decrease of interface bonding strength of composites with decrease in specimen temperature was ascertained by SEM photographs of Charpy impact fracture surface.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2001.11a
• /
• pp.26-27
• /
• 2001

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.3
• /
• pp.73-79
• /
• 2002

This paper presents the experimental results to verify the environmental consciousness with economic balances due to cutting fluid behaviors, effectiveness in machining process. Even though cutting fluid improves the Productivity through the cooling, lubricating effects, its environmental impact is also increased according to the cutting fluid usage. The primary mechanism considered in this study is the spin-off motion of fluids away from rotating workpiece. In this study some parameters arc adopted to analyze the productivity(tool wear), environmental impact(mist diffusion rate). The results present talc criteria for the resonable cutting fluid usage quantitative1y to develop the environmentally conscious machining process.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.42-47
• /
• 2004

Metallic glasses are amorphous meta-stable solids and are now being processed in bulk form suitable for structural applications including impact. Bulk metallic glasses have many unique mechanical properties such as high yield strength and fracture toughness, good corrosion and wear resistance that distinguish them from crystalline metals and alloys. However, only a few studies could be found mentioning the dynamic response and damage of metallic glasses under impact or shock loading. In this study, we employed a small explosive detonator for the dynamic indentation on a Zr-based bulk amorphous metal in order to evaluate the damage behavior of bulk amorphous metal under impact loading. These results were compared with those of spherical indentation under quasi-static and impact loading. The interface bonded specimens were adopted to observe the appearances of subsurface damage induced during indentation under different loading conditions.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.31 no.2 s.161
• /
• pp.236-246
• /
• 2007

The purpose of the current study is to investigate the underlying reasons of fashion brand repurchase intention formation based on means-end chain theory and to identify whether the price level moderates the relationships between attribute evaluation and re-purchase intention. Questionnaire data from 291 consumers who had purchase experience of casual wear during the last 6 month period through off-line retail shops were analyzed. The results showed that hedonic shopping value had a positive impact on aesthetic attribute and utilitarian shopping value also had a positive impact on physical attribute of fashion product. While aesthetic attribute had a positive influence on brand repurchase intention, physical attribute had no effect on brand repurchase intention. In addition, there was no moderating effect of price level between the links from shopping value to fashion product attribute evaluation. When casual wear companies have to devise price related strategies, they need to pay attention to diverse promotion factors except for product attributes to realize price-based differentiation.

• Proceedings of the KWS Conference
• /
• 2006.10a
• /
• pp.26-28
• /
• 2006

When materials such as metal are into the secondary side of steam generator, they, so called foreign objects, may have influences on the integrity of the steam generator tubes. They cause the tube wear due to the relative motion between the tubes and foreign objects and the tube impact due to flow. The best way to avoid the effects is to remove all the foreign objects. However, it is not easy to remove the foreign materials thoroughly due to their condition such as the location. Considering the wear and impact by the foreign materials, KEPRI(Korea Electric Power Research Institute) developed the methodology to evaluate the foreign materials analytically. This methodology was described with a computer program in order to obtain the fast results. The program informs whether the tubes have the structural integrity when the foreign material strikes the tubes. Moreover, this gives us the remaining life of the steam generator tubes. In this paper, the program, which evaluates the effects of the foreign objects in the secondary side of steam generator, is introduced.