• Tribology and Lubricants
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• 제11권5호
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• pp.31-39
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• 1995

The surface integrity of a machined surface is an important factor that dictates several performance characteristics of a metal part. In this paper, the surface integrity aspects are presented specifically with respect to the tribological properties of steel. Test specimens were prepared under varying conditions to induce different levels of surface deformation and hardness. Sliding and rolling experiments were performed to assess the friction and wear characteristics of these specimens using a pinon-disk type tribotester and a plate-on-ball type set-up. It is reaffirmed that heat treated steels possess superior sliding and rolling fatigue resistance than raw steel. However, for the case of raw steels machined under varying conditions, the harder specimen resulted in higher wear. This result is attributed to the presence of surface cracks that were induced during machining. The results of such findings will aid in the optimization of surface preparation process for tribological applications of steel.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제27권4호
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• pp.307-314
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• 2005

After dental implant are planted into their bony site among the various growth factors associated with bone formation. BMP is expressed in the bone surrounding the implant fixture. By taking a close look at BMP2, BMP4 which are growth factors that take put in bone formation, its histologic features and radiographic bone healing patterns we would like to examine the mechanism of osseointegration. We randomly used 8 male and female house rabbit amd used diameter 5 mm height spiral shaped implants(Ostem, Korea) for animal use handled as a resorbable blast machined(RBM) surface and machined surface. 2group were formed and each group had RBM surface and machined surface implant or a simple bone cavity. After 3, 7, 14 and 28 days post surgery 2 objects were sacrificed from each group and histologic specimens were acquired. RT-PCR analysis was conducted and after H&E staining the extent of osseointegration was measured applying a histologic feature and histomorphometric analysis program. Quanitity one -4.41(Bio-Rad, USA) was used after scanning the PCR product image of the growth factors manifested in each group. According to the histomorphometric features the RBM, Machined surface group showed increased contact between bone and implant surface at 3, 7, 14 and 28 days after surgery. The BMP2 level increased in both experiment groups but remained unchanged in the contrast group. BMP4 levels stayed steady after the early post implantation period for RBM but showed decreased in the machined surface group and contrast group. The amount of contact between bone and implant surface increased with the passage of time. BMP2, BMP4 were expressed in both experimental group and contrast group. These growth factors play a role in osseointegration of implant.

• 산업기술연구
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• 제21권A호
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• pp.27-32
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• 2001

This paper deals with the study on the culling characteristics in ball-end milling process. First of all, the effects of the geometric cutting conditions such as the spindle speed, feedrates on the surface integrity and machining stability were evaluated by the analytical and the experimental approaches. A large amount of experimental sets are performed to evaluate the effects of chatter phenomenon on the machined surface. The optical microscope and the surface roughness measuring machine are used to measure the surface integrity and roughness of the machined surfaces.

• 한국정밀공학회지
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• 제13권1호
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• pp.78-83
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• 1996

This paper presents the characteristics of surface roughness and cutting force in ultraprecision cutting of aluminium alloy using natural diamond tools whose edge radii are smaller than those of tools made of other materials. The feed rate and depth of engagement were set to be a micrometer order. After measuring the surface roughness of machined surface and cutting force for each cutting condition, the relations between the surface quality and its condition were investigated qualitatively. If the feed rate was under a certain limit, the machined surface quality was deteriorated unexpectedly. This is supposed to have happened due to vibration leading its condition to abnormal one. In a certain situation the machined surface roughness by a natural diamond tool was inferior to that made by a carbide tool whose cutting edge radius is larger. This is supposed to be caused by not normal machining but burnishing effect.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권6호
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• pp.514-523
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• 2006

The purpose of the present study was to evaluate the effects of several implant surface treatments to the bone formation, by placing Machined implants, 75${\mu}m$ Calcium phosphate-blasted implants and $Al_2O_3$-blasted and acid-etched implants in rabbit tibia through histomorphometric study. Two animals of each group were sacrificed at 2, 4, 8 weeks. The specimens containing the implants were dehydrated and embedded into hard methylmethacrylate plastic. Thereafter, the sections were ground to 50${\mu}m$. The specimens were stained with Villanueva bone stain for a light microscopic study. The results were as follows; 1. When the surface roughness of three different implants was measured by Surfcorder, the Ra of the Machined group, the RBM group and the SLA group was 0.16${\mu}m$, 0.44${\mu}m$, and 1.08${\mu}m$. 2. When examining the surfaces of the implants in the scanning microscope, Machined implant has the smooth surface with a few scratches, RBM implant has the rough surface with curled ridges and valleys, and SLA implant has the rough surface structures such as sharp protruding parts and micropits measuring 1-2${\mu}m$ in diameter. 3. After 2 weeks of implantation, the percentage of bone-to-implant contact of the Machined group, the RBM group and the SLA group was 26.86%, 35.40% and 45.99%. However, its differences between each group decreased during the healing periods. 4. After 2 weeks of implantation, the percentage of bone area inside the threads of the Machined group, the RBM group and the SLA group were 21.55%, 30.43% and 41.18%. However, its difference of bone area between machined group and surface treatment groups was maintained but the difference within the surface treatment groups decreased during the healing periods. In summary, the amount of bone formation in RBM and SLA group was greater than Machined group in early healing stage. These results suggest that RBM and SLA implants can reduce the healing period for osseointegration and may be suitable for early function.

• 대한치과교정학회지
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• 제41권4호
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• pp.268-279
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• 2011

본 연구의 목적은 유지력을 높이기 위하여 교정용 미니 임플랜트에 표면처리를 시행하되 식립 과정의 용이성에 영향을 주지 않는 표면처리 방법을 찾기 위함이다. 교정용 미니 임플랜트를 etching, resorbable blasting media (RBM), 상부 나사산 부위만 RBM 처리를 한 hybrid 등의 3가지 방법으로 표면처리한 후 machined (표면 미처리)군과 비교하였다. 주사전자현미경과 표면 거칠기 측정기로 표면 거칠기를 비교하였으며, driving torque tester를 이용해 실험용 인공골에 교정용 미니 임플랜트를 식립하여, 식립 토크(rotational torque)와 수직력(vertical loading)의 식립 패턴을 비교하였다. Machined surface군과 비교하여 acid etching군에서는 표면 거칠기(Ra 값)가 크지 않았으나 ($p$ > 0.05), RBM군이나 hybrid군에서 표면 거칠기(Ra 값)가 유의하게 컸다 ($p$ < 0.05). 최종 식립 토크는 모든 표면처리군에서 machined군보다 컸다 ($p$ < 0.05). 최대 식립수직력은 hybrid군이 machined군이나 etched군보다 유의하게 작았으며 ($p$ < 0.05), RBM군이 가장 컸다 ($p$ < 0.05). 교정용 미니 임플랜트의 유지력을 높이기 위하여 보철용 임플랜트와 같은 방법으로 전면 표면처리를 하면 self drilling type 고유의 골 삭제기능이 저하될 수 있다. 그러나 cutting edge 일정 부위를 제외하며 적절하게 조절된 표면처리를 하면 골 삭제 능력의 큰 저하 없이 용이한 식립이 가능할 것으로 보인다.

• 한국정밀공학회지
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• 제6권3호
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• pp.68-77
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• 1989

The surface rolling for cylindrical surface of a grey cast iron was carried out using a lathe with a simple newly-designed tool system. A surface rolling tool used was steel ball whose diameter was 3/8 inch (9.525mm) The effects of rolling feeds and number of rolling on surface rolling were investigated. The contact pressure between ball and workpiece which was considered as Hertz's contact problem was examined and the track of motion of a ball on the cylindrical surface of a work- piece was measured according to the rolling feed. The results obtained were as follows; 1. The roughness of the machined surface which was originally 5.3 .approx. 28 umRz decreased to 1.2 .approx. 5 umRz according to rolling feeds and numbers of rolling. 2. The hardness increased from Hv 260 to Hv 290 .approx. 310 through 2 .approx. 4 rollings according to the roughness of machined surfaces. 3. The reduction of diameter was found to be proportional to the variations of roughness of previous machined surfaces. About 60% to 90% of reduction in diameter was made during the first rolling process. 4. An equation relating the reduction of diameter and the variation of surface roughness after surface rolling was presented using a geometric surface model. 5. An equation for the calculation of dynamic contact area between pressure ball and workpiece according to the rolling feed was presented.

• Journal of Periodontal and Implant Science
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• 제38권3호
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• pp.503-510
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• 2008

Purpose: To evaluate bone formation on the implant surface between machined fixture and RBM surface fixture through analyzing of distribution and concentration of Ca and P by EPMA. Material and Methods: Fixtures had divided in 2 group: Machined(Group I), RBM (Group II). Total 4 fixtures were implanted on rabbit which sacrificed on 2 week and 4 week for the histological specimens. By these specimens EPMA value were measured, compared and analysed by each group to figure out the evidence of clinical use of RBM implant. Result: After 2 weeks and 4 weeks, it was analyzed that bone formation area, distribution and concentration of Ca and P by EPMA. In distribution and concentration of P Group II was higher than Group I, but there were no statistical significances. In new bone formation area, Group II was more higher than Group I with statistically significances. Both of group, after 4 weeks area is little bit higher than after 2 weeks area but there is no statistically significances. Conclusion: RBM implant was better than machined implant on the early bone formation.

• Journal of Periodontal and Implant Science
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• 제37권3호
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• pp.575-584
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• 2007

The present study was performed to evaluate the effect of citric acid on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, and HA coated surface were utilized. Pure titanium machined surface and HA coated surface were rubbed with pH 1 citric acid for 30s., 45s., 60s., 90s., and 120s. respectively. Then, the specimens were processed for scanning electron microscopic observation. The following results were obtained. 1. The specimens showed a few shallow grooves and ridges in pure titanium machined surface implants. The roughness of surfaces conditioned with pH 1 citric acid was slightly increased. 2. In HA-coated surfaces, round particles were deposited irregularly. The specimens were not significant differences within 45s. But, began to be changed from 60s. The roughness of surfaces was lessened and the surface dissolution was increased relative to the application time. In conclusion, pure titanium machined surface implants and HA coated surface implants can be treated with pH 1 citric acid for peri-implantitis treatment if the detoxification of these surfaces could be evaluated.

• 한국정밀공학회지
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• 제5권4호
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• pp.59-65
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• 1988

This paper describes the transmutation layer of CNC Wire electrical discharte machined surface. In order to analayze and invesigate transmutation layer of the carbon tool steel, workpieces was heat-treated by quenching, tempering, normaling. The obtained results are summarized as follows. 1. The result showed that wire electrical discharge machined surface region was transmuted into the recdast layer in the range of about 10${\mu}$m deep by resolidification and next zone was transmuted into the heat affected zone in the range of about 15${\mu}$m deep by high temperature. 2. The hardness of the recast layer and heat affected zone was decreased on its machined surface. 3. The more wire feedrate was increased, the more electrical discharge machine gap was decreased.