• Tribology and Lubricants
• /
• 제19권1호
• /
• pp.26-30
• /
• 2003

The stresses of surface and substrate under the rough surface contact are irregular. Using rainflow counting method for irregular stresses, the fatigue surface crack initiation lift was calculated. With the surface generated by computer, this paper figures out the random load generated by contacting to the rough surface, analyzes the stress of its subsurface, and calculates the fatigue crack initiation life of the rough surface fatigue theory.

• Tribology and Lubricants
• /
• 제22권5호
• /
• pp.276-281
• /
• 2006

The fractal dimension is quantitatively to define the irregular characteristic of the shape in natural. It can be useful in describing morphological characteristics of various wear particles. This paper was undertaken to diagnose failure condition for sliding members in lubrication by fractal dimension. It will be possible to diagnose wear mechanism, friction and damage state of machines through analysis of shape characteristics for wear particle on driving condition by fractal parameters. In this study, the calculating and analyzing methods of fractal dimensions were constructed for the condition monitoring and wear particle analysis in lubricant condition. So, we carried out the Friction and wear test with the ball on disk type tester, and the fractal parameters of wear particle in lubricated conditions were calculated. Fractal parameters were defined as texture fractal dimension ($D_{t}$), structure fractal dimension ($D_{s}$) and total fractal dimension (D).

• 한국안광학회지
• /
• 제10권3호
• /
• pp.237-240
• /
• 2005

The cause of poor visual acuity was connected to the damage by the ocular trauma related. Especially the most cause of visual disorder was identified as irregular pupil by ocular damage. Therefore most patients stopped the wearing of the contact lens immediately by the visual decrease effects from irregular pupil disorder. But we had suggested that the contact lens wear was a very intensive visual therapy. We had identified the visual recover from several tests using the contact lens treatment.

• 소성∙가공
• /
• 제24권3호
• /
• pp.205-211
• /
• 2015

The current investigation was performed to study sliding-wear-rate deviation (wear-rate data scatter) in carbon steels with various microstructures. Pure iron, 0.2 wt. % C steel, 0.45 wt. % C steel, and bearing steel (AISI52100) were used for the investigation. These steels possess different microstructures. Microstructures of the pure iron, two carbon steel and the bearing steel were full ferrite, ferrite + pearlite and full pearlite, respectively. Depending on the carbon content, the carbon steel had different pearlite-volume fractions. Dry sliding wear tests of the steel were conducted using a ball-on-disk wear tester at a sliding speed of 0.1 m/s using a bearing ball (AISI52100) as a counterpart. Applied load and sliding distance were 100 N and 300 m, respectively. More than three (up to twelve) tests were conducted for each steel under the same conditions, and the mean deviations in the wear rate of the steel (microstructure) were compared. The wear-rate deviation in the steel with ferrite + pearlite microstructure was higher than that with ferrite microstructure, and the deviation decreased with the increase of pearlite volume fraction. The pure iron and the bearing steel specimens showed much less deviation. The high deviation observed from the ferrite + pearlite steel was attributed to irregular subsurface-crack nucleation and growth at the interface between the two micro constituents (ferrite and pearlite) during the wear test.

• 한국기계가공학회지
• /
• 제10권1호
• /
• pp.80-86
• /
• 2011

This study compared and analyzed manual tapping and automatic tapping regarding tapping process characteristics of titanium hard-to-cut-material. Tapping process characteristics of titanium hard-to-cut-material are evaluated as the quality of a screw, wear of a tap, economic analysis, and cycle time etc. The type of screw threads after manual tapping is formed as an irregular type of screw threads, and perfect screw threads are created after automatic tapping. In addition, the chip type after manual tapping process is formed as the discontinuous chip due to work hardening, and the powder type of chip after automatic tapping process is created. In terms of cycle time, an automatic tapping process is shortened by 70% compared to manual tapping process. Insert tip wear of an automatic tapping shown in the process of 5-hole tapping is not found, but hand tap wear for finish cutting is most severe.

• 대한치과보철학회지
• /
• 제58권4호
• /
• pp.369-377
• /
• 2020

점진적으로 진행되는 치아의 생리적인 마모는 정상적 현상이지만, 과도한 병적 마모는 기능장애와 교합평면의 부조화 및 심미성의 상실을 야기한다. 과도한 치아마모로 인해 구치부 지지의 상실 및 보철수복의 공간이 부족한 경우 수직교합고경 증가를 동반한 전악 수복이 고려될 수 있다. 본 증례는 잔존치의 과도한 치아마모와 기울어진 치은정점, 전치부 과개교합을 보이는 환자에서 교합거상을 통해 교합고경을 회복하였으며 부족한 구치부 보철 수복공간을 확보하고, 전치부 심미성과 교합관계를 개선할 수 있는 수직교합거상을 동반한 전악수복을 시행하였다. 체계적인 분석과 진단을 통해 임시보철물을 제작하여 충분한 적응기간을 거쳤으며, 이중 스캔방식을 통하여 단일구조 지르코니아 블럭을 사용해 최종보철물로 이행하여 기능적이고 심미적인 구강회복 결과를 얻었기에 이를 보고하고자 한다.

• 복식
• /
• 제63권4호
• /
• pp.132-142
• /
• 2013

This study has evaluated the physiological reaction to wearing brassiere as well as the sensations that the wearer feels in order to understand the effect of brassiere use on the human body. Six healthy women in their twenties were used as subjects and the experiment measured the difference in their S.C.L, Skin Temperature, B.V.P and Pulse. The measurements were made in the following conditions: Women not wearing any brassiere, women wearing sports brassiere, and the women wearing wire brassiere. The results showed significant differences in the following areas. 1. S.C.L was found to be the highest when they didn't wear any brassiere, followed by when they wore wire-brassiere and then sports brassiere. 2. The Skin Temperature was found to be the highest when they wore wire-brassiere, followed by when they wore sports brassiere and when they didn't wear any of them. In particular, when they wore sports brassiere, the B.V.P was found to be the highest when they wore none of them, fir skin temperature dropped as time passed. 3.ollowed by when they wore sports brassiere and then wire brassiere. When they wore sports brassiere, they had irregular blood-flow. 4. Pulse was found to be the highest when they didn't wear any of them, followed by when they wore sports brassiere and then wire brassiere. 5. Those who didn't wear any brassiere felt the most chill, followed by those wearing wire brassiere and then sports brassiere. The moisture level was found to be the highest when they wore sports brassiere, followed by when they wore wire brassiere and then when they wore none of them. Comfort level was found to be the best with no brassiere, followed by wire brassiere and then sports brassiere.

• Journal of Welding and Joining
• /
• 제15권1호
• /
• pp.116-124
• /
• 1997

A scope of this study is to establish the optimum plasma spray conditions for fine ($5\mu\textrm{m}$) $Al_2O_3$ powder. However, the flowability of the $Al_2O_3$ powder is not so good because of irregular particle shape and fine particle size. Therefore, powder feeding system was modified by 1) change of powder feeding line material from polymer to copper 2) shorten the powder feeding tube length 3) heating the powder feeding system to $80^{\circ}C$4) vibrating the powder feeding line continuously, in order to feed the fine powder homogeneously. The homogeneous powder feeding conditions were obtained with the modified powder feeding system by controlling the powder carrier gas flow and the powder flow rate indicator. The best plasma spraying conditions for the fine $Al_2O_3$ powder were found out as 40kw gun power, 80 g/min. powder feed rate and 50 mm working distance after characterizing the microstructure, hardness and wear loss of the $Al_2O_3$ coating layer.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 1996년도 특별강연 및 추계학술발표 개요집
• /
• pp.3-15
• /
• 1996

The formation of a thicker hard alloyed layer have been investigated on the surface of aluminum cast alloy (AC2B) by PTA overlaying process with Cr, Cu and Ni motel powders under the condition of overlaying current 125-200A. overlaying speed 150 mm/min and different powder feeding rate 5-20 g/min. In addition the characteristics of hardening and wear resistance of alloyed layer here been examined in relation to the microstructure of alloyed layer. Main results obtained were summarized as follows: 1) There was an optimum overlaying condition to get a good alloyed layer with smooth surface. This good layer became easy to be formed as increasing overlaying current and decreasing powder feeding rate under a constant overlaying speed. 2) Cu powder was the most superior one in metal powders used due to a wide optimum overlaying condition range, uniform hardness distribution of Hv250-350, good oar resistance and freedom from cracking in alloyed layer with fine hyper-eutectic structure. 3) On the contrary, irregular hardness distribution was usually obtained in Cr ar Ni alloyed layers of which hardness was increased as Cr or Ni contents and reached to maximum hardness of about Hv400-850 at about 60wt%cr or 40wt%Ni in alloyed layer. 4) Cracking occurred in Cr or Ni alloyed layers with higher hardness than Hv250-300 at mere than 20-25wt% of Cr or Ni contents in alloyed layer. Porosity was observed in all alloyed layers but decreased by usage of spherical powder with smooth surface.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.356-356
• /
• 2007

Plasma immersion ion beam deposition (PIIBD) technique is a cost-effective process for the deposition of diamond like carbon thin film, the possible solid lubricant on large surface and a complex shape. We used PIIB process for the preparation of DLC thin film on $Al_2O_3$ with deposition conditions of deposition temperature range $200^{\circ}C$, working gas pressure of 1.310-1Pa. DLC thin films were coated by $C_2H_2$ ion beam deposition on $Al_2O_3$ after the ion bombardment of SiH4 as the bonding layer. Energetic bombardment of $C_2H_2$ ions during the DLC deposition to ceramic materials generated mixed layers at the DLC-Si interface which enhanced the interface to be highly bonded. Wear test showed that the low coefficient of friction of around 0.05 with normal load 2.9N and proved the advantage of the low energy ion bombardment in PIIBD process which improved the tribological properties of DLC thin film coated alumina ceramic. Furthermore, PIIBD was recognized as a useful surface modification technique for the deposition of DLC thin film on the irregular shape components, such as molds, and for the improvement of wear and adhesion problems of the DLC thin film, high temperature solid lubricant.