• 한국정밀공학회지
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• 제12권3호
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• pp.62-72
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• 1995

The present study was undertaken to investigate the dry wear mechanism of the alumina ceramics in the purity variation for the wear of STB2. The wear test was carried out under different experimental condition various sliding speed, contact pressure and sliding distance. According as the alumina purity increased, wear volume of the STB2 decreased and minimum value of wear volume was over to high speed side. According as the sliding speed and sliding distance increased, friction coefficient decreased owing to drop of the shear strength, it decresed largely owing to decreased of elastic modulus and thermal conductivity with decrease in alumina purity. Indicative of minimum, value of wear volume, low speed side was abrasive wear, high speed side was wear of heat softening. The friction surface of ceramics protacted by oxide was transfer from STB2.

• 한국지반공학회지:지반
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• 제8권3호
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• pp.13-22
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• 1992

Model pile tests using calibration chamber are performed in !his paper in order to clarify the effect of the fundamental differences between the newly developed SPLT(Simple Pile Loading Test)and the conventional pile loading test on the pile bearing capacity. They are : (1) the direction of the applied load to mobilize the skin friction ; and (2) the use of reduced sifted sliding core. The conclusions obtained from the model pile tests are as follows : (1) The skin friction in tension loading is found to be somewhat smaller than that in compression loading. The average ration is 0.73 with the coefficient of variation (COV) of 0.18. (2) The ratio of the tip resistance rosin연 the reduced sized sliding core to that using the whole shoe shows wide scattering ; its average is 0.99 and the COV is 0.28. The aver - age of 0.99 means that there is no considerable difference in the tip resistance whether the reduced sized sliding core or the whole shoe is used, on condition that penetration depth ratio is larger than 4 : if the boundary effect of the chamber test is considered, the resistance of the whole shoe might be even larger.

• Tribology and Lubricants
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• 제11권2호
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• pp.44-55
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• 1995

Frictional characteristics with the change of dynamic parameters, such as stiffness, inertia and damping, in the friction measurement at dry sliding surfaces were experimentally and theoretically investigated throughout the study. Dynamic frictional force and the variation in the normal load were mainly measured at the various conditions of system dynamic parameters with which stiffness in the normal direction, loading mechanisms and test materials were varied. For the normal load, mechanisms using both a dead weight and a pneumatic cylinder were applied, which resulted in change of the inertia and damping of the test rig. Test materials were steel, rosin and PTFE, which have different types of intrinsic frictional characteristics. Test results showed that frictional characteristics under different dynamic parameters could be different even though the operating variables were the same and also they could result in the variation in the normal load, which could consequently affect the wear mechanism.

• 한국지반공학회지:지반
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• 제12권5호
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• pp.55-62
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• 1996

Lateral loading model tests were performed on the rigid box-shaped cellular bulkhead by displacement-controlled method. The materials of ground and fill used in this study are two aluminium rods with different sections. The behalf·iotas of ground and fill were recorded by photo/video techniques and failure mechanism created in ground and fill has been simulated two-야mensionally. Also the theoretical consideration about the test results was done on the basis of Hansen's earth pressure theory. As a result, the shape of sliding face the location of sliding face and the loading height was also investigated.

• Tribology and Lubricants
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• 제12권2호
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• pp.55-64
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• 1996

Frictional characteristics with the change of loading method and normal stiffness at dry sliding surfaces were experimentally and theoretically evaluated in this study. For the study, a ball-on-disk typed test rig was built and implemented, which allowed a proper selection of loading mechanism and normal stiffness of the test rig. Loading method were varied from dead weight to pneumatic cylinder and spring loading, and the normal stiffness was varied by a spring of different stiffness. Test results showed that frictional characteristics at various loading methods were different even though the operating variables were the same. Discrepancy in the frictional characteristics, such as coefficient of friction and fluctuation in the normal load, were explained by the change in dynamic parameters of the test rigs. Results also showed that coefficient of friction, which defines as a ratio of frictional force divided a normal load, could be differently evaluated in the calculation when fluctuation in the normal load was significant.

• 전기전자학회논문지
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• 제8권1호
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• pp.128-135
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• 2004

본 논문에서는 sliding-DFT에 순환 구현에 기반한 위상 측정 앨고리즘을 제안하였다. 제안한 앨고리즘은 주파수 변이, 누적 잡음, 계수 근사 영향 등의 오차영향에 강인한 특성을 가지도록 설계되었다. DFT 계수의 유한 비트 근사 구현에 의한 위상 오차는 크기 오차에 비해 매우 작게 나타난다. 위상 오차의 혁신적인 감소는 근사 계수가 복소평면 상에서 4사분면상에 대칭적으로 존재함을 이용하여 얻을 수 있다. 제안한 앨고리즘을 시분할 공유 구조에 기반한 4-채널 전력선 위상 측정 시스템을 설계하고 구현하였다. 구현한 시스템의 동작은 실시간으로 host processor 시스템과 다채널 함수 발생기를 통한 test 환경에서 실험적으로 확인하였다. 제안한 앨고리즘의 위상 측정에 있어 정확한 특성과 유한비트 근사 영향에 강인한 특성은 특히, 빠른 처리 속도와 구현의 감소함이 주요 설계 고려사항인 ASIC 이나 microprocessor에 기반의 임베디드 시스템 적용에 중대한 효과를 제공할 수 있을 것이다.

• Physical Therapy Rehabilitation Science
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• 제3권1호
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• pp.38-42
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• 2014

Objective: In this study, we applied a neurodynamic sciatic nerve sliding technique to healthy adults to elucidate its effects on hamstring flexibility and postural balance. Design: Cross-sectional study. Methods: This study targeted twenty four healthy adults (16 men, 8 women). A neurodynamic sciatic nerve sliding technique was applied 5 times to all subjects' dominant leg. The subjects were asked to sit on the bed while performing cervical and thoracic flexion, as well as knee flexion with ankle plantar flexion. Then, they were asked to perform cervical and thoracic extension and knee extension with their ankle in dorsiflexion and maintain the position for 60 s. For postural balance, we measured postural sway while the subjects maintained a one-legged standing posture using the Good Balance System and measured the hip joint flexion range of motion using a standardized passive straight leg raise (SLR) test. Results: SLR test increased significantly from $79^{\circ}$ before the intervention to $91.67^{\circ}$ after the intervention (p<0.05). Regarding the participants' balance evaluated using the one-legged standing test, the X-speed decreased significantly from 18.61 mm/s to 17.17 mm/s (p<0.05), the Y-speed decreased from 22.28 mm/s to 20.52 mm/s (p<0.05), and the velocity moment was significantly decreased from $89.33mm^2/s$ to $74.99mm^2/s$ after the intervention (p<0.05). Conclusions: Application of the neurodynamic sciatic nerve sliding technique exhibited improved hamstring flexibility and postural balance of healthy adults.

• 한국재료학회지
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• 제15권4호
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• pp.224-232
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• 2005

Dry sliding wear behavior of electro-pressure sintered Fe-Ni and Co-Fe-Ni compacts was investigated. Pin-on-disk wear tests were performed on the sintered Fe-Ni, Co-Fe-Ni disk specimens against alumina $(Al_2O_3)$ and silica $(SiO_2)$ ball counterparts at various loads ranging from 3N to 12N. A constant sliding speed of 0.1m/sec was employed. Wear rate was calculated by dividing the weight loss measured after the test by specific gravity and sliding distance. Worn surfaces and cross sections of them were examined by a scanning electron microscopy, and wear mechanism of the compacts was investigated. Wear characteristics of the compacts were discussed as a function of composition of the compacts. Relationship between the wear rate and mechancial properties of the compact was explored, and effects of the oxide layer that was formed on wearing surface of the compacts on the wear were also studied.

• 소성∙가공
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• 제24권6호
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• pp.405-410
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• 2015

Sheet-forming of Mg alloys is conducted at elevated temperatures (250℃) due to the low formability at room temperature. The high-temperature process often gives rise to surface damage on the alloy (i.e. galling.) In the current study, the frictional characteristics of DLC coating slid against an AZ31 Mg alloy at various temperatures were investigated. The coating has been used widely for low-friction processes. Dry-sliding friction and galling characteristics of an AZ31 Mg alloy (disk), which slid against uncoated and a DLC-coated STD-61 steel (pin), were investigated using a reciprocating-sliding tribometer at room temperature and 250℃. To represent the real sliding phenomena during a sheet metal forming process, single-stroke tests were used (10mm stroke length) rather than a reciprocating long sliding-distance test. The DLC coating suppressed adhesion between the alloy and the tool steel at room temperature, and exhibited a low friction coefficient. However, during sliding at 250℃, severe adhesion occurred between the two surfaces, which resulted in a high friction coefficient and galling.

• 한국재료학회지
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• 제11권10호
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• pp.841-845
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• 2001

The steam generator tubes of power plant damaged by sliding wear due to flow-induced motion of foreign object. Amount of wear have been predicted by Achard's wear equation until now. However, there are large error and low reliability, because this equation regards wear coefficient(k) as constant. The sliding wears tests have been performed at room temperature to examine parameters of wear (wear distance, contact stress). The steam generator tube material for wear test is used Inconel 600 and foreign object material is used 304 austenite stainless steel. The sliding wear tests show that the amount of wear is not linearly proportional to the wear distance(for 374 austenite stainless steel). According to experimental result, wear coefficient is not constant k but function k(s) of wear distance. The newly modified wear predictive equation V=k(s)F have small error and high reliability.