초록 ▼

스케이트날의 미세패턴 공정기술 및 광섬유 레이저 가공시스템 개발을 위하여 두 가지 주요요소인 미세패턴 가공용 소형의 광섬유 레이저용 가공을 위한 광학계와 미세 가공시스템을 개발하였고, 개발한 시스템의 검증을 위한 얼음 마찰 측정 시스템 구현 및 금속 미세패턴 마찰 성능 평가 및 실현장 선수 적용성 평가를 진행함

○ 미세패턴 가공용 소형의 30w급 광섬유 레이저 모듈을 도입하여 광학적 성능을 검증하였고, 도입한 광섬유 레이저 모듈을 적용한 3축 가공 시스템을 반복정밀도 ± 2 ㎛이하의 고정밀 리니어 모션스테이지로 구현하였

스케이트날의 미세패턴 공정기술 및 광섬유 레이저 가공시스템 개발을 위하여 두 가지 주요요소인 미세패턴 가공용 소형의 광섬유 레이저용 가공을 위한 광학계와 미세 가공시스템을 개발하였고, 개발한 시스템의 검증을 위한 얼음 마찰 측정 시스템 구현 및 금속 미세패턴 마찰 성능 평가 및 실현장 선수 적용성 평가를 진행함

○ 미세패턴 가공용 소형의 30w급 광섬유 레이저 모듈을 도입하여 광학적 성능을 검증하였고, 도입한 광섬유 레이저 모듈을 적용한 3축 가공 시스템을 반복정밀도 ± 2 ㎛이하의 고정밀 리니어 모션스테이지로 구현하였고 스케이트날의 표면 굴곡을 따라 고정밀 가공을 위하여 2D 라인 레이저 스케너를 적용하여 모션스테이지의 정밀유도 장치를 개발 적용하였고, 이동형 차량용 함체 및 방진 패키지 장치를 개발함

○ 스케이트 날 표면에 미세 패턴을 형성하여 이에 따른 초발수성으로 인한 얼음 면에서의 마찰 특성을 향상시키기 위해 광섬유 레이저를 기반으로 효과적인 미세 패턴 형성을 위한 시뮬레이션 공정을 수행하여 최적화된 광학 프리즘 및 광학 모듈을 개발함

○ 광섬유 기반으로 구성된 고출력 광섬유 레이저 모듈의 효과적인 레이저 빔 전송 및 원하는 공간으로의 효율적 이송을 위해 스테인레스 스틸 기반의 SMA 905 커넥터와 유리봉이 결합된 대구경 광섬유 팁을 활용하여 대구경 광섬유 점퍼 코드를 제작하였으며, 고출력 광섬유 레이저 모듈 개발을 위한 구동 및 제어 모듈의 설정, 레이저 파워 조건을 만족하며 원활한 제어를 위한 LD array 레이저 모듈을 설계, 제작함. 이와 함께 제작된 고출력 광섬유 레이저 모듈과 함께 피코초 펄스 레이저 구현을 통한 미세 패턴 형상의 정밀도 향상을 위해 펄스 레이저 구동 모듈을 개발함

○ 제작된 광학 렌즈 및 레이저 집광 모듈 등의 광학 모듈을 통해 최적화된 광섬유 레이저 시스템 가공 조건에서 Spot형 3차원 미세 패턴을 형성하였으며, 바이킹 사의 스케이트 날 표면에 패턴의 깊이, 크기, 간격은 각각 1 ㎛, 4.5 ㎛, 그리고 30/20 ㎛ (x축/y축)의 미세 패턴을 생성하여 정량적 목표를 달성함

○ 스케이트 날의 마찰계수 성능을 향상시키기 위해 미세 패턴이 형성된 스케이트 날 표면에 PFOTS, PDMS와 같은 유기화학물질을 코팅하였으며, 코팅 후 물 접촉각은 150˚ 이상으로 측정됨

○ 스케이트 날의 마찰계수 측정을 위해 얼음 마찰계수 측정 시스템을 제작하였으며, 1 차년도엔 레이저 변위센서를 이용하여 마찰계수를 측정하였으며, 2 차년도엔 측정 데이터의 노이즈 개선을 위해 로드셀을 이용한 마찰계수 측정 방식으로 변경함

○ 미세 패턴 및 코팅 층이 형성된 스케이트 날은 일반 스케이트 날보다 향상된 마찰 성능을 가지고 있으며, 0.1 이하의 마찰계수의 값을 가지고 있음

○ 적용성 평가를 위한 테스트베드를 제작, 무게에 따른 스케이트 날의 반복측정 결과에도 오차(bias)는 5% 미만의 신뢰성을 가지는 실현장 적용평가 테스트베드를 구현함

○ 실현장 선수 적용성 평가를 위하여 국가대표 상비군급 선수 실현장 테스트 및 성능 평가를 진행하여 경기능력 향상 가능성을 검증함

(출처 : 보고서 요약서 3p)

Abstract ▼

Ⅳ. Result of research and development
1. Investigation and implementation of 3-D fine interference pattern technology based on high power laser
: Micro-fabrication and pattern formation using lasers are used to develop various parts and devices. In recent years, researches have been carried ou

Ⅳ. Result of research and development
1. Investigation and implementation of 3-D fine interference pattern technology based on high power laser
: Micro-fabrication and pattern formation using lasers are used to develop various parts and devices. In recent years, researches have been carried out in the field of femto-second laser to make nano/microstructure pattern on the metal surface to have self-cleaning ability, such as superhydrophobicity property. These surface nanostructures play a key role in amplifying the wettability of the material surface and serve as the basis for realizing a super water-repellent surface. Therefore, in this project, an interference technique for fine patterning on the surface of the blade to get uperhydrophobic property will be developed.

: The hydrophobicity will be improved through the formation of a three-dimensional fine pattern on the skate blade surface formed through the laser processing, and the friction coefficient characteristic will be controlled for improving the hydrophobicity. If the water contact angle is less than 90 degrees, it is called a hydrophilic surface and if the water contact angle is more than 90 degrees, the water accumulates in droplets and called being hydrophobicity. Such surface can be more hydrophilic (super-hydrophilic) or can be more hydrophobic (super-hydrophobic or super-hydrophilic) if a micrometer or nanometer size surface roughness factor is added.

: Specifically, when the water drops on one surface with circle shape, superhydrophobicity means the contact angle and the slip angle are 150° or more and 5° or less, respectively. By forming a fine pattern on the metal surface to increase the contact angle with water and minimizing the contact area to minimize the frictional force, it is possible to improve the performance on the short track and the speed skate blade to minimize contact area with ice.

In this project, a technique, which can form optical interferometer by using prism, will be implemented for forming fine patterning process by using the laser. The optimized prism shape was simulated on the change of pattern interval according to the incident wavelength of the laser having 4mm of laser beam diameter and the prism fabricated by using fused silica (n=1.4571) showed apex angle of 160. It can be concluded that the prism satisfies the conditions of the target of the present invention, that is, a pattern depth of < 10 μm, a pattern size of < 5 μm, and a pattern spacing of < 30 μm.

2. Development of optical interference and focusing lens module for the implementation of skate blade metal fine pattern array
: In order to construct the optical module by combining the previously developed fine pattern forming prism with the pulse type optical fiber laser module, it was fabricated to have a working distance of 17 mm and condensing depth of 1.6 mm by using a 50 times objective lens through a fiber optic transmission module and a lens-based spatial optical system configuration. In order to maximize the efficiency of machining by checking the quality of the workpiece and the quality of the material, a camera module was combined and manufactured.

: In the case of forming a fine pattern through an optical module based on the pulsed optical fiber laser, the shape of the processed surface will be excellent as the repetition rate of the pulse signal can be increased. However, when processing is performed at a melting point or more of the material, and the surface modification is reduced by forming an ablation by heat accumulation.
Therefore, in this project, it can be possible to using the optical modulator to effectively control the repetition rate of such ultra short pulse

3. Development of laser process technology for metal patterning on the skate blade
: The material analysis was carried out by polishing the speed skate blade of the

Viking company in the Netherlands. The surface of the skate blade was analyzed by fine grinding, and it was confirmed that different metal structures was properly bonded and a middle layered structure of about 300 μm thick was observed at the junction between the two tissues. The bottom (skate wedge), the interface, and the top part of the skate blade, which is made of Bi-metal material, has 66.5 HRC, 62.9 HRC and 52.2 HRC, respectively and the material at the bottom of the skate blade consisted of 58 % iron and an alloy of tungsten, cobalt, vanadium, chromium, and molybdenum.

: In order to inscribe fine patterns on the surface of the skate blade analyzed, laser processing technology was developed based on a high power laser with ultra short pulse and a prism optical system for forming a two-dimensional fine pattern.

- Pulse Duration : 150 ps
- Laser wavelength: 1,030～1,065
- Laser power : 30W
- Repetition Rate : 2,000 kHz
: The skate blades with the optimized fine pattern were superhydrophobic and the friction characteristics on the ice sheet were improved and the measured coefficient of friction was measured to be less than about 0.5, which is expected to help improve the record of speed skating for record shortening.

4. Fabrication of optical parts and devices for optical fiber laser for metal patterning on the skate blade
: All optical fiber laser transmission device is based on the optical fiber. In consideration of high output fiber laser characteristics, SMA 905 connector based on stainless steel as well as air-gap type SMA connector was used considering possible surface damage due to high power laser. The air-gap type SMA connector does not fix the optical fiber through the epoxy process, thus minimizing the laser power transmission loss due to the surface burning. In particular, an end-capped fiber laser delivery with the air-gap type SMA connector is suitable for heat dissipation and thermal stabilization of a high output laser beam emitted through a light emitting portion. Considering the fiber laser output power of 30 W at 1060 nm (to be used in this project), a fused silica glass block (rod) and an optical device using a module combined with large diameter optical fiber was fabricated for effective laser beam transmission through mechanical combination of large diameter optical fiber and prism. As a result of evaluating laser transmission characteristic through the high power laser launching of the fabricated optical device, the transmission characteristic was about 90% and this value is very excellent.

5. Implementing of Ice Friction Measuring System and Evaluating Friction Performance of Metal Micro Pattern
: This method measures the friction generated when the skate blade contact the ice that is cooled by the cylindrical shape.
: The friction coefficient of ice and skate blades is measured by measuring the displacement of the skate blade caused by the friction between ice and the skate blade with the laser displacement sensor.

: However, due to vibration generated during the rotation of the motor, noise is generated and the accuracy of the data is lowered. In order to improve the accuracy, the load cell measurement method is changed.

: Superhydrophobic is imparted by coating organic chemical (PFOTS, PDMS) on the laser-patterned skate surface in order to derive the factors affecting the coefficient of friction of skate blades on ice.

: Comparing the contact angle of organic chemical coating, the contact angle is 12 ˚ when before coating and 149 ˚ after coating PDMS and the contact angle is 18 ˚ before coating and 151 ˚ after coating were measured in PFOTS.

: The coefficient of friction of the skate blades subjected to the laser patterning, PDMS, and PFOTS coating process was measured through the laser displacement sensor type system. The friction coefficient of all the skate blades measured was less than 0.1

: A test bed for evaluation of applicability assessment was manufactured and the actual field application evaluation system was established through compensation.

: Measure the reliability of ice friction measuring bed. In order to find out whether the 20kg and each of weight can be reliably obtained, the 40kg and 60kg of barbell were used in addition, finally 20kg, 60kg and 80kg of weight is used. To analyze the objectivity in repeated experiment, the R studio 1.0.1 for macintosh program was used to calculate the value of intraclass correlation coefficient (R) which is an univariate statistic , and a 95% confidence interval plot was shown.

6. Optimization of laser process technology for skate blade metal with fine pattern array
: The fine pattern was fabricated to make superhydrophobic surface by using prism and optical module for the fine pattern on the skate blade and the pulsed optical fiber laser processing technology was optimized. In the first year, the line pattern shows more effective superhydrophobic property than the spot pattern. Therefore, in the second year, the patterning process was optimized for forming a line-shaped fine pattern by using the fiber laser.

: Using a laser system for the fabricated metal micropatterns, the laser pattern process is performed by laser irradiation process with a laser output wavelength of 1060 nm, a maximum output power of 30 W and a pulse width ranging from 150 ps to 5 ns.　　

: In the case of the line pattern, the depth, size, and spacing of the fine pattern are formed to be 1 μm, 4.5 μm, and 20 μm, respectively.
: The spot pattern has a pattern depth of about 1 ㎛, pattern size 4.5 ㎛ and a large pattern of about 15 ㎛ is formed due to excessive burr formation due to high laser energy.
: The pattern of the Triangular shape was formed by the V-shaped fine pattern through the pulse repetition rate and the speed control of the stage. The pattern size was 4.7 ㎛ and the pattern interval was 20 ㎛.

: After that, In order to improve the superhydrophobic property of the skate blades, a coating layer made of Polydimethylsiloxane(PDMS) reagents was used to form a coating layer on the fine patterned surface. The contact angles of water, line, spot, Triangular and Circular patterns were 126, 151, 153 and 150 degrees, respectively.

: Spot, Triangular, and Circular patterns can be confirmed to have more than 150 degrees and less than 0.1, satisfying the second year evaluation objective.

7. Design and manufacture of the integrated circuit for the high power optical fiber laser and moving stage for 3-dimensional metal surface modification

- Development of the high power optical fiber laser module
: LD array laser module was designed and manufactured for development of the high power optical fiber laser module with satisfying smooth control of the setting and laser power condition. We designed the system including all electronic parts such as control system and power supply by arraying 4 pieces of 30 W class Pigtailed LD with 11 A driving current from Oclaro company and driven to obtain stabilized LD power output through feed-back of control system circuit. The stable output power control was possible by attaching 4 channels of LD and light source drive circuit with composed of modulation part, analog par, PD detector part, DAC part, ADC part, and FPGA part as a processor.

8. Development of the pulsed high power optical fiber laser module for 3-dimensional metal surface modification
: The pulsed high power optical fiber laser drive module was developed to improve the precision of the fine pattern shape by implementing pico-second pulse laser together with fabricated high power optical fiber laser module. If the pulsed laser has a duration time of less than pico-second, the thermal diffusion length of the material becomes very short. So an ablation occurs before the formation of the plasma or the flow field, that is improving the machining accuracy, thereby enhancing the water repellent effect.

: Application of the high-speed arbitrary waveform generator (AWG) to the fiber laser processing system for skate blade metal fine pattern is as follows.

The arbitrary waveform set by the user is downloaded to the AWG processor with the combination of time and output signal level for each step through the GUI. And the pulse drive data stored in the processor is input to the machining system in the form of voltage pulse through the DAC and output signal generating circuit, and finally output in the form of the optical pulse of the machining system. The resolution of the output signal level could be adjusted to 4096 steps using a 12 bit DAC. In case of pulse width, it is set to drive a pulse with minimum 5 ns and maximum 10 ms. At repetition rate, it could be adjustable from maximum 100 MHz to minimum 1 Hz.

: The developed 100 ps pulse drive module has a pulse width of at least 100 ps, and output pulse voltage level of up to 500 mVp-p, and a level monitoring pulse output of up to 500 mVp-p of 16 pulse clock of the output pulse.

9. Development of small scale high power fiber optic laser machining system for the 3D surface reforming of metal
: Pulse duration < 200ps, Wavelength 1030~1065nm, Average Power > 30W, Repetition rate 2000 kHz, Size < 50 cm×50 cm×50 cm

: The integrated circuit and controller design of moving stage for small scale high power fiber optic laser machining system of the 3D surface reforming of metal

: GUI and incircuit design and development of small scale high power fiber optic laser machining system for the 3D surface reforming of metal
: Monitoring system development of small scale high power fiber optic laser machining system for the 3D surface reforming of metal

: High precision(Z axis : 0.2㎛, X asix 2.5㎛) 2D laser distance scanning system was adopted in 3D macining system to increase the high accuracy and high precision pattern marking

10. Performance test of laser machining system for micro pattern forming
: Test of laser power and beam characteristic of laser machining system for micro pattern forming

: Test of motion characteristics such as, iterative precision, mechanical straightness and mechanical high precision for machining system for micro pattern forming

11. Development of optimization technology for mobility of the machining system
: Compact and mobility design and development for end product commercialization

Development of all in one type vehicle onboard casing and anti-vibration package facility, can move safe and quickly without disassemble/assemble of the 3D laser machining stage, optic system.

: Maked of anti-vibration facility for installation and moving with lubber based anti-vibraion pads(Consideratgion of minimize the influence of system position precision and iterative accuracy)
: Maked the procedure for after moving installation, setting and calibration for service.

12. Optimization and Performance Evaluation of the Major Factors Related to Ice Friction for Performance Improvement
- Optimization of the shape of metal micro pattern and improvement of surface fabrication process.

: The roughness is one of the factors related to the friction coefficient of the skate blade, and varies depending on the pattern shape of the skate blade surface. Accordingly, after forming the pattern of line, spot, and triangular shapes on the skate blades, then coating the blades and measure the coefficient of friction for each pattern geometry using the friction coefficient measuring system.

: The frictional coefficient of the normal skate blade is 0.03716, the friction coefficient of the line pattern is 0.03535, the friction coefficient of the spot pattern is 0.03408, the friction coefficient of the triangular pattern is 0.03114 and the friction coefficient of the circular pattern is 0.03897. The frictional coefficient of the triangular pattern is the lowest.

: In order to shorten the time required for the coating process, a jig for skate blade coating was designed and manufactured, and the time required for the existing coating process using the oven of about 4 hours was shortened to 10 minutes.

- Improvement of ice friction coefficient measuring system
: In the case of the laser displacement sensor, it is determined that data accuracy is reduced due to noise. So, applied the load cell which can measure the tension when the skate blade contact the ice friction.

: In addition, the LM Guide is replaced with air bushing to minimize the frictional force inside the LM Guide when moving the measuring part horizontally / vertically during the friction coefficient measuring process.

: In order to solve the problem of separation of ice and ice during high-speed rotation of ice, the cylindrical shape of the ice is changed into a gear-like shape to improve stability.

- Verify performance of ice friction by applying surface chemical coating material
: In order to verify the frictional performance of various patterned and coated skate blades, compared the friction coefficients of normal skate blade and various patterned and coated skate blades by the ice friction coefficient measurement system. Since the coefficient of friction varies depending on the speed, the coefficients of friction were measured at speeds between 2.5 ~15 m/s and the coefficients of friction of the various patterned and coated skate blades were lower than that of the normal skate blade.

- Verification of durability of skate blade surface pattern and coating layer
: In order to verify the durability of the pattern (spot, triangular) and coating (PDMS) layers formed on the surface of the skate blade, skaters wore a pair of skates to skate 1000 m, and the change of contact angle was measured.

: In the case of the coated regular skate blade(Bare PDMS) without patterning, the reason why the contact angle of the water after skating is lower than before coating is caused by the increase of roughness due to friction with ice during the skating.

: In the case of pattern coating skate blades, the contact angle of water after skating is higher than that one before coating, and it is considered that the pattern and coating layer remain after skating.

13. Performance evaluation through field test of 3-dimensional patterned skate blade
: Based on the results of the interviews after applying to the athletes, we could summarize the following opinions. Most of the athletes felt different from the usual skate blades, and at the time of the first experiment, it seemed difficult to adapt. However after in the second and third experiments conducted for a total of three days, gradually seems to be adapted as the time gone, and they said that it is easier to adjust the timing gradually.

: Also, in the first and second experiments, One athlete said that "I felt that skate blade did not slip well, unlike the usual one, but the actual lap-time was faster than the feeling".

: In the third experiment, the athletes said that it was easier to adjust their timing in the start and run as a whole. And there are positive opinions like that "it was slipped well and rode lightly than usual", "The patterned skate blade was slipped well on the ice", and "Connection action and movement of the center of gravity were smoother than the usual one".

: The race speed and lap-time of the athletes were not much different from their best records in the season. And most of the athletes said that "I think the record will improve if I adapt over time". And there were opinions "In the third experiment, the patterned skate blade is better than the usual skate blade". With the exception of one out of six players, they answered that "I can play in the race with the patterned skate blade".

(출처 : SUMMARY 31p)

목차 Contents

• 표지 ... 1
• 제출문 ... 2
• 보고서 요약서 ... 3
• 요약문 ... 4
• SUMMARY ... 23
• CONTENTS ... 41
• 목차 ... 42
• 제1장 기술개발과제의 개요 ... 43
• 제2장 국내외 기술개발 현황 ... 48
• 제3장 기술개발 내용, 방법 및 결과 ... 52
• 1절 기술 개발 목표 및 내용 ... 52
• 2절 기술 개발 결과 ... 67
• 3절 기술 개발 결론 ... 232
• 제4장 목표달성도 및 관련분야에의 기여도 ... 238
• 1절 기술개발의 성과목표 및 지표 ... 238
• 제5장 연구개발결과의 활용계획 ... 240
• 1절 활용방안 ... 240
• 제6장 기술개발과정에서 수집한 해외과학기술정보 ... 245
• 제7장 참고문헌 ... 246
• 끝페이지 ... 248