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편영식,조인호,서창민,박진,Josh Rogers,Ravil Kayumov,Ri-ichi Murakami 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
Premature failure at the shear pin of stainless hot rolling mill caused by increasing productivity and fluctuation of roll torque raises significant downtime cost. To reduce downtime cost, UNSM (Ultrasonic Nanocrystal Surface Modification) treatment is applied to the neck groove of shear pin as the alternative to existing solutions. This treatment prevents premature failure, increases service life and reduces the number of replacements. Proper process variables of UNSM technology which give the strongest fatigue strength are determined by comparing with S-N curve of rotary bending test result. Surface roughness, hardness and compressive residual stress on three kinds of test specimens are analyzed together with SEM analysis of fracture surface. Real shear pins are produced by the property of highest fatigue strength and installed to the hot mill stand for validation. They come to pass as twice as the original operation cycle.
2000cc 이하급 가솔린엔진 흡배기밸브 수명복원 기초 기술 개발
김학두(Hakdoo Kim),카유모브 라빌(Kayumov Ravil),김준형(Junhyung Kim),편영식(Youngsik Pyun) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
During normal operation Internal Combustion Engine (ICE) valves exposed to high pressure and high temperature. For this reason SUH11, SUH35 heat resisting steels are used for valve manufacturing in S. Korea. The main failure modes are neck bending and face fracture. For the purpose of fatigue life restoration through improving surface hardness and residual strength Ultrasonic Nano Surface Modification (UNSM) was applied. Effect of UNSM treatement on valve fatigue life restoration is studied by two methods. Nitrided SUH11, SUH35 specimen were prerun until 70% and 63% of average fatigue life, treated with UNSM and run to break on Rotary-bending test equipment. Second approach employed actual engine valves treated with UNSM and tested for Wear and Friction by Pin-on-Disk method. Data showed restoration of fatigue life of steel specimen and fatigue life improvement of actual valves.
Restoration of rolling-contact-fatigued surfaces via nanoskin technology.
Pyun, Young Sik,Kim, Jun Hyong,Kayumov, Ravil,He, Yinsheng,Shin, Kee Sam American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.9
<P>Rolling contact fatigue (RCF) is known as the dominant factor determining the service life of bearing materials. In this work, the fatigue life of the typical bearing alloy was significantly improved by introducing a nanoskin layer on the surfaces of the test specimens. The nanoskin layer structure was obtained by means of the ultrasonic nanocrystal surface modification (UNSM) technology. The microstructure of the nanoskin was analyzed via scanning electron microscope (SEM), electron back-scatter diffraction (EBSD), and transmission electron microscope (TEM). SUJ2 and SUJ3 bearings at different states of fatigue were subjected to UNSM treatment. For SUJ2 a rotary-bending fatigue (RBF) life average for three untreated specimens was chosen as 100% life, and then several untreated specimens were fatigued to 25%, 50% and 75% of life with subsequent UNSM treatment. This way used bearing conditions were simulated. The rotary-bending fatigue (RBF) tests of fatigue+UNSM SUJ2 specimens have shown 377-430% improvement of fatigue life, comparing to untreated specimens. For SUJ3 a RCF life untreated specimen was chosen as 100% life, and then several specimens were fatigued to approximately 100% of surface damage with subsequent UNSM treatment. Thus damaged surface conditions were simulated. The RCF tests of fatigue+UNSM SUJ3 specimens have shown 218% improvement of fatigue life, comparing to untreated specimens. This indicates the possibility of the restoration of the RCF life of bearing alloys by means of nanoskin treatment via UNSM technology.</P>
Yasutoshi Tominaga,Jinsoo Kim,편영식,Ravil Kayumov,김준형,Juha Woo 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.10
Crankshaft translates reciprocating linear piston motion into rotation in internal combustion engine. So it receives complex combination of stresses. Therefore, crankshaft remanufacturing process is designed thoroughly with special attention to fatigue and tribological performance. Experimental study is carried out in order to show that UNSM (ultrasonic nanocrystal surface modification) technology which will be used as final surface treatment after 0.2 mm depth surface grinding, could restore original fatigue strength and tribological performance. Furthermore the feasibility steady to replace conventional overlay welding in crankshaft remanufacturing process by UNSM (ultrasonic nanocrystal surface modification) technology is carried out. Effects of UNSM technology are established through rotary bending test, rolling contact fatigue (RCF) test and wear simulation test. The test specimen used SCM435 material of crankshaft and commercial bush. The test result showed fatigue limit improved by 30% and RCF life increased by 40% for UNSM treated specimen. And friction coefficient decreased by 24% and wear amount decreased by 85%.
Micro cold forging 기술 적용한 베어링강의 피로층 복원
김준형(Jun Hyong Kim),편영식(Young Sik Pyun),카유모브라빌(Ravil Kayumov) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-2
베어링이 노후되거나 파손될 경우 궤도륜 및 강구의 표면층은 피로 누적으로 인한 피로층이 형성된다. 피로층 복원을 위하여 냉간단조 방식의 UNSM 기술을 통해 접근하였다. UNSM 기술은 1초에 20,000번 이상의 타격을 금속 표면에 주어, 강소성 및 탄성변형을 발생시키고, 표층부의 조직을 나노결정 조직으로 개질시킨다. 이로써 표면거칠기 및 표면경도가 향상되고, 압축잔류응력이 부가된다. 본 연구에서는 초기 베어링강과 UNSM 적용된 베어링강 시편을 이용하여 회전굽힘피로(RBF) 및 구름접촉피로(RCF) 시험을 진행하였고, 그 결과를 통해 피로층 복원에 대한 냉간단조 방식의 기술 적용 여부를 확인하였다. Bearings raceway & rolling element surface wear & damage due to fatigue. In this study application o f UNSM technology to restore raceway & rolling element surface is carried out. RCF & RBF tests are conducted for bearing steel specimen before & after UNSM. Results justify use of UNSM for restoration o f surface fatigue resistance layer of bearing raceway & rolling elements.
대형 상용차용 인젝터 볼 밸브의 수명 복원 기초 기술 개발
다리스렝 스르멩닥와(Shirmendagva Darisuren),편영식(Youngsik Pyun),김준형(Junhyong Kim),카유모브 라빌(Ravil Kayumov) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Significant wear occurs in the ball valve of heavy duty diesel injectors. This wear is due to the continuous contact stress. For this reason injector must be periodically changed. Although used injectors can be reused, used ball valves must be replaced by new set. The other option until now was ball valve seat polishing to remove cracks around the valve orifice, which does not provide full recovery. In this research, as a part of development of the basic method of injector parts restoration, UNSM technology was applied to the ball valve seat to remove cracks, enhance surface properties and restore valve’s life. Ball-on-Disk wear tests were carried out on untreated and treated specimens. Results are compared. The possibility of used injector parts restoration process is established and explained.
Pyun, Young Sik,Cho, In Ho,Suh, Chang Min,Park, Jin,Rogers, Josh,Kayumov, Ravil,Murakami, Riichi 한국정밀공학회 2013 International Journal of Precision Engineering and Vol.14 No.11
Premature failure at the shear pin of stainless hot rolling mill caused by increasing productivity and fluctuation of roll torque raises significant downtime cost. To reduce downtime cost, UNSM (Ultrasonic Nanocrystal Surface Modification) treatment is applied to the neck groove of shear pin as the alternative to existing solutions. This treatment prevents premature failure, increases service life and reduces the number of replacements. Proper process variables of UNSM technology which give the strongest fatigue strength are determined by comparing with S-N curve of rotary bending test result. Surface roughness, hardness and compressive residual stress on three kinds of test specimens are analyzed together with SEM analysis of fracture surface. Real shear pins are produced by the property of highest fatigue strength and installed to the hot mill stand for validation. They come to pass as twice as the original operation cycle.