VHCF PROPERTIES OF AISI 1045, 4137, 52100 & H13 STEEL BY UNSM TREATMENT

C.M. Suh,Y.S. Pyun 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5

There are many surface modification technologies aimed at improving fatigue strength by inducing big and deep compressive residual stress. The Ultrasonic Nanocrystal Surface Modification (UNSM) technology is one of them. The UNSM technology has been applied to carbon steel AISI1045, chrome molybdenum steel AISI4137, hot tool steel H13 (SKD61) and bearing steel AISI52100 (SUJ2). The mechanical properties of these steels before and after UNSM treatment are analyzed and compared, rotary bending fatigue test until 10? cycles (VHCF) is carried out in order to verify the UNSM effects. SEM, ESBD and TEM analysis are performed to investigate the effects of UNSM treatment. The contribution of mechanical properties to fatigue strength improvement is discussed.

Phase contrast radiography of Lewy bodies in Parkinson disease

Koh, S.B.,Suh, S.I.,Lee, D.H.,Kim, A.R.,Oh, C.H.,Yoon, J.S.,Weon, B.M.,Seol, S.K.,Pyun, A.R.,Je, J.H.,Hwu, Y.,Margaritondo, G. Elsevier 2006 NeuroImage Vol.32 No.2

<P><B>Abstract</B></P><P>Parkinson's disease (PD), defined as a neurodegenerative disorder, is characterized by the loss of dopaminergic neurons and the presence of Lewy bodies in neurons. Morphological study of Lewy bodies is important to identify the causes and the processes of PD. Here, we investigate a possibility of phase contrast radiography using coherent synchrotron X-rays to explore the microscopic details of Lewy bodies in thick (∼3?mm) midbrain tissues. Autopsied midbrain tissues of a PD patient were sliced in 3?mm thickness and then examined using synchrotron X-rays from the 7B2 beamline of the Pohang Light Source. Refraction-enhanced phase contrast radiography and microtomography were adopted to identify dark core and dim edge of Lewy bodies in neurons. The morphology of Lewy bodies was clearly revealed by the phase contrast radiography in very thick (3?mm) midbrain tissues without any staining treatment. Three-dimensional volume rendered microtomography of the autopsied midbrain tissues demonstrates striking evidence that several Lewy bodies are agglomerated by dim edges in a neuron. We suggest that the phase contrast radiography could be a useful tool to morphologically investigate the causes or the processes in PD.</P>

Effect of Inclusion Element on VHCF(Very High Cycle Fatigue) Strength of Bearing Steels

C.M. Suh(서창민),M.S. Suh,Y.S. Pyun 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.11

SU2 of bearing steel is used for roller bearing and ball bearing due to their high wear resistance and impact resistance. The test specimens for the rotary bending fatigue test were made of SUJ2 A-& B-bearing steels. In this study effect of inclusion element on VHCF strengthwas investigated and compared with that of the two kinds of bearing steel. The results showed that the rotary bending fatigue life and fatigue strength of the B-bearing steel’s specimen increased by about 10%, compared to those of the A-bearing steel. The fracture surface analysis showed that the fish eye crack initiation phenomenon was observed. These results might be attributed to the inclusion element difference of Ti and Cr at the fish eye crack initiation site.

Torsion Fatigue Properties of DIN17221 After UNSM Treatment

C.M. Suh,S. M. Jeong,U.B. Baek,Y.S. Pyun,I.H. Cho 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

The torsion bars of commercial vehicles, wind turbines and military vehicles are important elements that work to maintain stability, performance, safety and convenience of passengers or operators. Nevertheless, commercial torsion bar must be changed periodically throughout service life. A novel surface technology named Ultrasonic nanocrystal surface modification (UNSM) technology is applied onto the torsion bar made of DIN17221 in order to improve durability and torsion fatigue strength as an alternative to existing presetting method with shot peening technology. The mechanical properties of DIN17221 material before and after the UNSM treatment are analyzed and compared. Torsion fatigue test was performed until 107cycles in order to verify the UNSM effects on fatigue strength. SEM observation of fracture surface is performed to investigate crack initiation and growth behaviors.

Improvement of VHCF Chracteristics of AISI 4137, 52100 & H13 Steel by UNSM Treatment

C.M. Suh,Y.D. An,Y.S. Pyun,I.H. Cho,M.S. Suh 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

There are many surface technologies aimed at improving fatigue strength by inducing big and deep compressive residual stress. The Ultrasonic Nanocrystal Surface Modification (UNSM) technology is one of them. The UNSM technology has been applied to carbon steel AISI1045, chrome molybdenum steel AISI4137, hot tool steel H13 (SKD61) and bearing steel AISI52100. The mechanical properties of these steels before and after UNSM treatment are analyzed and compared. Rotary bending fatigue test until 109cycles(VHCF) is carried out in order to verify the UNSM effects. SEM, ESBD and TEM analysis are performed to investigate the effects of UNSM treatment. The contribution of mechanical properties to fatigue strength improvement is discussed.

초음파 나노 표면 개질(UNSM) 기술에 따른 베어링강의 VHCF 특성

서창민(C. M. Suh),안영동(Y. D. An),서민수(M. S. Suh),편영식(Y. S. Pyun) 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5

STB2 of bearing steel is used for roller bearing and ball bearing due to their high wear resistance and impact resistance. Among many useful surface strengthening technologies, ultrasonic nanocrystal surface modification (UNSM) technology is promising for increasing fatigue strength and wear resistance, and reducing friction as well. The main idea to apply UNSM technology for improving both bending fatigue strength and rolling contact fatigue strength of slim bearing rings is applying not only raceway but also the opposite side of the raceway - in other words, outer side of the outer ring and inner side of the inner ring. The test specimens for the rotary bending fatigue test were made of STB2 bearing steel and treated by the UNSM technology. In this study, fatigue result that was subjected to different loads of the UNSM treatment was investigated and compared with that of the untreated specimen. The microhardness of the UNSM-treated specimens increased by about 20%, higher than that of the untreated specimens. The X-ray diffraction analysis showed that a compressive residual stress of more than 1,000 MPa was induced after the UNSM treatment. Also, electron backscatter diffraction analysis was used to study the surface structure and nanograin refinement. The results showed that the rotary bending fatigue life and fatigue strength of the UNSM-treated specimens increased by about 80% and 31%, respectively, compared to those of the untreated specimen. These results might be attributed to the increased microhardness, the induced compressive residual stress, and the nanocrystal structure modification after the UNSM treatment. In addition, the fracture surface analysis showed that the fish eye crack initiation phenomenon was observed after the UNSM treatment.

초음파 나노 표면 개질(UNSM) 기술에 따른 베어링강의 VHCF 특성

서창민(C. M Suh),안영동(Y. D. An),서민수(M. S. Suh),편영식(Y. S. Pyun) 한국해양환경·에너지학회 2012 한국해양환경·에너지학회 학술대회논문집 Vol.2012 No.5

STB2 of bearing steel is used far roller bearing and ball bearing due to their high wear resistance and impact resistance. Among many useful surface strengthening technologies, ultrasonic nanocrystal surface modification (UNSM) technology is promising for increasing fatigue strength and wear resistance, and reducing friction as well The main idea to apply UNSM technology for improving both bending fatigue strength and rolling contact fatigue strength, of slim bearing rings is applying not only raceway but also the opposite side of the raceway - in other words, outer side of the outer ring and inner side of the inner ring. The test specimens for the rotary bending fatigue test were made of STB2 bearing steel and treated by the UNSM technology. In Ms study, fatigue result that was subjected to different loads of the UNSM treatment was investigated and compared with that of the untreated specimen. The microhardness of the UNSM-treated specimens increased by about 20%, higher than that of the untreated specimens. The X-ray diffraction analysis showed that a compressive residual stress of more than 1,000 MPa was induced after the UNSM treatment Also, electron backscatter diffraction analysis was used to study the surface structure and nanograin refinement. The results showed that the rotary bending fatigue life and fatigue strength of the UNSM-treated specimens increased by about 80% and 31%, respectively, compared to those of the untreated specimen. These results might be attributed to the increased micrchardness, the induced compressive residual stress, and the nanocrystal structure modification after the UNSM treatment In addition, the fracture surface analysis showed that the fish eye crack initiation phenomenon was observed after the UNSM treatment