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Characteristic of Friction on Texturing Bearing Steel with Ultrasonic Hole Machine
Shin, Mijung,H., Angga Senoaji,Kwon, SoonHong,Chung, SungWon,Kwon, SoonGoo,Park, JongMin,Kim, JongSoon,Choi, WonSik Korean Tribology Society 2015 한국윤활학회지(윤활학회지) Vol.16 No.4
We carry out experiments to characterize textured bearing steel with varying hole density and depth. Textured surface is believed to reduce the friction coefficient, and improve performance and wearing caused by third-body contact. We employ three lubrication regime conditions based on the Stribeck curve: boundary lubrication, mixed lubrication, and hydrodynamic lubrication. Ultrasonic machining is an untraditional machining method wherein abrasive grit particles are used. The hammering process on the work piece surface by abrasive provides the desired form. In this study, we create multi-holes on the bearing steel surface for texturing purposes. Holes are formed by an ultrasonic machine with a diameter of 0.534 mm and a depth of about 2-4 mm, and they are distributed on the contact surface with a density between 1.37-2.23%. The hole density over the surface area is an important factor affecting the friction. We test nine types of textured specimens using four times replication and compare them with the untextured specimen using graphs, as well as photographs taken using a scanning electron microscope. We use Analyzes variant in this experiment to find the correlation between each pair of treatments. Finally, we report the effect of hole density and depth on the friction coefficient.
최원식(Wonsik Chio),박종민(Jongmin Park),권순구(Soongoo Kwon),정성원(Sungwon Chung),권순홍(Soonhong Kwon) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
GFRP(glass fiber reinforced plastics) have lots of good points such as light weight, thermal resistance and strong mechanical characteristics. So GFRP is applied to so many industrial area. In this paper, the relationship between test conditions and surface roughness is examined from the drilling experiment, which is the drilling 1000rpm, 1400rpm, 1800rpm with φ 10㎜ of coated drill, HSS regular drill and EX-GDX drill. The results are analysed with consideration with test conditions and surface roughness according to drill types..
Characteristic of Friction on Texturing Bearing Steel with Ultrasonic Hole Machine
Mijung Shin(신미정),Angga Senoaji H,SoonHong Kwon(권순홍),SungWon Chung(정성원),SoonGoo Kwon(권순구),JongMin Park(박종민),JongSoon Kim(김종순),WonSik Choi(최원식) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.1
We carry out experiments to characterize textured bearing steel with varying hole density and depth. Textured surface is believed to reduce the friction coefficient, and improve performance and wearing caused by third-body contact. We employ three lubrication regime conditions based on the Stribeck curve: boundary lubrication, mixed lubrication, and hydrodynamic lubrication. Ultrasonic machining is an untraditional machining method wherein abrasive grit particles are used. The hammering process on the work piece surface by abrasive provides the desired form. In this study, we create multi-holes on the bearing steel surface for texturing purposes. Holes are formed by an ultrasonic machine with a diameter of 0.534 mm and a depth of about 2-4 mm, and they are distributed on the contact surface with a density between 1.37-2.23%. The hole density over the surface area is an important factor affecting the friction. We test nine types of textured specimens using four times replication and compare them with the untextured specimen using graphs, as well as photographs taken using a scanning electron microscope. We use Analyzes variant in this experiment to find the correlation between each pair of treatments. Finally, we report the effect of hole density and depth on the friction coefficient.
Friction Assessment of Canola Oil on Contact Bearing Materials
Nicholas Nnaemeka Okechukwu,JaeYoung Byun,JongSoon Kim,JongMin Park,SoonGoo Kwon,SungWon Chung,SoonHong Kwon,WonSik Choi 한국트라이볼로지학회 2020 한국윤활학회지(윤활학회지) Vol.36 No.1
In manufacturing operations, oil plays a crucial role in reducing friction and wear among interacting surfaces at varying velocities, loads, and temperature. Hydrocarbon oil is considered the origin of lubrication oils. However, this base oil has been limited in its use as it is a principal cause of pollution. This research focuses on identifying a biodegradable base oil lubricant that possesses a stable coefficient of friction and viscosity with temperature. Friction analysis is conducted by employing a pin on a disk tribotester with a fixed load of 10 N at varying sliding speeds ranging from 0.06 m/s to 0.34 m/s. Oil viscosity analysis is perfomed at room temperature by using a rotary viscometer. Tests are performed using canola oil and paraffin oil as lubricants. The results indicate that the viscosity of canola oil is more efficient than paraffin oil. The non-dimensional characteristic number according to the Stribeck curve reveals an elastohydrodynamic lubrication regime with canola oil lubrication. A comparison of both lubricants reveals that, the friction efficiency of canola oil and paraffin oil does not differ considerably. However, the friction in canola oil is observed to decrease more than that in paraffin oil at an elevated sliding speed. The tests confirm that canola oil is potent in minimizing the friction coefficient of SCM440 bodies interacting with one another as well as acted upon by load.
The Characteristic of Reward in Computer Assisted Learning
Eun Mo Yeon(연은모),Sun-Young Lee(이선영),Yoonkyung Chung(정윤경),Eun Soo Cho(조은수),Soongoo Kwon(권순구),Hun Jeon(전훈),Kye-Hyeng Lee(이계형),Sung-Hyun Yoon(윤성현),Yeonhee So(소연희),Sung-il Kim(김성일) 한국HCI학회 2008 한국HCI학회 학술대회 Vol.2008 No.2
Computer Assisted Learning (CAL) is quite different from in many aspects. CAL provides individualistic learning environment and facilitates autonomy of the learner. Thus the learners who uses CAL program has more sense of control and engages in more strategic learning than conventional learning environment. In this experiment, we used KORI (KORea university intelligent agent) which is a new type of ITS adopting TA (Teachable Agent) that fosters learning by teaching. So, we investigated the critical motivational factor that have influences in CAL learning and the effects of reward in CAL are another area of our interest. Thus, we divided two conditions that presence of reward and absence of reward. The 174 elementary school students(5th) were participated and they are randomly assigned the one of the reward conditions. Before entering the experimental instruction, all participants measured about metacognition, self-efficacy and goal orientation questionnaire as independent variables. Then, Participants were instructed of method of using KORI program and asked to study for ten days with KORI program at least 20 minutes everyday in their home, about 10 days. After 10 days, they were rated interest and comprehension. Regression results suggest that regardless of the presence of reward, metacognition is a positive predictor in interestingness. It indicate that metacognitive skills are required in CAL learning situation irrespective of reward. But on comprehension in the absence of reward, only self- efficacy appeared to be a positive predictor. In the presence of reward, performance goal orientation showed as a negative predictor of comprehension, whereas self-efficacy was a positive predictor. This result suggest that presence of reward especially interferes learning process of performance goal orientation in CAL learning situation. It could be interpreted that reward interferes the learning process of performance goal orientation by debilitating intrinsic motivation.