• International Journal of Automotive Technology
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• 제8권6호
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• pp.723-730
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• 2007

The typical design of automotive driveshafts generally utilizes Constant Velocity(CV) joints as a solution to NVH. CV joints are an integral part of vehicles and significantly affect steering, suspension, and vehicle vibration comfort levels. Thus, CV joints have been favored over universal joints due to the constant velocity torque transfer and plunging capability. Although CV joints are common in vehicle applications, current research works on modeling CV joint friction and assumes constant empirical friction coefficient values. However, such models are long known to be inaccurate, especially under dynamic conditions, which is the case for CV joints. In this paper, an instrumented advanced CV joint friction apparatus was developed to measure the internal friction behavior of CV joints using actual tripod-type joint assemblies. The setup is capable of measuring key performance of friction under different realistic operating conditions of oscillatory speeds, torque and joint installation angles. The apparatus incorporates a custom-installed triaxial force sensor inside of the joint to measure the internal CV joint forces(including friction). Using the designed test setup, the intrinsic interfacial parameters of CV joints were investigated in order to understand their contact and friction mechanisms. The results provide a better understanding of CV joint friction characteristics in developing improved automotive driveshafts.

• KSTLE International Journal
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• 제3권1호
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• pp.43-48
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• 2002

Dry sliding wear and friction test of CrN coaling on two types of aluminum alloy substrates,6061 Al and 7075 Al deposited by arc ion plating, was peformed with a ball-on-disk tribometer. The effects of normal Bead and the mechanical properties of substrate on the friction coefficient and wear-resistance of CrN coating were investigated. The worn surfaces were observed by SEM. The results show that surface micro-hardness of CrN- coated 7075 Al is higher than that of CrN-coated 6061 Al. With an increase in normal lead, wear volume increases, while the friction coefficient decreases. The friction coefficient of CrN-coated 6061 Al is higher than that of CrN-coated 7075 Al, while the wear-resistance of CrN-coated 6061 Al is lower than the CrN-coated 7075 Al's, which indicates that the substrate mechanical properties have strong inf1uences on the friction coefficient and wear of CrN coating. The main wear mechanism was fragments of CrN coating, which were caused by apparent plastic deformation of substrate during wear test.

• KSTLE International Journal
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• 제3권1호
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• pp.68-73
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• 2002

A fretting wear experiment in roam temperature air was performed to evaluate the wear mechanism of fuel rod using a fretting wear tester, which has been developed for experimental study, The main focus was to compare the wear behaviors of fuel rod against support springs with different contact contours (i.e. concave and convex). Wear volume, degree or surface hardening and adhesion tendency of wear particle were examined by the surface roughness tester. The result indicated that with a change of contact condition from contact force of 5 N to 0.1 mm gap, the wear volume of tube increased in the condition of concave spring, but slowly decreased in convex spring. From the results of SEM observation, wear mechanism of each test condition was also dependent on the spring shapes. The wear mechanism of each test condition in room temperature air is discussed.

• 한국재료학회지
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• 제17권11호
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• pp.601-605
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• 2007

The tribological properties of acrylonitrile-butadiene rubber (NBR) filled with two kinds of carbon black filler were examined. Different types of Semi-Reinforcing Furnace (SRF), and High Abrasion Furnace (HAF) blacks were used as filler material to test the influence of carbon black particle size on the friction and wear of NBR. Results from tribological tests using a ball on disk method showed that the smaller HAF particles were more effective for reducing the wear of NBR during frictional sliding. The hardness, elastic modulus at 100% elongation, and elongation at break were measured to examine the correlation between the effects of carbon black on the mechanical and tribological properties of the NBR specimens. The wear tracks of the NBR specimens were observed with scanning electron microscopy (SEM). The wear tracks for NBR with different ratios of SRF and HAF showed clearly different abrasion patterns. Mechanisms for the friction and wear behavior of NBR with different sizes of carbon black filler were proposed using evidence from wear track observation, as well as the mechanical and tribological test results.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.219-224
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• 1999

The effects of solid lubricants on wear and friction characteristics of friction materials were studied using a pad-on-disk type friction tester. Friction materials with ten formulations containing different relative amounts of solid lubricants(graphite, MoS$_2$and Sb$_2$S$_3$) were investigated. Results of this work showed that each formulation with different relative amounts of the lubricants had unique friction characteristics. At low brake temperatures, friction materials containing rich graphite showed a small amount of $\mu$ change during sliding. At elevated temperatures, on the other hand, friction materials with rich Sb$_2$S$_3$and graphite showed smaller $\mu$ changes suggesting complementary lubrication of Sb$_2$S$_3$and graphite during sliding. However, the friction materials with rich Sb$_2$S$_3$showed a large amount of wear.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.72-78
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• 2001

An experimental investigation was conducted to examine the tribological behavior of NAO (non-asbestos organic) type brake linings containing different volume ratios of graphite and antimony trisulfide (Sb$_2$S$_3$). In order to investigate the effect of the solid lubricants on brake performance, three different friction tests (pressure, speed, and temperature sensitive tests) were carried out using a scale dynamometer. The test results showed that the friction characteristics were strongly affected by the type and the amount of solid lubricants in the brake lining. It was found that the brake linings with both solid lubricants were better in friction stability due to the complementary role of the two disparate lubricating properties at various pressure and speed conditions. In particular, the brake lining containing higher concentrations of graphite showed better fade resistance than others during high temperature friction test.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.81-88
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• 2001

To study the influence of the shape of contacting bodies (especially the end profile) on slip regime, wear test is conducted in the case of the contact between tube and support. Two different end profiles of the support are used such as truncated wedge and rounded punch. During the test, 10, 30 and 50 N are applied as normal force and slip displacement varies between 10-200 $\mu\textrm{m}$. The tube and the support specimens are made of Zircaloy-4 and a specially designed wear tester is used. Tests are carried out in air at room temperature. Wear on the tube is examined by measuring microscope. Partial and gross slip regimes are classified from the observed wear shape. Surface roughness tester is also used to measure the wear depth and contour, from which wear volume is evaluated. The transition from partial to gross slip is also investigated by investigating the considerable increase of wear volume. From the result, the boundary between the partial and the gross slip is newly determined in the conventional fretting map for the present specific contact configuration. Since the transition is related with the amount of energy dissipation from the contact surface so is wear, it is regarded that wear can be restrained by designing a proper shape of support.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.111-116
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• 2004

Li-complex and urea type greases (each 10 species) which were furnished by Chang-Am LS, analyzed anti-wear performance into fretting wear tester & four-bail wear tester. from the results of fretting wear test, the wear volume of Li-complex greases are $4.6\~8.9mg\;and\;8.3\~14.4mg$ with the test of urea greases. The anti-wear performance for 4-ball wear test of greases produced results around 0.5mm at the value of WSD. The grease life performance were evaluated by SKF-ROF Grease Tester and wheel bearing life tester. From the results of SKF-ROF tester, the life performance evaluated by whole working time produced results $50\~300hr$ with the Li-complex greases and 100-1000hr with the urea greases. That is to say, in spite of severe condition at the higher of $10^{\circ}C$ reaction temp, the life performance with Urea type greases are much superior to Li-complex type greases. Prior to wheel bearing life tester, the grease selected performance evaluation(=anti-wear test) are tested by wheel bearing tester. In this results, we can confirm results those are similar with SKF-ROF tester. In this study, we can draw two major conclusions, one is that Li-complex greases are superior to urea greases with anti-wear properties and the other is that urea greases are much superior to Li-complex greases with life performance.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.313-323
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• 2003

The sliding wear behaviors of Zircaloy-4 nuclear fuel rod were investigated using two support springs with convex and concave shapes in room temperature air and water. The main focus is to compare the wear behavior of various test variables such as slip amplitude, environment, contact contours with different spring shape and a number of cycles. The results indicated that wear volume and maximum wear depth increased with slip amplitude in both air and water, but their trends tended to change according to the spring shapes and test environments. In air condition, the wear volume was controlled by wear debris behavior generated on worn surface. As a result, final wear volume and maximum wear depth decreased if a ratio of protruded wear volume to worn area $(D_p)$ would be saturated to specific value. This is because wear particle layer could accommodate large strain by accumulating and transforming wear particle layer. However, in water condition, metal-to metal contact was more dominant and wear volume was greatly affected by changed mechanical behavior between contact surfaces since wear debris should be generated after repeated plastic deformation and fracture. After wear test, worn surfaces were examined using optical microscope and SEM and details of wear mechanism were discussed using a ratio of wear volume to worn area $(D_e)$ at each test condition.

• Tribology and Lubricants
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• 제27권6호
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• pp.308-313
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• 2011

본 연구에서는 수직 하중과 미끄럼 속도가 DLC (a-C:H)와 WC/C (a-C:H:W)의 마찰 특성에 미치는 영향을 파악하기 위해 ball-on-disk 형태의 마찰 실험 장치를 이용하여 실험을 수행하였다. 연구 대상 고체 윤활막인 DLC와 WC/C는 AISI 52100 steel ball의 표면에 증착되었으며, 상대 마찰면의 재질은 침탄 경화된 SCM 415 Cr-Mo steel이다. 실험은 상대 습도가 20~40 %이고 온도가 $16{\sim}24^{\circ}C$인 대기 분위기에서 다양한 미끄럼 속도 (0.1, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50, 100 mm/s) 및 수직 하중 (2.4, 4.8, 9.6 N) 조건에 대해 수행되었다. 실험 결과로 각각의 실험 조건에서의 DLC와 WC/C의 운동 마찰 계수를 얻었다. 실험 결과 DLC와 WC/C의 운동 마찰 계수는 미끄럼 속도가 증가할 수록 대체로 증가하였으며, 수직 하중에 관계없이 거의 일정한 값을 보였다. 그리고 동일한 실험 조건에서 DLC의 마찰 계수가 WC/C의 마찰 계수에 비해 대체로 낮은 값을 보였다.