• Steel and Composite Structures
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• 제53권2호
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• pp.227-241
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• 2024

Advancements in additive manufacturing technology, notably for its efficiency, accuracy, automation, and streamlined procedures, are increasingly relevant in civil engineering. This study evaluates the mechanical properties of 316L stainless steel bolted connections fabricated using Powder Bed Fusion (PBF) additive manufacturing. Eleven single-lap bolted connection specimens were tested under monotonic loading to assess the influence of various factors, including plate thickness, manufacturing direction, bolt end and edge distances, and bolt quantity, on the connections' anti-sliding and shear capacities. Material tests conducted prior to the connection tests revealed that PBF-manufactured stainless steel plates possess higher yield and ultimate strength, as well as greater elongation capacity, compared to traditional stainless steel plates. The connection tests indicated that the anti-sliding coefficient values range from 0.348 to 0.698, aligning with current standards for stainless steel bolted connections. Three distinct failure modes were identified: net section failure in the stainless-steel plate, bolt shear failure, and plate shear failure. It was determined that existing standards for anti-sliding capacity may not be entirely applicable to PBF-manufactured connections. Therefore, a modified model for the anti-sliding capacity of these connections is proposed. Additionally, a more accurate formula for calculating their shear capacity, which addresses the oversight of friction forces in current standards, is introduced.

• 동력기계공학회지
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• 제9권2호
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• pp.57-64
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• 2005

This paper is the study on dry sliding wear behavior of carbon fiber reinforced epoxy matrix composites against lay-up orientation. Tests were investigated on the effect of the lay-up orientation, fiber sliding direction, load and sliding velocity when circumstance keep continuously at $21^{\circ}C$, 60%RH. Pin-on-disk dry sliding wear tests for each experimental condition were carried out with a carbon fiber reinforced plastic pin on stainless steel disk in order to search the friction and wear characteristics. The wear rates and friction coefficients against the stainless steel counterpart were experimentally determined and the wear mechanisms were microscopically observed. The effect on friction and wear behavior are observed differently, according to various conditions. When sliding took place against counterpart, the highest wear resistance and the lowest friction coefficient were observed in the $[0]_{24s}$ lay-up orientation at anti-parallel direction.

• 제어로봇시스템학회논문지
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• 제4권4호
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• pp.525-533
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• 1998

A conventional contact type brake system which uses a hydraulic system has mny Problems such as time delay response due to pressure build-up, brake pad wear due to contact movement, bulky size, and low braking performance in high speed region. As vehicle speed increases, a more powerful brake system is required to ensure vehicle safety and reliability. In this work, a contactless brake system of an eddy current type is proposed to overcome problems. Optimal torque control which minimizes a braking distance is investigated with a scaled-down model of an eddy current type brake. It is possible to realize optimal torque control when a maximum friction coefficient (or desired slip ratio) corresponding to road condition is maintained. Braking force analysis for a scaled-down model is done theoretically and experimentally compensated. To accomplish optimal torque control of an eddy current type brake system, a sliding mode control technique which is, one of the robust nonlinear control technique is developed. Robustness of the sliding mode controller is verified by investigating the braking performance when friction coefficient is varied. Simulation and experimental results will be presented to show that it has superior performance compared to the conventional method.

• 한국공작기계학회논문집
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• 제15권5호
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• pp.91-96
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• 2006

The friction and wear properties of ceramics are very important in the applications to engineering ceramic parts such as seal rings, pump parts, automobile meter parts, and so on. In this study, the effects of each other purity on the mechanical and tribological properties of purity zirconia ceramics were investigated. Also in order to determine the effects of sliding distance, sliding speed, contact load, friction coefficient, the amount of worn out material at a certain time, and the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The results show that we obtained the good properties of friction coefficient and wear resistance at the purity 99.5% of zirconia. than this of the purity 95% were great at the wear amount of worn out material.

• Tribology and Lubricants
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• 제39권2호
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• pp.43-48
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• 2023

In this study, we investigate the tribological behavior of AISI 304 stainless steel pairs under deionized water and hexagonal boron nitride (h-BN) water dispersion lubrication. The specimen friction and wear properties are evaluated using a reciprocating ball-on-flat tribometer. The coefficient of friction remains nearly constant throughout the test under both lubricant conditions. The wear depth of the specimens under h-BN lubrication is smaller than that under deionized water lubrication, indicating the inhibition behavior of h-BN nanolubricants on direct metal-metal contacts. Optical micrographs and stylus profilometer measurements are performed to evaluate the severity of damage caused by the sliding motion and to determine the wear morphology of the specimens, respectively. The results show that h-BN nanolubricants does not have a significant effect on the friction behavior but demonstrates reduced wear owing to their trapping effect between the sliding interfaces. Moreover, scanning electron microscopy and energy-dispersive X-ray spectroscopy images of the specimens were acquired to confirm the trapping effect of h-BN between the sliding interfaces. The results also suggest that the trapped lubricants can distribute the contact pressure, reducing the wear damage caused by the metal-metal contact at the interface. In conclusion, h-BN nanolubricants have potential as an anti-wear additive for lubrication applications. Further investigation is needed to provide direct evidence of the trapping effect of h-BN nanoparticles between the sliding interfaces. These findings could lead to the development of more efficient and effective lubricants for various industrial applications.

• 수산해양기술연구
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• 제40권4호
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• pp.337-343
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• 2004

탄소 섬유강화 에폭시기지 복합재의 경면 가공한 스테인레스 강 상대재와 마찰과 마모에 바탕을 둔 연구에서 다음과 같은 결론을 얻었다. (1) 일방향 탄소섬유 강화 복합재의 마모 거동에 미치는 미끄럼 방향의 효과는 다르며 작용하는 마모 메커니즘의 형태에 의존한다. (2) 상온에서 경면 가공한 스테인리스 스틸에 대하여 미끄럼이 일어나면 AP 방향에서 높은 마모 저항과 낮은 마찰계수가 관찰되었다. (3) 복합재의 비마모율은 미끄럼 속도가 증가하면 N방향과 P방향에서는 감소하는 경향을 보이며, AP 방향에서는 증가하다가 감소한다. 이것은 마모 메카니즘의 영향으로 속도가 증가하면 마모 이착막의 생성이 빨라져 이착막 속의 탄소섬유가 윤활제의 역할을 하기 때문이다. (4) 복합재의 마찰계수는 미끄럼 속도가 증가하면 3방향 모두 증가하다가 일정한 값에 수렴하면 N방향이 가장 크며, P방향과 AP방향 순이다. 이는 N방향에서 마찰초반에 발생한 섬유의 쟁기질에 의한 상대재 표면의 손상과 돌기변형에 따른 것이며, AP방향의 마찰계수가 가장 낮다.

• Tribology and Lubricants
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• 제14권1호
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• pp.70-78
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• 1998

Two different friction materials (organic and low-metallic pads) for automotive brakes were studied to investigate the anti-fading phenomena during stop. The anti-fading phenomena were pronounced more in the case of using low metallic friction materials than organic friction materials. The main cause of the anti-fading phenomena was the high dependence of friction coefficient on a sliding speed. The anti-fading was prominent when the initial brake temperature was high in the case of low-metallic friction materials due to the strong stick-slip event at high temperature. On the other hand, the anti-fading was not severe in organic friction materials and the effect was reduced at high braking temperature due to the thermal decomposition of organic friction materials. The strong stickslip phenomena of low metallic friction materials at high temperature induced high torque oscillations during drag test. During this experiment two different braking control modes (pressure controlled and torque controlled modes) were compared. The type of the control mode used for brake test significantly affected the friction characteristics.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.419-431
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• 2004

The dynamic response of a cracked functionally graded piezoelectric material (FGPM) under transient anti-plane shear mechanical and in-plane electrical loads is investigated in the present paper. It is assumed that the electroelastic material properties of the FGPM vary smoothly in the form of an exponential function along the thickness of the strip. The analysis is conducted on the basis of the unified (or natural) crack boundary condition which is related to the ellipsoidal crack parameters. By using the Laplace and Fourier transforms, the problem is reduced to the solutions of Fredholm integral equations of the second kind. Numerical results for the stress intensity factor and crack sliding displacement are presented to show the influences of the elliptic crack parameters, the electric field, FGPM gradation, crack length, and electromechanical coupling coefficient.

• International Journal of Automotive Technology
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• 제8권2호
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• pp.211-217
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• 2007

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS (Anti-lock Brake System) systems. In realizing the wheel slip control systems, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance and stability enhancement. In this paper, a robust wheel slip controller is developed based on the adaptive sliding mode control method and an optimal target slip assignment algorithm is proposed for maximizing the braking force. An adaptive law is formulated to estimate the braking force in real-time. The wheel slip controller is designed based on the Lyapunov stability theory considering the error bounds in estimating the braking force and the brake disk-pad friction coefficient. The target slip assignment algorithm searches for the optimal target slip value based on the estimated braking force. The performance of the proposed wheel slip control system is verified in HILS (Hardware-In-the-Loop Simulator) experiments and demonstrates the effectiveness of the wheel slip control in various road conditions.

• 한국공작기계학회논문집
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• 제14권2호
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• pp.1-7
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• 2005

In order to determine the wear Properties of PECVD ceramic coatings, wear process was evaluated using the coated pin of Falex Tribosystem. Coating materials deposited wear the TiC, TiN and Ti(CN). An experimental process was established to determine the tribological characteristics of friction and wear behavior under the variation of applied load, temperature and sliding distance by the Falex test machine. The experimental results indicate that TiN coating compared with TiC coating on e materials have e excellent friction and wear characteristics. However TiC coating compared i친 TiN coatings have a low friction coefficient with steel and good thermal stability, and Ti(CN) has the excellent anti-wear properly as well as the superiority of extreme pressure property. Compound coating compared wi simple coatings show improved tribological characteristics.