• Advances in Automotive Engineering
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• v.1 no.1
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• pp.21-39
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• 2018

Clutch energy is the thermal energy dissipated on the clutch disc, and it reaches its highest level during drive-off as a result of the difference between the angular speeds of the flywheel and clutch disc, and the torque transmitted. The thermal energy dissipated effects the clutch life. This study presents a new drive-off and thermal model to calculate the clutch energy for a rear wheel driven heavy-duty vehicle and to analyze the effects of clutch energy on temperatures of clutch pressure plate, flywheel and clutch housing. Three different driver profiles are used, based on the release of the clutch pedal in modulation zone: i) the pedal travels with the same speed all the way, ii) the travel speed of the pedal increases, iii) the travel speed of the pedal decreases. Vehicle test is performed to check the accuracy of the model. When compared to a simpler model that is widely used in the literature to calculate the clutch energy, the model used in this study calculates the clutch energy and angular speed behaviors of flywheel and transmission input shaft in better agreement with experimental results. Clutch wear and total clutch life are also estimated using the mean specific friction power.

• Tribology and Lubricants
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• v.24 no.6
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• pp.285-290
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• 2008

The purpose of this paper is to present the case study of tribological failure analysis on the gear damages, oil leakage, and sealant sealing in a manual transmission of front engine and front wheel drive vehicle. The manual transmission is to change the speed range and direction of the engines depending on the driving conditions by friction driving forces with input and output gear system. The material property and surface roughness of the gears are strongly related to the gear noise and micro-vibration, oil leakage and wear, which may decrease the real contact area of the gear and the strength of the oil film thickness between the driving gear and driven one. The O-ring damage of speedometer driven gear and bad sealant sealing of oil pan may produce oil leakage through the contact surfaces, which cause the oil shortage and seizure on the sliding surfaces of the transaxle gears. In the failure case study, the proper repair working and good lubrication are very important for the long life of the transaxle without any tribological failures and oil leakage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.324-324
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• 2008

Piezoelectric ceramics is an active element that makes stator to vibrate to generate rotational force in ultrasonic motors. In drive of ultrasonic motors, many factors that affect to the resonance characteristics of piezoelectric ceramics exist. For example, those factors are bonding condition with elastic body, the magnitude of electric field, the normal force for frictional drive and the emission of heat due to vibration and friction and so on. Therefore, it is important to research the inclination of property variation of piezoelectric ceramics in circumstance that has complex elements. In this paper, we focused and analyzed the resonance characteristics of ultrasonic motor due to the magnitude of the driving voltage and normal force.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4166-4178
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• 2021

The Control Rod Drive Mechanism (CRDM) is an essential part of the reactor, which realizes the start-stop and power adjustment of the reactor by lifting and lowering the control rod assembly. As a moving part in CRDM, the latch directly contacts with the control rod assembly, and the life of latch is closely related to the service life of the reactor. In this paper, the relationship between the life of the latch and the step stress, friction stress, and impact stress in the process of movement is analyzed, and the optimization methodology and process of latch life based on the approximate model are proposed. The design variables that affect the life of the latch are studied through the experimental design, and the optimization objective of design variables based on the latch life is established. Based on this, an approximate model of the life of the latch is built, and the multi-objective optimization of the life of the latch is optimized through the NSGA-II algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.4
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• pp.391-395
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• 2010

In our paper, we propose an asymmetric single-tracked wheel system, and describe its structure and the method for maintaining the length of a transformable track system. And the method is reducing the gap of lengths. Therefore, we propose an efficient structure for transforming and explain motions with kinematics. Our transformable shape single-tracked mobile system has an advantage to overcome an obstacle or stairs by the variable arms in the single unity track system. But we will make the variable shape of tracked system get a drive that has a force to stand against a wall. In this case, we can consider this system to a rigid body and have a notice that this single tracked system is able to get vary shape with the variable arm angle. Considering forces balance along x-axis and y-axis, and moments balance around the center of the mass we have. If this rigid body is standing against a wall and doesn't put in motion, the force of flat ground and the rigid body sets an equal by a friction. In the same way, the force of a wall and the rigid sets an equal by a friction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.748-752
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• 2004

Fluid dynamic bearings (FDBs) have been replacing ball bearings of the HDD spindle motor very rapidly. But there are several demerits of HDB, such as high friction torque, variable viscosity of the fluid lubricant depending on operating temperature, low stiffness, and etc. Eccentricity is one of the major parameters which affects the static and dynamic characteristics. As the static eccentricity is larger, the stiffness and the damping coefficients become bigger. But friction torque is relatively unaffected by the static eccentricity. This research proposes a new type of journal bearing with asymmetric journal grooves which results in better dynamic characteristics. The static and dynamic characteristics of the new journal bearing are investigated by solving the Reynolds' equation with FEM, and the transient analysis is performed to predict the dynamic behavior of rotor by solving the equations of motion of a HDD spindle system with Runge-Kutta method. The result shows that the proposed Journal bearings have much bigger stiffness and damping coefficients compared with the conventional symmetric ones. And consequently, it has smaller whirl radius and tilting angle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.106-114
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• 1998

Tribological investigation of ultra thin film magnetic storage disks which have two different kinds of start/stop zone of laser textured bump disk and mechanically textured disk for before CSS test and after CSS test. To measure surface roughness, height reduction before/after CSS test and obtain accurate topographies, AFM(Atomic Force Microscope) which is most powerful recently has been used. The result of statistical analysis showed that both laser textured bump height and mechanically textured zone height have been reduced about 4~7nm after 15000 cycle CSS test. Using commercial Nano-Indenter, ramping load scratch test has been performed to investigate friction characteristic for laser textured zone and mechanically textured zone before/after CSS test.

• Journal of Drive and Control
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• v.13 no.3
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• pp.47-52
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• 2016

This paper presents a control method for the performance improvement of a proportional solenoid actuator using a Pulse Width Modulation (PWM) signal. It is very difficult to obtain excellent response performance from a proportional solenoid actuator using a simple proportional controller with no PWM signal or dither because the mass and structure of a proportional solenoid actuator changes according to the application target, friction force in the proportional solenoid tube, operating force and displacement range. To solve the above problems, first, a controller with a PWM function for experimenting with attraction force characteristics was designed and manufactured. Secondly, an experimental setup for solenoid performance measurement with a force sensor and a displacement sensor was also manufactured. The attraction force characteristics according to the frequency and duty ratio variations of a PWM signal were tested and the relationships among the frequency, duty ratio, plunger mass and friction characteristics were analyzed. Finally, response characteristics improvements for proportional solenoid actuators are discussed.

• Journal of Drive and Control
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• v.11 no.1
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• pp.8-13
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• 2014

Hydraulic servo valves are widely used in various fluid power systems because of their fast response and precision control. In this paper, we studied the effect of metering notch shapes and amount of their openings on the flow characteristics within the spool valve using a computational fluid dynamic (CFD) code, FLUENT. To obtain the results for more realistic operating conditions, viscous heating due to the jet flow and viscosity variation of the hydraulic fluid with temperature were considered. For two types of notch shape, streamlines, oil temperature and viscosity distributions, and variations of flow and friction forces acting on spool were showed. The flow and friction forces affected by the metering notch shapes and their openings, and oil temperature rise near metering notch was significant enough to results in the jamming phenomenon. A thermohydrodynamic (THD) flow analysis adopted in this paper can be used in optimum design of hydraulic servo valves.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.131-140
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• 2015

This paper presents overall procedure by experimental study in order to deriving design factors of snow removal machine on roof of multi-span greenhouse. For the purpose of the testing, the scale model of the machine was made in the form to drive above the monorail. The test was performed in order to calculating friction coefficient of the machine and shear coefficient between sliced horizontal section of snow at constant temperature and humidity room in National Academic of Agricultural Science. As a result of the laboratory test, shear coefficient between sliced horizontal section of snow were calculated 1.60~2.37. Further investigation, we will study to derive the relationship between the real and scaled model through the field test.