• Tribology and Lubricants
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• v.34 no.4
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• pp.146-159
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• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.159-165
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• 2000

In this paper the residual stresses on lubricated sliding surfaces were measured during break-in procedure and up to scuffing by the X-ray diffraction method. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were done using a constant load. In the break-in procedure the loads were increased from very low values in several steps. It was found that the sliding surfaces with break-in represented relatively higher values of residual compressive stresses than those without break-in. The residual stresses below the surfaces showed the small amount of stress increases. The results of scuffing tests with and without break-in showed the same trends as break-in tests did. However, in case of tests with break-in procedure the stresses below the surfaces showed very large increases in the residual compressive stresses. From the tests of break-in and scuffing, it was found that the increases in scuffing lives were related with the increases of residual stresses on the lubricated sliding surfaces with break-in.

• Tribology and Lubricants
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• v.26 no.5
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• pp.277-282
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• 2010

The purpose of this paper is to study and analysis the failure examples for parasitic current leakage produced in starting system on gasoline engine. It verified the discharge of battery by electric leakage because of internal wiring damage problem for CD auto changer installed in car. Also, it verified the no-stating phenomenon because of deposit forming by chemical reaction of battery fluid between battery post and cable fixing parts. It verified the damage for brush holder and commutator mixing by internal short phenomenon because of brush carbon a particle and engine oil that was flowed into internal of starting motor. It verified the working phenomenon of audio by a point of contact even if the driver turn to "LOCK" position the key.

• Journal of Drive and Control
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• v.16 no.4
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• pp.9-15
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• 2019

Bucket trajectory is crucial regarding precision work with an excavator. In general, the bucket trajectory deviation is determined by the machining deviation of the frame, driving deviation of the driving hydraulic cylinder, clearance in the joints, and deformation of the structure. This paper investigated the relationship between the respective clearance in joints and the trajectory deviation of the bucket at the finishing work of the ditching for a 20-ton excavator. As a result, the larger the clearance, the larger deviation is increased at trajectory. However, it was found that the deviation of the rotation angle and displacement of the bucket was limited and the size of clearance does not affect closely on the contact angle of the pin shaft.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.288-297
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• 1990

The method of analyzing flexible mechanisms with clearances was studied considering flexibility of beams in the mechanism using finite elements. Both ends of a beam were modeled as free following Dubowsky's impact pair model. Instead some force constraints were imposed at imposed at the connections between adjoining links. Coulomb model has been developed using dry frictions in place of tangential damping forces in the impact pair model and the contact compliance and damping coefficient approximated in a form of root function were used. As examples, impacts of a rigid ball in a cylinder, impact beam model and four-bar mechanisms made up of three flexible links with clearance connections were simulated numerically. The results from examples showed similar but a little bit smaller magnitude of impact forces compared with published studies.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1961-1965
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• 2003

The flow analysis is needed to verify the physical phenomena through interruption processes for improving the capacity and the reliability of gas circuit breakers. Moreover the small current interruption performance of GCBs could be predicted by coupling the flow characteristics with the electric field one. In this paper, the unsteady flow characteristics and the traveling trajectory are depicted with a commercial CFD code, PHOENICS, programmed for moving motion of objects. In order to validate computational results, the measured pressure data in cylinder and in front of arcing contact are compared with the test results of small current interruption.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.136-142
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• 2005

The function of main starting valve for marine engine is to supply cylinder with the air to start marine engine. But, if the spindle, one of the main starting valve components, doesn't rotate accurately at the designated air pressure, the marine engine may have some trouble in starting. So, to resolve the problem due to spindle .elation in the main starting valve, the blocking device (blocking plate, limit switch, etc.) is installed in the upper part of spindle to constrain the rotation. So, in this paper we introduced the rotation constraining ability of blocking plate prevent the spindle from mis-working in the main starting value of the marine engine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.28-34
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• 2014

A non-contact type measurement system is specially devised to measure the width of a piston ring groove in the grinding process. This system comprises a line camera with an imaging lens, collimated white light source, and a one axis translation stage. When the measurement system movesalong the diagonal direction of the cylinder, the line camera captures an image. By analyzing such images, the width of the piston ring groove can be determined. The experimental results prove that the proposed system is useful, especially as a monitoring system in grinding piston ring grooves on cylinders with accuracy of several micrometers in an area of dozens of millimeters.

• Journal of Drive and Control
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• v.9 no.1
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• pp.18-24
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• 2012

The paper deals with the design of a new low-friction seal for a pneumatic cylinder with high speed actuation. The seal performance with variation of the cross sections in piston seals with elastomeric material was investigated to minimize the friction forces using ABAQUS. The contact stress and strain distributions and frictional forces of the piston seals were investigated with variation of interference fits, supply pressures and friction coefficients. To develop adequate and productive procedures, the finite element models of the piston seals were created and nonlinear analysis of a seal design was conducted in order to build further knowledge and understanding of the seal's performance characteristics.

• Tribology and Lubricants
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• v.27 no.1
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• pp.25-33
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• 2011

Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.