• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.129-136
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• 1998

I obtained result like these to practice accommodation test using Spherical Add method and Cross cylinder lens method. The 242 eyes(121 persons) in test was the young and middle age people and their age was from 19 to 41. 1. Using Spherical Add, I tested accommodation. The twenties's limits of accommodation were 9~13 Diopter, and thirties to fourties's limits of accommodation were 6~8.5 Diopter. 2. Using Cross cylinder lens in the test of accommodation twenties's average accommodation limits were appeared 6.13 Diopter~10.13 Diopter, thirties average accommodation limits were 5.75 Diopter~8.75 Diopter and fourties's average accommodation limits were 4.38 Diopter~7.25 Diopter. All men women have had more good accommodation of the horizontal direction than the vertical direction. 3. Using Spherical Add method and Cross cylinder lens method, the results of accommodation were shown like these. Accommodation that measured with spherical add method was more big than cross cylinder's accommodation measuring method. Finally I found the fact accommodation decreases as age goes.

• Transactions of Materials Processing
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• v.17 no.5
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• pp.343-349
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• 2008

The wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. This study will discuss characteristics of wear between hard and soft piston ring coatings with running surface of cylinder liner. Detailed tribological analysis by using Pin-on-Disk(POD) testing machine describes the lubricity mechanism between piston ring coatings and cylinder liner at different temperature with and without oil. The effect of surface roughness of the cylinder liner on the friction coefficient and wear amount of piston ring coatings will also be analyzed. To simulate scuffing mechanism between piston ring and cylinder liner, accelerated lab testing was performed. This study will provide the data from tribological testing of hard and soft piston ring coatings against cylinder liner. Furthermore, the microstructures and morphological features of the surface and the near-surface materials during wear will be investigated. From the scuffing test by using POD testing machine, scuffing mechanisms for the soft and hard coating will be analyzed and experimentally confirmed.

• Journal of Fisheries and Marine Sciences Education
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• v.10 no.2
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• pp.226-238
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• 1998

With the advent of high speed and high output diesel engines, cavitation erosion-corrosion of wet cylinder liners is one of the most prevalent types of failure. The cavitation erosion-corrosion at cylinder liners in water cooled diesel engines is considered to be to the collapse of cavitation bubbles attributed to the cylinder liner vibration. To suppress cavitation damage in cylinder liner, the addition of an inhibitor would be more general method and innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, photomicrographs from vibratory facility cavitation specimens and from an eroded liner of a field diesel engine are compared. The behavior of cavitation bubbles grown in fluid is observed under vibration conditions by taking direct photographs with high speed camera. In order to determine the contributions of pure cavitation erosion and of pure corrosion to the total cavitation damage are be studied by following an experimental programme which includes three types of test: (1)pure cavitation erosion test, (2)pure corrosion test, and (1)cavitation erosion-corrosion test. Also cavitation damage under vibratory cavitation is reduced by using flow in tap water.

• Tribology and Lubricants
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• v.22 no.3
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• pp.131-136
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• 2006

Cylinder bore wear may not be a problem in most current automotive engines. However, a small change in cylinder bore diameter can significantly affect the lubrication characteristics and ring axial motion. This in turn can cause to change inter-ring pressure, blow-by and oil consumption in an engine. Therefore, by predicting the wear of piston ring face, ring groove and cylinder bore altogether, the changed ring end gap and the changed volume of gas reservoir can be calculated. Then the excessive oil consumption can be predicted. Being based on the calculation of gas flow amount by the theory of piston ring dynamics and gas flow, and the calculation of oil film thickness and friction force by the analysis of piston ring lubrication, the calculation theory of oil amount through top ring gap into combustion chamber will be set. This is estimated as engine oil consumption. Furthermore, the wear theories of ring, groove and cylinder bore are included. Then the each amount of wear is to be obtained. The changed oil consumption caused by the new end gap and the new volume of oil reservoir around second land, can be calculated at some engine running interval. Meanwhile, the wear amount and oil consumption occurred during engine durability cycle are compared with the calculated values. Next, the calculated amount of oil consumption and wear are compared with the guideline of each pare0s wear and oil consumption. So, the timing of part repair and engine life cycle can be predicted in advance without performing engine durability test. The wear data of cylinder bore diameter are obtained from three engines before and after engine durability test. The calculated wear data of cylinder bore diameter are turn out to be twice of the lower bound of averaged test values at TDC and the lower bound at BDC.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.21-26
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• 2011

Type-3 cylinder liner has a limitation of machining the standard specimen for fracture toughness test because it has approximately 5 mm in thickness as well as a curvature. Hence, it needs to be employed a miniature specimen test technique to evaluate fracture toughness of the cylinder liner. In this study, small punch (SP) test method was employed to evaluate fracture toughness of the cylinder liner. Load-displacement curve result measured from the SP test showed that the liner material was failed during membrane stretching in the general SP load-displacement curve. Additionally, it was shown that liner material was isotropic although the amount of plastic deformation was different depending on the direction due to manufacturing process characteristics. Fracture toughness, $J_{Ic}$, was evaluated using the SP test data. The value of fracture toughness obtained was $13.0kJ/m^2$. This value was similar to that of the same kind of materials. Therefore, the fracture toughness evaluated using the SP test data was reasonable.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.375-378
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• 2007

Abrasive wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. Wear by abrasion are forms of wear caused by contact between a particle and solid material. Abrasive wear is the loss of material by the passage of hard particles over a surface. From the pin-on-disk test, particle dent test and scuffing test, abrasive wear characteristics of diesel engine cylinder liner-piston ring have been investigated. Pin-on-disk test results indicate that abrasive wear resistance is not simply related to the hardness of materials, but is influenced also by the microstructure, temperature, lubricity and micro- fracture properties. In particle dent test, dent resistance stress decreases with increasing temperature. From the scuffing test by using pin-on-disk tester, scuffing mechanisms for the soft coating and hard coating were proposed and experimentally confirmed.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.287-288
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• 2006

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules, welding repairs of cylinder block made of cast irons are generally not permitted. However, such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the cylinder blocks, made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding methods of packing seat and o-ring seat of cylinder block and apply them to the practice. It is concluding remarks that the suspected crack by a magnetic particle test due to different magnetic permeability can be identified, which are not associated with a mechanical discontinuity.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2270-2280
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• 2005

An experimental study is performed for turbulent swirling flow behind a circular cylinder using 2-D PIV technique. The Reynolds number investigated are 10,000, 15,000, 20,000 and 25,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the round cylinder along the test tube. A comparison is included with non swirl flow behind a circular and square cylinder. The recirculation zones are showed asymmetric profiles.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.407-408
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• 2002

This paper presents a split cooling system for a new inline 4-cylinder automotive engine. The split cooling system circulates coolant to the cylinder head and cylinder block separately. The coolant flow in the cylinder block is controlled by a $2^{nd}$ Thermostat installed at the outlet of cylinder block. The $2^{nd}$ thermostat closes when the coolant temperature is low. And this makes the coolant flow in cylinder block nearly stagnant, thereby reducing the coolant-side heat transfer coefficient and raising cylinder bore temperature. The $2^{nd}$ thermostat starts to open when the coolant temperature reaches a specified temperature. The test results on engine dynamometer show improved fuel economy and lower exhaust emission which result from the decrease in friction works and cooling loss. Also, several vehicle tests, with application of the new engine have been performed. Fuel economy improvement of 0.5{\sim}2.0%$ yields from different test modes and details are discussed in this paper.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.143-150
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• 2007

Ring and cylinder bore wear may not be a problem in most current automotive engines. However, a small change in ring face and cylinder bore diameter can significantly affect the lubrication characteristics and ring axial motion. This in turn can cause to change inter-ring pressure, blow-by and oil consumption in an engine. Therefore, by predicting the wear of piston ring face and cylinder bore altogether, the changed ring end gap and the changed volume of gas reservoir can be calculated. Then the excessive oil consumption can be predicted. Here, the oil amount through top ring gap into combustion chamber is estimated as engine oil consumption. Furthermore, the wear theories of ring and cylinder bore are included. The changed oil consumption caused by the new end gap and the new volume of oil reservoir around second land, can be calculated at some engine running interval. Meanwhile, the wear amount and oil consumption occurred during engine durability cycle are compared with the calculated values. The wear data of rings and cylinder bore are obtained from three engines after engine durability test. The calculated wear data of each part are turn out to be around the band of averaged test values or a little below. It is shown that the important factor regarding oil consumption increasement is the wear of ring face.