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장시열 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.3
Hydrodynamic lubrication is simulated under the contact conditions that the direction of contact velocity reverses with a sudden high applied load in the contact of piston top ring and cylinder liner. Hydrodynamic lubrication film formation and pressure between piston ring and cylinder liner at the top dead center (TDC) location are investigated in detail because most friction loss and wear damage happen at this location due to the thin-film thickness resulting from the slow-down and reversal contact velocities as well as high applied load. The surface roughness on the cylinder liner by the honing process that is similar scale to the lubrication film thickness at TDC location is considered. Around the TDC location, laser surface textured (LST) surface that is larger scale than the surface roughness is designed for the favorable film formation. These two surface roughness parameters are simulated to study the effects of favorable film formation and less frictional loss of piston top ring at TDC location where most of damage and friction loss occur. Frictional power loss and minimum film thickness of the cylinder surfaces of the honed roughness are compared with those of patterned designs.
초저종횡비 나노 스케일의 탄성유체윤활 유막 두께 측정에 관한 연구
장시열,공현상 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-
The measurement of ultra low aspect ratio fluid film thickness is a necessity for the verification of lubrication media characteristics and clearance design in many precision components such as MEMS, bearings and other slideways. Many technologies are applied to the measurement of ultra low aspect ratio fluid film thickness (i.e. elastohydrodynamic lubrication film thickness). In particular, in-situ optical interferometric method has many advantages in making the actual contact behaviors realized with the experimental apparatus. Careful selection of incident lights greatly enhances the fringe resolutions up to ~1.0 nanometer scale with digital image processing technology. In this work, it is found that coaxial aligning trichromatic incident light filtering system developed by the author can provide much finer resolution of ultra low aspect ratio fluid film thickness than monochromatic or dichromatic incident lights, because it has much more spectrums of color components to be discriminated according the variations of film thickness. With some measured interferometric images of ultra low aspect ratio fluid film thickness it is shown how the film thickness is resolutionized and measured in nanometer scale with digital image processing technology and space layer method.