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Thermal-Mechanical Coupled FE Analysis for Rotary Shaft Seals

Modern Mechanical Engineering 2018年第1期8卷 95-110页

作者： gyorgy szabó Károly Váradi Department of Machine and Product Design Budapest University of Technology and EconomicsBudapestHungary

The aim of this paper is to model the steady-state condition of a rotary shaft seal (RSS) system. For this, an iterative thermal-mechanical algorithm was developed based on incremental finite element analyzes. The behavior of the seal’s rubber material was taken into account by a large-strain viscoelastic, so called generalized Maxwell model, based on Dynamic Mechanical Thermal Analyses (DMTA) and tensile measurements. The pre-loaded garter spring was modelled with a bilinear material model and the shaft was assumed to be linear elastic. The density, coefficient of thermal expansion and the thermal conductance of the materials were taken into consideration during simulation. The friction between the rotary shaft seal and the shaft was simplified and modelled as a constant parameter. The iterative algorithm was evaluated at two different times, right after assembly and 1 h after assembly, so that rubber material’s stress relaxation effects are also incorporated. The results show good correlation with the literature data, which state that the permissible temperature for NBR70 (nitrile butadiene rubber) material contacting with ~80 mm shaft diameter, rotating at 2600/min is 100°C. The results show 107°C and 104°C for the two iterations. The effect of friction induced temperature, changes the width of the contact area between the seal and the shaft, and significantly reduces the contact pressure.

关键词： Coupled FE Analysis Thermal-Mechanical Coupling Rotary Shaft Seals NBR Rubber Viscoelasticity

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Failure Mechanism of O-Ring Seals under Extreme Operating Conditions

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Modern Mechanical Engineering 2018年第1期8卷 11-30页

作者： gyorgy szabó Károly Váradi Department of Machine and Product Design Budapest University of Technology and EconomicsBudapestHungary

In this paper the behavior of an O-ring made of NBR rubber was investigated under extreme conditions. The effect of the extreme initial compression, operating pressure and extreme temperature conditions were examined. The rubber material was tested in simple tension, pure shear and equibiaxial tension modes complemented with a Dynamic Mechanical Thermal Analysis (DMTA) to capture the viscoelastic behavior of the material. For the investigation, a large-strain viscoelastic material model was developed by the authors, to take into account the large deformations caused by extreme conditions. Insufficient space during installation causes extreme initial compression consequently leading the material to crack on the contacting outer surfaces. It was found that the excessive strain and friction induced shear stress contributes primarily to this phenomenon. Extreme operating pressure causes the seal to penetrate into the gap between the shaft and the housing. This behavior damages the material and cracks appear on the seal. High strain areas were found in the proximity of the gap in the material. The analysis of the extreme operating temperature showed that during cooling the O-ring can completely loose its ability to seal at -70°C. There are three contributing factors: the speed of cooling, the temperature and the coefficient of thermal expansion.

关键词： O-Rings Finite Element Analysis Initial Pressure Overpressure Temperature Extremes

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Surgical stress and cytoskeletal changes in lens epithelial cells following manual and femtosecond laser-assisted capsulotomy

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International Journal of Ophthalmology(English edition) 2020年第6期13卷 927-934页

作者： ANDrea Krisztina Sükosd Krisztina szabadfi Edina szabó-Meleg Beáta Gáspár Pavel Stodulka gyorgy SétálóJr Róbert Gábriel Miklós Nyitrai Zsolt Biró Hajnalka Abrahám Department of Ophthalmology University of Pecs Medical School and Clinical CentrePecs 7623Hungary Department of Experimental Zoology and Neurobiology University of PecsPecs 7624Hungary Department of Biophysics University of Pecs Medical School and Clinical CentrePecs 7624Hungary Janos Szentagothai Research Centre University of PecsPecs 7624Hungary Optimum Laser Centre Budapest 1124Hungary Gemini Eye Clinics Zlin 76001Czech Republic Department of Medical Biology and Central Electron Microscopic Laboratory University of Pecs Medical SchoolPecs 7624Hungary

AIM:To study the effect of mechanical stress on the cytoskeleton in lens epithelial cells following conventional phacoemulsification surgery(CPS)and femtosecond laserassisted cataract surgery(FLACS).METHODS:The cytoskeleton of the epithelial cells of the anterior lens capsules(ALC)removed by CPS and FLACS was examined by *** of the intermediate filament,glial fibrillary acidic protein(GFAP),and glutamine synthetase(GS)immunoreactivity were *** order to map the actin network of cells,fluorescently labeled phalloidin was *** samples were examined using confocal laser scanning ***:GFAP expression was visible in a larger number of the epithelial cells after CPS compared to *** CPS sample’s epithelial cells,GFAP immunoreactivity indicated robust morphological *** the actin filaments,the presence of tubular elements connecting epithelial cells,regular actin pattern and marked cortical network after CPS were *** FLACS,the actin cytoskeleton of the epithelial cells remained densely structured,and the tubular elements were undetectable,however,the above-mentioned regular actin pattern and the marked cortical network were ***:The conventional removal of the ALC induces more robust changes of the cytoskeleton of the lens epithelial cells.

关键词： lens epithelial cell cytoskeleton capsulotomy glial fibrillary acidic protein actin

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