• Steel and Composite Structures
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• v.35 no.4
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• pp.555-566
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• 2020

This paper aims to present an analytical methodology to investigate influences of nanoscale and surface energy on buckling stability behavior of perforated nanobeam structural element, for the first time. The surface energy effect is exploited to consider the free energy on the surface of nanobeam by using Gurtin-Murdoch surface elasticity theory. Thin and thick beams are considered by using both classical beam of Euler and first order shear deformation of Timoshenko theories, respectively. Equivalent geometrical constant of regularly squared perforated beam are presented in simplified form. Problem formulation of nanostructure beam including surface energies is derived in detail. Explicit analytical solution for nanoscale beams are developed for both beam theories to evaluate the surface stress effects and size-dependent nanoscale on the critical buckling loads. The closed form solution is confirmed and proven by comparing the obtained results with previous works. Parametric studies are achieved to demonstrate impacts of beam filling ratio, the number of hole rows, surface material characteristics, beam slenderness ratio, boundary conditions as well as loading conditions on the non-classical buckling of perforated nanobeams in incidence of surface effects. It is found that, the surface residual stress has more significant effect on the critical buckling loads with the corresponding effect of the surface elasticity. The proposed model can be used as benchmarks in designing, analysis and manufacturing of perforated nanobeams.

• Tribology and Lubricants
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• v.38 no.3
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• pp.115-119
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• 2022

This paper selected three kinds of grease with the same type but different consistency for the experiment. The purpose of the experiment is tested the effect of different consistency of grease on the wear of the gear surface. Different torque test groups were selected in the test, and the lubrication effect of different greases was tested in the test groups with the same torque. After each set of tests, the wear of the gear surfaces was observed and recorded. The data recorded in the experiment included the area of the wear area on the gear surface, the type of wear and the volume of wear. After the test, the gear surface roughness was measured. By calculating the wear volume, the effects of different concentrations of grease on the gear surface wear were compared. The experimental results show that under different stress conditions, the consistency of the grease has a great influence on the lubricating effect of the gear surface and the gear wear. Under the condition with low speed and high torque, different grease consistency affect the gear surface wear, the high consistency grease can reduce the wear of the gear surface, so that the gear can get better lubrication effect during the work.

• Journal of Welding and Joining
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• v.21 no.7
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• pp.65-70
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• 2003

Thermal emissivity is generally affected by surface situation of material such as roughness. In this study, the effect of surface roughness on measuring thermal emissivity is experimented. And emissivity measurement method and equipment using hemisperical mirror is also reviewed. As the result of this research, thermal emissivity increased as long as increasing surface roughness. So, surface roughness is a essential check point when we measure the emissivity.

• Communications for Statistical Applications and Methods
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• v.7 no.3
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• pp.741-757
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• 2000

In may experimental situations, whenever a block design is used, the block effect is usually considered to be fixed. There are, however, experimental situations in which it should be treated as random. The choice of a blocking arrangement for a response surface design can have a considerable effect on estimating the mean response and on the size of he prediction variance even if the experimental runs re the same. Therefore, care should be exercised in the selection of blocks. In this paper, in the presence of a random block effect, we propose a graphical method or evaluating the effect of blocking in response surface designs using cuboidal regions. This graphical method can be used to investigate how the blocking has influence on the prediction variance throughout all experimental regions of interest when this region is cuboidal, and compare the block effects in the cases of the orthogonal and non-orthogonal block designs, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.3
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• pp.91-100
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• 1988

Surface rolling which is one of the plastic deformation have advantages to imporve surface roughness, hardness and fatigue strength with relatively simple processes. In this study, the effect of previous cutting process before rolling on the surface roughness in surface rolling for mild steel was investigated. The results obtained are as follows. (1) Waveness of the previous process has the effect on the precision of the works and coarse waveness resulted in less improvement of the surface roughness. (2) The reduction of diameter and increase of hardness can be obtained at the first rolling process.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1148-1153
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• 2004

Recently the high speed end-milling processing is demanded the high-precise technique with good surface rougj1ness and rapid time in aircraft, automobile part and molding industry. The working factors of high speed end-milling has an effect on surface roughness of cutting surface. Therefore this study was carried out to analyze the working factors to get the optimum surface roughness by design of experiment. From this study, surface roughness have an much effect according to priority on Spindle speed, feed rale, hardness and axial depth of cut By design of experiment, it is effectively represented shape characteristics of surface roughness in high speed end-milling And determination($R^2$) coefficient of regression equation had a satisfactory reliability of 89.7% and regression equation of surface roughness is made by regression analysis.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.428-432
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• 1999

As metallic surface has its unique lustrous appearance and optical reflectance in visible range of light, the metallization of plastic surface has been an essential drive toward weight reduction for fuel economy and decorations in transportation industry and has been put into practiced from wet chemical-electrochemial to dry vacuum process in view of an environmental effect. Electron-beam metallization was used in this work with an aim at improving the scratchproof surface hardness of plastic substrate with metallic finish character. Thin film of Al ($1000\AA$) and $SiO_2$($7000\AA$) were metallized on substrate of PC and PMMA and the films were evaluated by pencil test for surface hardness and by cross-cut tape test for adhesion. The ion beam treatment improved around twice as hard as non-treat surface. The ion beam is effect on its hardness and adhesion to surface hardened PC substrate.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.337-343
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• 2018

The present study investigated the effect of heat treatment process on the surface wettability of an Al-Si-Mg alloy. After solution-treated at $525^{\circ}C$ and aged at $160^{\circ}C$, the alloy showed high hardness due to the formation of precipitates. In addition, surface wettability was improved in such a way that the contact angle of distilled water droplet on the flat surface decreased to $37.6{\sim}42.1^{\circ}$ after the heat treatment. The surface energy predicted by Owens-Wendt equation also confirmed the increase of surface energy after the heat-treatment. However, when the surface roughness increased, the positive effect of the heat treatment on wettability diminished due to the geometrical factors of the rough surface.

• Tribology and Lubricants
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• v.30 no.1
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• pp.59-63
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• 2014

Laser Surface Texturing(LST) is a surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact surface. In LST technology, a pulsated laser beam is used to create arranged dimples on a surface by a material ablation process, which can improve such as load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on the bearing steel(AISI 52100) to create arranged dimples. To optimize the surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by combining circles, ellipses and the laser ablation process. The tribological testing of multi-scale textured surface was performed by a flat-on-flat unidirectional tribometer under lubrication and the results compared with that of the non-textured surface. Through an increase in sliding speed, the beneficial effect of multi-scale LST performance was achieved. The multi-scale textured surface had lower friction coefficient performances than the non-textured surface due to the hydrodynamic lubrication effect.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.26-31
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• 1998

The effect of tool angles on the surface roughness in face milling is studied. First, the relation between tool angles and rotation angles is identified. Using this relationship, it is obtained that the projection of insert nose shape on cutting profile, which is a part of ellipse. The effect of spindle tilt is also considered for the tool angles. It si shown that tool angles along with nose radius and feed rate have an effect on surface roughness.