Theoretical model of transverse and longitudinal surface roughness and study on brittle-ductile transition mechanism for turning Fluorophlogopite ceramic

2019 ◽  
Vol 150 ◽  
pp. 715-726 ◽  
Author(s):  
Lianjie Ma ◽  
Chongyan Cai ◽  
Yanqing Tan ◽  
Yadong Gong ◽  
Lida Zhu
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Brittle Ductile Transition ◽  
Transition Mechanism

scholarly journals Mobility Limitations due to Dislocations and Interface Roughness in AlGaN/AlN/GaN Heterostructure

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Qun Li ◽  
Jingwen Zhang ◽  
Li Meng ◽  
Jing Chong ◽  
Xun Hou
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Interface Roughness ◽  
Mobility Limitations ◽  
Gaussian Form ◽  
Quantitative Measurements ◽  
Transmission Electron ◽  
Dimensional Electron Gas ◽  
Exponential Correlation Function ◽  
Gan Heterostructure

The dislocations and surface roughness in an AlGaN/AlN/GaN heterostructure were analyzed by transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively, and the mobility limitation mechanisms in the two-dimensional electron gas (2DEG) were studied using a theoretical model that took into account the most important scattering mechanisms. An exponential correlation function provides a better description of the statistical properties of surface roughness than the Gaussian form and thus is adopted in the theoretical model. The calculated results are in good agreement with Hall data. The quantitative measurements of dislocations and surface roughness allow the evaluation of the relative importance of each extrinsic scattering mechanism.

Separation and Transition Control on an Aft-Loaded Ultra-High-Lift LP Turbine Blade at Low Reynolds Numbers: High-Speed Validation

2006 ◽  
Vol 129 (2) ◽  
pp. 340-347 ◽  
Author(s):  
Maria Vera ◽  
Xue Feng Zhang ◽  
Howard Hodson ◽  
Neil Harvey
Keyword(s):  
Surface Roughness ◽  
Mach Number ◽  
Surface Finish ◽  
High Speed ◽  
Reynolds Numbers ◽  
High Lift ◽  
Low Reynolds Numbers ◽  
Low Speed ◽  
Transition Mechanism ◽  
Low Reynolds

This paper presents the second part of an investigation of the combined effects of unsteadiness and surface roughness on an aft-loaded ultra-high-lift low-pressure turbine (LPT) profile at low Reynolds numbers. The investigation has been performed using low- and high-speed cascade facilities. The low- and high-speed profiles have been designed to have the same normalized isentropic Mach number distribution. The low-speed results have been presented in the first part (Zhang, Vera, Hodson, and Harvey, 2006, ASME J. Turbomach., 128, pp. 517–527). The current paper examines the effect of different surface finishes on an aft-loaded ultra-high-lift LPT profile at Mach and Reynolds numbers representative of LPT engine conditions. The surface roughness values are presented along with the profile losses under steady and unsteady inflow conditions. The results show that the use of a rough surface finish can be used to reduce the profile loss. In addition, the results show that the same quantitative values of losses are obtained at high- and low-speed flow conditions. The latter proves the validity of the low-speed approach for ultra-high-lift profiles for the case of an exit Mach number of the order of 0.64. Hot-wire measurements were carried out to explain the effect of the surface finish on the wake-induced transition mechanism.

Study on the Critical Cutting Thickness and the Precision Cutting Experiments of Isotropic Pyrolyric Graphite

2011 ◽  
Vol 228-229 ◽  
pp. 458-463
Author(s):  
Ming Hai Wang ◽  
Hu Jun Wang ◽  
Zhong Hai Liu
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
Prediction Model ◽  
Feed Rate ◽  
Cutting Speed ◽  
Carbon Composite ◽  
Cutting Depth ◽  
Brittle Ductile Transition ◽  
Roughness Prediction ◽  
Turbine Shaft

Isotropic pyrolyric graphite (IPG) is a new kind of brittle material, it not only has the general advantages of ordinal carbonaceous materials such as high temperature resistance, lubrication and abrasion resistance, but also has the advantages of impermeability and machinability that carbon/carbon composite doesn’t have. So it can be used for sealing the aeronautics and astronautics engines turbine shaft and the ethylene high-temperature equipment. The mechanism of this material removal during the precision cutting was analyzed by using the theory of strain gradient. The critical cutting thickness of IPG was calculated for the first time. Furthermore, the cutting process parameters such as cutting depth and feed rate which corresponding to the scale of brittle-ductile transition deformation of IPG was calculated. The prediction model of surface roughness in precision cutting of IPG was developed based on the Genetic algorithm. Using the surface roughness prediction model, the study investigates the influence of the cutting speed, the feed rate and the cutting depth on surface roughness in precision turning process was researched.

The Profile Development of a Twin-Land Oil-Control Ring During Running-In

1998 ◽  
Vol 120 (3) ◽  
pp. 616-621 ◽  
Author(s):  
M. Visscher ◽  
D. Dowson ◽  
C. M. Taylor
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Twist Angle ◽  
Theoretical Modeling ◽  
Experimental Results ◽  
Roughness Height ◽  
Profile Development ◽  
Motored Engine

This paper presents experimental results of motored engine tests on the wear and profile development of a twin-land oil-control ring. It is shown that the roughness height of the plateau honed liner decreases during running-in, indicating that the deeper grooves remain unaffected. The piston lands are much smoother, and do not show a significant overall change in surface roughness. The profile development results are compared with computer predictions in order to verify the theoretical modeling. It is indicated that the worn land profiles remain tapered, with an inclination resembling the twist angle of the ring. However, there remains a difference in the experimental and the numerically predicted land inclinations. This is probably due to the piston tilt, which was not included in the theoretical model.

Leakage analysis of bolted flange joints considering surface roughness: A theoretical model

2017 ◽  
Vol 232 (2) ◽  
pp. 203-233 ◽  
Author(s):  
Benben Ma ◽  
Fan Jin ◽  
Zhi Sun ◽  
Xu Guo
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Three Dimensional ◽  
Element Analysis ◽  
Low Leakage ◽  
Theoretical Predictions ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Bolted Flange ◽  
Bolt Spacing

In the present paper, a theoretical model for leakage analysis of bolted flange joints without gaskets, which can take the surface roughness into consideration, is proposed based on percolation theory. In this model, Persson’s rough contact theory is employed to predict the height of the critical constriction along the percolating path. Based on this model, a criterion of maximum allowable bolt spacing is also suggested to guarantee a low leakage rate. The reasonable agreement between the theoretical predictions and detailed three-dimensional finite element analysis results verifies the validity and usefulness of the proposed theoretical model.

Changes of Surface Topography During Running-In Process

2004 ◽  
Vol 126 (3) ◽  
pp. 620-625 ◽  
Author(s):  
Yeau-Ren Jeng ◽  
Zhi-Way Lin ◽  
Shiuh-Hwa Shyu
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Surface Topography ◽  
Experimental Results ◽  
Wear Model ◽  
Initial Height ◽  
Different Types

This study investigated the surface topographical changes during running-in. A theoretical model, which is composed of Johnson translatory system and a microscopic wear model, was used to describe the changes of surface roughness during running-in for general surfaces. Running-in tests were conducted for engine bores with different surface height distributions in order to understand surface topographical changes and validate the theory. Experimental results show that the theoretical model provides a good indication of changes of surface topography for surfaces with different types of initial height distributions.

Suppression of Frost Propagation With Micropillar Structure Engineered Surface

2016 ◽  
Author(s):  
Yugang Zhao ◽  
Chun Yang
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Aspect Ratio ◽  
Surface Morphology ◽  
Superhydrophobic Surface ◽  
Small Aspect Ratio ◽  
Pattern Design ◽  
Patterned Substrate ◽  
High Aspect Ratio Structure ◽  
Surface Ice

Despite that using surface-roughness-induced superhydrophobic surface as a solution for ice/snow accretion issues has achieved extensive progresses, its icephobicity breaks down in case of condensation frosting, while the high aspect ratio structure brings more concerns on its durability and sustainability. In this work we investigated condensate frosting on substrates fabricated with patterned micropillars having a small aspect ratio, and studied the freezing propagation with different pattern sizes. The results show that a coarse patterned substrate can effectively suppress the freeing propagation while a fine patterned one can drastically promote the freezing propagation. Frost coverage can also be reduced with proper pattern design. A theoretical model was developed to explain the mechanism of surface ice propagation, and agrees well in tendency with experiment measurements. The aim of this study is to provide some new insights on the influence of surface morphology on ice growth.

scholarly journals Theoretical-Probability Model for Calculating Roofness in Magnetic Abrasive Machining

2021 ◽  
Vol 346 ◽  
pp. 01045
Author(s):  
Alexey Ikonnikov ◽  
Sergey Leonov
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Probability Model ◽  
Abrasive Machining ◽  
Theoretical Probability ◽  
Removal Of Metal

The work is devoted to the problem of calculating the surface roughness during magnetic abrasive processing. Cutting grains have random dimensional characteristics, are randomly located on the surface of the tool, the workpiece has an irregular profile. The cutting parts of the grains partially remove the chips and partially elastoplastically deform the metal. Some of the vertices fall into the marks on the surface of the workpiece formed by the previous processing, and some - on the marks from the passage of the previous vertices. This process is determined by the probability of contact of the top of the grain with the metal. The developed probabilistic-theoretical model makes it possible to predict the removal of metal from the treated surface depending on the time and parameters of the operation, which creates the prerequisites for their use in the design of polishing operations.

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