The Effect of Surface Conditions on Friction by Tip Test

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Ki-Ho Jung ◽  
Hyun-Chul Lee ◽  
Joseph S. Ajiboye ◽  
Seong-Hoon Kang ◽  
Yong-Taek Im
Keyword(s):  
Linear Relationship ◽  
Corn Oil ◽  
Relative Effect ◽  
Oil And Grease ◽  
Experimental Conditions ◽  
Surface Conditions ◽  
Friction Factors ◽  
Shear Friction ◽  
Tip Test ◽  
Effect Of Surface

In the present investigation, a tip test based on upsetting and backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools, and the type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O, and single punch and two die sets with different surface topologies, were used with four lubricants such as VG32, VG100, corn oil, and grease. The load levels and tip distances were measured for both materials, and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately, depending on the variation in surface topologies and lubrications using finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at the punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation in surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data. This value can be used for characterizing the relative effect on friction due to surface conditions at the punch and counter punch, and lubrication quality of the lubricant for the given processing conditions.

Measurement of the Effect of Surface Topology on Friction by Tip Test

2009 ◽  
Author(s):  
Yong-Taek Im ◽  
Ki-Ho Jung ◽  
Hyun-Chul Lee ◽  
Joseph S. Ajiboye ◽  
Seong-Hoon Kang
Keyword(s):  
Linear Relationship ◽  
Corn Oil ◽  
Flow Behavior ◽  
Surface Topology ◽  
Experimental Conditions ◽  
Surface Conditions ◽  
Friction Factors ◽  
Shear Friction ◽  
Tip Test ◽  
Effect Of Surface

In the present investigation, tip test based on backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools and type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O with four lubricants such as VG32, VG100, corn oil, and grease were used. Single punch and two die sets with different surface topologies were manufactured in order to investigate the effect of surface conditions on friction and flow behavior. The load levels and tip distances were measured for both materials and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately depending on the variation of surface topologies using the finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation of the surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was clearly demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data based on the simulation results. The value for the frictionless case can be used for characterizing the relative effect due to surface topologies at punch and counter punch and lubrication qualities of lubricants under various processing conditions.

The Effect of Deformation Speed on Frictional Behavior by Tip Test

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Ki-Ho Jung ◽  
Yong-Taek Im
Keyword(s):  
Corn Oil ◽  
Hydrodynamic Pressure ◽  
Maximum Load ◽  
Experimental Conditions ◽  
Frictional Behavior ◽  
Friction Factors ◽  
Surface Topographies ◽  
Deformation Speed ◽  
Lubrication Characteristics ◽  
Tip Test

In this study, a tip test was carried out under various ram velocities of 0.01 mm/s, 0.1 mm/s, 1.0 mm/s, and 5.0 mm/s to investigate the effect of deformation speed on friction using the commercially available AL6061-O. For experiments, four different lubrication conditions with grease, corn oil, VG100, and VG32 were used to investigate the lubrication characteristics. During the test, temperature was measured in the specimen by a K-type thermocouple to determine the temperature increase induced by heat generation due to plastic deformation. In the present investigation, the linearity between tip distance and experimentally measured maximum load was consistently observed in spite of different orders of ram velocity and types of lubrication. As the ram velocity increased, loads were reduced for liquid lubricants and increased for grease. To better understand such a lubrication phenomenon, white-light interferometer microscopy and laser confocal microscopy were used to observe and compare surface topographies on the bottom and circumferential side of the deformed specimens at various experimental conditions, which formed lubrication pockets incurring hydrodynamic pressure of liquid lubricants. Finally, the effect of deformation speed on the level of shear friction factors at the punch and die interfaces was characterized by the finite element simulations and was determined to be expressed as an exponential function depending on the lubricant. This investigation demonstrates the capability of the tip test to experimentally characterize the effect of deformation speed on the frictional behavior for practical use.

Finite Element Investigation of Friction Condition in a Backward Extrusion of Aluminum Alloy

2003 ◽  
Vol 125 (2) ◽  
pp. 378-383 ◽  
Author(s):  
Yong-Taek Im ◽  
Seong-Hoon Kang ◽  
Jae-Seung Cheon
Keyword(s):  
Finite Element ◽  
Linear Relationship ◽  
Friction Factor ◽  
Friction Condition ◽  
Global Average ◽  
Backward Extrusion ◽  
Shear Friction ◽  
Shear Friction Factor ◽  
Tip Test ◽  
The One

Finite element simulations are being widely used to increase the efficiency and effectiveness of design of bulk metal forming processes. In such simulations, proper consideration of friction condition is important in obtaining reliable results. For this purpose, the shear friction factor is widely used for bulk deformation analyses. In the earlier work, it was found that a radial tip was formed on the extruded end of the workpiece and that the radial tip distance had a linear relationship with the forming load in the tip test. In order to characterize the global average shear friction factor, a linear relationship between the nondimensionalized radial tip distance and shear friction factor was numerically determined in this study for AL6061-O for various lubrication conditions. The global average friction condition at the bottom die interface was determined to be about 60 percent of the one at the punch in the backward extrusion under the present conditions.

EFFECT OF SURFACE CONDITIONS ON COERCIVITIES FOR Nd-Fe-B MAGNETS

1988 ◽  
Vol 49 (C8) ◽  
pp. C8-641-C8-642
Author(s):  
Y. Otani ◽  
H. Miyajima ◽  
S. Chikazumi ◽  
S. Hirosawa ◽  
M. Sagawa
Keyword(s):  
Surface Conditions ◽  
Effect Of Surface

scholarly journals Comparison of Satellite and Drone-Based Images at Two Spatial Scales to Evaluate Vegetation Regeneration after Post-Fire Treatments in a Mediterranean Forest

2021 ◽  
Vol 11 (12) ◽  
pp. 5423
Author(s):  
Jose Luis Martinez ◽  
Manuel Esteban Lucas-Borja ◽  
Pedro Antonio Plaza-Alvarez ◽  
Pietro Denisi ◽  
Miguel Angel Moreno ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Spatial Scales ◽  
Soil Surface ◽  
Plant Biodiversity ◽  
Mediterranean Forests ◽  
Experimental Conditions ◽  
Vegetation Growth ◽  
Surface Conditions ◽  
Vegetation Regeneration ◽  
Forest Managers

The evaluation of vegetation cover after post-fire treatments of burned lands is important for forest managers to restore soil quality and plant biodiversity in burned ecosystems. Unfortunately, this evaluation may be time consuming and expensive, requiring much fieldwork for surveys. The use of remote sensing, which makes these evaluation activities quicker and easier, have rarely been carried out in the Mediterranean forests, subjected to wildfire and post-fire stabilization techniques. To fill this gap, this study evaluates the feasibility of satellite (using LANDSAT8 images) and drone surveys to evaluate changes in vegetation cover and composition after wildfire and two hillslope stabilization treatments (log erosion barriers, LEBs, and contour-felled log debris, CFDs) in a forest of Central Eastern Spain. Surveys by drone were able to detect the variability of vegetation cover among burned and unburned areas through the Visible Atmospherically Resistant Index (VARI), but gave unrealistic results when the effectiveness of a post-fire treatment must be evaluated. LANDSAT8 images may be instead misleading to evaluate the changes in land cover after wildfire and post-fire treatments, due to the lack of correlation between VARI and vegetation cover. The spatial analysis has shown that: (i) the post-fire restoration strategy of landscape managers that have prioritized steeper slopes for treatments was successful; (ii) vegetation growth, at least in the experimental conditions, played a limited influence on soil surface conditions, since no significant increases in terrain roughness were detected in treated areas.

Effect of Surface Conditions on the Adhesion of Crystallization Fouling

2010 ◽  
Author(s):  
Yong Zou ◽  
Yida Liu ◽  
Gongming Xin ◽  
Wen Liu ◽  
Lin Cheng
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Oxide Layer ◽  
Crystalline Structure ◽  
Lattice Parameter ◽  
Hexagonal Structure ◽  
Experimental Results ◽  
Obvious Effect ◽  
Surface Conditions ◽  
Effect Of Surface

In this study, effects of surface conditions in terms of surface roughness and oxide layer, on adhesion of crystallization fouling on heat transfer surfaces were investigated. The experimental results showed that the surface roughness has no obvious effect on the adhesion of crystallization fouling. The polished sample did not present better anti-fouling properties compared to other rough samples. While the formation of Fe2O3 layer on the surface is proved to be able to accelerate the adhesion of calcite fouling with hexagonal structure, because there are similar crystalline structure and lattice parameter between the Fe2O3 and calcite fouling. Therefore, in order to improve the anti-fouling property of heat transfer surfaces, inhibiting the formation of oxide layer is more important than efforts to improve surface roughness.

Inferring the effects of surface canopy water on VOD estimation from L-band backscatter 

2021 ◽  
Author(s):  
Saeed Khabbazan ◽  
Paul.C. Vermunt ◽  
Susan.C. Steele Dunne ◽  
Ge Gao ◽  
Mariette Vreugdenhil ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Linear Relationship ◽  
Water Content ◽  
Growing Season ◽  
Empirical Parameter ◽  
Vegetation Water Content ◽  
L Band ◽  
Vegetation Water ◽  
Canopy Water ◽  
Effect Of Surface

<p>Quantification of vegetation parameters such as Vegetation Optical Depth (VOD) and Vegetation Water Content (VWC) can be used for better irrigation management, yield forecasting, and soil moisture estimation. Since VOD is directly related to vegetation water content and canopy structure, it can be used as an indicator for VWC. Over the past few decades, optical and passive microwave satellite data have mostly been used to monitor VWC. However, recent research is using active data to monitor VOD and VWC benefitting from their high spatial and temporal resolution.</p><p>Attenuation of the microwave signal through the vegetation layer is parametrized by the VOD. VOD is assumed to be linearly related to VWC with the proportionality constant being an empirical parameter b. For a given wavelength and polarization, b is assumed static and only parametrized as a function of vegetation type. The hypothesis of this study is that the VOD is not similar for dry and wet vegetation and the static linear relationship between attenuation and vegetation water content is a simplification of reality.</p><p>The aim of this research is to understand the effect of surface canopy water on VOD estimation and the relationship between VOD and vegetation water content during the growing season of a corn canopy. In addition to studying the dependence of VOD on bulk VWC for dry and wet vegetation, the effect of different factors, such as different growth stages and internal vegetation water content is investigated using time series analysis.</p><p>A field experiment was conducted in Florida, USA, for a full growing season of sweet corn. The corn field was scanned every 30 minutes with a truck-mounted, fully polarimetric, L-band radar. Pre-dawn vegetation water content was measured using destructive sampling three times a week for a full growing season. VWC could therefore be analyzed by constituent (leaf, stem, ear) or by height. Meteorological data, surface canopy water (dew or interception), and soil moisture were measured every 15 minutes for the entire growing season.</p><p>The methodology of Vreugdenhil et al.  [1], developed by TU Wien for ASCAT data, was adapted to present a new technique to estimate VOD from single-incidence angle backscatter data in each polarization. The results showed that the effect of surface canopy water on the VOD estimation increased by vegetation biomass accumulation and the effect was higher in the VOD estimated from the co-pol compared with the VOD estimated from the cross-pol. Moreover, the surface canopy water considerably affected the regression coefficient values (b-factor) of the linear relationship between VOD and VWC from dry and wet vegetation. This finding suggests that considering a similar b-factor for the dry and the wet vegetation will introduce errors in soil moisture retrievals. Furthermore, it highlights the importance of considering canopy wetness conditions when using tau-omega.</p><ul><li>[1] Vreugdenhil,W. A. Dorigo,W.Wagner, R. A. De Jeu, S. Hahn, andM. J. VanMarle, “Analyzing the vegetation parameterization in the TU-Wien ASCAT soil moisture retrieval,” IEEE Transactions on Geoscience and Remote Sensing, vol. 54, pp. 3513–3531, 2016</li> </ul>

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