Granular Collision Lubrication: Experimental Investigation and Comparison to Theory

2007 ◽  
Vol 129 (4) ◽  
pp. 923-932 ◽  
Author(s):  
Karim N. Elkholy ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Friction Coefficient ◽  
Kinetic Theory ◽  
Rotational Speed ◽  
Applied Load ◽  
Vertical Displacement ◽  
Shear Cell ◽  
Sliding Motion ◽  
Annular Shear Cell

An experimental investigation of the friction and lift characteristics of granular lubrication is presented. Experiments are carried out to demonstrate the vertical displacement (lift) observed in an annular shear cell apparatus. Results are presented for the friction coefficient as a function of the rotational speed and the applied load for several surface roughness combinations. Simulations of the kinetic theory for the granular material are performed and compared to the experimental results. The experiments provide an evidence for the formation of granular lift between two disks undergoing sliding motion.

Experimental Investigation on the Stick-Slip Phenomenon in Granular Collision Lubrication

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Karim N. Elkholy ◽  
M. M. Khonsari
Keyword(s):  
Experimental Investigation ◽  
Friction Coefficient ◽  
Granular Materials ◽  
Applied Load ◽  
Stick Slip ◽  
Shear Cell ◽  
Parallel Disks ◽  
Sliding Motion ◽  
Annular Shear Cell ◽  
Slip Phenomenon

An investigation on the nature of stick-slip associated with granular materials sheared between two parallel disks within the context of granular lubrication is presented. Experiments are carried out in an annular shear cell apparatus to demonstrate the effect of the stick-slip on the friction coefficient. Results are presented for the friction coefficient and the displacement as a function of the rotational speed and the applied load. The results reveal the occurrence of stick-slip at low speed and provided further evidence for the formation of granular lift between two disks undergoing sliding motion.

Experimental Investigation of the Influence of Machining Condition on the Contact Sliding Behavior of Metals

1998 ◽  
Vol 120 (2) ◽  
pp. 395-400 ◽  
Author(s):  
Dae-Eun Kim ◽  
Dong-Hwan Hwang
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Friction And Wear ◽  
Dimensional Accuracy ◽  
Tribological Performance ◽  
Cutting Condition ◽  
Sliding Motion ◽  
Machined Parts ◽  
Friction And Wear Characteristics ◽  
Counter Surface

In many instances machined parts experience sliding motion while in contact with a counter surface. The performance of the contacting parts depends on their friction and wear characteristics. In this work the effects of the machining condition on the tribological performance of steel, brass, and duralumin are investigated. For steel, it is shown that the friction coefficient value remains about the same whereas the rate of wear varies as the cutting condition is altered. The friction coefficients for brass and duralumin were lower than that of steel and their tribological properties seem to be less sensitive to the machining condition. In conclusion, it is emphasized that the machining condition directly influences the surface integrity which in turn affects the tribological performance of the machined parts, and therefore, the machining condition for parts that experience contact sliding motion should be optimized for best tribological performance in addition to dimensional accuracy and surface roughness.

scholarly journals Theoretical and Experimental Investigation on Friction in Lubricated Line Contacts with Different Materials and Textures in Presence of Wear

2016 ◽  
Vol 681 ◽  
pp. 142-154 ◽  
Author(s):  
Francesca Di Puccio ◽  
Enrico Ciulli
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Friction Coefficient ◽  
Boundary Lubrication ◽  
Flat Surface ◽  
Surface Conditions ◽  
Lubrication Regimes ◽  
Line Contacts ◽  
Lubrication Conditions ◽  
Theoretical Procedure

An experimental investigation on the friction coefficient in line contacts under mixed and boundary lubrication regimes is described. Rectangular contacts between cylindrical specimens and the flat surface of discs of different material and surface roughness combinations were analyzed. Very low Stribeck numbers have been considered, resulting also in low dimensionless film thickness, so that the morphology of the surfaces and the material had a remarking role. In this work, the theoretical procedure for assessing the friction coefficient in the tested cases is described and compared to experimental results. Additionally, wear effects obtained in boundary lubrication conditions are shown. The surface conditions are put in relation with some particular trends of the friction coefficient obtained for certain combinations of materials and roughness.

Experimental Investigation on Effects of Surface Roughness Geometry Affecting to Flow Resistance

2011 ◽  
Author(s):  
Takahiro Ito ◽  
Ayumu Matsumoto ◽  
Toshihisa Ito ◽  
Masaaki Motozawa ◽  
Kaoru Iwamoto ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Friction Coefficient ◽  
Flow Resistance ◽  
Outer Cylinder ◽  
Concentric Cylinder ◽  
Test Cylinder ◽  
Roughness Profile ◽  
Grain Roughness ◽  
Ridge And Valley

Experimental investigation on effects of surface roughness geometry affecting to flow resistance has been carried out. The concentric cylinder device composed of outer cylinder and inner test cylinder was employed to the experiment. We prepared 24 different roughness models having various skewness of roughness profile as test inner cylinders. Surface of test cylinder has ridge and valley roughness whose shapes are isosceles right triangle V-shape. These ridge and valley are arranged at equal intervals. Therefore, RMS roughness of the surface and skewness of the surface roughness profile can be evaluated. In the experiment, inner cylinder is rotated but outer cylinder is stationary, torque of rotating inner cylinder was measured. Based on the torque measurement, we investigated the effect of skweness of the surface roughness on flow resistance. As a result, when the roughness profile has Gaussian distribution (skewness = 0), friction coefficient increases with increasing RMS roughness. Moreover, friction coefficient also increases with increasing skewness of surface roughness under same RMS roughness. In order to predict the friction coefficient from the geometric information of the surface, we estimated the equivalent sand grain roughness from surface roughness parameters. Results showed that it was clarified the relation among skewness of roughness profile, equivalent sand grain roughness and the root mean square of surface roughness.

The Effect of Surface Irregularities on the Tribological Behavior of Steel Rollers Under Rolling-Sliding Contact

1994 ◽  
Vol 116 (2) ◽  
pp. 209-218 ◽  
Author(s):  
Jeng Hour Horng ◽  
Jen Fin Lin ◽  
Ke Yang Lee
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Rotational Speed ◽  
Applied Load ◽  
Tribological Behavior ◽  
Operating Conditions ◽  
Asperity Height ◽  
Surface Irregularities ◽  
Minimum Wear ◽  
Effect Of Surface

Experiments were conducted utilizing a gear-cam adapter to simulate line-contact lubrication and wear. Roller specimens with various asperity heights and roughness patterns were riding on the roller plates and sliding over the two lands of the lower specimen. The experimental results reveal that the roughness pattern and the asperity height are of importance in determining the friction coefficient, whereas asperity height is more related to the wear rate. The temperature rise of the lubricant seems to be seldom affected by the foregoing factors, but is governed by the combined effect of applied load and driver’s rotational speed. Surface roughness with a transversely oriented pattern, irrespective of the asperity height, normally generates a smaller friction coefficient and a relatively larger wear rate compared to the other two roughness patterns. Rollers having a smooth surface (0.2 μm) do not always lead to the smallest friction, but usually produce the minimum wear rate. The operating conditions, including the increase in applied load, and the reduction of the driver’s rotational speed, along with the increase of asperity height, form the controlling factors of increasing wear rate.

Experimental investigation and modelling of light scattering in a-Si:H solar cells deposited on glass/ZnO:Al substrates

2002 ◽  
Vol 715 ◽  
Author(s):  
J. Krc ◽  
M. Zeman ◽  
O. Kluth ◽  
F. Smole ◽  
M. Topic
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Solar Cells ◽  
Angular Distribution ◽  
Light Scattering ◽  
Optical Model ◽  
Distribution Functions ◽  
Interface Roughness ◽  
Scattering Parameters ◽  
Good Agreement

AbstractThe descriptive scattering parameters, haze and angular distribution functions of textured ZnO:Al transparent conductive oxides with different surface roughness are measured. An approach to determine the scattering parameters of all internal interfaces in p-i-n a-Si:H solar cells deposited on the glass/ZnO:Al substrates is presented. Using the determined scattering parameters as the input parameters of the optical model, a good agreement between the measured and simulated quantum efficiencies of the p-i-n a-Si:H solar cells with different interface roughness is achieved.

Influence of surface roughness, friction coefficient, and wrap angle on clinching joint strength and its correlation with belt friction phenomenon

2021 ◽  
pp. 135065012110253
Author(s):  
Santosh Kumar ◽  
Vimal Edachery ◽  
Swamybabu Velpula ◽  
Avinash Govindaraju ◽  
Sounak K. Choudhury ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Joint Strength ◽  
Joint Interface ◽  
Cross Sectional ◽  
Lap Shear ◽  
Mathematical Correlation ◽  
Mechanical Clinching ◽  
Wrap Angle

Clinching is an economical sheet joining technique that does not require any consumables. Besides, after its usage, the joints can be recycled without much difficulty, making clinching one of the most sustainable and eco-friendly manufacturing processes and a topic of high research potential. In this work, the influence of surface roughness on the load-bearing capacity (strength) of joints made by the mechanical clinching method in cross-tensile and lap-shear configuration is explored. Additionally, a correlating mathematical model is established between the joint strength and its surface parameters, namely, friction coefficient and wrap angle, based on the belt friction phenomenon. This correlation also explains the generally observed higher strength in lap-shear configuration compared to cross-tensile in clinching joints. From the mathematical correlation, through friction by increasing the average surface roughness, it is possible to increase the strength of the joint. The quality of the thus produced joint is analyzed by cross-sectional examination and comparison with simulation results. Experimentally, it is shown that an increment of >50% in the joint strength is achieved in lap-shear configuration by modifying the surface roughness and increasing the friction coefficient at the joint interface. Further, the same surface modification does not significantly affect the strength in cross-tensile configuration.

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