scholarly journals Effect of different rubber materials on husking dynamics of paddy rice

2012 ◽  
Vol 226 (6) ◽  
pp. 516-528
Author(s):  
A Baker ◽  
RS Dwyer-Joyce ◽  
C Briggs ◽  
M Brockfeld
Keyword(s):  
Shear Stress ◽  
High Speed ◽  
Sliding Friction ◽  
Normal Load ◽  
Normal Pressure ◽  
Applied Normal Load ◽  
Limiting Shear Stress ◽  
Governing Factor ◽  
The Coefficient Of Friction ◽  
Husk Rice

The conventional way to husk rice is to pass it between two rubber rollers that are rotating with a surface speed differential. The resulting normal pressure and shear stress causes the husk to be peeled away from the kernel. The process is suited to high-rice flow rates, but is energy intensive and can result in considerable wear to the surfaces of the rollers. The operating parameters for machines of this design are usually determined and set empirically. In this article, some experiments and calculations had been carried out in order to explore the mechanisms involved in husking rice grains using this method. A simple sliding friction rig with load cell and high-speed camera was used to observe the mechanisms that occur during husking. The husking performance of different rubbers was compared for changes in the applied normal load. It was found that grains rotate between the rubber counterfaces on initial motion before being husked. In addition, harder rubbers were found to husk a higher proportion of entrained grains at lower applied normal load. By measuring the coefficient of friction between rice and rubber samples, the shear force required to husk a given percentage of grains could be calculated and was shown to be constant regardless of rubber type. Based on the mechanism seen in the high-speed video, it was evident that there was a limiting shear stress that was the governing factor over the husked ratio.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

AbstractAn experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τb, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τb and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τbVb. For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

Micro-EHL in Lubricated Concentrated Contacts

1990 ◽  
Vol 112 (2) ◽  
pp. 392-397 ◽  
Author(s):  
D. J. Schipper ◽  
P. H. Vroegop ◽  
A. W. J. de Gee ◽  
R. Bosma
Keyword(s):  
Shear Stress ◽  
Liquid State ◽  
Sliding Friction ◽  
Measuring Method ◽  
Limiting Shear Stress ◽  
State Regime

In sliding friction experiments, performed with lubricated concentrated contacts macroscopically operating in the lubricants’ liquid-state regime, the existence of micro-EHL has been shown. With the measuring method used, the lubricants’ limiting shear stress τ1 or the ratio of the limiting shear stress with pressure, τ1/p, can easily be obtained.

Plowing Friction Under Harmonic Normal Loads

1999 ◽  
Vol 121 (2) ◽  
pp. 282-285 ◽  
Author(s):  
D. P. Hess
Keyword(s):  
Shear Strength ◽  
Coefficient Of Friction ◽  
Metal Surfaces ◽  
Sliding Friction ◽  
Normal Load ◽  
Hard Materials ◽  
Lubricated Contacts ◽  
Highly Nonlinear ◽  
Average Coefficient ◽  
The Coefficient Of Friction

The influence of harmonic normal loads on sliding friction is investigated through analysis of contacts consisting of conical and spherical sliders of hard materials on softer metal surfaces. Friction for such contacts is assumed to result from a plowing component and a shearing component. Calculations and experiments show that the coefficient of friction is essentially independent of normal load for contacts with conical sliders. However, for spherical sliders the relation between the coefficient of friction and normal load is highly nonlinear. In the presence of harmonic variations in normal load, this non-linearity causes a shift in the average coefficient of friction. For ideal lubricated contacts, the shearing component of friction is very small and for this case, it is shown that the maximum average reduction in the coefficient of friction is ten percent. When the shearing component is more significant, as with dry contacts, the shift is less. For example, when the shear strength is one-sixth the hardness of the softer material, the maximum average reduction in the coefficient of friction is five percent.

State and Rate Dependent Friction Laws for Modeling High-Speed Frictional Slip at Metal-on-Metal Interfaces

2006 ◽  
Vol 129 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Hamid Ullah ◽  
M. A. Irfan ◽  
V. Prakash
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
High Speed ◽  
Friction Stress ◽  
Normal Pressure ◽  
Friction Model ◽  
Friction Laws ◽  
Rate Dependent ◽  
Applied Shear Stress ◽  
Slip Event

In the present paper the applicability of state and rate dependent friction laws in describing the phenomena of high speed slip at metal-on-metal interfaces is investigated. For the purpose of model validation, results of plate-impact pressure-shear friction experiments were conducted by Irfan in 1998 and Irfan and Prakash in 2000 using a Ti6Al4V and Carpenter Hampden tool-steel tribo pair are employed. In these experiments high normal pressures (1-3GPa) and slip speeds of approximately 50m∕s were attained during the high-speed slip event. Moreover, these experiments were designed to investigate the evolution of friction stress in response to step changes in normal pressure and also in the applied shear stress during the high-speed slip event. A step drop in normal pressure is observed to result in an exponential decay of the friction stress to a new steady-state characteristic of the current normal pressure and the current slip velocity. A step drop in applied shear stress is observed to lead to an initial drop in friction stress, which later increases toward a new steady-state friction stress level. In response to the step drop in applied shear stress the slip velocity initially increases and then decreases to a new steady-state level consistent with the new friction stress level. A modified rate and state dependent friction model that employs both velocity and normal stress dependent state variables is used to simulate the experimental results. A good correlation is found between the experimental results and the predictions of the proposed state and rate dependent friction model.

scholarly journals Nanodiamond Particles as Secondary Additive for Polyalphaolefin Oil Lubrication of Steel–Aluminium Contact

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1438
Author(s):  
Ankush Raina ◽  
Mir Irfan Ul Haq ◽  
Ankush Anand ◽  
Sanjay Mohan ◽  
Rajiv Kumar ◽  
...  
Keyword(s):  
Coefficient Of Friction ◽  
Hexagonal Boron Nitride ◽  
Normal Load ◽  
Lubricant Additive ◽  
Oil Lubrication ◽  
Volumetric Wear ◽  
Base Oil ◽  
Applied Normal Load ◽  
Lubrication Performance ◽  
The Coefficient Of Friction

Nanodiamond (ND) particles are effective lubricant additives. Attention of research has shifted towards investigating the particles as secondary additives. ND particles provide more benefits as secondary additives than as the sole lubricant additive for steel–steel contacts. In this work, the influence of ND particles as secondary additives on oil lubrication of steel–aluminium tribopair (hard–soft contact) was examined. AISI 52100 steel balls were slid against AA2024 aluminium alloy discs, in the presence of polyalphaolefin (PAO) base oil, in boundary lubrication regime (applied normal load: 10 N to 50 N). Primary additives were copper oxide (CuO) and hexagonal boron nitride (h-BN) nanoparticles. The addition of ND particles to PAO, with CuO and h-BN as primary additives, at the lowest applied normal load of 10 N: (i) decreased the volumetric wear of the aluminium discs by 28% and 63%, respectively, and (ii) decreased the coefficient of friction by 15% and 33%, respectively. At the highest applied normal load of 50 N, it: (i) decreased the volumetric wear of the aluminium discs by 20% and 38%, respectively, and (ii) decreased the coefficient of friction by 5.4% and 8%, respectively. ND particles as secondary additives significantly reduce energy loss and power loss as a consequence of an effective reduction in friction during sliding. Unique characteristics of ND particles—such as their (a) physicochemical and thermal properties, (b) ball bearing and polishing effects and (c) synergistic interaction with primary additives to form stable tribofilms—enhance the lubrication performance of steel–aluminium contact. ND particles in combination with h-BN nanoparticles showed the best performance, due to better synergy between the primary additive and the secondary additive. Results from the investigation indicate that ND particles taken as secondary additives in small amount (0.2 wt%) can improve oil lubrication performance of hard–soft contacts in engineering systems.

A Recursive Characteristics Analysis-Based Stationarity Evaluation Model for Friction-Induced Attractors in the Sliding Friction Process

2021 ◽  
Vol 143 (10) ◽  
Author(s):  
Guodong Sun ◽  
Ying Zhang ◽  
Chao Zhang ◽  
Shihui Lang ◽  
Hua Zhu
Keyword(s):  
Sliding Friction ◽  
Evaluation Model ◽  
Normal Pressure ◽  
Recurrence Quantification Analysis ◽  
Friction Process ◽  
Recurrence Quantification ◽  
Characteristics Analysis ◽  
The Coefficient Of Friction ◽  
Quantification Analysis ◽  
Scalar Time Series

Abstract In this study, the coefficient of friction (COF) signals throughout the running-in process were examined by sliding a ring against a static disc. By reconstructing the scalar time-series into multi-dimensional phase spaces, friction-induced attractors were obtained and quantified by recursive characteristics analysis, which can effectively realize the running-in status identification. Moreover, a recursive characteristics analysis-based evaluation model was established to investigate the stationarity of the friction-induced attractors based on the recurrence quantification analysis (RQA) measures. The analyses of the numerically simulated signals and experimental results indicate that the extracted model is an intuitive and effective method. Furthermore, to improve the stationary of the friction-induced attractors, the normal pressure should be low, whereas the relative sliding velocities should be increased appropriately. These results would contribute to the revelation of the recursive characteristics of the tribosystem and the improvement of the stationarity of friction-induced attractors.

Effect of Micro-Size Cenosphere Content on Friction and Dry Sliding Wear Behavior of Vinylester Composites – A Taguchi Method

2012 ◽  
Vol 585 ◽  
pp. 569-573 ◽  
Author(s):  
S.R. Chauhan ◽  
Sunil Thakur
Keyword(s):  
Wear Rate ◽  
Coefficient Of Friction ◽  
Sliding Wear ◽  
Friction And Wear ◽  
Normal Load ◽  
Dry Sliding ◽  
Sliding Speed ◽  
Applied Normal Load ◽  
The Coefficient Of Friction ◽  
Sliding Distance

In this paper the friction and wear characteristics of vinylester and vinylester composites have been investigated under dry sliding conditions for different applied normal load, sliding speed and sliding distance. The experiments have been carried on a pin on disc arrangement at normal room temperature conditions. The influence of friction and wear parameters like normal load, speed, sliding distance and percentage of filler content on the friction and wear rate has been investigated. In this study, a plan of experiments based on the techniques of Taguchi was performed to acquire data in a controlled way. An orthogonal array L27 (313) and Analysis of variance (ANOVA) were applied to investigate the influence of process parameters on the coefficient of friction and sliding wear behaviour of these composites. The Taguchi design of experiment approach eliminates the need for repeated experiments and thus saves time, material and cost. The results showed that with increase in the applied normal load and sliding speed the coefficient of friction and specific wear rate decreases under dry sliding conditions. It is also found that a thin film formed on the counterface seems to be effective in improving the tribological characteristics. The results showed that the inclusion of cenosphere as filler materials in vinylester composites will increase the wear resistance of the composite significantly.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

Abstract An experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τ b, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τ b and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τ b Vb . For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

A Comparative Study of Microstructure, Coefficient of Friction and Wear Rate of Alloy Ni-Cr-B-Si-C-W

2021 ◽  
Vol 406 ◽  
pp. 229-239
Author(s):  
Mohamed Nabil Bachirbey ◽  
Mohammed Seyf Eddine Bougoffa ◽  
Chahrazed Benouali ◽  
Tahar Sayah
Keyword(s):  
Wear Rate ◽  
Coefficient Of Friction ◽  
Friction And Wear ◽  
Sliding Friction ◽  
Wear Behavior ◽  
Normal Load ◽  
New Approach ◽  
The Coefficient Of Friction ◽  
Loss Of Mass ◽  
Tribological Parameters

The present work aims at the study of the dry disc pion contact and the complex phenomenon of the wear as well as the sliding friction of our sample elaborated by a hot isotactic compression and the pion. This study consists in determining the coefficient of friction and the influence of the tribological parameters on this phenomenon as well as determining the loss of mass and the wear rate of study sample. In order to enhance the assurance of the validity of the results of tribological study of Ni-Cr-B-Si-C-W alloy in laboratories and compare that to the tribological conditions in reality and industries. This work presents the results of the new approach to compares the wear behavior of the sample between a theoretical study (tribometer)and another in service (a test bench) that reproduces approximately the same conditions as the tribometer (normal load, sliding speed and distance traveled) by measuring the loss of mass and wear rate.

Numerical Simulation of Traction in Rolling/Sliding Contacts

1997 ◽  
Vol 119 (4) ◽  
pp. 869-874 ◽  
Author(s):  
Jiugen Wang ◽  
Jianrong Tan
Keyword(s):  
Shear Stress ◽  
Normal Load ◽  
Maximum Shear Stress ◽  
Shear Stresses ◽  
Stress Distributions ◽  
Lubricated Contacts ◽  
Limiting Shear Stress ◽  
Low Load ◽  
Load Effects ◽  
Lubricated Contact

A new model of traction in elastohydrodynamically lubricated contact is presented to study shear stress distributions. Results of full numerical analyses of elliptical contacts under rolling and sliding are presented. This study is confined to elastohydrodynamically lubricated contacts of relatively low load. Effects of dimensionless parameters such as speed, normal load, and elliptical parameter and coefficient of limiting shear stress on shear stress distributions have been analyzed. Moreover, the influence of slide-roll ratio on visualized shear stress in EHD contacts has been studied. It has been found that the higher slide-roll ratios induce higher maximum shear stress. Shear stresses in fluid film and those on surfaces vary with many factors that reveal the mechanism of traction in EHD conjunction zones.

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