scholarly journals Friction Coefficients for Arborist Ropes Passing Through Cambium Saver Rings

2007 ◽  
Vol 33 (1) ◽  
pp. 31-42
Author(s):  
Brian Kane
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Physical Models ◽  
Kinetic Friction ◽  
Friction Coefficients ◽  
Ring Material ◽  
Tree Care

Friction is important in tree care operations; climbers encounter friction when ascending into, working in, and descending out of a tree. Twelve commonly used climbing ropes were tested on cambium saver rings made of three different materials to determine rope on ring static and kinetic friction coefficients. All ropes were tested before any field use. In addition, two ropes were tested after they had been used in the field for 2 years and were evaluated to determine the effect of rope wear on friction. Friction coefficients varied among ropes and ring materials, and surface roughness of ring material was the best predictor of friction coefficient. Used ropes exhibited higher friction coefficients than new ropes and, in most cases, superseded the influence of surface roughness of cambium saver rings. Simple physical models were developed to illustrate how friction coefficients can affect different aspects of tree climbing. There are important implications of these results for further studies on rope friction as it relates to reducing climber fatigue.

Robustness of polyisobutylene for friction coefficients between bearing surfaces of bolted joints

2019 ◽  
Vol 234 (1) ◽  
pp. 50-62
Author(s):  
Shinji Hashimura ◽  
Toshiumi Miki ◽  
Takefumi Otsu ◽  
Kyoichi Komatsu ◽  
Shota Inoue ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Surface Hardness ◽  
Bolted Joints ◽  
Friction Coefficients ◽  
Clamp Force

In bolted joints, clamp force must be accurately controlled to secure their reliability. However, the clamp force varies widely in each tightening because friction coefficients at thread surfaces and bearing surfaces vary in each tightening due to lubricants, configuration error of bolts, surface roughness, and surface hardness, among other things. In this study, we investigated the robustness of polyisobutylene and ISO VG46 machine oil during the tightening process for several parameters of tightening conditions. We especially focused on variations of the friction coefficient between bearing surfaces at an appropriate target clamp force of M8 bolt/nut assemblies and change rates of the friction coefficients from the middle to the end of the appropriate target clamp force. Results showed that the friction coefficients at the target clamp force varied widely if ISO VG46 machine oil was used as a lubricant. In contrast, the variations of the friction coefficients in which polyisobutylene was used for tightening were small. Results also showed that the friction coefficients invariably decreased about 20% from the middle to the end of the target clamp force if ISO VG46 machine oil was used for the lubricant. However, if polyisobutylene was used, the friction coefficients were almost constant for all tightening instances.

Static Friction and Initiation of Slip at Magnetic Head-Disk Interfaces

1999 ◽  
Vol 122 (1) ◽  
pp. 246-256 ◽  
Author(s):  
S. Wang ◽  
K. Komvopoulos
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Contact Resistance ◽  
Friction Force ◽  
Static Friction ◽  
Electric Contact ◽  
Magnetic Head ◽  
Friction Coefficients ◽  
Lubricant Films

The apparent friction force and electric contact resistance at the magnetic head-disk interface were measured simultaneously for textured and untextured disks lubricated with perfluoropolyether films of different thicknesses. The initial stick time, representing the time between the application of a driving torque and the initiation of interfacial slip, was determined based on the initial rise of the apparent friction force and the abrupt increase of the electric contact resistance. Relatively thin lubricant films yielded very short initial stick times and low static friction coefficients. However, for a film thickness comparable to the equivalent surface roughness, relatively long initial stick times and high static friction coefficients were observed. The peak value of the apparent friction coefficient was low for thin lubricant films and increased gradually with the film thickness. The variations of the initial stick time, static friction coefficient, and peak friction coefficient with the lubricant film thickness and surface roughness are interpreted in the context of a new physical model of the lubricated interface. The model accounts for the lubricant coverage, effective shear area, saturation of interfacial cavities, limited meniscus effects, and the increase of the critical shear stress of thin liquid films due to the solid-like behavior exhibited at a state of increased molecular ordering. [S0742-4787(00)03101-5]

scholarly journals The Effect of Graphene Coating on Surface Roughness and Friction Properties of Polyester Fabrics

2021 ◽  
Vol 27 (4) ◽  
pp. 470-476
Author(s):  
Gizem MANASOGLU ◽  
Rumeysa CELEN ◽  
Mine AKGUN ◽  
Mehmet KANIK
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Experimental Results ◽  
Kinetic Friction ◽  
Roughness Parameters ◽  
Polyester Fabrics ◽  
Graphene Coating ◽  
Friction Tester ◽  
Coated Fabrics ◽  
Fabric Surface

In this article, the surface roughness and friction coefficient values of graphene coated fabrics were examined. Fabrics were coated with three different graphene concentrations (5 %, 10 % and 20 %) with the knife-over-roll principle. The surface roughness of samples was measured by Accretech Surfcom 130A. Various surface roughness parameters of the coated fabrics were evaluated. Static and kinetic friction coefficients of coated fabrics were measured by Labthink Param MXD-02 friction tester using the standard wool abrasive cloth. It was observed that the coating concentration affected the frictional and roughness properties of fabrics. Experimental results showed that fabric surface roughness and friction coefficient values decreased significantly, especially at 20 % concentration. It was concluded that the coated fabrics produced could be used in applications such as anti-wear clothing.

scholarly journals Determination of The Rotational Friction Coefficients of Solid Cylinder with Various Inclined Plane Angle

2019 ◽  
Vol 15 (1) ◽  
pp. 52-59
Author(s):  
T. Firdaus ◽  
M. Toifur ◽  
Y. Pramudya
Keyword(s):  
Friction Coefficient ◽  
Learning Activities ◽  
Kinetic Friction ◽  
Plane Angle ◽  
Solid Cylinder ◽  
Inclined Plane ◽  
Friction Coefficients ◽  
Experimental Learning ◽  
Aluminum Cylinder

The layer texture differences of an object have an influence on the friction force caused by both planes. This research aims to determine the static and kinetic friction coefficient on several solid cylinder materials. The benefits of this research can be used to develop experimental learning activities on friction coefficient. This research used experimental method. The research was carried out by rolling samples at various inclined plane angles and measuring the traveled distance traveled in one rotation (D). The results showed that the static and kinetic friction coefficients between aluminum cylinder and glass were 0.146 and 0.097, iron cylinder and glass were 0.136 and 0.096, glass cylinder and brass were 0.132 and 0.094, nylon cylinder and glass were 0.101 and 0.090, and stainsless cylinder and glass were 0.122 and 0.094, respectively.Perbedaan tekstur lapisan sebuah benda mempunyai pengaruh pada gaya gesek yang ditimbulkan oleh kedua bidang. Penelitian ini bertujuan untuk menentukan nilai koefisien gesek statis dan koefisien gesek kinetik pada beberapa bahan silinder pejal. Manfaat yang dapat diambil dari hasil penelitian ini adalah dapat digunakan sebagai mengembangkan kegiatan pembelajaran praktikum koefisien gesekan benda. Penelitian ini menggunakan metode eksperimen. Penelitian dilaksanakan dengan menggelindingkan sampel pada berbagai sudut kemiringan dan mengukur jarak tempuh untuk satu kali putaran (D). Hasil penelitian menunjukkan bahwa nilai koefisien gesek statis dan koefisien gesek kinetik secara berurutan untuk silinder aluminium dengan kaca sebesar 0,146  dan 0,097,  untuk silinder besi dengan kaca sebesar 0,136 dan 0,096, untuk silinder kuningan dengan kaca 0,132 dan 0,094, untuk silinder nylon dengan kaca sebesar 0,101 dan 0,090, dan untuk stainsless dengan kaca sebesar 0,122 dan 0,094.

THE INFLUENCE OF DEFORMATION OF SELECTED THERMOPLASTICS ON THE FRICTION WITH STEEL

Tribologia ◽  
2016 ◽  
Vol 268 (4) ◽  
pp. 137-144 ◽  
Author(s):  
Maciej KUJAWA ◽  
Aneta NIEMIEC ◽  
Wojciech WIELEBA
Keyword(s):  
Friction Coefficient ◽  
Plastic Strain ◽  
Tensile Stress ◽  
Friction And Wear ◽  
Elastic Limit ◽  
Kinetic Friction ◽  
Scientific Publications ◽  
Friction Coefficients ◽  
Wear And Friction ◽  
Friction Analysis

Friction and wear of materials with additional deformation or stress is not a broadly described case. However, scientific publications considering this issue point out that additional deformation and stress ought to be taken into account during wear and friction analysis. In this article, the influence of strain in thermoplastics (POM, PTFE, PE-HD, PMMA) over the friction coefficient is described. Materials were deformed under tensile stress and examined after 24 hours. For specimens in which plastic strain was maintained, the decline of hardness (PE-HD: approximately 70% decrease, PTFE: approximately 40% decrease) and the reduction of the coefficient of kinetic friction (both PTFE and PE-HD: about 20% decrease) were observed. POM returned to its pre-deformed shape and PMMA was deformed without reaching its elastic limit. In these cases, only small changes in hardness (POM: approximately 10% decrease, PMMA: approximately 6% increase) and friction coefficients (maximum 4% change) occurred.

Calculated Behavior and Effective Factors for Bolt Self-Loosening Under a Transverse Cyclic Load Generated by a Linearly Vibrating Washer

2005 ◽  
Author(s):  
Yasuo Fujioka ◽  
Tomotsugu Sakai
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Contact Pressure ◽  
Common Knowledge ◽  
Axial Direction ◽  
Element Analysis ◽  
Friction Coefficients ◽  
Friction Forces ◽  
Contact Surfaces ◽  
The Individual

It is common knowledge that a bolt is apt to loosen due to slippage between the contact surfaces of joined parts. Loosening tests using real parts enable precise scrutiny of real phenomena under the influence of multiple factors such as slip distance, surface roughness, and coefficient friction. However, estimating the influence of the individual factors is very difficult because the friction forces of real contact surfaces are compiled based on variations in friction coefficients, meaning friction is not stable. Therefore, the effects of factors were investigated using Finite Element Analysis (FEA) to control friction coefficients. The procedures were as follows. Assuming a joined structure consisting of a bolt, nut, and washer, bolt axial tension was generated through constant movement of a washer in the bolt’s axial direction, following which the washer was constantly vibrated in one direction transverse to the bolt axis. This vibration generated displacements equivalent to the degree of slippage between the two clamped parts. During vibration, the rotating angles of the bolt and the contact pressure of the threads and bearing surfaces were calculated. The results were as follows. The vibrating displacements of a washer have considerable influence on the rotational loosening of a bolt. In cases where there was only minor displacement of the washer vibrations, the rotational loosening angle rapidly decreased, although the loosening did not cease completely. Therefore, the magnitude of what is called “critical slip” was not confirmed under the conditions of this study. In addition, the friction coefficient has a significant influence on the rotational loosening of a bolt. When the respective friction coefficient values of the threads and bearing surfaces are not balanced, rotational loosening cannot continue. Surface roughness readily affects contact pressure, so it tends to make the contact pressure localized. In particular, high-pressure areas were affected by several projections set on the threads. However, under those conditions the rotational loosening did not differ greatly from the results of the fine surface models subject to the same vibrating amplitude and friction coefficient. Consequently, the localized contact pressure had little evident effect on loosening. Above all, FEA reproduced the loosening of the bolt, and the reference made in this analysis is useful.

scholarly journals Developing Smart Measurement Device to Measure Kinetic Friction Coefficients of Bi-Tilt Isolator

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ming-Hsiang Shih ◽  
Wen-Pei Sung
Keyword(s):  
Friction Coefficient ◽  
Image Correlation ◽  
Kinetic Friction ◽  
Measurement Device ◽  
Friction Coefficients ◽  
Measuring Device ◽  
Contact Surfaces ◽  
Relationship Of ◽  
The Relationship ◽  
Smart Measurement

A sliding vibration isolation system, affected by a kinetic friction force, provides a flexible or energy dissipation system for a structure. The kinetic friction coefficient of the contact surfaces between the moving parts changes with the relative moving velocity of the two contact surfaces. In this study, a smart measuring device is proposed to measure the kinetic friction coefficients of materials. The Arduino boards Arduino Nano, Arduino MPU-9250, and Arduino SD modules were combined to create this proposed smart device and mounted on three aluminum extrusions constructed as a horizontal platform. Then, varying amounts of steel gaskets were applied to adjust the various slopes for sliding tests. The time history of the acceleration and displacement responses of test object movements in the sliding process were respectively, recorded and detected by this proposed smart measuring device and the digital image correlation method (DIC). Statistical analyses of all test responses were used to derive the relationship of velocity to kinetic friction coefficient. Test and analysis results showed that (1) the relationship of velocity to kinetic friction coefficient for the conditions of mild lubrication and no lubrication displayed a trend of first decreasing and then increasing with increasing speed, respectively and (2) the relationship of velocity to kinetic friction coefficient for the condition of full lubrication revealed that the kinetic friction coefficient decreased with increasing speed. Test results demonstrated that this proposed smart measurement device, which is low in price and easy to assemble, can easily measure the kinetic friction coefficient of a material under various lubrication conditions.

scholarly journals New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 611
Author(s):  
Yeon-Woong Choe ◽  
Sang-Bo Sim ◽  
Yeon-Moon Choo
Keyword(s):  
Friction Coefficient ◽  
Accurate Determination ◽  
Mean Velocity ◽  
Friction Coefficients ◽  
Flow Discharge ◽  
Comparison Results ◽  
Flow Loss ◽  
Key Variables ◽  
New Equation

In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse’s experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.

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.

scholarly journals Theoretical Studies of the Interaction between Screw Surface and Material in the Mixer

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 962
Author(s):  
Andrzej Marczuk ◽  
Vasily Sysuev ◽  
Alexey Aleshkin ◽  
Petr Savinykh ◽  
Nikolay Turubanov ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
High Efficiency ◽  
Animal Feed ◽  
Structural Features ◽  
Power Demand ◽  
Friction Coefficients ◽  
Length Unit ◽  
Mixing Chamber ◽  
Size Of Particles ◽  
The Impact

Mixing is one of the most commonly used processes in food, animal feed, chemical, cosmetic, etc., industries. It is supposed to provide high-quality homogenous, nutritious mixtures. To provide appropriate mixing of materials while maintaining the process high efficiency and low energy consumption it is crucial to explore and describe the material flow caused by the movement of mixing elements and the contact between particles. The process of mixing is also affected by structural features of the machine components and the mixing chamber, speed of mixing, and properties of the mixed materials, such as the size of particles, moisture, friction coefficients. Thus, modeling of the phenomena that accompany the process of mixing using the above-listed parameters is indispensable for appropriate implementation of the process. The paper provides theoretical power calculations that take into account the material speed change, the impact of the material friction coefficient on the screw steel surface and the impact of the friction coefficient on the material, taking into account the loading height of the mixing chamber and the chamber loading value. Dependencies between the mixer power and the product degree of fineness, rotational speed of screw friction coefficients, the number of windings per length unit, and width of the screw tape have been presented on the basis of a developed model. It has been found that power increases along with an increase in the value of these parameters. Verification of the theoretical model indicated consistence of the predicted power demand with the power demand determined in tests performed on a real object for values of the assumed, effective loading, which was 65–75%.

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