MEASUREMENT OF THE STATIC FRICTION COEFFICIENT BETWEEN A poly-V belt 5pk AND A PULLEY UNDER DRY CONDITIONS

Tribologia ◽  
2018 ◽  
Vol 277 (1) ◽  
pp. 57-62
Author(s):  
Krzysztof KUBAS
Keyword(s):  
Friction Coefficient ◽  
Nonlinear Function ◽  
Static Friction ◽  
Friction Forces ◽  
Good Accordance ◽  
Dry Conditions ◽  
Rest Time ◽  
Wrap Angle ◽  
Different Shapes ◽  
Static Coefficient

The paper presents the results of experimental measurements of static friction forces between a poly-V belt 5pk and a pulley on a specialised research stand. An average effective static coefficient is assumed depending on the wrap angle and preload force. Different shapes and positions of curves of the measured values for lower wrap angles are found, with similar curves in the set of measurements with higher angles. The Nelder-Mead optimisation method is proposed to approximate the measured results by a nonlinear function and to achieve good accordance. The dependence of the effective friction coefficient on the rest time between measurements is also presented.

The effect of moisture on friction coefficient of fabrics used on taekwondo personal protective equipment

2018 ◽  
Vol 233 (1) ◽  
pp. 87-94
Author(s):  
WL Li ◽  
HY Shen ◽  
JT Hung ◽  
CP Shih
Keyword(s):  
Friction Coefficient ◽  
Personal Protective Equipment ◽  
Static Friction ◽  
Original Position ◽  
Protective Equipment ◽  
Friction Characteristics ◽  
Weft Knitted Fabric ◽  
Forearm Skin ◽  
Dry Conditions ◽  
Selection Of

The purpose of this study was to investigate the friction characteristics of different fabrics used in personal protective equipment worn during competition and matches. During vigorous taekwondo activity, sweat, movement, and body collisions may cause personal protective equipment to slide from its original position and accordingly fail to protect the athletes effectively. Therefore, a thorough study investigating the friction characteristics among different fabrics used in personal protective equipment and its effect on the skin is needed. This study is intended to be helpful for the athletes in the selection of appropriate personal protective equipment fabrics. Universal Nano + Micro + Macro Materials Tester was used in friction tests between six different personal protective equipment fabrics and the dorsum forearm skin to obtain the coefficients of kinetic friction and static friction. The results indicated that PVC faux leather showed better anti-skid performance under dry conditions. Under wet conditions, however, the friction coefficient of PVC faux leather decreased significantly due to lubrication, and thus lowered the anti-skid performance. In addition, the friction coefficient of fabrics with better water absorption or drainage capacity showed greater adhesion with the increasing of skin hydration. In particular, 100% polyester weft-knitted fabric showed better anti-skid performance under wet conditions. The result of this study provides a good reference in the selection and design of Taekwondo personal protective equipment for athletes, coaches, and manufacturers.

THE ANALYSIS OF THE INFLUENCE OF GAMMA IRRIADIATED POLYSULFONES ON THE STATIC FRICTION COEFFICIENT

Tribologia ◽  
2017 ◽  
pp. 65-70
Author(s):  
Aneta NIEMIEC
Keyword(s):  
Friction Coefficient ◽  
Radiation Dose ◽  
Contact Pressure ◽  
Coefficient Of Friction ◽  
Static Friction ◽  
Water Recovery ◽  
Initial State ◽  
Static Friction Coefficient ◽  
Static Coefficient Of Friction ◽  
Static Coefficient

The paper presents the results of studies on the effects of gamma irradiation on the static friction coefficient of thermoplastic polymer – polysulfone. These polar polymers belong to the group of amorphous thermoplastics and are widely used for various applications, e.g., automotive and electronic industries (dielectrics in capacitors), waste water recovery, medical uses (hemodialysis membranes), requiring autoclave, and steam sterilization. Polysufones are known for their toughness and stability at high temperatures. The aim of this study is to analysed changes in the static coefficient of friction in association with a contact pressure (in the range 0.2 – 0.8 MPa) depending on the ionizing radiation dose of PSU (in the range 50-150 kGy). Additionally, microhardness, and wear intensity were measured, because tribological properties of polymers as well as mechanical properties that influence their durability and applications. The studies confirmed that the static coefficient of friction increases with an increase in contact pressure (in the test range). The research has shown that mechanical (microhardness) and tribological (static coefficient of friction and tribological wear) improve as the radiation dose of irradiated material increase. Moreover, the tribological wear increases with increasing the sliding velocity. This gamma irradiated polymer is characterized by higher microhardness, a static coefficient of friction, and a higher wear rate compared to PSU in the initial state, because of changes in structure. It requires further research.

scholarly journals Manipulation of nanoparticles of different shapes inside a scanning electron microscope

2014 ◽  
Vol 5 ◽  
pp. 133-140 ◽  
Author(s):  
Boris Polyakov ◽  
Sergei Vlassov ◽  
Leonid M Dorogin ◽  
Jelena Butikova ◽  
Mikk Antsov ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Tuning Fork ◽  
Quartz Tuning Fork ◽  
Static Friction ◽  
Si Substrate ◽  
Friction Forces ◽  
Different Shapes ◽  
Particle Geometry ◽  
Scanning Electron

In this work polyhedron-like gold and sphere-like silver nanoparticles (NPs) were manipulated on an oxidized Si substrate to study the dependence of the static friction and the contact area on the particle geometry. Measurements were performed inside a scanning electron microscope (SEM) that was equipped with a high-precision XYZ-nanomanipulator. To register the occurring forces a quartz tuning fork (QTF) with a glued sharp probe was used. Contact areas and static friction forces were calculated by using different models and compared with the experimentally measured force. The effect of NP morphology on the nanoscale friction is discussed.

3D Numerical Friction Contact Model and Its Application to Nonlinear Blade Damping

2010 ◽  
Author(s):  
Weiwei Gu ◽  
Zili Xu
Keyword(s):  
Friction Coefficient ◽  
Nonlinear Vibration ◽  
Fourier Transforms ◽  
Three Dimensional ◽  
Harmonic Balance Method ◽  
Static Friction ◽  
Contact Model ◽  
Friction Contact ◽  
Friction Forces ◽  
Discrete Fourier Transforms

A three dimensional numerical friction contact model is proposed to investigate the nonlinear vibration of damped blade. The model describes the discrete friction forces in the time domain. By using Discrete Fourier Transforms, the discrete friction forces can be transformed into a series of harmonic functions which are used to solve the nonlinear vibration of damped blade in the frequency domain. The difference between static friction coefficient and dynamic friction coefficient is considered in the model. To consider microslip effect, an array of spring-slider contact pairs (friction contact model) is distributed on the contact surfaces. Additionally, the effect of area of the contact surface on the vibration of damped blade can be studied by altering the number of the contact pairs. Finally, the nonlinear vibration of a real turbine blade with shrouded friction dampers is solved using the proposed friction contact model, Multi-Harmonic Balance Method and Receptance Method.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

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.

Measurements of the Static Friction Coefficient Between Tin Surfaces and Comparison to a Theoretical Model

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Rebecca D. Ibrahim Dickey ◽  
Robert L. Jackson ◽  
George T. Flowers
Keyword(s):  
Theoretical Model ◽  
Friction Coefficient ◽  
Human Error ◽  
Surface Profile ◽  
Static Friction ◽  
Quantitative Agreement ◽  
High Plasticity ◽  
Static Friction Coefficient ◽  
Experimental Apparatus ◽  
Rough Surface Contact

A new experimental apparatus is used to measure the static friction between tin surfaces under various loads. After the data is collected it is then compared to an existing theoretical model. The experiment uses the classical physics technique of increasing the incline of a plane and block until the block slides. The angle at the initiation of sliding is used to find the static friction coefficient. The experiment utilizes an automated apparatus to minimize human error. The finite element based statistical rough surface contact model for static friction under full stick by Li, Etsion, and Talke (2010, “Contact Area and Static Friction of Rough Surfaces with High Plasticity Index,” ASME Journal of Tribology, 132(3), p. 031401) is used to make predictions of the friction coefficient using surface profile data from the experiment. Comparison of the computational and experimental methods shows similar qualitative trends, and even some quantitative agreement. After adjusting the results for the possible effect of the native tin oxide film, the theoretical and experimental results can be brought into reasonable qualitative and quantitative agreement.

scholarly journals Brittle Fracture Theory Describes the Onset of Frictional Motion

2019 ◽  
Vol 10 (1) ◽  
pp. 253-273 ◽  
Author(s):  
Ilya Svetlizky ◽  
Elsa Bayart ◽  
Jay Fineberg
Keyword(s):  
Friction Coefficient ◽  
Brittle Fracture ◽  
Static Friction ◽  
Quantitative Agreement ◽  
Interface Fracture ◽  
Earthquake Dynamics ◽  
Rupture Dynamics ◽  
Static Friction Coefficient ◽  
Fracture Theory ◽  
Macroscopic Motion

Contacting bodies subjected to sufficiently large applied shear will undergo frictional sliding. The onset of this motion is mediated by dynamically propagating fronts, akin to earthquakes, that rupture the discrete contacts that form the interface separating the bodies. Macroscopic motion commences only after these ruptures have traversed the entire interface. Comparison of measured rupture dynamics with the detailed predictions of fracture mechanics reveals that the propagation dynamics, dissipative properties, radiation, and arrest of these “laboratory earthquakes” are in excellent quantitative agreement with the predictions of the theory of brittle fracture. Thus, interface fracture replaces the idea of a characteristic static friction coefficient as a description of the onset of friction. This fracture-based description of friction additionally provides a fundamental description of earthquake dynamics and arrest.

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