scholarly journals Anisotropy of Graphene Nanoflake Diamond Interface Frictional Properties

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1425 ◽  
Author(s):  
Ji Zhang ◽  
Ehsan Osloub ◽  
Fatima Siddiqui ◽  
Weixiang Zhang ◽  
Tarek Ragab ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Md Simulations ◽  
Equilibrium Distance ◽  
Sliding Angle ◽  
Stick Slip ◽  
Single Crystalline ◽  
Frictional Properties ◽  
Diamond Substrate ◽  
Graphene Nanoflake

Using molecular dynamics (MD) simulations, the frictional properties of the interface between graphene nanoflake and single crystalline diamond substrate have been investigated. The equilibrium distance between the graphene nanoflake and the diamond substrate has been evaluated at different temperatures. This study considered the effects of temperature and relative sliding angle between graphene and diamond. The equilibrium distance between graphene and the diamond substrate was between 3.34 Å at 0 K and 3.42 Å at 600 K, and it was close to the interlayer distance of graphite which was 3.35 Å. The friction force between graphene nanoflakes and the diamond substrate exhibited periodic stick-slip motion which is similar to the friction force within a graphene–Au interface. The friction coefficient of the graphene–single crystalline diamond interface was between 0.0042 and 0.0244, depending on the sliding direction and the temperature. Generally, the friction coefficient was lowest when a graphene flake was sliding along its armchair direction and the highest when it was sliding along its zigzag direction. The friction coefficient increased by up to 20% when the temperature rose from 300 K to 600 K, hence a contribution from temperature cannot be neglected. The findings in this study validate the super-lubricity between graphene and diamond and will shed light on understanding the mechanical behavior of graphene nanodevices when using single crystalline diamond as the substrate.

Uncertainty Analysis of CNC Machine Tools Based on Monte Carlo Method

2020 ◽  
Vol 900 ◽  
pp. 9-13
Author(s):  
Yunn Lin Hwang ◽  
Thi Na Ta
Keyword(s):  
Monte Carlo ◽  
Friction Coefficient ◽  
Numerical Simulations ◽  
Friction Force ◽  
System Performance ◽  
Numerical Control ◽  
Machining Accuracy ◽  
Force Model ◽  
Stick Slip ◽  
System Components

The uncertainty of mechanical system performance is strongly influenced by the properties of system components such as mass, stiffness-damping coefficient, and friction coefficient. Based on computational simulations, the system performance under uncertainty conditions can be estimated. However, the nonlinear dynamic behavior of friction is difficult to simulate in numerical simulations, this research is therefore employed a smooth stick-slip friction force model instead of the Coulomb friction force model. Monte Carlo simulation (MCS) combined with multibody dynamic (MBD) simulation is proposed to evaluate the uncertainty characteristics of the system components and stick-slip friction force between two contacting bodies. Numerical simulations applied the proposed method were performed to consider the effects of uncertainty of friction coefficient on the machining accuracy of a three axes CNC (Computer Numerical Control) machine tool.

A Numerical Simulation of Interfacial Slip and its Role in Friction

2012 ◽  
Author(s):  
Jeffrey L. Streator
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Lateral Displacement ◽  
Reaction Force ◽  
Static Friction ◽  
Constant Load ◽  
Interfacial Slip ◽  
Stick Slip ◽  
Elastic Slab ◽  
Static Coefficient Of Friction

The transition from static friction to kinetic friction results from the attainment of a point of instability, whereby interfacial slip becomes more energetically favorable than sticking. Such an instability is explored in this work via a plane-strain elastostatic analysis. A rigid pin of prescribed geometry is placed in contact with an elastic slab and translated horizontally under conditions of constant load. An intrinsic static coefficient of friction is prescribed, which limits the ratio of shear stress to contact pressure at each location within the interface. Additionally, the surface of the elastic slab is given a desired undulation to simulate the effects of surface roughness. As the pin is translated horizontally, a lateral reaction force (i.e., friction force) is developed and is observed to grow nearly linearly with increasing lateral displacement. At a critical point, a substantial portion of the interface experiences slip, leading to a large decrease in the friction force and thereby revealing a stick-slip behavior. It is found that the overall (macroscopic) static friction coefficient can be significantly less than the intrinsic friction coefficient and that the presence of even a small amount of roughness can have a large effect on the friction force.

Effect of shape/size and distribution of microgeometries of textures on tribo-performance of crankpin bearing

2021 ◽  
pp. 135065012110105
Author(s):  
Nguyen Van Liem ◽  
Wu Zhenpeng ◽  
Jiao Renqiang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Contact Force ◽  
Distribution Density ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Combined Model ◽  
Obvious Effect ◽  
Area Density

The effect of the shape/size and distribution of microgeometries of textures on improving the tribo-performance of crankpin bearing is proposed. Based on a combined model of the slider-crank mechanism dynamic and hydrodynamic lubrication, the distribution density, area density, and shape of spherical textures, square-cylindrical textures, wedge-shaped textures, and a hybrid between spherical texture and square-cylindrical texture on the crankpin bearing's tribo-performance are investigated under different operating conditions of the engine. The tribological characteristic of the crankpin bearing is then evaluated via the indexes of the oil film pressure p, asperity contact force, friction force, and friction coefficient of the crankpin bearing. The research results show that the distribution density with n = 12 and m = 6, and area density with α = 30% of various microtextures have an obvious effect on ameliorating the crankpin bearings tribo-performance. Concurrently, at the mixed lubrication region, the shape of the square-cylindrical texture on improving the tribo-performance is better than the other shapes of the spherical texture, wedge-shaped texture, and spherical and square-cylindrical texture. Particularly, all the average values of the asperity contact force, friction force, and friction coefficient with a square-cylindrical texture are significantly reduced by 14.6%, 19.5%, and 34.5%, respectively, in comparison without microtextures. Therefore, the microtextures of the spherical texture applied on the bearing surface can contribute to enhance the durability and decrease the friction power loss of the engine.

A novel technique for modeling friction behavior in knitted fabric simulation

2017 ◽  
Vol 29 (6) ◽  
pp. 776-792
Author(s):  
Vajiha Mozafary ◽  
Pedram Payvandy
Keyword(s):  
Friction Coefficient ◽  
Uniform Distribution ◽  
Friction Force ◽  
Experimental Result ◽  
Knitted Fabric ◽  
Friction Behavior ◽  
Content Type ◽  
Novel Technique ◽  
Fabric Structure ◽  
Fabric Surface

Purpose Fabric-object friction force is a fundamental factor in cloth simulation. A large number of parameters influence the frictional properties of fabrics such as fabric structure, yarn structure, and inherent properties of component fibers. The purpose of this paper is to propose a novel technique for modeling fabric-object friction force in knitted fabric simulation based on the mass spring model. Design/methodology/approach In this technique, unlike other studies, distribution of friction coefficient over the fabric surface is not uniform and depends on the fabric structure. The main reason for considering non-uniform distribution is that in various segments of fabric, contact percent of fabric-object is different. Findings The proposed technique and common methods based on friction coefficient uniform distribution are used to simulate the frictional behavior of knitted fabrics. The results show that simulation error values for proposed technique and common methods are 2.7 and 9.4 percent as compared with the experimental result, respectively. Originality/value In the existing methods of the friction force modeling, the friction coefficient of fabric is assumed uniform. But this assumption is not correct because fabric does not have an isotropic structure. Thus in this study, the friction coefficient distribution is considered based on fabric structure to achieve more of realistic simulations.

Study of Friction Coefficient and Friction Force on Magnetic Abrasive Finishing

2011 ◽  
Vol 675-677 ◽  
pp. 663-666
Author(s):  
Yan Chen ◽  
Akira Shimamoto ◽  
X. Gao ◽  
M.M. Zhang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Magnetic Particles ◽  
Good Effect ◽  
Magnetic Abrasive Finishing ◽  
Abrasive Particles ◽  
Abrasive Finishing ◽  
Alumina Particles ◽  
The Cost ◽  
Grinding Efficiency

In order to enhance grinding efficiency of the magnetic abrasive finishing (MAF) method, we usually use the sinter method or the cementation method to mix the magnetic particles and abrasive particles together. However, the cost is high, and the variety is incomplete. Therefore, with the ferromagnetism to iron particles, the alumina particles and the lipin three kind of material simple mixture participate in the magnetic abrasive finishing which directly polishes, already obtained the good effect through the experiment. This paper analyses and explains the characteristic of the friction coefficient and the friction force on magnetic abrasive finishing according as account and experiment data.

scholarly journals Experimental Study on the Transition between Static and Kinetic Frictions of Steel/Shale Pairs

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qin Lian ◽  
Chunxu Yang ◽  
Jifei Cao
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Critical Distance ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Dynamic Friction Coefficient ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Stick Slip Motion ◽  
Insight Into

The transition between static and kinetic frictions of steel/shale pairs has been studied. It was found that the coefficient of friction decreased exponentially from static to dynamic friction coefficient with increasing sliding displacement. The difference between static and dynamic friction coefficients and the critical distance Dc under the dry friction condition is much larger than that under the lubricated condition. The transition from static to dynamic friction coefficient is greatly affected by the normal load, quiescent time, and sliding velocity, especially the lubricating condition. Maintaining continuous lubrication of the contact area by the lubricant is crucial to reduce or eliminate the stick-slip motion. The results provide an insight into the transition from static to dynamic friction of steel/shale pairs.

Experimental Study of a Variable Pressure Damper on Automotive Valve Motion

1996 ◽  
Author(s):  
Jin-Jang Liou ◽  
Grodrue Huang ◽  
Wensyang Hsu
Keyword(s):  
Experimental Study ◽  
Friction Coefficient ◽  
Friction Force ◽  
High Speed ◽  
Experimental Results ◽  
Variable Pressure ◽  
Friction Forces ◽  
Valve Spring ◽  
Valve Motion

Abstract A variable pressure damper (VPD) is used here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve bouncing phenomenon. The friction force on the valve spring is found experimentally, and the corresponding friction coefficient is also determined. Dynamic valve displacements at different speeds with different friction forces are calibrated. Bouncing and floating of the valve are observed when the camshaft reaches high speed. From the measured valve displacement, the VPD is shown to have significant improvement in reducing valve bouncing distance and eliminating floating. However, experimental results indicate that the valve bouncing can not be eliminated completely when the camshaft speed is at 2985 rpm.

Tribology research of the turned zirconium-dioxide ceramics

2012 ◽  
Vol 3 (3) ◽  
pp. 181-190
Author(s):  
G. Fledrich ◽  
R. Keresztes ◽  
L. Zsidai
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Dry Friction ◽  
Zirconium Dioxide ◽  
Steel Specimen ◽  
Friction Condition ◽  
Normal Direction ◽  
Basic Material ◽  
Series Production ◽  
Ceramic Specimen

The zirconium dioxide as basic material is suitable to machine by tool with regular edge derivingfrom lower ceramic hardness and from other characteristics so in case of piece production or small – andmedium series production, at quick prototype production can become potential material alike. The aims tocompare the arising frictional characteristics in case of dry friction condition in case of ceramic – steelsurface pairs machined with different sets. We have developed for an equipment to carry out tribologicaltests. During the test we pressure the steel counter face with determined normal direction force thecasing surface of the rotating ceramic specimen and in the meantime we measure the value of the frictionforce with force meter cell. We have calculated the friction coefficient characterizing the system from thenormal direction force and the friction force as well as we measured the wear of the steel specimen andits deformation.

Friction Induced Vibrations in Aircraft Disk Brakes

1997 ◽  
Author(s):  
Lisle B. Hagler ◽  
Per G. Reinhall
Keyword(s):  
Friction Coefficient ◽  
Multiple Scales ◽  
Primary Resonance ◽  
Rotational Model ◽  
Stick Slip ◽  
Numeric Simulation ◽  
Constant Friction ◽  
The Stability ◽  
Rotor Stiffness ◽  
Friction Induced Vibration

Abstract This paper presents a detailed analysis of the dynamic behavior of a single rotor/stator brake system. Two separate mathematical models of the brake are considered. First, a non-rotational model is constructed with the purpose of showing that friction induced vibration can occur in the stator without assuming stick-slip behavior and a velocity dependent friction coefficient. Self-induced vibrations are analyzed via the application of the method of multiple scales. The stability boundaries of the primary resonance, as well as the super-harmonics and sub-harmonics are determined. Secondly, rotational effects are investigated by considering a mathematical brake model consisting of a spinning rotor engaging against a flexible stator. Again, a constant friction coefficient is assumed. The stability of steady whirl is determined as a function of the system parameters. We demonstrate that only forward whirl is stable for no-slip motion of the rotor. The interactions between chatter, squeal, and rotor whirl are investigated through numeric simulation. It is shown that rotor whirl can be an important source of the torsional oscillations (squeal) of the stator and that the settling time to no-slip decreases as the ratio of the stator to rotor stiffness is increased.

scholarly journals A Novel Stick-Slip Nanopositioning Stage Integrated with a Flexure Hinge-Based Friction Force Adjusting Structure

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 765
Author(s):  
Junhui Zhu ◽  
Peng Pan ◽  
Yong Wang ◽  
Sen Gu ◽  
Rongan Zhai ◽  
...  
Keyword(s):  
Friction Force ◽  
High Speed ◽  
Simulation Analysis ◽  
Load Capacity ◽  
Dynamic Performance ◽  
Critical Role ◽  
Vertical Direction ◽  
Flexure Hinge ◽  
Stick Slip ◽  
Static Performance

The piezoelectrically-actuated stick-slip nanopositioning stage (PASSNS) has been applied extensively, and many designs of PASSNSs have been developed. The friction force between the stick-slip surfaces plays a critical role in successful movement of the stage, which influences the load capacity, dynamic performance, and positioning accuracy of the PASSNS. Toward solving the influence problems of friction force, this paper presents a novel stick-slip nanopositioning stage where the flexure hinge-based friction force adjusting unit was employed. Numerical analysis was conducted to estimate the static performance of the stage, a dynamic model was established, and simulation analysis was performed to study the dynamic performance of the stage. Further, a prototype was manufactured and a series of experiments were carried out to test the performance of the stage. The results show that the maximum forward and backward movement speeds of the stage are 1 and 0.7 mm/s, respectively, and the minimum forward and backward step displacements are approximately 11 and 12 nm, respectively. Compared to the step displacement under no working load, the forward and backward step displacements only increase by 6% and 8% with a working load of 20 g, respectively. And the load capacity of the PASSNS in the vertical direction is about 72 g. The experimental results confirm the feasibility of the proposed stage, and high accuracy, high speed, and good robustness to varying loads were achieved. These results demonstrate the great potential of the developed stage in many nanopositioning applications.

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