Analytical/Experimental Study of the Contribution of Individual Seals to Friction Force in Pneumatic Actuators

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Luigi Mazza ◽  
Guido Belforte
Keyword(s):  
Friction Force ◽  
Experimental Validation ◽  
Friction Forces ◽  
Pneumatic Actuators ◽  
Test Conditions ◽  
Lumped Parameter ◽  
Experimental Approaches ◽  
Friction Measurements ◽  
Rod Seals ◽  
Pneumatic Cylinders

This paper presents an analytical model and its experimental validation for assessing friction forces in reciprocating seals for single and double rod pneumatic cylinders. The contributions of individual piston and rod seals are analyzed using a combination of analytical and experimental approaches. The former entails a friction force formulation based on a lumped parameter seal model, whereas the latter involves carrying out measurements on complete actuators. Selecting appropriate test conditions made it possible to analyze separately the contributions that individual seals make to the overall friction measured on complete actuators. Analysis results were validated by means of friction measurements on the actuators seals, which were tested individually in specific devices. The experimental results were interpreted on the basis of the proposed analytical formulation and confirmed its validity.

Study of the effects of relative humidity and velocity on the friction characteristics of pneumatic cylinders

2020 ◽  
Vol 34 (22n24) ◽  
pp. 2040139
Author(s):  
Thuy-Duong Nguyen ◽  
Van-Hung Pham
Keyword(s):  
Relative Humidity ◽  
Sliding Friction ◽  
Static Friction ◽  
Pneumatic Cylinder ◽  
Dynamic Friction ◽  
Friction Forces ◽  
Measuring Device ◽  
Friction Characteristics ◽  
Rod Seals ◽  
Pneumatic Cylinders

The movement of a piston rod in a pneumatic cylinder is directly affected by the air humidity in the atmosphere, especially in the case of piston rods without any means of protection or grease on their surfaces. In a pneumatic cylinder system, the friction between the piston rod and the rod seal is sliding friction, and it has a significant value that varies with the variation in the moisture on the piston rod’s surface. In this paper, an investigation of the friction characteristics of piston rods and rod seals in a pneumatic cylinder was carried out with different humidity and velocity values to understand the effect of lubricants on the moving parts of pneumatic systems in humid environments, where the friction characteristics of the displacements corresponding to the static and dynamic friction forces were displayed on a measuring device. The research results showed that the static friction forces tended to decrease by [Formula: see text] and that the dynamic friction forces tended to decrease by [Formula: see text] when the relative humidity increased from 51% to 99% at different velocities between 5 and 100 mm/s.

Atomic-Scale Friction Measurements Using Friction Force Microscopy: Part I—General Principles and New Measurement Techniques

1994 ◽  
Vol 116 (2) ◽  
pp. 378-388 ◽  
Author(s):  
Ju-Ai Ruan ◽  
Bharat Bhushan
Keyword(s):  
Friction Force ◽  
Microelectromechanical Systems ◽  
Atomic Scale ◽  
Magnetic Storage ◽  
Basic Operation ◽  
Friction Force Microscopy ◽  
Force Measurements ◽  
Friction Forces ◽  
Force Microscopy ◽  
Friction Measurements

Friction force measurements using modified atomic force microscopy, called here Friction Force Microscopy (FFM), are becoming increasingly important in the understanding of fundamental mechanisms of friction, wear, and lubrication, and to study interfacial phenomena in micro- and nanostructures used in magnetic storage systems and Microelectromechanical Systems (MEMS). FFMs can be used to study engineering surfaces in dry or wet conditions. A review of existing designs of FFMs and methods of friction force measurements is presented. In terms of friction force measurements, there are important issues related to the basic operation and calibration of these instruments which have not been fully studied. A new method of measuring friction fore using a commercial FFM and a calibration procedure for conversion of measured data to normal and friction forces are presented. Microscale friction data of selected materials are presented and discussed in light of macro-friction measurements.

scholarly journals Influence of Nanoscale Textured Surfaces and Subsurface Defects on Friction Behaviors by Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1617 ◽  
Author(s):  
Ruiting Tong ◽  
Zefen Quan ◽  
Yangdong Zhao ◽  
Bin Han ◽  
Geng Liu
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Friction Force ◽  
Copper Substrate ◽  
Dynamics Simulation ◽  
Textured Surfaces ◽  
Friction Forces ◽  
Subsurface Structures ◽  
Texture Orientation ◽  
Subsurface Defects

In nanomaterials, the surface or the subsurface structures influence the friction behaviors greatly. In this work, nanoscale friction behaviors between a rigid cylinder tip and a single crystal copper substrate are studied by molecular dynamics simulation. Nanoscale textured surfaces are modeled on the surface of the substrate to represent the surface structures, and the spacings between textures are seen as defects on the surface. Nano-defects are prepared at the subsurface of the substrate. The effects of depth, orientation, width and shape of textured surfaces on the average friction forces are investigated, and the influence of subsurface defects in the substrate is also studied. Compared with the smooth surface, textured surfaces can improve friction behaviors effectively. The textured surfaces with a greater depth or smaller width lead to lower friction forces. The surface with 45° texture orientation produces the lowest average friction force among all the orientations. The influence of the shape is slight, and the v-shape shows a lower average friction force. Besides, the subsurface defects in the substrate make the sliding process unstable and the influence of subsurface defects on friction forces is sensitive to their positions.

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.

Vibration and Analysis of Multi-Disk Friction Systems

1998 ◽  
Author(s):  
Henric Larsson ◽  
Kambiz Farhang
Keyword(s):  
Frictional Contact ◽  
Vibration Characteristics ◽  
Lumped Parameter Model ◽  
Stick Slip ◽  
Friction Forces ◽  
Lumped Parameter ◽  
Modes Of Vibration ◽  
The Coefficient Of Friction ◽  
Slip Region ◽  
Stiffness And Damping

Abstract The paper presents a lumped parameter model of multiple disks in frictional contact. The contact elastic and dissipative characteristics are represented by equivalent stiffness and damping parameters in the axial as well as the torsional directions. The formulation accounts for the coupling betwen the axial and angular motions by viewing the contact normal force to be the result of axial behavior of the system. The frictional contact of two disks in contact is modeled in two dynamic states (i.e. sticking and slipping state) having individual lumped parameter models and the conditions that control the switching between the two states are established. The friction forces are represented by assuming the coefficient of friction to be a function of the sliding velocity, varying exponentially from its static value at zero relative velocity to its kinetic value at high velocities. A computer simulation of an eight-rotor disk assembly is presented. The torsional vibration characteristics and how it is liked to the axial modes of vibration is analyzed. The vibration characteristics in the transient, steady-state and stick-slip region is compared. In the stick-slip region, the angular velocity of the interfaces in frictional contact is depicted and the sticking and slipping states are defined. It is shown that the duration of slip is approximately constant and the duration of stick increases almost exponentially until a final sticking is achieved.

scholarly journals Mathematical Modeling of Impact of Possible Shock Dynamic Loads on the Modern Composite Materials

2019 ◽  
Vol 224 ◽  
pp. 02012
Author(s):  
Eugenе Sosenushkin ◽  
Oksana Ivanova ◽  
Elena Yanovskaya ◽  
Yuliya Vinogradova
Keyword(s):  
Composite Materials ◽  
Friction Force ◽  
Equations Of Motion ◽  
Elastic Fiber ◽  
Dynamic Loads ◽  
Friction Forces ◽  
Absolute Value ◽  
A Value ◽  
The Absolute ◽  
The Impact

In this paper, we study the dynamic processes in materials reinforced with fibers, that can be represented as composite rods. There has been developed a mathematical model of wave propagation under the impact of a shock pulse in semi-infinite composite rods. It is believed that the considered composite rod consists of two layers formed by simpler rods of different isotropic materials with different mechanical properties. The cross sections of such rods are considered to be constant and identical. When such composite materials are impacted by dynamic loads, a significant part of the energy is dissipated due to the presence of friction forces between the contact surfaces of the rods. In this regard, we study the propagation of waves in an elastic fiber-rod, the layers of which interact according to Coulomb law of dry friction. The case of instantaneous excitation of rods by step pulses is investigated. The blow is applied to a rod made of a harder material. In the absence of slippage, the friction force gets a value not exceeding the absolute value of the limit. In the absence of slippage, the friction force takes a value not exceeding the absolute value of the limit. Let us consider the value of the friction force constant. Normal stresses and velocities satisfy the equations of motion and Hooke’s law. The problem statement results in the solution of inhomogeneous wave equations by the method of characteristics in different domains, which are the lines of discontinuities of the solution. Solutions are found in all constructed domains. On the basis of the analysis of the obtained solution, qualitative conclusions are made and curves are constructed according to the obtained ratios. From the found analytical solution of the problem it is possible to obtain ratios for stresses and strain rates in composite rods and composite materials.

scholarly journals Prophylaxis protocols and their impact on bracket friction force

2019 ◽  
Vol 89 (6) ◽  
pp. 883-888
Author(s):  
Sérgio Elias Neves Cury ◽  
Silvio Augusto Bellini-Pereira ◽  
Aron Aliaga-Del Castillo ◽  
Sérgio Schneider ◽  
Arnaldo Pinzan ◽  
...  
Keyword(s):  
Sodium Bicarbonate ◽  
Qualitative Analysis ◽  
Friction Force ◽  
Friction Forces ◽  
Debris Accumulation ◽  
Intergroup Comparison ◽  
Group 3 ◽  
Group 2 ◽  
Sliding Mechanics

ABSTRACT Objective: To evaluate the effect of two different prophylaxis protocols on the friction force in sliding mechanics during in vivo leveling and alignment. Materials and Methods: The sample comprised 48 hemi-arches divided into three groups according to the prophylactic protocol adopted. Group 1 consisted of patients undergoing prophylaxis with sodium bicarbonate, group 2 consisted of patients submitted to prophylaxis with glycine, and group 3 consisted of patients without prophylaxis, as a control. All patients received hygiene instructions and, with the exception of group 3, prophylaxis was performed monthly. After 10 months, the brackets were removed from the oral cavity and submitted to friction force tests and qualitative analysis by scanning electron microscopy. Analysis of variance followed by Tukey tests was performed for intergroup comparison regarding the friction force. Results: The experimental groups presented significantly smaller friction forces than the group without prophylaxis. Accordingly, qualitative analysis showed greater debris accumulation in the group without the prophylactic procedures. Conclusions: Prophylactic blasting with sodium bicarbonate or glycine can significantly prevent an increase of the friction force during sliding mechanics.

Fluid-Hammer Effects on Coiled-Tubing Friction in Extended-Reach Wells

SPE Journal ◽  
2016 ◽  
Vol 22 (01) ◽  
pp. 365-373 ◽  
Author(s):  
Silviu Livescu ◽  
Steven Craig ◽  
Bill Aitken
Keyword(s):  
Friction Force ◽  
Numerical Models ◽  
Laboratory Data ◽  
Friction Reduction ◽  
Friction Modeling ◽  
Radial Vibrations ◽  
Friction Forces ◽  
Planning Stage ◽  
Force Matching ◽  
Coiled Tubing

Summary The lateral reach and residual bottomhole-assembly (BHA) loads in extended-reach wells strongly depend on the coiled-tubing (CT) mechanical friction. Detailed CT-friction modeling becomes crucial in the prejob planning stage to ensure successful job predictability. However, current numerical simulators consider constant coefficients of friction (CoFs) that are determined from similar operations without taking into account the effects of the operational and downhole parameters on the CoF for a specific operation. This study outlines the modeling of CT-friction force, CoF, and axial BHA loads depending on the operational and downhole parameters when a fluid-hammer tool is used. Recent theoretical, laboratory, and field data have established how CoF depends on the downhole parameters (Livescu and Wang 2014; Livescu and Watkins 2014; Livescu et al. 2014a, b; Livescu and Craig 2015). Previously, these effects were not considered in the CT numerical models, leading to significant CoF differences among available commercial simulators. For instance, the default CoFs in the current prejob simulations for cased holes, when no lubricant or friction-reducing tools such as fluid-hammer tools and tractors are used, vary between 0.24 and 0.30 or even higher. This makes it extremely difficult to consistently evaluate and compare the friction-reduction effects of lubricants, fluid-hammer tools, and tractors in extended-reach wells, especially when the field operator may be consulting with several service companies that use different commercial force-modeling software. This study presents the CT-force matching and fundamental physics on the basis of modeled fluid forces, including radial forces, drag forces, and, most importantly, pressure forces on the CT-friction forces caused by fluid-hammer tools. Extending the method of characteristics, regularly used for studying pressure pulses in straight pipes, the perturbations method also accounts for the helical shape of the CT. The new CT fluid-hammer model is validated against laboratory data. This rigorous method for calculating the axial BHA load and reduced CT-friction force caused by radial vibrations can be easily implemented in currently available tubing-force analysis (TFA) software for CT operations. This novel approach, which uses detailed CT mechanical-friction modeling to take into account parameters such as temperature, internal pressure, pumping rate, and others, improves predictions for CT reach in lateral wells. These findings broaden the current industry understanding of the CT mechanical friction modeling in extended-reach wells, and show benefits for the industry when considering variable friction modeling in commercial CT simulators.

Stirling Thermocompressor: Lumped Parameter Modeling and Experimental Impact of Displacer Motion Profile on Work Output

2019 ◽  
Author(s):  
Seth Thomas ◽  
Eric J. Barth
Keyword(s):  
Experimental Validation ◽  
Model Parameters ◽  
Work Output ◽  
System Dynamics Model ◽  
Dynamics Model ◽  
Lumped Parameter ◽  
Stirling Engines ◽  
Simplified Modeling ◽  
Parameter Approach ◽  
Motion Profile

Abstract The thermocompressor, a little-known class of Stirling devices that efficiently compresses gas, presents new challenges for modeling and experimental validation. In modeling, traditional analytic assumptions about displacer motion are limiting. In experimental verification, few devices have actually been built and tested. In this paper, the authors test the feasibility of a lumped-parameter approach for predicting the performance of Stirling thermocompressors subject to different displacer motion profiles. Since the displacer of a thermocompressor can be controlled independently, unlike kinematic Stirling engines or dynamic Stirling engines, and has a large influence on output power and efficiency of the device, it is crucial that this is well captured by a system dynamics model for control. Key model parameters are simulated and results are experimentally verified on one of the few, if only, experimental thermocompressor platforms in the world. Conclusions are drawn regarding simplified modeling of the regenerator’s effectiveness and the effects on device work output by varying the displacer piston’s motion profile using different waveforms.

Friction Force Measurements Using the Instantaneous IMEP Method and Comparison With RINGPAK Simulations

2005 ◽  
Author(s):  
Myoungjin Kim ◽  
Thomas M. Kiehne ◽  
Ronald D. Matthews
Keyword(s):  
Friction Force ◽  
Piston Ring ◽  
Cost Effective ◽  
Firing Condition ◽  
Force Measurements ◽  
Connecting Rod ◽  
Friction Forces ◽  
Bench Tests ◽  
Ring Assembly ◽  
Analysis System

Even though many researchers have measured the piston/ring assembly friction force over the last several decades, accurate measurement of the piston/ring assembly friction force is a still challenging problem. The floating liner method is not widely used, in spite of its accuracy, due to the substantial modifications required to the engine. On the other extreme, bench tests of the piston/ring assembly cannot completely simulate the real firing condition although bench tests are rapid, consistent, and cost effective. In this study, friction forces of the piston/ring assembly were measured using the instantaneous IMEP method and compared with modeling results using Ricardo’s RINGPAK software. In this research, a flexible flat cable was used to connect the connecting rod strain gage signal to the analysis system instead of using a grasshopper linkage. Therefore, the piston/ring assembly friction force was measured with the minimum change to the engine hardware.

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