An Empirical Model for the Coefficient of Friction in Injection Molding of Thermoplastics

2013 ◽  
Author(s):  
Omar Bataineh
Keyword(s):  
Injection Molding ◽  
Coefficient Of Friction ◽  
Empirical Model ◽  
Complex Task ◽  
Roughness Effect ◽  
Friction Forces ◽  
The Coefficient Of Friction ◽  
Ejector System ◽  
Contact Surfaces ◽  
Adhesion Effect

Predicting friction forces present between part and mold surfaces in injection molding of thermoplastics is considered an important step in the design of the ejector system. However, this requires calculating the coefficient of friction at the contact surfaces, which is usually a complex task. In this study, an empirical model is developed in an attempt to estimate the coefficient of friction as applicable for the injection molding of thermoplastics. It is assumed in this model that the coefficient of friction is a sum of two correlated effects: adhesion effect and surface roughness effect. Both effects are treated as functions of mold surface’s average asperity slope.

Finite element analysis of fretting wear considering variable coefficient of friction

2018 ◽  
Vol 233 (5) ◽  
pp. 758-768 ◽  
Author(s):  
Ling Li ◽  
Le Kang ◽  
Shiyun Ma ◽  
Zhiqiang Li ◽  
Xiaoguang Ruan ◽  
...  
Keyword(s):  
Finite Element ◽  
Coefficient Of Friction ◽  
Variable Coefficient ◽  
Friction Model ◽  
Slip Condition ◽  
Fretting Wear ◽  
Partial Slip ◽  
Wear Volume ◽  
The Coefficient Of Friction ◽  
Contact Surfaces

Fretting wear is a kind of material damage in contact surfaces caused by microrelative displacement between two bodies. It can change the profile of contact surfaces, resulting in loosening of fasteners or fatigue cracks. Finite element method is an effective method to simulate the evolution of fretting wear process. In most studies of fretting wear, the coefficient of friction was assumed to be constant to simplify model and reduce the difficulty of solving. However, fretting wear test showed that the coefficient of friction was a variable related to the number of fretting cycles. Therefore, this paper introduces the coefficient of friction as a function of the number of fretting cycles in numerical simulation. A wear model considering variable coefficient of friction is established by combining energy consumption model and adaptive grid technique. The nodes of contact surfaces are updated through the UMESHMOTION subroutine. The effects of constant coefficient of friction and variable coefficient of friction on fretting wear are analyzed by comparing the wear amount under different loading conditions. The results show that when compared with coefficient of friction model, fretting wear is obviously affected by variable coefficient of friction and the variable coefficient of friction model has a larger wear volume when the fretting is in partial slip condition and mixed slip condition. In gross slip condition, the difference of wear volume between variable coefficient of friction model and coefficient of friction model decreases with the increase in the displacement amplitudes.

Experimental Studies of Deformation and Temperature Processes Mandrelling in the Deform-3D System

2021 ◽  
Vol 1037 ◽  
pp. 357-368
Author(s):  
Mikhail F. Selemenev ◽  
Arkady A. Cherepenko ◽  
Elena A. Zvyagina ◽  
Artem N. Tkachenko ◽  
Elena M. Selemeneva
Keyword(s):  
Heat Transfer ◽  
Coefficient Of Friction ◽  
Experimental Studies ◽  
Contact Stresses ◽  
Temperature Analysis ◽  
Friction Forces ◽  
The Coefficient Of Friction ◽  
Cutting Zone ◽  
Deform 3D

The article discusses the effect of epilamated coatings during mandrelling. The picture of the change in contact stresses in the DEFORM-3D system is presented. It was established that a decrease in the coefficient of friction from 0.9 to 0.6 leads to a decrease in the number of foci and areas of contact stresses, as well as temperature analysis showed that a decrease in the friction forces reduces heat transfer in the cutting zone by about 40 ° C.

Sliding Characteristics in the Copper Contacts

1993 ◽  
Vol 5 (3) ◽  
pp. 292-298
Author(s):  
Yoshitada Watanabe ◽  
Keyword(s):  
Contact Resistance ◽  
Coefficient Of Friction ◽  
Heat Generation ◽  
Electrical Contact ◽  
Rotational Frequency ◽  
Contact Spot ◽  
Electrical Contact Resistance ◽  
The Coefficient Of Friction ◽  
Contact Surfaces ◽  
Sliding Test

A low rotational frequency sliding tester which could measure electrical contact resistance and coefficient of friction simultaneously was trially fabricated. Relations between electrical contact resistance and coefficients of friction were investigated by making sliding test on clean copper and surface oxidized copper contacts respectively, which were used relatively frequently in industries. As far as the measurement work made this time, of which rotational frequency was low, was concerned, it was found that the heat generation due to mechanical friction was low and the heat generation due to Joule's heat in the case of sliding clean contact surfaces was also low because of low contact resistance. It was, however, found that CU²0, etc. were formed due to rapid progress of oxidation by the generation of Joule's heat at the contact surfaces, of which real contact areas were extremely small, being roughened along with the increase of the sliding frequency. On the other hand, it was further found that although the existence of oxides in advance at the sliding surface extremely lowered the coefficient of friction (0.07 for example) in which the oxidized film indicating contrarily (70mΩ for example). It was presumed that formations and destroys of oxidation film were repeated by flow of electric current at the contact spot to cause Fritting Phenomenon.

Thermal EHL Analysis of Circular Contacts With Measured Surface Roughness

1996 ◽  
Vol 118 (3) ◽  
pp. 473-482 ◽  
Author(s):  
Gang Xu ◽  
Farshid Sadeghi
Keyword(s):  
Surface Roughness ◽  
Coefficient Of Friction ◽  
Three Dimensional ◽  
Time Dependent ◽  
The Coefficient Of Friction ◽  
Contact Surfaces ◽  
Energy Equations ◽  
Thermal Ehl ◽  
Circular Contact ◽  
Ehl Contact

Time dependent thermal EHL circular contact results with measured surface roughness were obtained to analyze the effects of roughness on pressure, film thickness, temperature, and coefficient of friction. Both contact surfaces are considered to be rough. Multilevel multigrid techniques (with multigrid integration) were used to solve the system of two dimensional Reynolds, elasticity and three dimensional energy equations simultaneously. The effects of surface roughness under various loads, speeds, and slip conditions have been studied. Surface roughness causes pressure and temperature spikes and increases the coefficient of friction, and surface roughness flattens due to the high pressure in EHL contact. The higher the load, speed and slide to roll ratio, the more significant the effect of the surface roughness. A comparison between rough EHL and smooth EHL results indicates that surface roughness cannot be ignored in EHL analysis.

On the Mechanics of Crack Initiation and Propagation in Elasto-Plastic Materials in Impact Fretting Wear

2004 ◽  
Vol 126 (2) ◽  
pp. 395-403 ◽  
Author(s):  
Y. B. Gessesse ◽  
M. H. Attia
Keyword(s):  
Crack Initiation ◽  
Contact Pressure ◽  
Coefficient Of Friction ◽  
Contact Area ◽  
Plastic Material ◽  
Oblique Impact ◽  
Fretting Wear ◽  
Isotropic Hardening ◽  
Friction Forces ◽  
The Coefficient Of Friction

Normal and oblique impact wear processes are characterized by unique features, which include the development of some residual stress components that vanish in unidirectional sliding. Parametric finite element analyses were conducted to estimate the likelihood locations for crack initiation, and the subsequent direction and rate of crack propagation in an elasto-plastic material with bi-linear isotropic hardening properties. The results showed that the increase in contact pressure can cause a significant increase in the size of the plastically deformed crack initiation zone and allows it to reach the surface. Such behavior is not predicted under continuous sliding conditions. The presence of surface friction forces in oblique impact, can also result in the development of a secondary region of high tensile stresses at the contact area. Using the crack tip slip displacement CTSD method, the rate of crack growth was found to be linearly proportional to the crack length, and significantly dependent on the contact pressure and the coefficient of friction at the crack surface. The small effect of the coefficient of friction at the micro-contact area on wear suggests that the effect of shear traction is mainly due to the increase in the depth of the crack nucleation zone. As expected, the increase of the material flow stress with strain-hardening has a wear reducing effect.

scholarly journals Method for determining the coefficient of friction between fence and scraped object in equilibrium of the friction force

2018 ◽  
Vol 19 (6) ◽  
pp. 790-794
Author(s):  
Mirosław Wolski ◽  
Tomasz Piątkowski ◽  
Przemysław Osowski
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Coefficient Of Friction ◽  
Conveyor Belt ◽  
Determination Method ◽  
Friction Forces ◽  
The Coefficient Of Friction

In this paper presents friction coefficient determination method between scraped object's material and fence material, determined directly on the conveyor belt, which then is introduced in the FEM program (LSDyna) for simulation of the scraping process in the automated sorting plant. In this case, the necessity of using an additional laboratory stand to determine the coefficient of friction is omitted. Due to the existing balance of friction forces, the model of the phenomenon can be treated as static, therefore the measurement is very simple and does not depend on time.

scholarly journals MODELLING OF A GLASS GATHERER ROBOT'S ARM WITH A FRICTIONAL DAMPER

2018 ◽  
Vol 18 (4) ◽  
pp. 127-140
Author(s):  
Marek STEMBALSKI ◽  
Pawel PRES ◽  
Waclaw SKOCZYNSKI ◽  
Paweł TUREK
Keyword(s):  
Numerical Model ◽  
Finite Elements ◽  
Coefficient Of Friction ◽  
Normal Pressure ◽  
Operating Parameters ◽  
Sliding Velocity ◽  
Friction Damper ◽  
Damping Decrement ◽  
The Coefficient Of Friction ◽  
Contact Surfaces

A numerical model of a friction damper used for damping vibration in glass gatherer robots was described. The damper with a lance was modelled using finite elements. Primary natural frequency of the system was determined. Numerical calculations were performed to determine the best operating parameters of the damper for excitations using a impulse of a force. Results of the damping decrement calculations for the friction damper model with a constant coefficient of friction and for the model, in which the coefficient of friction varied depending on the sliding velocity and the normal pressure occurring at the contact surfaces of the damper’s friction rings, were presented. Based on numerical simulations, the values of relative displacements between the damper’s friction rings were also determined.

scholarly journals CAM FITTING UNIT OF DEVICEFOR UNSCREWING CATCHED PIPES IN THE WELL

2021 ◽  
pp. 151-164
Author(s):  
S. Yu. Gavryliv ◽  
M. M. Lyakh ◽  
Yu. L. Gavryliv
Keyword(s):  
Coefficient Of Friction ◽  
Operating Conditions ◽  
Geometric Parameters ◽  
Initial Angle ◽  
Friction Forces ◽  
Repair Work ◽  
Oil Companies ◽  
Urgent Task ◽  
The Coefficient Of Friction ◽  
The Moment

Improving the efficiency of repair work in elimination of drilling pipe accidents in the well is an urgent task of oil companies and is achieved through usage of special devices and tools. Authors patented and manufactured a device for unscrewing pipes in casing with a nominal diameter of D = 114 mm. Cycle of the device for unscrewing pipes in the well consists of three periods: freewheeling, jamming of the carrier of the device for unscrewing the trapped pipes and the period of wedging. The article analyses the operating conditions of the device locking unit during the first two periods. Formulas for determining the force of pressing the cams to the casing during freewheel, as well as the moment of friction forces and friction power for this case are proposed. We obtain the dependence of the maximum allowable initial angle of jamming on the coefficient of friction and geometric parameters of the device. It is planned to test the device for unscrewing pipes in industrial conditions of LLC "Factorial" (Poltava).

Identification of Friction Coefficient for Constrained Robotic Tasks

2002 ◽  
Vol 124 (4) ◽  
pp. 529-538 ◽  
Author(s):  
I. Sharf ◽  
G. Gilardi ◽  
C. Crawford
Keyword(s):  
Coefficient Of Friction ◽  
Normal Load ◽  
Point Contact ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Identification Algorithm ◽  
Test Bed ◽  
Accurate Identification ◽  
Friction Forces ◽  
The Coefficient Of Friction

Correct modeling of friction forces during constrained robotic operations is critical to high-fidelity contact dynamics simulation. Such simulations are particularly important for the development, mission planning and operations analysis of space robotic systems. Most existing friction models employ the coefficient of friction to capture the relationship between the friction force and the normal load. Hence, accurate identification of this parameter is prerequisite to accurate simulation. This issue is particularly important for space robotic operations since friction characteristics of materials are very different in space. In this manuscript, the problem of identification of the coefficient of friction is investigated experimentally and numerically. The motivating application being space manipulator systems, our principal objective is to develop a practical off-line identification algorithm, requiring minimum number of measurements from sensors available on space robots. To this end, a strategy is proposed to determine the coefficient of friction by using only the measured end-effector forces. The key idea behind the method is that during one-point contact, these forces represent the contact force and hence, can be directly used to calculate the coefficient of friction. The proposed approach is tested with the experimental data from peg insertion experiments conducted on a planar robotics test-bed with a specially designed contact interface. The algorithm is generalized to arbitrary complex geometries and applied to identify the coefficient of friction for a simulated battery drop test.

A Parametric Study of a Cottage-Roof Damper and Comparison With Experimental Results

2001 ◽  
Author(s):  
Martin H. Jareland
Keyword(s):  
Simulation Model ◽  
Coefficient Of Friction ◽  
Contact Surface ◽  
Time Domain ◽  
Parametric Study ◽  
Normal Load ◽  
Resonance Amplitude ◽  
The Coefficient Of Friction ◽  
Contact Surfaces ◽  
The Time Domain

Platform dampers are commonly used in turbomachinery to reduce the vibration amplitudes of the turbine blades. A blade-to-blade platform damper is simply a piece of metal which is pressed against two adjacent blade platforms by centrifugal force. Relative motions of the platforms lead to slip in the contacts and friction damping is provided in the system. The studied platform damper is designed with inclined contact surfaces. This type of damper is often called a cottage-roof damper or wedge damper. The inclination of the contact surfaces leads to variation of the normal load, which complicates the analysis of such dampers. In this paper, a simulation model is presented for a tuned bladed disk with cottage-roof dampers. This model includes normal load variation on the contact and a friction interface model valid for both macroslip and microslip. The elasticity of the damper body is often an important parameter for the performance of the damper and is included in the model. A comparison between solving the equation of motion in the frequency domain and the time domain is performed. It is found that the frequency domain solution with the fundamental frequency alone gives a result close to the time domain solution. The simulation model is validated with experimental data and it is found that the reduction of the resonance amplitude agrees well for the tested dampers. A parametric study is performed to find the optimal friction damper design. The studied parameters are the inclination of the contact surface, the coefficient of friction and the damper body stiffness. It is found that an increase in inclination of the contact surface and an increase in the coefficient of friction lead to a reduction of the optimal damper mass. An increase of the damper body stiffness results in a decrease of the resonance amplitude of the blade tip, particularly for high damper masses.

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