scholarly journals Effects of varying friction coefficient on rolling pressure distribution

2019 ◽  
Vol 37 (2) ◽  
pp. 11-25
Author(s):  
F. Davis ◽  
A. Andrews ◽  
M. N. Sackey ◽  
S. P. Owusu-Ofori
Keyword(s):  
Plastic Deformation ◽  
Friction Coefficient ◽  
Pressure Distribution ◽  
Deformation Process ◽  
Contact Region ◽  
Quantitative Relationship ◽  
Current Approach ◽  
Roll Pressure ◽  
Constant Friction ◽  
Variable Friction

Accurate characteristics of roll pressure distribution is essential in the estimation of the energy and power requirements for parts undergoing plastic deformation. The nature of the pressure distribution is very sensitive to the friction coefficient between the roller and the deformed part. The physics of the deformation process points to a variable friction coefficient, however, current research and practices result in the use of a constant friction coefficient. This work explored the development of a technique to determine a quantitative relationship between the variable friction coefficient and the process parameters. The pressure distribution was then developed within the contact region using the variable friction coefficient model. Results show that current approach used by industry (‘the rule of thumb’) overestimates the pressure distribution, compared to the current research, thus wasting power needed for the rolling operation by about 18%. Keywords: Rolling; varying friction coefficient; pressure distribution; power 

Influence of Tool - Semi-Product Friction on the Force Evolution at the Simulation of the Deformation Process with Flat Wedge Tools

2013 ◽  
Vol 837 ◽  
pp. 93-98
Author(s):  
Doina Iacomi ◽  
Monica Iordache ◽  
Eduard Niţu ◽  
Stefan Tabacu
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Friction Coefficient ◽  
Deformation Process ◽  
Design Stage ◽  
Cold Plastic Deformation ◽  
High Productivity ◽  
Hardening Law ◽  
Deformation Force ◽  
As Stress

Processing through volumetric cold plastic deformation (cold rolling) with flat wedge tools is a procedure used in mass production to process profiles (circular, threads, grooves, teeth) on revolution pieces. Complex profiles obtained by cold plastic deformation with flat wedge tools have important advantages: material economy, high productivity, continuous fibre, superior mechanic properties, low values of the roughness parameters, low costs. In recent years, the simulation of processes of volumetric plastic deformation by the finite element method is used to obtain the optimization of the deformation process and the improvement of the product quality even from the design stage. By numerical simulation there is observed the evolution during the process of different parameters such as: stress and deformations in the deformed body, mode of material flow, final shape and sizes of the product etc. Therefore, it becomes possible to analyse the process even from the design stage by identifying the problems which can appear and their influence on some characteristics of the product obtained: geometry, state of deformations and stress.This paper presents the experimental determination of the deformation force at the processing of complex profiles with flat wedge tools and the influence of the friction coefficient between tool and semi-product on its value; influence established by simulating the deformation process. The process also has been simulated by means of finite element calculations using the Abaqus/Explicit code. The material behaviour is described by using a 5-parameter strain-hardening law and by accounting for thermal effects at high strain-rates. The comparison between the values and the variation of the deformation force recorded experimentally and at simulation allows establishing the optimal value of the friction coefficient and validating the numerical model developed.

Non-Uniform Pressure Distribution in Draw-Bend Friction Test and a New Methodology to Determine Non-Constant Friction Coefficient From the Test

2006 ◽  
Author(s):  
Young Suk Kim ◽  
Mukesh K. Jain ◽  
Don R. Metzger
Keyword(s):  
Friction Coefficient ◽  
Pressure Distribution ◽  
Uniform Pressure ◽  
Friction Coefficients ◽  
Average Value ◽  
Pressure Distributions ◽  
Element Simulation ◽  
Constant Friction ◽  
Pressure Dependency ◽  
Friction Models

Friction under lubricated conditions is known to depend on pressure, and experimental determination of this dependence has typically quantified pressure as an average value over the contact area. However, non-uniform pressure distributions at the contact interfaces of draw-bend tests have been reported from various experiments and simulations. A previous study by the authors has evaluated the current methodology, which assumes uniform pressure distribution to estimate friction coefficients from draw-bend friction tests, and has concluded that the current methodology is only valid for measuring an average friction coefficient over the pressure range, which exists in the specific draw-bend system. In this paper, a new methodology to extract non-constant friction coefficients from draw-bend friction tests is suggested. In the methodology, contact pressure maps obtained from simulations, instead of the uniform pressure assumption, are included in the analysis of test data to measure the pressure dependency of friction coefficient. The methodology is tested by applying the method to back predict the input friction data from finite element simulation results of draw-bend friction tests, in which non-constant friction models are used as friction input.

scholarly journals Modeling and design of tuned mass dampers using sliding variable friction pendulum bearings

2020 ◽  
Vol 231 (12) ◽  
pp. 5021-5046
Author(s):  
Emiliano Matta ◽  
Rita Greco
Keyword(s):  
Friction Coefficient ◽  
Pressure Distribution ◽  
Analytical Model ◽  
Seismic Isolation ◽  
Outer Region ◽  
Design Parameters ◽  
Sliding Surface ◽  
Restoring Force ◽  
Variable Friction ◽  
Friction Pendulum

Abstract An effective vibration control device, the pendulum tuned mass damper (P-TMD), can be easily realized as a mass supported on rolling or sliding pendulum bearings. While the bearings’ concavity provides the desired gravitational restoring force, the necessary dissipative force can be obtained either from additional dampers installed in parallel with the bearings or from the same friction resistance developing within each bearing between the roller/slider and the rolling/sliding surface. The latter solution may prove cheaper and more compact but implies that the P-TMD effectiveness will be amplitude dependent if the friction coefficient is kept uniform along the rolling/sliding surface, as in conventional friction bearings. In this case, the friction P-TMD will be as efficient as a viscous P-TMD only at a given vibration level, with large performance reductions at other levels. To avoid this inconvenience, this paper proposes a new type of sliding variable friction pendulum (VFP) TMD, called the VFP-TMD, in which the sliding surface is divided into two concentric regions: a circular inner region, having the lowest possible friction coefficient and the same dimensions of the slider, and an annular outer region, having a friction coefficient set to an optimal value. A similar arrangement has been recently proposed to realize adaptive seismic isolation devices, but no specific application to TMDs is reported. To assess the VFP-TMD performance, first its analytical model is derived, rigorously accounting for geometric nonlinearities as well as for the variable (in time and space) pressure distribution along the contact area, and then, an optimal design methodology is presented. Finally, numerical simulations show the influence of the main design parameters on the device behavior and demonstrate that the VFP-TMD can achieve nearly the same effectiveness of viscous P-TMDs, while considerably outperforming conventional uniform-friction P-TMDs. The proposed analytical model can be used to enhance or validate existing models of VFP isolators that assume a constant and uniform contact pressure distribution.

scholarly journals Analysis of Sheet Metal Forming (Stamping Process): A Study of the Variable Friction Coefficient on 5052 Aluminum Alloy

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 853 ◽  
Author(s):  
Shasha Dou ◽  
Jiansheng Xia
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Sheet Metal ◽  
Boundary Lubrication ◽  
Thickness Distribution ◽  
Sliding Velocity ◽  
Spring Back ◽  
Stamping Die ◽  
Constant Friction ◽  
Variable Friction

Under a boundary lubrication regime, the effect of sliding velocity and normal loads on the friction coefficient in the sheet metal stamping process was investigated using a pin-on-disk sliding wear test. Software was used to analyze both the data generated and the friction coefficient; in addition, a variable friction model based on different velocities and normal loads was also initiated. Under different experimental conditions and numerous influences, both the analysis and microtopography examination of sheet metal helped to obtain the mechanism influence on the friction coefficient. Through further analysis of the microtopography of sheet metal, the law of the surface roughness of sheet metal after grinding with stamping die was established. The model was established to simulate the thickness distribution and spring-back of U-bend parts using ABAQUS software. The results show that the friction coefficient values between the sheet metal and the stamping die generally decrease with increasing sliding velocity and normal loads, and the decreasing tendency slows down under a higher sliding velocity and normal load. Furrow wear and abrasive wear are the main wear mechanisms, with slight sticking wear under the boundary lubrication; the surface roughness after grinding with stamping die generally increases with increasing normal loads and decreasing sliding velocity. The predicted results of thickness distribution with a constant friction coefficient of 0.1 and with the variable friction coefficient model are more consistent with the actual measured values, but the predicted accuracy of spring-back in the variable friction coefficient model is higher than that of the constant friction coefficient model.

Numerical analysis of plastic deformation evolution into metallic materials during spherical indentation process

2009 ◽  
Vol 24 (3) ◽  
pp. 1270-1278 ◽  
Author(s):  
M. Beghini ◽  
L. Bertini ◽  
V. Fontanari ◽  
B.D. Monelli
Keyword(s):  
Plastic Deformation ◽  
Friction Coefficient ◽  
Deformation Process ◽  
Indentation Depth ◽  
Spherical Indentation ◽  
Plastic Strains ◽  
Metallic Materials ◽  
Contact Conditions ◽  
Plastic Deformation Process ◽  
Load Indentation

The present paper deals with the plastic deformation process into metallic materials occurring in the subindenter region during the loading cycle of spherical indentation test. Load–indentation-depth curve and plastic strains field evolution in the region beneath the indenter are examined using finite element analysis (FEA). The FE model was set up and validated by comparison with experimental spherical indentations carried out on two different materials (Al6082-T6, AISI H13) under four different friction conditions, corresponding to friction coefficients equal to 0.0, 0.1, 0.3, and 0.5. It is confirmed that friction effects on load–indentation-depth curves are negligible for the investigated penetration depths, whereas the plastic deformation process is affected by the contact conditions. The investigation shows that, although the L–h curve is not affected by the contact conditions up to medium values of the penetration depth, remarkable effects are produced in the overall plastic core under the indenter. A strong correlation between plastic strains field and friction coefficient is especially observed at low values of this parameter, whereas a saturation of the phenomena is found for medium-high values of the friction coefficient.

Analysis of the Contact Deformation of a Radial Tire with Camber Angle

1995 ◽  
Vol 23 (1) ◽  
pp. 26-51 ◽  
Author(s):  
S. Kagami ◽  
T. Akasaka ◽  
H. Shiobara ◽  
A. Hasegawa
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Contact Region ◽  
Contact Deformation ◽  
Contact Pressure Distribution ◽  
Radial Tire ◽  
Ring Model ◽  
Camber Angle ◽  
Contact Free ◽  
Good Agreement

Abstract The contact deformation of a radial tire with a camber angle, has been an important problem closely related to the cornering characteristics of radial tires. The analysis of this problem has been considered to be so difficult mathematically in describing the asymmetric deformation of a radial tire contacting with the roadway, that few papers have been published. In this paper, we present an analytical approach to this problem by using a spring bedded ring model consisting of sidewall spring systems in the radial, the lateral, and the circumferential directions and a spring bed of the tread rubber, together with a ring strip of the composite belt. Analytical solutions for each belt deformation in the contact and the contact-free regions are connected by appropriate boundary conditions at both ends. Galerkin's method is used for solving the additional deflection function defined in the contact region. This function plays an important role in determining the contact pressure distribution. Numerical calculations and experiments are conducted for a radial tire of 175SR14. Good agreement between the predicted and the measured results was obtained for two dimensional contact pressure distribution and the camber thrust characterized by the camber angle.

Tribological characterization of all-polymer prosthesis based on multi-directional motion

2021 ◽  
pp. 089270572110286
Author(s):  
Xinyue Zhang ◽  
Dekun Zhang ◽  
Kai Chen ◽  
Handong Xu ◽  
Cunao Feng
Keyword(s):  
Friction Coefficient ◽  
Abrasive Wear ◽  
Wear Mechanism ◽  
Friction And Wear ◽  
Quantitative Relationship ◽  
Motion Path ◽  
Aspect Ratios ◽  
Directional Motion ◽  
Motion Paths ◽  
Prosthesis Material

The complex movement of artificial joints is closely related to the wear mechanism of the prosthesis material, especially for the polymer prosthesis, which is sensitive to motion paths. In this paper, the “soft-soft” all-polymer of XLPE/PEEK are selected to study the influence of motion paths on the friction and wear performance. Based on the periodic characteristics of friction coefficient and wear morphology, this paper reveals the friction and wear mechanism of XLPE/peek under multi-directional motion path, and obtains the quantitative relationship between friction coefficient and the aspect ratios of “∞”-shape motion path, which is of great significance to reveal and analyze the wear mechanism of “soft” all-polymer under multi-directional motion path. The results show that the friction coefficient is affected by the motion paths and have periodicity. Morever, under the multi-directional motion paths, the wear of PEEK are mainly abrasive wear and adhesive wear due to the cross shear effect, while the wear of XLPE is mainly abrasive wear with plastic accumulation. In addition, the friction coefficient is greatly affected the aspect ratios Rs-l of “∞”-shape and loads. Meanwhile, the wear morphologies are greatly affected by the aspect ratios Rs-l of “∞”-shape, but less affected by loads.

The Effect of Grain Boundary State on Deformation Process Development in Nanostructured Metals Produced by the Methods of Severe Plastic Deformation

2011 ◽  
Vol 683 ◽  
pp. 69-79 ◽  
Author(s):  
Evgeny V. Naydenkin ◽  
Galina P. Grabovetskaya ◽  
Konstantin Ivanov
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Deformation Process ◽  
Process Development ◽  
Grain Boundary Sliding ◽  
Total Deformation ◽  
Nanostructured Metals ◽  
Boundary State ◽  
Boundary Sliding

In this review the investigations of deformation process development are discussed which were carried out by tension and creep in the temperature range Т<0.4Tm (here Тm is the absolute melting point of material) for nanostructured metals produced by the methods of severe plastic deformation. The contribution of grain boundary sliding to the total deformation in the above temperature interval is also considered. An analysis is made of the effect of grain size and grain boundary state on the evolution of grain boundary sliding and cooperative grain boundary sliding in nanostructured metals.

scholarly journals A Dislocation-Based Theory for the Deformation Hardening Behavior of DP Steels: Impact of Martensite Content and Ferrite Grain Size

2010 ◽  
Vol 2010 ◽  
pp. 1-16 ◽  
Author(s):  
Yngve Bergström ◽  
Ylva Granbom ◽  
Dirk Sterkenburg
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Deformation Process ◽  
Volume Fraction ◽  
High Energy ◽  
Martensite Content ◽  
Plastic Deformation Process ◽  
Deformation Hardening ◽  
Dp Steels ◽  
Ferrite Grain Size

A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a nonhomogeneity parameter, f(ε), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

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