Determination of Friction Coefficient by Employing the Ring Compression Test

2000 ◽  
Vol 123 (3) ◽  
pp. 338-348 ◽  
Author(s):  
Hasan Sofuoglu ◽  
Hasan Gedikli ◽  
Jahan Rasty
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Material Properties ◽  
Rate Sensitivity ◽  
Compression Tests ◽  
Element Analysis ◽  
Test Conditions ◽  
Calibration Curves ◽  
Ring Compression ◽  
Friction Calibration

The main objective of this research was to investigate the effect of material properties, strain-rate sensitivity, and barreling on the behavior of friction calibration curves. The compression tests were conducted to obtain the necessary material properties for the finite element analysis. A series of ring compression tests were then conducted in order to determine the magnitude of the friction coefficient, μ. The experiments were first conducted for the modeling materials, namely, white and black plasticine and later on, for aluminum, copper, bronze, and brass. The experiments were then simulated via an elastic-plastic finite element code (ABAQUS). Contrary to the results available in the literature, where the same friction calibration curves are recommended for all types of materials and test conditions, the results of this investigation showed that friction calibration curves are indeed affected by the material properties and test conditions.

scholarly journals A Finite Element Study of Thermo-Mechanical Fields and Their Relation to Friction Conditions in Al1050 Ring Compression Tests

2018 ◽  
Vol 2 (4) ◽  
pp. 83 ◽  
Author(s):  
Brigit Mittelman ◽  
Elad Priel ◽  
Nissim Navi
Keyword(s):  
Finite Element ◽  
Flow Stress ◽  
Friction Coefficient ◽  
Computational Models ◽  
Experimental System ◽  
Pure Aluminium ◽  
Compression Tests ◽  
Element Analysis ◽  
Ring Compression ◽  
Flow Stress Data

The most accepted method for determining friction conditions in metal forming is the ring compression test (RCT). At high temperatures, extraction of the friction coefficient, μ, commonly requires numerical analysis due to the coupling between the mechanical and thermal fields. In the current study, compression tests of cylindrical specimens and RCT experiments were conducted on commercially pure aluminium (Al1050) at several temperatures, loading rates, and lubrication conditions. The experiments were used in conjunction with a coupled thermo-mechanical finite element analysis to study the dependence of the friction coefficient on those parameters. It is demonstrated that due to the coupling between friction conditions and material flow stress, both μ and flow stress data should be determined from the cylinder and ring specimens simultaneously and not subsequently. The computed friction conditions are validated using a novel method based on identification of the plastic flow neutral radius. It is shown that, due to heat loss mechanisms, the experimental system preparation stage must be incorporated in the computational analysis. The study also addresses the limitation of the RCT in the presence of high friction conditions. The computational models are finally used to examine the thermo-mechanical fields, which develop during the different processes, with an emphasis on the effect of friction conditions, which were then correlated to the resulting microstructure in the RCTs.

An Approximate Model to Calculate Foldover and Strains During Cold Upsetting of Cylinders Part I: Formulation and Evaluation of the Foldover Model

1990 ◽  
Vol 112 (3) ◽  
pp. 260-266 ◽  
Author(s):  
O. M. Ettouney ◽  
K. A. Stelson
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Approximate Model ◽  
Ring Test ◽  
Forming Limit ◽  
Cold Upsetting ◽  
Element Analysis ◽  
Forming Limit Diagrams ◽  
Volume Equations ◽  
Friction Calibration

In this paper, a new approximate model to calculate foldover of a cylinder undergoing nonuniform compression test (simple upsetting) is presented. The model is formulated using constant-volume equations and workpiece geometry. In addition to foldover, the model can be used to calculate equatorial-axial strains. This eliminates the need for inscribing grids (when determining forming-limit diagrams) on the cylinder’s free surface to find these strains. Combined with friction-calibration curves (prepared using finite-element analysis) that relate foldover to friction, the model enables one to estimate the friction coefficient. This eliminates the need for a separate test (e.g., the ring test) to determine friction or evaluate type of lubrication to be used. When compared to finite-element results and experiments, the new model showed excellent results in calculating foldover, strains, and friction coefficient.

scholarly journals Thermo-mechanical forging of 708M40 steel ring samples: experiments and modelling

2021 ◽  
Author(s):  
Steven Hill ◽  
Richard P.Turner
Keyword(s):  
Finite Element ◽  
Experimental Parameter ◽  
Compression Tests ◽  
Molybdenum Disulphide ◽  
Heating Unit ◽  
Modelling Framework ◽  
Process Understanding ◽  
Ring Compression ◽  
Water Based ◽  
Temperature Variable

AbstractA series of ring compression tests using BS970:708M40 alloy steel samples were studied. These tests were conducted using a 2-factor soak-temperature variable, namely 1030 °C and 1300 °C, and a 4-factor lubricant variable consisting of unlubricated samples, synthetic water-based, graphite water-based, and graphite and molybdenum disulphide viscous grease. The lubricant agents were all applied to the tool/billet interface. Process variables such as blow force and heating were controlled with the use of a gravitationally operated drop hammer and an automated programmable induction-heating unit. This matrix of the experimental parameters offered a sound base for exploring dominant factors impacting upon bulk deformation. This deformation was measured using fully calibrated equipment and then systematically recorded. A finite element modelling framework was developed to further improve the thermo-mechanical deformation process understanding, with finite element (FE) predictions validated through experimental measurement. Through the combined experimental and FE work, it was shown that temperature variation in the experimental parameter matrix played a larger role in determining deformation than the lubrication agent. Additionally, the use of synthetic and graphite water-based lubricants does not necessarily produce greater deformation when used in high-temperature forgings due to the lubricants breaking down, evaporating, or inducing rapid billet cooling as a result of the carrier used (water). Graphite-molybdenum disulphate grease far outperforms the other lubricants used in this trial in reducing friction and allowing deformation to occur across a die-face.

3D Coupled Thermomechanical Finite Element Analysis of Ultrasonic Consolidation

2007 ◽  
Vol 539-543 ◽  
pp. 2651-2656 ◽  
Author(s):  
C.J. Huang ◽  
E. Ghassemieh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Friction Coefficient ◽  
Stress Field ◽  
Ultrasonic Wave ◽  
Ultrasonic Vibration ◽  
Softening Effect ◽  
Element Analysis ◽  
Consolidation Process ◽  
Ultrasonic Consolidation

A 3-D coupled temperature-displacement finite element analysis is performed to study an ultrasonic consolidation process. Results show that ultrasonic wave is effective in causing deformation in aluminum foils. Ultrasonic vibration leads to an oscillating stress field. The oscillation of stress in substrate lags behind the ultrasonic vibration by about 0.1 cycle of ultrasonic wave. The upper foil, which is in contact with the substrate, has the most severe deformation. The substrate undergoes little deformation. Apparent material softening by ultrasonic wave, which is of great concern for decades, is successfully simulated. The higher the friction coefficient, the more obvious the apparent material softening effect.

Investigating the Calibration Curves for a Two Component Cutting Tool Lathe Dynamometer Using Finite Element Analysis

2016 ◽  
Vol 24 ◽  
pp. 71-84
Author(s):  
Osezua Obehi Ibhadode ◽  
Ishaya Musa Dagwa ◽  
Akii Okonigbon Akhaehomen Ibhadode
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cutting Tool ◽  
Von Mises Stress ◽  
Equation Modeling ◽  
Element Analysis ◽  
Calibration Curves ◽  
Two Component ◽  
Applied Forces ◽  
Von Mises

Calibration curves of a multi-component dynamometer is of essence in machining operations in a lathe machine as they serve to provide values of force and stress components for cutting tool development and optimization. In this study, finite element analysis has been used to obtain the deflection and stress response of a two component cutting tool lathe dynamometer, for turning operation, when the cutting tool is subjected to cutting and thrust forces from 98.1N to 686.7N (10 to 70kg-wts), at intervals of 98.1N(10kg-wt). By obtaining the governing equation, modeling the dynamometer assembly, defining boundary conditions, generating the assembly mesh, and simulating in Inventor Professional; horizontal and vertical components of deflection by the dynamometer were read off for three different loading scenarios. For these three loading scenarios, calibration plots by experiment compared with plots obtained from simulation by finite element analysis gave accuracies of 79%, 95%, 84% and 36%, 57%, 63% for vertical and horizontal deflections respectively. Also, plots of horizontal and vertical components of Von Mises stress against applied forces were obtained.

scholarly journals On the Design of a Biodegradable POC-HA Polymeric Cardiovascular Stent

2012 ◽  
Author(s):  
Joonas Ponkala ◽  
Mohsin Rizwan ◽  
Panos S. Shiakolas
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Polymeric Composite ◽  
Coronary Stent ◽  
Element Analysis ◽  
Material Models ◽  
Solid Models ◽  
Biodegradable Stents

The current state of the art in coronary stent technology, tubular structures used to keep the lumen open, is mainly populated by metallic stents coated with certain drugs to increase biocompatibility, even though experimental biodegradable stents have appeared in the horizon. Biodegradable polymeric stent design necessitates accurate characterization of time dependent polymer material properties and mechanical behavior for analysis and optimization. This manuscript presents the process for evaluating material properties for biodegradable biocompatible polymeric composite poly(diol citrate) hydroxyapatite (POC-HA), approaches for identifying material models and three dimensional solid models for finite element analysis and fabrication of a stent. The developed material models were utilized in a nonlinear finite element analysis to evaluate the suitability of the POC-HA material for coronary stent application. In addition, the advantages of using femtosecond laser machining to fabricate the POC-HA stent are discussed showing a machined stent. The methodology presented with additional steps can be applied in the development of a biocompatible and biodegradable polymeric stents.

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