Development of Lubricants Evaluation for Different Friction Laws by Using Rigid-Plastic Finite Element Method

2012 ◽  
Vol 626 ◽  
pp. 584-588
Author(s):  
Heng Keong Kam ◽  
Wen Chiet Cheong ◽  
Chan Chin Wang ◽  
Ying Pio Lim
Keyword(s):  
Finite Element Method ◽  
Coulomb Friction ◽  
Ring Compression Test ◽  
Rigid Plastic ◽  
Friction Law ◽  
Calibration Curves ◽  
Ring Compression ◽  
Shear Friction ◽  
Coulomb Friction Law ◽  
Friction Calibration

A simulator based on rigid-plastic finite element method is developed with two common friction law: Coulomb friction law and constant shear friction law are imposed. This project is to develop a simple method to identify tribological properties of various lubricants by metal forming method. In this project, the influence of different lubricants was studied by using ring compression test. The deformation of the ring compression test was measured to obtain an experimental friction calibration curves under different lubricants. To model the friction effect, theoretical friction calibration curves for Coulomb friction law and shear friction law are generated under various parameter of μ, coefficient of friction (Coulomb friction law) and m, shear factor (constant shear friction law). The experimental and theoretical friction calibration curves were compared and the result shows corresponding. The friction of the lubricants was further verified by using a common method: pulling a block on flat surface with load sensor yields the friction force, F in the basic equation F=μN where N is the normal force. The results match the calibration curves too.

Analysis of Ring Compression Test for Determination of Friction Circumstances in Forging Process

2012 ◽  
Vol 249-250 ◽  
pp. 663-666 ◽  
Author(s):  
Mojtaba Dehghan ◽  
Fathallah Qods ◽  
Mahdi Gerdooei ◽  
Javad Doai
Keyword(s):  
Friction And Wear ◽  
Fe Analysis ◽  
Ring Test ◽  
Ring Compression Test ◽  
Friction Behavior ◽  
Forging Process ◽  
Calibration Curves ◽  
Ring Compression ◽  
Friction Calibration

Friction is a major factor in determining the characteristics ofmetals as they are forged.Regularand efficient lubrication is one of the best ways in controlling friction and wear in this process.One of the best ways of testing the lubricant is the ringCompression test. In this research the effect of mixed graphite in water and also the effect of the amount of graphite in the lubricant in the reduction of friction between the sample-die are calculated using the ring test. Friction behavior is changed fromsticking friction to sliding frictionby using the lubricant; but the changes in the amount of graphite in water didnot have a great effect on the reduction of the friction coefficient. Furthermore, after viewing differences in the friction coefficients calculated by the means of FE analysis and the friction calibration curves, it is concluded that the sole calibration curves could not be used for hot working conditions.

Some Consequences of Coulomb Friction in Modeling Longitudinal Traction

1990 ◽  
Vol 18 (1) ◽  
pp. 13-65 ◽  
Author(s):  
W. W. Klingbeil ◽  
H. W. H. Witt
Keyword(s):  
Shear Force ◽  
Coulomb Friction ◽  
Interfacial Shear ◽  
Force Generation ◽  
Behavior Patterns ◽  
Inflation Pressure ◽  
Friction Law ◽  
The Coefficient Of Friction ◽  
Coulomb Friction Law ◽  
Perfect Adhesion

Abstract A three-component model for a belted radial tire, previously developed by the authors for free rolling without slip, is generalized to include longitudinal forces and deformations associated with driving and braking. Surface tractions at the tire-road interface are governed by a Coulomb friction law in which the coefficient of friction is assumed to be constant. After a brief review of the model, the mechanism of interfacial shear force generation is delineated and explored under traction with perfect adhesion. Addition of the friction law then leads to the inception of slide zones, which propagate through the footprint with increasing severity of maneuvers. Different behavior patterns under driving and braking are emphasized, with comparisons being given of sliding displacements, sliding velocities, and frictional work at the tire-road interface. As a further application of the model, the effect of friction coefficient and of test variables such as load, deflection, and inflation pressure on braking stiffness are computed and compared to analogous predictions on the braking spring rate.

On Some Problems With Modeling of Coulomb Friction in Self-Locking Speed Reducers

2014 ◽  
Author(s):  
Marek Wojtyra
Keyword(s):  
Rigid Body ◽  
Coulomb Friction ◽  
Equations Of Motion ◽  
Velocity Ratio ◽  
Friction Forces ◽  
Friction Law ◽  
Rigid Body Model ◽  
Feasible Sets ◽  
Unstable Solutions ◽  
Coulomb Friction Law

A simple mathematical model of friction in speed reducers is presented and discussed. A rigid body approach, typical for multibody simulations, is adopted. The model is based on the Coulomb friction law and exploits the analogy between reducers and wedge mechanisms. The first version of the model is purely rigid, i.e. no deflections of the mechanism bodies are allowed. Constraints are introduced to maintain the ratio between input and output velocity. It is shown that when friction is above the self-locking limit, paradoxical situations may be observed when kinetic friction is investigated. For some sets of parameters of the mechanism (gearing ratio, coefficient of friction and inertial parameters) two distinct solutions of normal and friction forces can be found. Moreover, for some combinations of external loads, a solution that satisfies equations of motion, constraints and Coulomb friction law does not exist. Furthermore, for appropriately chosen loads and parameters of the mechanism, infinitely many feasible sets of normal and friction forces can be found. Examples of all indicated paradoxical situations are provided and discussed. The second version of the model allows deflection of the frictional contact surface, and forces proportional to this deflection are applied to contacting bodies (no constraints to maintain the input-output velocity ratio are introduced). In non-paradoxical situations the obtained results are closely similar to those predicted by the rigid body model. In previously paradoxical situations no multiple solutions of friction force are found, however, the amended model does not solve all problems. It is shown that in regions for which the paradoxes were observed only unstable solutions are available. Numerical examples showing behavior of the model are provided and analyzed.

Friction in Hot Forging of Chrome Steel Covered with Oxide Scale Film Generated at Steam Atmosphere

2014 ◽  
Vol 622-623 ◽  
pp. 194-200
Author(s):  
Ryo Matsumoto ◽  
Shohei Harada ◽  
Hiroshi Utsunomiya
Keyword(s):  
Oxide Scale ◽  
Compression Test ◽  
Hot Forging ◽  
Chemical Compositions ◽  
Ring Compression Test ◽  
Chrome Steel ◽  
Air Atmosphere ◽  
Ring Compression ◽  
Plastic Deformation Behavior ◽  
Shear Friction

The hot ring compression test of chrome steel covered with an oxide scale film is carried out to examine the effects of the oxide scale film on the hot forging characteristics. For changing the chemical compositions of the oxide scale, the oxide scale film is generated at air or steam atmosphere. The nominal coefficient of shear friction of the chrome steel covered with the oxide scale film is estimated from the plastic deformation behavior during the ring compression test. The estimated coefficient of shear friction of the chrome steel covered with the oxide scale film is found to be lower than that of the chrome steel without the oxide scale film. Furthermore, the oxide scale generated at steam atmosphere provides lower friction characteristics in comparison with the oxide scale generated at air atmosphere. The mechanism of the reduction of friction with the oxide scale is discussed.

scholarly journals Crack in a solid under Coulomb friction law

2000 ◽  
Vol 45 (4) ◽  
pp. 265-290 ◽  
Author(s):  
Victor A. Kovtunenko
Keyword(s):  
Coulomb Friction ◽  
Friction Law ◽  
Coulomb Friction Law
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