MATHEMATICAL MODELING OF FRICTION FORCE AND FRICTION COEFFICIENT AT DEEP DRAWING PROCESS
This paper includes: experimental determination of process and blank holder forces at plate deep drawing, calculation of friction force and friction coefficient on the basis of achieved experimental results, determination of mathematical models Ft = f (SHP, φ, pd) and μ = f (SHP, φ, pd), as well as graphical simulations and analyses of achieved mathematical models. As substance for cooling and lubrication molybdenum disulfide and oil EP50 were used, while tribological conditions of contact surfaces were varied using phosphated and non-phosphated plate (EN 10027-1: DC04; DIN: RRSt14). Research results have shown that the best tribological conditions were achieved with molybdenum disulfide on phosphated plate, and the most influencing parameter is material deformation degree.
NUMERICAL AND EXPERIMENTAL METHODS FOR DETERMINATION FRICTION COEFFICIENT
In this paper is analyzed and determined the coefficient of friction between the wheels of the vehicle and asphalt. Coefficient of friction is gained through practical measurements and theoretical methods. It is set changes between values gained through practical measurements and theoretical methods. Coefficient of friction is presented as a system of forces applied in engineering, which is described in a system of forces acting on a rigid body. The model for determining the coefficient of friction is built based on a rigid body and to elaborate was taken the vehicle tires which are loaded with a testing mass, with different physical parameters of roughness (asphalt, concrete, gravel road congestion, ice, etc). Analyzed changes of static coefficient subjected to rigid body forces, changes the dynamic coefficient of friction, geometric constraints, values calculated with mathematical method through variables. Measurements were made with gauge forces applied to enable more accurate measurements and also are seen changes of values depending on the solid foundation for testing. Keyword: Values of coefficient of friction, static and dynamic friction coefficient, the system of displacement forces.
Modelling Of Tribological Parameters In Process Of Cold Drawing And Selection Of Optimal Lubricators
The obtained results and mathematical modelc indicate that the coefficients of friction and temperature depend on the drawing velocity, degree of strain and technological lubricant used. Experimental results were estemated with multiple regression analysis and adequacy of the matematical model was confirmed. Results of investigations in working conditions show that the desired effects can be achived: increased durability of tools 20 to 40 per cent, reduced stagnation time in the machining process 20 to 30 per cent, increase on the prodictivity of the machining process 15 to 30 per cent and lower energy consumption up to 15 per cent.