№61-16

Determination and relationship between shift and friction angles in chapter formation

Yu. Kravchenko¹, V. Derbaba¹, D. Smagin¹

¹ Dnipro University of Technology, Dnipro, Ukraine

Coll.res.pap.nat.min.univ. 2020, 61:193-201

https://doi.org/10.33271/crpnmu/61.193

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ABSTRACT

Purpose. Derive the calculated formulas of shear angles sum, internal friction-shear in the shear plane and external friction-sliding of chips through the components of the cutting force with a sharp blade. Carry out comparative calculations of the shear angle according to the most common formulas of known authors and determine the angle of friction of the chips through the shear angle and the constant value of the friction-shear angle for individual groups of steels.

Methodology. The study is based on the use of analytical-probabilistic methods of calculations to determine the relationship between shear angles, internal friction-shear in the shear plane and external friction-sliding of the chips on the front surface of the blade. The values of the axial and normal components were determined by the method of dynamometer for specific cutting conditions or based on empirical dependences by the method of "inverse calculation". The accepted model of chip formation allowed analytically to obtain the formulas for the coefficient of friction-shear and the sum of the studied angles using the method of projecting the friction forces and chip pressure on the front surface of the blade in the direction of the tangent and normal components of the shear force.

Findings. The formula for studying the sum of shear angles, internal friction-shear and external friction-sliding is obtained.

Originality. The research was performed and the parametric relationship of chip formation angles was established. The obtained values and functional dependences of chip formation angles are intended for application in analytical calculation of forces and cutting temperature. It is experimentally confirmed that for specific groups of machining materials the sum of shear angles is a constant value. It is proved that the determination of all angles can be performed by calculating the components of the cutting force from empirical dependences using the method of "inverse calculation". This makes it possible to determine these angles without the use of time-consuming dynamometer components of the cutting force with a sharp blade of the cutter.

Practical value. A practical achievement of the detected constancy of the friction-shear angle for specific groups of machining materials is the ability to determine the friction-sliding angle from the sum of angles through one simple output index of the cutting process - shear angle as a function of chip thickness.

Key words: turning of steels, sharp blade, front surface, chip, shear angle, friction-shear angle, friction-sliding angle.

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