Modeling of twist drills wear by a temperature-dependent friction law

Abstract

In this paper an analytical model is developed which predicts thrust force in the drilling with a twist drill. The thermomechanical properties are accounted for to describe the material flow in the primary shear zone and at the element–chip interface. The chip flow is determined by the assumption that the friction force on the tool face is collinear to the chip flow direction. The model permits to predict the chip flow direction, the contact length between the chip and the tool and the temperature distribution at the tool–chip interface which has an important effect on the tool wear. A temperature friction law is introduced as μ ¯ = μ ¯ 0 ( 1 − ( T ¯ int / T f ) q ) and the pressure on the tool–chip interface was modeled as p ( Z fl ) = p 0 ( 1 − Z fl / l C ) ξ where T ¯ int is the mean temperature in the shear interface and l C is the contact length between the chip and the drill. Using the thermo-viscoplastic model and the temperature friction law, the tangential forces, friction coefficient and contact length on the cutting element as a function of radius, for different feed rate and cutting speed, are obtained. The proposed model results are compared with experimental results and good agreement is obtained.