Investigation on the Elemental Chip Formation Process in Hard-to-Machine Material Cutting

Abstract

The mechanism of discontinuous chip formation has been studied less than the mechanism of continuous chip formation. However, when most modern materials having specific physical and mechanical properties are subject to machining, such processes are featured by discontinuous chip formation. The paper describes the basic dependencies of discontinuous chip parameters on machining modes. This is a trial undertaken to introduce an explanation of how the basic factors of the cutting process influence over parameters of chip formation.

Calculation of Contact Stresses during Titanium Alloy Cutting

“…Taking into account the small value of shear contact stresses on the rake surface τ ≈ 25 MPa, it is possible to assert that near the cutting edge, the friction coefficient is very small: μ edge = τ / σ max = 0.025 MPa, as the average coefficient is: μ av = F / N = 0.052 MPa. We explain it by the presence of pseudo liquid state of a thin contact layer of a chip that indirectly proves to be true by welding of chip elements only in this layer [11]. High temperature of a contact layer t≈1000 °C also has been elucidated during titanium alloy (Ti-6Al-2Mo-2Cr) turning with the cutting speed v = 1 m / s and feed rate f from 0.11 to 0.41 mm/r.…”

“…In machining of titanium alloy type of forming chip is serrated which is similar to a discontinuous [1,2,4,5,8,10,11]; therefore, the length of contact of a chip with a rake surface of the cutter is small c ≈ 3 • a (mm), where a is uncut chip thickness (mm).…”