Abstract
In this paper, a stressed state of a non-worn cutting wedge in a machined titanium alloy (Ti6Al2Mo2Cr) is analyzed. The distribution of contact loads on the face of a cutting tool was obtained experimentally with the use of a ‘split cutting tool’. Calculation of internal stresses in the indexable insert made from cemented carbide (WC8Co) was carried out with the help of ANSYS 14.0 software. Investigations showed that a small thickness of the cutting insert leads to extremely high compressive stresses near the cutting edge, stresses that exceed the ultimate compressive strength of cemented carbide. The face and the base of the insert experience high tensile stresses, which approach the ultimate tensile strength of cemented carbide and increase a probability of cutting insert destruction. If the thickness of the cutting insert is bigger than 5 mm, compressive stresses near the cutting edge decrease, and tensile stresses on the face and base decrease to zero. The dependences of the greatest normal and tangential stresses on thickness of the cutting insert were found.Abbreviation and symbols: m/s - meter per second (cutting speed v); mm/r - millimeter per revolution (feed rate f); MPa - mega Pascal (dimension of specific contact loads and stresses); γ - rake angle of the cutting tool [°]; α - clearance angle of the sharp cutting tool [°].
Highlights
In machining of difficult-to-machine titanium alloys, brittle fracture of the cutting wedge occurs in the form of chipping and spalling, which is especially dangerous for indexable inserts made from cemented carbides commonly used in industry
The shear stress near the cutting edge of the cutting insert with small thickness (h=2 mm) exceeds the ultimate shear strength of cemented carbide (Figure 3a), which leads to destruction of a cutting part
In machining of titanium alloy (Ti6Al2Mo2Cr) with an insert having thickness equal to or less than 5 mm, high compressive stresses, which exceed the ultimate compressive strength of cemented carbide (WC8Co), arise near the cutting edge, which leads to chipping of the major cutting edge
Summary
In machining of difficult-to-machine titanium alloys, brittle fracture of the cutting wedge occurs in the form of chipping and spalling, which is especially dangerous for indexable inserts made from cemented carbides commonly used in industry. The investigations of stresses distribution were carried out to determine the optimal thickness of indexable inserts made from cemented carbide BK8 (WC8Co). 2. Research methods A finite element method along with ANSYS 14.0 software was used to calculate stresses in free orthogonal cutting of difficult-to-machine titanium alloy BT3-1 (Ti6Al2Mo2Cr). The distribution of specific contact loads on the face and on the flank surfaces was found experimentally It was found by the methods of a ‘split cutting tool’ and the artificial flank-land of the variable width in free orthogonal cutting of the difficult-to-machine titanium alloy (Ti6Al2Mo2Cr), having a constant geometry of the cutting part and with the following cutting conditions: (rake angle γ = 0°, cutting speed v = 1m/s, radial feed f = 0.21 mm/r, wear on the flank surface (artificial flankland) hf = 0.2 mm) [1].
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