The chip-flow behaviors and formation mechanisms in the orthogonal cutting process of Ti6Al4V alloy

Abstract

A B S T R A C TThis work involves experimental and analytical investigations of chip flow stability in metal cutting process. First, in cutting experiments of Ti6Al4V alloy, the transformation of chip morphology from continuous to serrated and later to discontinuous was observed as the cutting speed increased. Scanning electron microscopic (SEM) observation of the shear fracture surface demonstrated shear-localized instability and intergranular failure behaviors. Then we used the improved orthogonal cutting model (OCM) to analyze the plastic flow process of work materials in a plane strain state. A corresponding governing equation system was set up, the dimensionless governing parameters were determined by dimensional analysis, and an instability criterion was established by linear perturbation analysis. Analytical results showed that the plastic instability of chip flow could take place in a continuous chip, which is different from the shear-localized instability in a serrated chip. Finally, in terms of the balance conditions between the kinetic energy and the surface energy, the sawtooth growth behavior in serrated chips and the formation mechanism of discontinuous chips were studied.

Material embrittlement in high strain-rate loading

“…Wang et al [94] studied the ductile-to-brittle transition in machining and found that as strain rate increased, chip morphology changed from the continuous to discontinuous types. Ma et al [95] carried out a high-speed orthogonal cutting experiment of TC4 on a modified SHPB and found that the brittle fracture occurred on the free surface of the chips. They also found that brittle fracture increased while ductile fracture decreased with an increase in cutting speed.…”

Failure mode change and material damage with varied machining speeds: a review

“…Its mechanical framework, named as ASB onset system, was established by Wright and Batra in the 1980s [5]. The mechanical framework was subsequently modified by many researchers to define more applicable systems [6][7][8][9][10][11][12][13] for HSM. By applying appropriate boundary and initial conditions, these systems can be solved using numerical methods, such as the finite difference method.…”

“…By applying appropriate boundary and initial conditions, these systems can be solved using numerical methods, such as the finite difference method. Additionally, these systems can be handled by the perturbation method to establish ASB onset criteria [8,11,[13][14][15][16]. These criteria are convenient to assess if the ASB occurs under specific conditions.…”

On the Machinability Evolution in Asymmetric Milling of TC25 Ti Alloy Aiming at High Performance Machining

“…Yang et al [ 10 ] concluded that using a low cutting speed, large feed per tooth, and a large cutting depth could reduce the generation of saw-tooth-shaped cutting chips. Ma et al [ 11 ] experimentally analyzed the stability of chip flow in cutting Ti6Al4V alloy. It was observed that the chip morphology transformed from continuous to saw-tooth-shaped and then serrated cutting chips with the increase of cutting speed.…”