A Methodology to Determine Work Material Flow Stress and Tool-Chip Interfacial Friction Properties by Using Analysis of Machining

Abstract

In this paper, we develop a methodology to determine flow stress at the machining regimes and friction characteristics at the tool-chip interface from the results of orthogonal cutting tests. We utilize metal cutting analysis originally developed by late Oxley and present some improvements. We also evaluate several temperature models in calculating the average temperatures at primary and secondary deformation zones and present comparisons with the experimental data obtained for AISI 1045 steel through assessment of machining models (AMM) activity. The proposed methodology utilizes measured forces and chip thickness obtained through a basic orthogonal cutting test. We conveniently determine work material flow stress at the primary deformation zone and the interfacial friction characteristics along the tool rake face. Calculated friction characteristics include parameters of the normal and frictional stress distributions on the rake face that are maximum normal stress σNmax, power exponent for the normal stress distribution, a, length of the plastic contact, lp, length of the tool-chip contact, lc, the average shear flow stress at tool-chip interface, kchip, and an average coefficient of friction, μe, in the sliding region of the tool-chip interface. Determined flow stress data from orthogonal cutting tests is combined with the flow stress measured through split-hopkinson pressure bar (SHPB) tests and the Johnson-Cook work material model is obtained. Therefore, with this methodology, we extend the applicability of a Johnson-Cook work material model to machining regimes.

Effect of rake angle on Johnson-Cook material constants and their impact on cutting process parameters of Al2024-T3 alloy machining simulation

“…Shrot [11] has also shown that based on the chip shape and the cutting force, it was possible to find different sets of material constants that lead to indistinguishable results such as chip morphology and cutting force for the same cutting condition. An alternative method known as the inverse method has also been developed based on machining tests used for characterization [10,[12][13][14]. The main advantage of such an approach is that extreme conditions such as strain rates up to 10 6 s −1 , temperature up to 1000°C and strains up to 4 are achieved directly with machining tests.…”

Experimental Characterization of Behavior Laws for Titanium Alloys: Application to Ti5553

“…The thermal softening effect is not inserted in restricted Johnson-Cook model. In [3], Ozel used also this model but in its complete definition with thermal softening effect. The target is to verify these assumptions and to see if it is always true in high mechanical and poor thermal properties materials.…”

“…In his paper, Ozel ([3]) uses the Oxley model ( [8]) to estimate the cutting temperatures. He shows in [3] that the cutting temperatures of Ti64 machining are range from 750°C to 940°C. Consequently, they are always less than the transus beta temperature.…”

“…[8] uses the Hollomon model and neglects the temperature and strain rate effects. [3], [11] and [12] use the Johnson-Cook law. Other models can be considered.…”

“…No cutting force model has been defined in his work. However, some works have been made on the cutting model and especially on Ti64 machining ( [3]). The machining is a process where stress appears according to strain, strain rate and temperature.…”