Abstract

Milling with minimum quantity lubrication (MQL) is now a commonly used machining technique in industry. This paper proposed an analytical model for residual stress prediction in milling with MQL based on chip formation orthogonal cutting model and boundary lubrication effect. The effect of lubrication is considered to the change of friction coefficients and the heat loss at the flank surface, which would further affect the prediction of the cutting force and temperature. The proposed model is validated with experimental data done to AZ61A magnesium alloy and obtained a reasonable validation result. The predictive results show at the case investigated, neither feed per tooth nor depth of cut has a significant influence to the general trend of residual stress, where at the surface the residual stress is highly tensile and come to compressive at deeper depth. However, the application of MQL is shown to be able to significantly reduce the average magnitude of the residual stress.

Highlights

  • Minimum quantity lubrication (MQL) is a commonly used technique in industry because of its effectiveness on the cost and its sustainable features

  • The generation of residual stress is often considered from three main sources: mechanical stresses led by plastic deformation, thermal stress led by material temperature changes, and volume changes led by phase changes of the materials [5]

  • This article presents an analytical model to the residual stress in end milling operation based on boundary layer lubrication condition and chip formation model in orthogonal cutting

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Summary

Introduction

Minimum quantity lubrication (MQL) is a commonly used technique in industry because of its effectiveness on the cost and its sustainable features. Su et al [15] furthered their research to milling operation by considering the cutting action into axial segment with the inclination angle of each slice same as the helix angle based on Li et al.’s work [16] This model is validated with milling data obtained in literature with Ti-6Al-4V. Masmiati et al [26] conducted experiments on end milling on S50C medium carbon steel to investigate the effect of lubricants on residual stress, cutting force and surface roughness. This article presents an analytical model to the residual stress in end milling operation based on boundary layer lubrication condition and chip formation model in orthogonal cutting. The proposed model is validated with data published in literature [30,31]

Analytical residual stress predictive model
Transferring end-milling condition into orthogonal cutting
Friction coefficient calculation under minimum quantity lubrication condition
Heat loss under MQL condition in orthogonal cutting
Temperature calculation in end milling with MQL
Mechanical stresses
Thermal stresses
The total elastic stress
Elastic-plastic incremental model
Experimental data validation
Discussion and conclusions
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