C. Courbon

New Thermal Issues on the Modelling of Tool-Workpiece Interaction: Application to Dry Cutting of AISI 1045 Steel

The present work proposes to enhance the thermal interface denition in Finite Element (FE) simulations of machining. A user subroutine has been developed in Abaqus/Explicit

An Investigation of the Effect of Nitrogen Phase on Cryogenic Machining Performance and a Case Study on Machining of Inconel 718 Alloy

Sustainable manufacturing trends dictate the need for cleaner processes that are environmentally benign and with no adverse health effects. Cryogenic machining in recent times has emerged as such an effective and clean manufacturing process. In this field, a strong collaboration among partnering researches in the EU and US has been established. Prior research has proven that cooling effect in such sustainable machining operation is significant, while the lubrication effect is still either marginal or questionable. The nitrogen phase that is delivered to the cutting zone has a significant effect on this. The constant phase of the delivered fluid is first necessary condition to avoid the occurrence of thermal shocks. The first step in this direction for phase control is to be able to sense and accurately quantify the phase of the cryogenic fluid at the delivery. Therefore, this paper aims at presenting new experimental results on the use of a novel optical nitrogen phase sensor from the investigation of its robustness and response time. Additionally, a case study has been performed to show how the nitrogen phase affects the tribological properties of Inconel 718 alloy against a carbide tool. To examine this, experiments have been performed with a specially designed open tribometer to characterize the macroscopic friction coefficient and heat partition coefficient in the contact surface versus sliding velocity. Also, a simplified FEM model of cryogenic machining has been constructed to simulate the behavior of the machining process when delivering different phases of nitrogen. The delivered cryogenic fluid has been characterized in gas and liquid phases. It has been shown that liquid nitrogen can improve friction conditions more efficiently than gas phase nitrogen. Liquid phase has in general lower temperature and more dominant capability for heat evacuation and better lubrication properties than the gas phase, with the novel sensor being shown as capable of robustly characterizing the phase of the cryogenic fluid in the delivery itself.Copyright

Metallurgical Aspects of Material Behaviour in Cutting of AISI 1045

This contribution first aims at providing a more detailed analysis of the cutting mechanisms of a normalized carbon steel from a microscopic and metallurgical point of view. SEM and EBSD are used to highlight, in the main intensive deformation zones of the chip, a drastic grain refinement induced by a dynamic recrystallization process. The second part of this study intends to emphasize the consequences of the latter on the workmaterial behaviour. A rheological study based on dynamic compression tests is briefly presented and enables to understand their occurrence as well as their influence on the flow stress of the material. A metallurgy based constitutive equation is identified to reach a better description of the flow stress. Finally, this one is implemented in a Finite Element code (Abaqus/Explicit) to assess the potential of this method. It is shown that microstructural evolutions could be relatively well predicted especially when considering the level of recrystallization.

A First Step towards a Tribological Approach to Investigate Cutting Tool Wear

The present work is motivated by the will to improve Finite Element (FE) Modelling of cutting tool wear. As a first step, the characterisation of wear mechanisms and identification of a wear model appear to be fundamental. The key idea of this work consists in using a dedicated tribometer, able to simulate relevant tribological conditions encountered in cutting (pressure, velocity). The tribometer can be used to estimate the evolution of wear versus time for various tribological conditions (pressure, velocity, temperature). Based on this design of experiments, it becomes possible to identify analytically a wear model. As a preliminary study this paper will be focused on the impact of sliding speed at the contact interface between 304L stainless steel and tungsten carbide (WC) coated with titanium nitride (TiN) pin. This experiment enables to observe a modification of wear phenomena between sliding speeds of 60 m/min and 180 m/min. Finally, the impact on macroscopic parameters has been observed.