Modelling, simulation and experimental validation of tool flank wear during orthogonal turning process with stick-slip friction

Arti Siddhpura

    Research output: ThesisDoctoral Thesis

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    [Truncated abstract] The objective of this research work is to study the flank wear taking place during orthogonal turning considering stick-slip friction taking place at the flank-workpiece interface by developing mathematical model, carrying out numerical simulations and validating the results through experiments. Flank wear is the most commonly observed and unavoidable phenomenon in metal cutting which is also a major source of economic loss resulting due to material loss and machine down time. The worn tools adversely affect the surface finish of the workpiece; and they can be replaced in time if a tool wear monitoring system is used. As cutting progresses, the freshly generated workpiece surface comes into contact with the flank face and friction takes place at the interface. As a result of friction, flank wear occurs. Increasing flank wear results in an increase in the contact area at the flankworkpiece interface. This in turn increases the coefficient of friction and due to this stick slip vibration is likely to occur. The friction at the flank-workpiece interface is still considered as complex but the occurrence of stick-slip as a result of flank wear can be utilized to develop tool wear monitoring systems. Turning is one of the oldest and most widely used processes of metal cutting. The initial phase of work was concerned with a thorough literature review to investigate various flank wear modelling efforts as well as flank wear monitoring techniques and their implementation in a Tool Condition Monitoring System. It was evident from the review that in spite of almost a century old efforts in the direction of modelling flank wear and its effect on force, vibrations and sound emissions, no mathematical model to correlate stick-slip friction with flank wear has been identified yet. In order to develop mathematical model, the equations of motion of the cutting tool were derived considering stick-slip friction taking place at the flank-workpiece interface, and the resulting forces acting on the tool flank were correlated with flank wear. The effect of friction on the tool flank wear was studied using MATLAB simulations and an increase in the amplitude of tool vibration, worn tool cutting forces and coefficient of friction with increasing flank wear were observed. Based on the findings obtained from the MATLAB simulations, an experimental investigation was carried out. An experimental test rig comprising of a Macson lathe and various sensors (a triaxial dynamometer, two accelerometers and a microphone) along with a data acquisition system (NI PCI/PXI 4472 and a personal computer) was used to perform facing operations. A number of facing tests were carried out in order to check the effects of various process parameters on the behaviour of the signals for sharp and worn tools. The acquired signals were analysed in the time domain and the frequency domain to obtain an overview of the effects of the cutting conditions on tool life and flank wear. Analysis and discussion of results was carried out in order to understand the effect of increasing flank wear under stick-slip friction on the cutting forces, vibrations and sound emitted from the cutting process. Also, time domain analysis of the occurrence of stick-slip events has been carried out...
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2013


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