INVESTIGATION OF THERMOELASTIC AND DYNAMIC PHENOMENA FOR IMPROVED DESIGN AND CONTROL OF MANUFACTURING AND TRIBOLOGICAL SYSTEMS

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This proposal deals with high performance machining processes and the prediction of fretting wear under complex excitation. These issues are interrelated, since the integrity of machined surfaces controls its tribological behaviour. Four projects P1 to P4 are proposed: P1-Development of a real-time tool wear prediction, and pre-failure detection system In Phase-1, a novel approach was developed to detect and stop the turning operation before tool chipping (within 20 milliseconds). The objective of the proposed work is to extend this approach to monitoring tool wear level and to detect tool pre-failure in high speed milling of Ti alloys and difficult-to-cut materials, where thermal effects have significant effect. The system should also be operating in the presence of an adaptive control system. Outcome and impact: It is anticipated the proposed system will be unique and can reduce the cost by 20%. P2-Process development for cryogenic deep-hole drilling Building on the success in Phase-1 for turning, the objective is to develop a cryogenic deep hole drilling process, using liquid nitrogen (LiN), overcoming the challenge of injecting LiN in a confined space through a rotating tool. Combining LiN with a minimum quantity lubrication (MQL) jet will be investigated, through CFD modeling to understand the flow characteristics of the dual LiN and MQL jets when supplied through the tool. Comparison between the performance of LiN and supercritical CO2 cryogens will be carried out. Outcome and impact: Compared to flood cooling of Ti6Al4V, it is anticipated that the tool life improvement will be ~ 100% and the environmental impact will be two orders of magnitude. P3-Development of a mixed-regime vibration-assisted drilling (VAD) process for hybrid stacked composites-metal structure The objective is to develop a novel mixed-regime VAD process that superimposes low frequency-high amplitude (LFHA ) and high frequency-low amplitude (HFLA) excitations to explore the possibility of gaining the benefits of both regimes and to allow adaptive control of the process through adjustment of the frequency/amplitude levels and/or the feedrate when drilling FRP/metal stacks. Outcome and impact: From simulation results, it is anticipated that the reduction in forces and temperature will exceed the individual benefits of each regime. As enabling technology, this development will overcome the challenges of robotized machining of stacked structures. P4-Modeling and experimental investigation of fretting wear under random vibration The main objective is to extend the `generalized fretting wear theory' proposed by the applicant to predict the damage under random excitation, and to develop a new experimental methodology for the standardization of fretting wear tests under random excitations. Outcome and impact: Preliminary test results showed that conventional sinusoidal excitation testing is non-conservative and could have significant safety and economic implications.