Investigation of thermoelastic and dynamic phenomena for improved design and control of manufacturing and tribological systems

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This proposal deals with two major issues; high performance machining processes, and predictive capability for fretting wear under complex excitation. These two issues are interrelated, since the integrity of machined surfaces control the tribological behaviour of the component. The proposal consists of the following elements (E1 to E5): ***E1. Integrated Laser Assisted Machining, Cryogenic Cooling and Minimum Quantity Lubrication: The objective is to investigate the synergetic effect of cryogenic cooling (LiN), minimum quantity lubrication on tool wear, productivity. and surface integrity in laser-assisted machining. Process optimized will defined through experimental investigation and process simulation. ***E2. Intermittent Drilling of Composites using Conventional and Superabrasive Tools: A predictive cutting force model was developed, based on a fundamental understanding of FRP composites cutting by a single diamond grain. The model will be extended to predict and optimize the orbital drilling process using superabrasive tools. Vibration-assisted drilling at high frequency-low amplitude regime will also be investigated using conventional tools. ***E3. Detection of Tool Pre-Failure in Turning Processes: The objective is to develop a system to detect unexpected tool breakage in machining. Various signals will be evaluated and special consideration will be given to feature extraction using different signal processing techniques in the time and frequency domains. A multi-sensor fusion model will be developed for 2-way communication with the NC controller. ***E4. Prediction of Machining-Induced Residual Stresses and Micro-structural Changes: A 2D FE model was developed to predict machining-induced residual stress (RS), assuming non-segmental chip formation. To improve prediction accuracy, it is proposed to consider the effects of chip segmentation, flank tool wear, and material phase transformation. For validation, oblique cutting experiments will be conducted for conventional and laser-assisted machining. ***E5. High Temperature Fretting Wear of Superalloys under Pseudo Random Excitation: Following the experiments on the role of surface oxide in fretting wear of cobalt-based superalloys at 550oC, a FE-based model was developed to estimate friction-induced temperature rise, considering the spatial and height random distributions of contact asperities. The applicant's `generalized fretting wear theory', will be extended by considering the effect of: (a) crack initiation and propagation due to frictional heating, (b) oxidation kinetics, and (c) random excitation; an aspect that has not been investigated before. **