Experimental and Finite Element Modelling of High Speed Machining Process: Establishing Integrity of Model Input

Despite many recent developments in manufacturing technology, machining remains the most widely used process in the production of various products and has tremendous economic impact. Important developments in this technology include High Speed Machining (HSM) and dry cutting. The benefits of HSM include high material removal rates, lower cutting forces, reduced cycle time and improved surface finish. Dry cutting reduces the cost of lubricants and promotes more environmental friendly machining. However, dry HSM is characterised by high interface temperature and consequently high tool wear rate. In machining, simulations based on the Finite Element Method (FEM) can be used to analyse the effects of the process conditions and tooling on cutting variables. The output from Finite Element (FE) simulation gives information about difficult to measure machining parameters such as distribution of temperature and stresses in the cutting tool. However, the accuracy of FEM simulations is highly influenced by the quality of input data. Physical and thermomechanical properties of the tool and the workpiece material, tool-chip interface phenomena such as interface friction, and interface heat transfer coefficient are important input parameters for FE modelling of machining processes. Literature review highlighted that such input data is not well established for a wide range of cutting speeds and in particular for the HSM process. The work reported in this thesis developed a methodology to provide reliable input data for FEM simulations of HSM processes. The workpiece and tooling material selected for the study was AISI 1045 steel and P10/20 carbide. The former is well characterised. The research has made significant and novel contributions, both methodological and conceptual, in the area of modelling of metal cutting process. With the aim to characterise the interface phenomena at the tool chip interface at high cutting speed, successful modelling strategy is presented which covers comparisons of the flow stress material models, definition of interface friction, evaluation of interface heat transfer coefficient and determination of stress distribution along the tool rake face for a wide range of cutting speeds. The implementation of cutting speed dependent friction distribution schemes show marked improvement in simulation results at high cutting speeds. Evaluation of the tool-chip contact length and examination of tool rake face sticking/sliding contact phenomenon was undertaken using SEM/EDXA compositional analysis and white light interferometry for tool rake face topology. A novel approach based on a pin-on-workpiece rubbing setup was used to evaluate the interface heat transfer coefficient between the workpiece and tool materials for a wide range of speeds. Additionally the stress distribution along the tool rake face was established for different cutting speeds using the split tool dynamometer technique. The established tool chip contact phenomena and material flow stress data were accommodated in the development of an FE model. The model was used to predict shear angle, contact length, chip morphology, cutting forces and rake stress distribution over a wide range of cutting speeds. The results show that the model inputs established in this project help to significantly improve the capability of FEM models when applied to the HSM regime.