Numerical modelling and mechanical analysis of the machining of large aeronautical parts : Machining quality improvement

Abstract : The manufacturing of aluminium alloy structural aerospace parts involves multiple forming (rolling, forging, etc.) and heat treatment steps. The mechanical and thermal loads that the workpieces undergo during these manufacturing steps result in unequal plastic deformation and in metallurgical changes which are both sources of residual stresses. Machining is usually the last manufacturing step during which the final geometry of the parts is obtained. Up to 90% of the initial volume of the workpiece can be removed during the machining of aerospace structural parts which can furthermore have complex geometries. The residual stress redistribution is one of the main causes of the non-conformity of parts with the geometrical and dimensional tolerance specifications and therefore of the rejection of parts.Nowadays, initial residual stresses and their effect during the machining are often not taken into account in the definition of the machining process plan. This work aims to propose an evolution in the establishment of machining process plans of aluminium structural parts. It has been organised along two principal lines of research: a numerical line and a mechanical analysis line.The numerical line is based on the development of a modelling approach and of a numerical tool adapted to the simulation of the machining process. The modelling approach has been defined based on assumptions deduced from literature reviews on aluminium alloys, on the machining process and on residual stresses. A massive material removal approach has then been developed. All the numerical developments have been implemented into the finite element software FORGE® and are suited to a parallel computing environment.The mechanical analysis line is based on the study of the residual stress redistribution and its effect on the workpiece deflections during the machining as well as on the post-machining distortion. A first study on the layer removal method used to determine the initial residual stress profiles in an AIRWARE® 2050-T84 2050-T84 alloy rolled plate has been realised. The simulation of these experiments has allowed a first validation of the numerical tool and to demonstrate the necessity to define machining process plans in function of the residual stresses. Other studies on the influence of some machining process parameters on the machining quality have then been performed. Simulation results have been validated by multiple comparisons with experimental tests, showing the capability of the numerical tool to predict the final machined part geometries.Using the results of the studies mentioned above, a numerical procedure and first recommendations for the definition of machining process plans allowing to obtain the desired machining quality depending on the initial residual stresses have been established.
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  • HAL Id : tel-01132857, version 2

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Xavier Cerutti. Numerical modelling and mechanical analysis of the machining of large aeronautical parts : Machining quality improvement. Mechanics of materials [physics.class-ph]. Ecole Nationale Supérieure des Mines de Paris, 2014. English. ⟨NNT : 2014ENMP0029⟩. ⟨tel-01132857v2⟩

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