Characterization of the clamping and internal residual stresses effects on the distortion of Inconel 718 parts resulting from turning

Abstract

The understanding of phenomena related to machining processesintheaerospace industry isstill the subject of study intheresearch community. This is due to the constrained geometric tolerances to ensure optimal performance and safety. Few studies have yet focused on the effect of the clamping sequence on part distortions during the machining process. Thus, the development of machining sequences, in particular the positioning of clamping points, still requires optimisation regarding the geometry to be machined. This contribution focuses on a first step of a study that aims to characterize workpiece distortions resulting from a multi-stageprocess in relation tothe clamping, cutting forcesand the initial ormachining induced stresses. To validate the approach, an insitu methodology for characterising the defects has been developed alongside a particular workpiece holder based on an industrial procedure is set up in order to observe and limit the part distortion along the whole process.The machining sequence is divided into two machining stepsseparated by unclampingand clampingoperations. Frontal axisymmetric grooves are machined in turning on both sides of a thin Inconel718 elementary disks. These operations are subject to in situ measurement on bothside of the workpiece. A laser profilometer and laser point sensorsare usedbetween each pass and at each stage of the machining sequenceoperation. The collected data will beused in a next step to validate a numerical model that predicts the evolution of the distortions of the part during the entire machining process