Structural analysis for flexible components with freeform surfaces with the aid of a coordinate measuring machine

A non-rigid part could be subjected to significant distortion after the removal of manufacturing forces. This condition, known as free state variation, is principally due to weight and flexibility of the part and the release of internal stresses resulting from fabrication. The present work deals with the inspection of freeform surfaces belonging to non-rigid parts with the objective of analysing the internal stress and relative strain due to assembly sequences. A manufactured aeronautic component, named Mid Cowling, is considered as a case study. An appropriate fixture equipment has been used in the inspection process to simulate the mating part interface and to locate the part in the coordinate measuring machine (CMM) working volume. In this way the assemblage in the final product has been reproduced. The results of the measurement process are used to evaluate the quality of the real surfaces in terms of deviation from the nominal one. Therefore, these deviations are used as input in a finite element model (FEM) analysis to estimate the stress and strain fields due to the constraint of the assembly.