Simultaneous measurement of external and internal surface shape and deformation based on photogrammetry and stereo-DIC

Abstract

Mechanical structures with cavities such as auto rim and aero-engine casing are widely used in engineering. It is of great significance for their dynamic performance evaluation if one can measure the shape and deformation of the internal and external surfaces together. However, due to the narrow interior space and self-occlusion of complex structures, the conventional stereo-DIC unit is not applicable to impose the simultaneous measurement in the outer and inner areas. This paper is therefore concerned with a systematic solution for the issue. A reflection-assisted multi-view DIC system is configured, which consists of the stereo-DIC (SDIC) unit and the reflection-assisted stereo-DIC (RSDIC) unit. The design idea and selection essential of the RSDIC unit are stated. Subsequently, a correction model for reflection imaging is detailed. Close-range photogrammetry is specially adopted to compute the 3D global points. The extrinsic parameters of each DIC unit are estimated via the rear resection so that the individual reference frame can be transformed into a common coordinate system. Five experiments, including two tests of calibration accuracy, shape and deformation measurement accuracy, and applications in an aero-engine casing prototype, prove the precision and effectiveness of the proposed method.