Micropipe flow visualization using digital in-line holographic microscopy

International audienceDigital in-line holography is used to visualize particle motion within a cylindrical micropipe. Analytical expression of the intensity distribution recorded in the CCD sensor plane is derived using the generalized Huygens-Fresnel integral associated with the ABCD matrices formalism. Holograms obtained in a 100µm in diameter micropipe are then reconstructed using fractional Fourier transformation. Astigmatism brought by the cylindrical micropipe is finally used to select a three dimensional region of interest in the microflow and thus to improve axial localization of objects located within a micropipe. Experimental results are presented and a short movie showing particle motion within a micropipe is given

A laboratory transmission diffraction Laue setup to evaluate single-crystal quality

International audienceA scanning laboratory Laue transmission setup is developed to probe extended quasi-monocrystalline samples. Orientation mapping is achieved by controlling the collimation of the incident beam and by scanning the position of the specimen. An automated indexing algorithm for transmission Laue patterns is presented together with a forward simulation model adapted for a laboratory setup. The effect of the main parameters composing the system is studied to aim for exposure time in the order of one second. Applications are presented to probe the orientation of an extended part and detect disoriented regions within the bulk. Finally the analysis of diffraction spot shapes showed that the misorientation within the illuminated volume can be measured and a new method is proposed to evaluate its complete mean lattice rotation tensor

Model-based dimensional NDE from few X-ray radiographs: Application to the evaluation of wall thickness in metallic turbine blades

The extraction of 3D dimensional measurements based on a limited number of 2D X-ray radiographs of a part would offer a significant speed up of quality control procedures in industry. However, there are challenges with respect to both measurements and uncertainties. This work addresses these questions by creating an estimated numerical model of the imaged part, on which dimensional measurements can be made. The numerical model is chosen as a parametric deformation model that encodes the expected variability of the part shape resulting from the manufacturing process. The parameters and uncertainties of the deformation model are estimated by the registration of the computed projections of the model and the observed radiographs. The proposed approach is applied to the NDE of turbine blades manufactured by investment casting, and in particular to the measurement of their wall thickness, which is a critical element. The deformable model consists in partitioning the inner ceramic core into multiple subparts, which may undergo a rigid body motion with respect to the master die. Wall thickness measurements are determined from the estimation of these rigid body motions. To assess the reliability of the proposed procedure, a repeatability study is performed, as well as a direct comparison with ground truth measurements from a reconstructed tomogram. Both of them show that such measurements are reliable and efficient. Furthermore, residual differences between captured and computed projections reveal localized shape deviations from the CAD model, meaning that despite localized model errors, the approach is operable