Digital 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 100microm 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.

We propose in this paper an analytical solution to the problem of scalar diffraction of a partially coherent beam by an opaque disk. This analytical solution is applied in digital in-line holography of particles. We demonstrate that the reconstruction by means of fractional Fourier transformation is still possible when a spatially partially coherent beam is used. Numerical simulations and experiments have been carried out.

Background: As aerospace cast parts move to more complex geometries, the impact of process variabilities must be evaluated more precisely to provide new, less empirical acceptation criteria. However, experimental lifetime assessment with Thermal Gradient Mechanical Fatigue (TGMF) are still complicated to reproduce in a laboratory environment. Objective : This paper investigates the impact of geometrical variability on thermo-mechanical fatigue life of Nickel-based superalloy single crystal parts. Methods : To this end, hollow specimens with cooling holes drilled in their centre have been produced with parametrized variations of the wall thickness and have been characterized by Xray tomography. An experimental fatigue setup operating at 1100 • C, with a thermal gradient of 50 • C across the wall, has been developed to assess the life of each specimen. Results : Experimental lifetime assessment were conducted on a sample of specimens containing geometrical defects. Optical observations during the tests have permitted to study crack initiation and propagation in the vicinity of the cooling hole, an area of high thermal and stress gradients where damage localize. Axial strains (in the loading direction) were also gathered and TGMF on Cooling Holes compared to prove the impact of process variabilities on mechanical behaviour. Conclusions : Significant mechanical differences are observed during the tests which can related to the geometrical variations of the specimens and their interaction with the shaped hole. Tests results will be further used to calibrate a creep-fatigue model for lifetime predictions.

Artifacts due to imperfect determination of the scanner geometry, beam hardening and diffuse Compton scattering, limit the quantitative exploitation of radiographs or tomographies for non-destructive evaluation. Exploiting the CAD model of an industrial part, a methodology is proposed to refine the estimation of the CT-scanner geometry up to a scale factor, to correct or account for artifacts, and to assess the metrology of the part. A projective model describing the formation of X-ray images in CT-scanners is first introduced. The optimal parameters of the projective model are identified using a novel CAD-based calibration method that relies on the registration of simulated projections onto experimental ones. A metrological analysis based on the comparison between acquired and simulated X-ray images is proposed. A turbine blade, for which an automatic inspection procedure from few views is under development, is used as an example to illustrate the proposed methodology. The parametrization accounts for the refinement of the projection geometry, the calibration of beam hardening and the estimation of scattering. It is shown that, using the proposed procedure, the differences between acquired and simulated radiographic images are significantly reduced, indicating that the optimal parameters are properly identified. These differences are then exploited to detect flaws of the part.

Wavelet analysis provides an efficient tool in numerous signal processing problems and has been implemented in optical processing techniques, such as in-line holography. This paper proposes an improvement of this tool for the case of an elliptical, astigmatic Gaussian (AEG) beam. We show that this mathematical operator allows reconstructing an image of a spherical particle without compression of the reconstructed image, which increases the accuracy of the 3D location of particles and of their size measurement. To validate the performance of this operator we have studied the diffraction pattern produced by a particle illuminated by an AEG beam. This study used mutual intensity propagation, and the particle is defined as a chirped Gaussian sum. The proposed technique was applied and the experimental results are presented.