Demodulation of Spatial Carrier Images: Performance Analysis of Several Algorithms Using a Single Image

http://link.springer.com/article/10.1007%2Fs11340-013-9741-6#Optical full-field techniques have a great importance in modern experimental mechanics. Even if they are reasonably spread among the university laboratories, their diffusion in industrial companies remains very narrow for several reasons, especially a lack of metrological performance assessment. A full-field measurement can be characterized by its resolution, bias, measuring range, and by a specific quantity, the spatial resolution. The present paper proposes an original procedure to estimate in one single step the resolution, bias and spatial resolution for a given operator (decoding algorithms such as image correlation, low-pass filters, derivation tools ...). This procedure is based on the construction of a particular multi-frequential field, and a Bode diagram representation of the results. This analysis is applied to various phase demodulating algorithms suited to estimate in-plane displacements.GDR CNRS 2519 “Mesures de Champs et Identification en Mécanique des Solide

Experimental Analysis of the Shot Peening Particle Stream Using Particle Tracking and Digital Image Correlation Techniques

The conventional air pressure shot peening process consists of multiple impacts of particles propelled with pressurized air through a nozzle at the surface of mechanical components. An experimental study of the flow of particles exiting the nozzle was conducted. A high speed camera was used for image acquisition of the particle flow. This particle flow was analyzed using a particle tracking (PT) technique and using a digital image correlation (DIC) technique. Those two methods were compared and applied to the characterization of an industrial shot peening flow with several parameters of jet pressure and mass flow rate.IRT M2

Development of a full-field displacement measurement technique at the microscale and application to the study of strain fields in a tensile steel specimen

International audienc

Characterization of the mechanical behaviour of materials at a microscopic scale : development of a optical full-field measurement method

International audienc

Optimization of the unnotched Iosipescu test on composites for identification from full-field measurements

Publié suite au congrès Modern Practice in Stress and Vibration Analysis VIInternational audienceThe paper presents the use of an optimization routine in order to find the best combinaison of free length and fibre angle in an unnotched Iosipescu test processed with the virtual fields procedure are used to build up a cost function aiming at balancing out the different coefficients of the three main orthotropic stiffnesses so that the same confidence level can be reached on these three stiffnesses. Then, experimental validation was performed using an ESPI system. Full-fields were measured and stiffnesses identified and compared to the usual 0°,30 nm configuration. The outcome of the optimization was confirmed by testing the same specimen result on the way to the design of a new test for orthotropic stiffness identifaction on a single specimen form full-field measurements

Identification of Orthotropic Elastic Stiffnesses of Composites with the Virtual Fields Method: Sensitivity Study and Experimental Validation

This paper presents the use of a sensitivity study to find the best combinations of free length and fibre angle in an unnotched Iosipescu test processed with the virtual fields method. The sensitivity to noise coefficients arising from the special virtual fields procedure are used to build up a cost function. This function is aimed at balancing out the coefficients of the different orthotropic stiffnesses so that the same confidence level can be reached on all these parameters. Then, experimental validation was performed using a speckled interferometry (ESPI) system. Full-field strains were measured and stiffnesses identified and compared between the usual 0°, 30 mm configuration and an improved 25°, 40 mm configuration. The outcome of the optimisation was confirmed by testing the same specimen several times and comparing scatter between the two configurations. This is a first promising result on the way to the design of a new test for orthotropic stiffness identification on a single specimen from full-field measurements

Identification of shear bands in wrought magnesium alloy friction stir welds and laser beam welds

The microstructural study of hot rolled magnesium friction stir and laser beam welds revealed the presence of shear band features starting from the weld edge and propagating in the base metal. These shear bands present a highly twinned microstructure and strain localisation occurs preferentially in this region. This influences the resulting mechanical properties of wrought magnesium alloy friction stir and laser beam weld

Methodology for metrological analysis of periodic coding images: measurement resolution and spatial resolution

Optical full-field techniques have a great importance in modern experimental mechanics. Even if they are reasonably spread among the university laboratories, their diffusion in industrial companies remains very weak for several reasons, especially a lack of metrological performance assessment. A full-field measurement can be characterized by its resolution, bias, measuring range, and by a specific quantity, the spatial resolution. The present communication proposes an original procedure for the estimation in one single step of the resolution, bias and spatial resolution for a given operator (decoding algorithm, such as image correlation, low-pass filters, derivation tools, ...). This procedure is based on the construction of a particular multi-frequential field, and a Bode diagram representation of the results. This analysis is applied to various phase demodulating algorithms for the estimation of in-plane displacements