Avancees sur la controlabilite ultrasonore des materiaux et des structures

National audienceLa controlabilite d'un materiau ou d'une structure peut etre definie comme la facilite avec laquelle ils peuvent etre examines de facon non destructive, avec un diagnostic fiable. Nos travaux precedents introduisaient la notion de RC-CND, Regles de Conception issues du CND, permettant de faciliter le controle des structures. Par exemple, la forme d'un composant, son accessibilite, doivent etre anticipees de maniere differente si l'on prevoit un controle ultrasonore, ou radiographique. Nos recherches actuelles portent sur la nouvelle notion de RE-CND, Regles d'Elaboration issues du CND, qui seraient introduites en amont, dans les specifications siderurgiques, afin d'obtenir une qualite CND suffisante pour qu'un materiau soit controlable, notamment en termes d'attenuation des ondes et de bruit de structure. Les pieces non controlables en phase de fabrication (donc rebutees) seraient ainsi evitees, de meme qu'en service apres endommagement. Nous definissons d'abord la qualite ultrasonore d'un materiau (methode CND la plus utilisee), qui s'appuie sur des mesures fiables des parametres attenuation et vitesse des ondes, et bruit de structure. Pour cela, nous presentons la complexite de realisation d'echantillons representatifs de la microstructure (taille du grain, macles, precipites ...). La hierarchisation de l'influence des parametres permet d'avancer dans la comprehension des phenomenes, en vue d'une application industrielle

Acoustoelastic effect in concrete material under uni-axial compressive loading

International audienceno abstrac

POTENTIAL OF ULTRASOUNDS FOR NDT OF A STRUCTURE LOCATED BEHIND PARALLEL IMMERSED PLATES

International audienceThe in‐service inspection (ISI) of internal structures in future liquid sodium‐cooled fast reactors is studied in‐depth by the CEA. Among the different options available, ultrasounds from outside the sodium circuit can be used for this purpose. The need to propagate the maximum energy possible orientated the study towards Lamb waves. This study aims at controlling ultrasonic propagation in these multilayered structures in order to determine the best conditions for the NDT of a plate behind n screens

Etude de l'évaluation ultrasonore des contraintes dans les bétons

National audienceno abstrac

Study of acoustoelasticity behavior of concrete material under uniaxial compression

International audienceThe general subject concerns the non destructive testing of prestressed structures in civil engineering. In this topic we are interested in the feasibility of stress evaluation in concrete by ultrasonic methods. To do that, we use the acoustoelasticity theory which exploits the nonlinear behaviour of media to establish the link between stress and ultrasonic velocity. This theory has been validated in homogeneous media and used in steel (to evaluated stresses in steel bolt for example). Concrete is a heterogeneous medium where the ultrasonic velocity measurement is more difficult than in steel. The scattered waves induce uncertainty in the measured values but the nonlinear behaviour of concrete is more important than the one of steel. We show an application in high performance concrete submitted to uniaxial compression. We measure velocities of longitudinal and transversal transmitted ultrasonic waves in the direction and perpendicularly to the stress at different level of the stress test. The sensibility of the different velocities is observed and the potential to evaluate stress in concrete is shown. Prospects particularly concern extension of tested formulations and in situ measurements. This study is supported by ANR‐ACTENA, a French research program

Inspection specifications leading to extended ASTRID Design rules

International audienceCEA initiated a study in 2008 to improve the design rules of fast reactors with French utilities(EDF), French designers (AREVA) and non-destructive examination (NDE) specialists (Aix MarseilleUniversity), focusing on the specific issue of in-service inspection (ISI). Thus, at the end of 2012, the RCC-MRxspecifications for NDEs was enlarged, orienting design and manufacturing choices and rules to account forfuture in service inspection. Due to the complexity of the links between design, materials, access, inspectiontechniques and tools, these rules cannot be considered as strict instructions, but rather as leading to fruitfuldialogue between designers and inspectors. The links between in-service inspection and manufacturing processesand specifications are now being explored in further detail. This article describes the approach and RetDprogram in support of this specific work. This initiative should lead to better connections and compromisebetween design work, material specifications and in-service inspection, called RC-CND rules (Design rulestaking into account NDE requirements)