Non-destructive evaluation and control

The aim of this theme is to characterize materials and structures (mechanical, acoustic properties, etc.), as well as to identify and characterize any defects (nature, position and dimensions), non-destructively.

The starting point for each study is the reality of the material and its use. All NDT techniques (ultrasonic, X-ray, eddy current, thermography, etc.) are considered before selecting a particular methodology. As ultrasonic waves are often the preferred method for testing and characterizing materials or structures, research activities in this theme focus mainly on modeling both the material and ultrasonic propagation, as well as appropriate experiments on test specimens representative of industrial issues.

The interaction between ultrasonic waves and the structure is studied in order to obtain, by inverse reasoning, the properties of the material and/or the characteristics of the defects sought. This requires a thorough understanding of the material being inspected and the stresses to which the structure is subjected, in order to predict the type of potential defect and provide an accurate and reliable diagnosis.

Permanent members : J.F. Chaix (Prof. AMU), G. Corneloup (Prof. Em. AMU), V. Garnier (Prof. Em. AMU), A. Geay (PAST AMU), C. Gueudré (MCF AMU), P. Lasaygues (IR CNRS), I. Lillamand (MCF AMU), J. Mailhé (MCF AMU), J. Moysan (Prof. AMU), C. Payan (Prof. AMU), M.A. Ploix (IR Protisvalor), S. Rakotonarivo (MCF AMU), M. Ramaniraka (MCF AMU)

Associated resource center : Contrôle et Evaluation Non Destructifs (CND-END)

NDT/END of metallic materials 

Soldering For many years now, there has been a growing interest in improving the ultrasonic testing of highly anisotropic metallic media. In particular, thick multi-pass welds in austenitic stainless steel feature columnar grains whose direction of growth depends on numerous parameters, such as the local thermal gradient during cooling. The resulting structure is highly anisotropic and spatially variable. The MINA model was developed to reproduce local grain growth without having to cut the weld. Knowledge of the local anisotropy can then be used to simulate ultrasound propagation and thus improve diagnosis.

Submerged multi-plate structures The main difficulty in controlling such structures lies in the loss of energy from plate to plate. Our work shows that the combination of leaky Lamb waves with the principle of time reversal (via the topological energy imaging method) not only makes it possible to control a plate behind one or two screens, but also to localize the detected defect.

Partially closed cracks The study of the characterization of the closed part of cracks in metal parts is of prime importance, as the closed part is invisible to conventional ultrasonic methods (using volume waves), implying that the cracks are undersized. Several avenues are being explored, particularly in the field of non-linear acoustics. The aim is to stress (always non-destructively) the closed part of the crack. This solicitation can take various forms: acoustic, thermal, etc., and enables better dimensioning of the actual crack to be envisaged.

Influence of microstructure

Ultrasonic propagation, and hence control, of metal parts is strongly influenced by microstructure (grain size, shape, orientation and distribution, quantity of macles, dislocations, precipitates, etc.). The aim here is to understand and analyze the influence of each parameter on ultrasonic velocity and attenuation, in order to improve controllability.

NDT for Civil Engineering

Non-destructive testing for civil engineering is a major validation element in research projects as well as in the construction and maintenance of structures. Analytical, experimental and numerical tools are developed in both linear and non-linear domains. These are multi-scale tools, complementary from the laboratory to on-site measurement. 

Concrete

Our research focuses on the early assessment of damage, gradients in the internal properties of concrete and the detection of defects, taking account of concrete microstructure in propagation models and analysis on a structural scale. The aim is to gain a better understanding and definition of the material in order to analyze wave-matter interactions and integrate them into models and experimental methods. The main inherent characteristics of concrete are its highly heterogeneous and naturally micro-cracked nature.

One of the solutions for monitoring the state of a structure, known as SHM, is to flood the first few tens of centimeters of concrete with translators using a variety of physical methods, including ultrasound. The data acquired is then processed either individually (signal processing, image processing, etc.) or as a whole (data fusion, etc.).

Another complex control situation is that of concrete tubes with a metal liner, the aim being to detect and characterize liner corrosion.

From a modeling point of view, the description of the Interfacial Transition Zone (transition zone between aggregates and cementitious matrix) is studied, with the aim of strengthening the link between the physics and acoustic properties (attenuation, phase and group velocity, diffusivity...) of aging concrete.

Dikes

On a macroscopic scale, the analysis of dike compactness is a recurrent topic in geophysics. The aim is to map the small-scale density heterogeneities (decimetric to metric) present in the near surface of a river dike foundation (of the order of ten meters), as part of the detection and localization of internal erosion signatures.

END for archaeology / heritage

Part of our research also concerns the characterization of human and animal bones for applications in archaeoanthropology (study of ancient and Paleolithic funerary rites) and zooarchaeology (study of conservation in taphonomy, and Paleolithic subsistence strategies through bone fracturing). There is an abundant literature on the identification of the physico-mechanical properties of various elements and portions of recent or early human or animal bones, but very few studies, other than densitometry, have been undertaken on prehistoric human or animal bones. The study of these bones represents a challenge for the acoustic engineering and paleoarchaeology communities.

END on trees

Organizational and human factors in NDT

The reliability of the results of non-destructive investigation methods depends on the skills and motivation of the people using them. Much progress has been made in modeling wave/material/defect interactions, enabling the use of realistic simulations and even virtual or augmented reality. New research is beginning to take account of organizational and human factors when estimating measurement reliability. The idea is to question the meaning of detection probabilities based on a set of deterministic, physical criteria, but estimated independently of human factors.