Non destructive evaluation of absorbing materials using microwave stimulated infrared thermography

The electromagnetic wave nondestructive evaluation methods that appeared some years ago are attractive because many materials can absorb hyperfrequency energy. Nevertheless, generally the detections are achieved point by point which is highly time consuming for NDE of extended structures. We developed a global method which associates electromagnetic stimulation and a detection by an IR camera (EMIR method). For others applications, this method has been used over the past several years [1,2]. The aim of this paper is to give the first results about the possibilities of this new method for NDE

Detection of Open Cracks by a Photothermal Camera

The number of methods which allows for non destructive testings of opening cracks is always increasing but, for industrial applications, the visual testings are still the most widely used especially during the processing steps and the maintenance operations. Among these visual techniques, penetrant testing is one of the most popular methods because its cost is very tow and its versatility is large. Nevertheless, sometimes, this simple technique cannot be used. A few typical cases should be mentionned : unsecured human interventions, forbidden contact with the surface specimen, possibility of false alarms when the surface roughness is important, necessity of an automatised control

A Critical Review on the Structural Health Monitoring Methods of the Composite Wind Turbine Blades

With increasing turbine size, monitoring of blades becomes increasingly im-portant, in order to prevent catastrophic damages and unnecessary mainte-nance, minimize the downtime and labor cost and improving the safety is-sues and reliability. The present work provides a review and classification of various structural health monitoring (SHM) methods as strain measurement utilizing optical fiber sensors and Fiber Bragg Gratings (FBG’s), active/ pas-sive acoustic emission method, vibration‒based method, thermal imaging method and ultrasonic methods, based on the recent investigations and prom-ising novel techniques. Since accuracy, comprehensiveness and cost-effectiveness are the fundamental parameters in selecting the SHM method, a systematically summarized investigation encompassing methods capabilities/ limitations and sensors types, is needed. Furthermore, the damages which are included in the present work are fiber breakage, matrix cracking, delamina-tion, fiber debonding, crack opening at leading/ trailing edge and ice accre-tion. Taking into account the types of the sensors relevant to different SHM methods, the advantages/ capabilities and disadvantages/ limitations of repre-sented methods are nominated and analyzed

Pathways to sustainability: a critical review of the sustainable development paradigm

Different methods of NDT of carbon-epoxy laminates have been used up till now, including ultrasonics, X-ray photography and vibrothermography. Thermal methods are now appearing, because they can be contactless and single ended [1–3]. Among these methods, pulsed back emission photothermal radiometry seems attractive because it is a simple method, where elasticity is uncoupled. So the possibility of quantitatively characterizing delaminations is offered, as the model describing the phenomenon is simple. Results recently obtained at the Office National d’Etudes et de Recherches Aérospatiales (ONERA) are presented here to demonstrate that the method is well suited to the detection, in-depth localization and characterization of delaminations in carbon-epoxy composites

Dimensioning and location planning for wireless networks under multi-level cooperative relaying

This paper studies the problem of network dimensioning and location planning in multi-hop wireless networks. A key technology of wireless multi-level cooperative relaying (CR) is incorporated, which has been recognized as an effective design paradigm for achieving throughput enhancement. A mathematical formulation is presented to capture the nature of the problem, and characterize the behavior of multi-level CR. The tasks of dimensioning, relay placement, relay allocation, and relay sequence design have been considered in a unified optimization framework. The formulation is a nonlinear integer program. To avoid the intractable computation complexity in solution, an efficient two-phase algorithm is developed. We conduct a series of case studies to verify the proposed algorithm, in which the results demonstrate the efficiency of our proposed algorithm and the significant benefits in terms of deployment cost reduction under multi-level CR. © IFIP International Federation for Information Processing 2009.link_to_subscribed_fulltex

Advanced thermal imaging techniques for quantitative damage mapping of composite materials

International audienceWith today’s advanced processing data, such as the Thermographic Signal Reconstruction (TSR), pulse thermography has become a relevant and reliable NDT technique for the inspection of composite materials. Recent developments have even shown how it was possible to produce a unique thermal image including all useful data for defect detection. However two steps have still to be crossed by: the applicability of such processing techniques to real-life damage, whether occurring right after the manufacturing process or induced by accidental events, such as low-velocity impacts ; the possibility to associate these thermal images to actual quantitative information, such as the defect depths.The present paper addresses both aspects by introducing an industrially-applicable two-step procedure leading to the production of thermal depth-mappings comparable to standard ultrasonic D-scans

Common tools for quantitative pulse and step-heating thermography -Part II: experimental validation

International audienceSeveral advanced pre- and post-processing tools have been developed over the last two decades, to enhance the performances of pulse thermography, in terms of defect detection and characterization. Two of the most efficient techniques are the Thermographic Signal Reconstruction, including a recent development using the polynomial coefficient images, and the early detection. This work, which shows how these tools, commonly used for pulse-heating, are complementary and applicable to step-heating, is in two parts: the first one, reported in a companion article, is dedicated to the theoretical and analytical demonstration; the second one, reported here, is the matching experimental investigation

Common tools for quantitative pulse and step-heating thermography - Part I: theoretical basis

International audienceSeveral advanced pre- and post-processing tools have been developed over the last two decades, to enhance the performances of pulse thermography, in terms of defect detection and characterization. Two of the most efficient techniques are the Thermographic Signal Reconstruction (TSR), proposed by Shepard et al. in 2001, including a recent development based on the use of the polynomial coefficient images proposed by Roche et al. in 2014, and the early detection at emerging contrast, proposed by Krapez et al. in 1994. The stake of this work is to show how these tools, commonly used for pulse-heating, can be applied to step-heating.The work was divided in two parts: the theoretical and analytic study is reported in the present article; the matching experimental results are discussed in a second, separate article

Pulsed Photothermal Nondestructive Testing — Application to Carbon Epoxy Laminates

Different methods of NDT of carbon-epoxy laminates have been used up till now, including ultrasonics, X-ray photography and vibrothermography. Thermal methods are now appearing, because they can be contactless and single ended [1–3]. Among these methods, pulsed back emission photothermal radiometry seems attractive because it is a simple method, where elasticity is uncoupled. So the possibility of quantitatively characterizing delaminations is offered, as the model describing the phenomenon is simple. Results recently obtained at the Office National d’Etudes et de Recherches Aérospatiales (ONERA) are presented here to demonstrate that the method is well suited to the detection, in-depth localization and characterization of delaminations in carbon-epoxy composites.</p