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

Electromagnetic health monitoring system for composite materials

A model of electromagnetic behavior o f composite materials such as carbon epoxy or glass epoxy structures has been developed. Based on this model, an electromagnetic method to evaluate the electric conductivity and the electric polarization of this type of material, by measurement of magnetic and electric components of an incident electromagnetic field crossing through the material, has been also developed. A Health Monitoring System (HMS) derived from this technique is presented, which allows to detect and characterize a wide variety of defects inside composite structures. The HMS is constituted of emitting and receiving networks sensitive to magnetic or electric fields, integrated into the composite structure. This system delivers electric images in which the damages can be detected and localized. Various electric images obtained by each type of measurement (magnetic and electric) and related to structures including various damages such as impact delamination, fiber breaking, local burning and liquid ingress, are presented and compared to images resulting from classical ultrasonic NDE. The complementary of the present technique with acousto-ultrasonic technique based on Lamb waves propagation, and the interest of combining them in a unique integrated system is evoked

Photomécanique

Issu du Congrès Photomécanique 2004 (Jun. 2004, Albi, France)National audienc

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.</p

Optimization of the photothermal camera for crack detection&apos;, QIRT open archives,

Abstract We present recent advances about the application of the photothermal camera for the detection of cracks on metallic surfaces of industrial quality. We describe a normalization procedure designed to clean the photothermal images of the optical noise and thereby to increase the propability of detection of the cracks. A theoretical analysis about the spatial resolution of the photothermal camera is finally exposed

Quantitative assessment of the improvement of the detection of defects by pulse thermography thanks to the TSR approach in the case of a smart composite repair patch

Abstract The work aims to assess quantitatively the improvement given by using the Thermographic Signal Reconstruction (TSR) approach to the detectivity of defects in structures. The considered structure is a smart composite repair patch used in aeronautics. Artificial defects simulating a debond at the patch/structure interface are to be detected. The signal to noise ratio of the defect in the sound structure background is calculated as an index of detectivity. A strategy is proposed for optimizing the time of observation allowing the best detection and characterization