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

Human rights, non-refoulement and the protection of refugees in Hong Kong

Although the 1951 Convention relating to the Status of Refugees and its 1967 Protocol do not apply to Hong Kong, asylum seekers have challenged Hong Kong's lack of an adequate refugee policy in a series of judicial review actions grounded in human rights and common law principles. This article focuses on two cases in particular in which the applicants have attempted to rely, in part, on a right to non-refoulement, derived from international and domestic law, to compel the Government to establish procedures to determine the status of refugees and other similar categories of claimants. The first, Secretary for Security v. Sakthevel Prabakar, led to the creation of a 'torture screening' mechanism based on article 3 of the Convention against Torture and other Cruel, Inhuman, or Degrading Treatment or Punishment. In the second, C v. Director of Immigration, the court considered whether a rule of non-refoulement has emerged in customary international law and, if so, whether it applies to Hong Kong and requires government-administered refugee status determination. Although the applicants failed at first instance,1 an analysis of the judgment with reference to Hong Kong's human rights obligations reveals gaps in the court's reasoning and demonstrates the potential for greater reliance on these standards as the basis for developing a more comprehensive protection framework. This examination of the Hong Kong experience may have broader comparative value, especially in the Asian region and in jurisdictions not bound by the Refugee Convention or its Protocol. © The Author (2010). Published by Oxford University Press. All rights reserved.postprin

Picosecond Transient Thermoreflectance: Time-Resolved Studies of Thin Film Thermal Transport

The advent of new and sophisticated material growth processes (molecular beam epitaxy, chemical vapor deposition and ion sputter deposition) has produced new exotic materials such as amorphous alloys and compositionally modulated structures [1]. The atomic level structure of these materials can be proved by techniques such as x-ray diffraction. The electrical and thermal transport properties are also used to characterize these materials, which are usually deposited as thin films onto supporting substrates. Although the substrate may be electrically isolated from the film, complete thermal isolation is more difficult to achieve and thermal transport measurements are complicated.</p

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

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

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.</p

Bonds Nde Using Stimulated Infrared Thermography

Among all the photothermal techniques that have appeared since some years, the photothermal radiometry is very attractive because of its noncontact and rapid-scanning ability [1,2]. In our laboratory, we developed pulsed stimulated infrared (IR) thermography [3]. Due to the relatively low refreshment frequency of the currently used IR cameras, the application of the method was restricted to low thermal conductors. In particular, we applied it to carbon/epoxy composites [4,5]. Some new developments of the data reduction procedure were presented last year [6] to use this technique with good heat conductors. Satisfactory results were obtained in the case of delaminations in C/C composites. We present here an improvement of this data reduction procedure which is able now to work with any kind of material. We will focus our attention on the especially difficult case of the characterization of adhesive joints in metallic structures.</p

Quantitative Nondestructive Evaluation of Carbon-Carbon Composites by Pulsed Infrared Thermography

Among all the nondestructive evaluation (NDE) techniques that are used in industry, Stimulated Infrared Thermography (SIRT) is very attractive because of its noncontact and rapid-scanning ability [1]. In our laboratory, we applied this technique to composite materials which are often used in aerospace structures. In particular, we applied it to carbon/epoxy composites [2,3]. Due to the relatively low refresh frequency of the monocell IR cameras, the application of the method was restricted to low thermal conductors. Some new developments of the data reduction procedure were presented last year [4] to use this technique with good heat conductors. Satisfactory results were obtained in the case of delaminations in carbon/carbon (c/c) composites which will constitute the hottest parts of the thermal protection of the european space shuttle Hermes. A few months ago, we presented an improvement of this data reduction procedure which is able now to work with any kind of material and we applied it on the especially difficult case of the characterization of adhesive joints in metallic structures [5]. We present here the last results obtained in c/c composites by our SIRT techniques with the new data reduction procedure.</p