This PDF file contains the front matter associated with SPIE Proceedings Volume 6939, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We report infrared micro-thermography measurements and analysis of static and transient temperature maps of an actively heated micro-fabricated preconcentrator device that incorporates a dual serpentine platinum heater trace deposited on a perforated polyimide membrane and suspended over a silicon frame. The sorbent coated perforated membrane is used to collect vapors and gases that flow through the preconcentrator. After heating, a concentrated pulse of analyte is released into the detector. Due to its small thermal mass, precise thermal management of the preconcentrator is critical to its performance. The sizes of features, the semi-transparent membrane, the need to flow air through the device, and changes in surface emissivity on a micron scale present many challenges for traditional infrared micro-thermography. We report an improved experimental test-bed. The hardware incorporates a custom-designed miniature calibration oven which, in conjunction with spatial filtering and a simple calibration algorithm, allows accurate temperature maps to be obtained. The test-bed incorporates a micro-bolometer array as the infrared imager. Instrumentation design, calibration and image processing algorithms are discussed and analyzed. The procedure does not require prior knowledge of the emissivity. We show that relatively inexpensive uncooled bolometers arrays can be used in certain radiometric applications. Heating profiles were examined with both uniform and non-uniform air flow through the device. The conclusions from this study provide critical information for optimal integration of the preconcentrator within a detection system, and in the design of the heater trace layout to achieve a more even temperature distribution across the device.

State of the art IR-Imager in the near infrared spectral range for monitoring high temperatures in industrial applications are characterized by a number of small measurement ranges. Scenes with a high temperature contrast require several measures switching between these ranges and result in pictures with under range and saturated parts. A newly developed high temperature IR-Imager with a spectral range in the near infrared provides a wide dynamic range by utilizing specialized signal processing. A continuous temperature measurement range from 600°C up to 1500°C is realized with a resolution of 640x480 points and a measuring frequency of 25Hz. Each resulting image contains the full dynamic range and is transmitted via a Fast Ethernet interface in real time.

Uncertainty of a target emissivity and environment transmittance and possible reflected radiation are major origins of pyrometer inaccuracy. Measurement without knowledge of emissivity requires gaining at least two independent signals relating to the target. The patented method takes advantage of two same infrared detectors but maintained on different temperatures. A simplified approach implies a radiation enclosure that consists of 2 bodies (target vs. detector), thus a formula for temperature obtained from a set of 2 equations appears simple. Infrared detectors that can work at considerable high temperature are unavailable so temperature range of this method is limited. In an experimental facility, the first thermopile detector is heated by a transistor, the second one is cooled by a Peltier cooler. The swivel radiant heater of cube shape exhibits single of 4 surfaces with different emissivity towards the detectors. The radiation is both concentrated and switched to single detector by a pivoted toric mirror. Close mutual arrangement without optics is optional. All sensors and actuators are connected to a Data Acquisition Switch Unit. The experiment including control loops is fully managed by a PC program. Various side effects of realization like probably an influence of housing radiation at ambient temperature and reflection cause that simple formula is not adequate so that multivariable regression had to be involved. Experimental results are shown in graphs.

A flat plate calibrator is one instrument used in calibrating infrared (IR) thermometers, primarily in the 8 - 14 μm band. One such family of flat plate calibrators is the 418X Precision IR Calibrator from Fluke Corporation Hart Scientific Division. This product is calibrated with a radiometric calibration. To support this radiometric calibration and its traceability, a number of developments have been made at Hart Scientific. These developments include the construction of a new IR calibration laboratory with radiometric traceability. This presentation discusses the research done to establish IR calibration capabilities. Among the topics discussed are the need for radiometric traceability for flat plate calibrators, the traceability chain to national laboratories included in radiometric calibrations at Hart Scientific, the development of blackbody cavity baths in Hart's IR calibration laboratory, and Hart Scientific's IR uncertainty budgets.

The Technical Specification IEC 62492-1 TS: Industrial process control devices - Radiation thermometers - Part 1: Technical data for radiation thermometers will define the technical data, i.e. metrological data, to be given in data sheets and operating instructions for radiation thermometers with one wavelength range and one measurement field. It has been developed within the working group IEC SC 65B WG5 "Temperature Sensors". The content and structure of the IEC 62492-1 TS is briefly explained and an outlook on further work on radiation thermometry planned within the IEC SC 65B WG5 is given.

In 2003 a group of interested Thermographers headed by Greg Stockton of Stockton Infrared Services and Lee Allen began an effort to develop a professional organization to serve the Thermography community. It was named ISPOT and resulted in a Constitution, committees, legal registration and a group of dues-paying members. However, it has waned and there appears little organization left and more than a few people disappointed. Clearly there was a need. There still seems to be a need and issues in the education, continuing education and certification of Thermographer skills as well as standards for development of procedures. Applications in the Non Destructive Testing (NDT) field seem to have grown beyond the scope of present certification recommendations and promise to expand even faster. Who speaks objectively for the minimal training and in-service experience required to make a Thermographers fully qualified in areas outside NDT? How does a Thermographer extend his skill set into the newer fields of Building Thermography, Pest Control, Mold Remediation and the Next New Thing? What of the needs for purchasers of thermographic services? How can they judge the capabilities of individuals or organizations hired to perform services? What requirements exist for trained Thermographers to maintain their skills? Perhaps we can start to define some guidelines for an organization to meet the needs of the individuals, the trainers, the equipment suppliers and the users and purchasers of thermographic services.

Issues concerning the certification of thermographers continue to command a great deal of interest within our profession and among the customers we serve. A recent literature search suggests the topic is as poorly understood as ever. In the United States the only viable means of establishing certification is through compliance, to one degree or another, with the standards and guidelines of the American Society for Nondestructive Testing (ASNT). These means, which, interestingly, also serve well the needs of ten additional NDT methods, are widely recognized throughout much of the rest of the world. Unfortunately for thermographers and their customers, ASNT-compliant certification for our NDT method has failed to gain significant "traction" over the years despite being used by a number of large companies and for many critical applications. The reasons are numerous and diverse. However, the gap has also not been filled by any other viable means of certification. One of the consequences of our failure to embrace uniform, meaningful certification is that our impact has been inconsistent and falls far short of the optimum possible. The framework for qualifying and certifying thermographers still exists, ready, as it has been since 1992, to be filled and used effectively in all applications.

American, European and International societies establish standards for individuals and companies within the field of infrared thermography. Historically addressing non-destructive testing (NDT) applications and personnel, standards exist and are being developed within the fields of condition monitoring (CM) and building diagnostics. Incorrect reference to or application of standards and guidelines create widespread market confusion. What type of claim can be made against which standards? Does the standard apply to a company or an individual? To what or whom is the standard intended? Does reference to a standard guarantee compliance or imply quality? How does one become educated or involved in standards? An overview of international standards within the field of thermography (with brief reference to recognizable guidelines and standards such as ASNT SNT-TC-1A and CEN 473), their status and application will be presented.

Multi-focus function is a unique solution to overcome "depth of filed" issue, which is essential for correct temperature measurement by thermography when the space between thermography camera and target object is limited, or objects are located distantly even though they are within angle of single thermal image. This paper describes about the multi-focus function, a new way of image fusion, as well as about typical applications of the function.

A non-intrusive infrared sensor for the detection of spurious elements in an industrial raw material chain has been developed. The system is an extension to the whole near infrared range of the spectrum of a previously designed system based on the Vis-NIR range (400 - 1000 nm). It incorporates a hyperspectral imaging spectrograph able to register simultaneously the NIR reflected spectrum of the material under study along all the points of an image line. The working material has been different tobacco leaf blends mixed with typical spurious elements of this field such as plastics, cardboards, etc. Spurious elements are discriminated automatically by an artificial neural network able to perform the classification with a high degree of accuracy. Due to the high amount of information involved in the process, Principal Component Analysis is first applied to perform data redundancy removal. By means of the extension to the whole NIR range of the spectrum, from 1000 to 2400 nm, the characterization of the material under test is highly improved. The developed technique could be applied to the classification and discrimination of other materials, and, as a consequence of its non-contact operation it is particularly suitable for food quality control.

Imaging in the short wave infrared (SWIR) can bring useful contrast to situations and applications where visible or thermal imaging cameras are ineffective. This paper will define the short wave infrared technology and discuss developing imaging applications; then describe newly available 2-D (area) and 1-D (linear) arrays made with indium-gallium-arsenide (InGaAs), while presenting the wide range of applications with images and videos. Applications mentioned will be web inspection of continuous processes such as high temperature manufacturing processes, agricultural raw material cleaning and sorting, plastics recycling of automotive and consumer products, and a growing biological imaging technique, Spectral-Domain Optical Coherence Tomography.

A new nondestructive methods based on optical properties at multiple wavelengths is being applied to measure the freshness of some vegetables. The principle of this method is to determine the absorbance and the reflectance of a sample in visible and near infrared region. When a light beam is illuminated upon a piece of vegetable sample, the majority of the lights penetrate into the sample tissue. Upon entering the tissue, photons scatter in different directions. Some are absorbed, some pass-through to the whole sample and emerge from the opposite side, and some scatter back and reemerge from the region adjacent to the incident center. While the absorption is related to certain chemical constituent of the sample, scattering is influenced by the density, compositions, cells and intercellular structures of samples and therefore can be useful for measuring samples freshness. Our objectives are to investigate the spectral behavior of some vegetables and to develop an algorithm for a non-destructive freshness sensor system using visible and near infrared light sources. The preliminary results of the study showed that the freshness of green mustard leaf and onion using a red (λ = 633 nm) and green (λ = 808 nm) light sources were closely related.

Technology miniaturization has made new advancements in high voltage electrical surveying possible. A solar-blind ultraviolet image overlaid onto infrared, combined with a solar-blind ultraviolet image and then overlaid onto color visible in the same camera with a weight of 6 pounds provides the comparison images and portability to allow an operator to do on-the-spot analysis and repair priority assignment. The UV-VIS image provides the quickest location and identification. The UV-IR image allows analysis to determine if there is damage and the severity. This can be accomplished in just seconds thru menu selection: before it required two separate cameras. This presentation will provide examples of different images and analysis, with operating time from hand-held, laboratory, vehicle and aerial camera mounts.

We are well aware of the benefits of the Long-wave, Mid-wave, Short-wave and Near Infrared within the NDT world. This presentation will produce an overview and expansion of the wavelength bands and their use now available far into the area below Visible. There is exciting use of the UVc and UVb Ultraviolet bands for detection of Electrical Corona, Target identification, camouflage research and evaluation. With the new digital high-resolution UVb camera systems, art forgings and UV-sun protection evaluation can easily be accomplished.

Thermography (IR) allows global visualization of temperature distribution on surfaces with high accuracy. This potential can be used for visualization of fluid mechanics effects at the intersection of laminar and turbulent flows, where temperature jumps appear due to convection and friction i.e. for the optimization in the design of airplane geometries. In civil engineering too it is the aspiration of the modern engineer of light weight structures to meet singular loads like wind peaks rather by intelligent structures and materials than by massive structures. Therefore the "Institute of Conceptual and Structural Design" of the Technical University of Berlin (TUB) is working on the development of adaptive structures, optimized geometry and intelligent microstructures on surfaces of structural elements. The paper shows the potential of modern computational fluid dynamics (CFD) in combination with thermography (IR) to optimize structures by visualization of laminar-tumultuous border layer currents. Therefore CFD simulations and IR wind tunnel experiments will be presented and discussed. For simulations and experiments - artificial and structural elements of the cable-stayed Strelasund Bridge, Germany, are used.

The Eclipse infrared electro-chromic device (IR-ECD) is an all-solid-state monolithic vacuum deposited thin film system functioning as an electrically controlled dimmable mirror in the IR region. The maximum reflectance corresponding to the bleached condition of the system is around 90% (low-e condition, e=0.1). The minimum reflectance reaches nearly zero in the colored condition of the system (high emmittance, e=1). It is a variable emittance electro-chromic device (VE-ECD). The average emissivity modulation of the Eclipse VE-ECD is 0.7 in the 8-12 micron region, and at 9.7 micron (room temperature) it reaches a value of 0.9. Half and full emissivity modulations occur within 2 and 10 minutes, respectively. Because of its low mass (5 g/m²), low voltage requirement (±1 V), extremely good emissivity control properties (from 0 to 0.9 at 300 K), and highly repeatable deposition process, the VE-ECD technology is very attractive for satellite thermal control applications. The Eclipse VE-ECD has been under evaluation in a real space environment since March 8, 2007. This paper presents recent developments on Eclipse's VE-ECD including space test results.

An imaging technique of the hand vein tree is presented in this paper. Using the natural human circulatory system and a controlled armband pressure around the arm, a lock-in thermography technique with an internal excitation is carried out. Since the stimulation frequency is inversely proportional to the inspection depth, the subcutaneous layer requires the use of a very slow frequency. Thus, a sawtooth waveform is preferred to minimize the duration of the pressure applied to the armband during the experiment. A frequency of approximately 0.03 Hz and a pressure range between 100 and 140 mmHg, according to the diastolic and systolic blood pressure, are used as stimulation. Then, dorsal hand amplitude and phase images are obtained with IR_view (Klein, 1999), a tool specifically designed to analyze infrared images. The hand vein structure is thermally mapped by an infrared camera operating in the middle wavelength infrared range (MWIR) at room temperature. Parasitic frequencies are avoided by keeping the hand fixed. The resulting images show a gradient of temperature between surrounding tissues and the back-of-hand veins. The vascular signature segmentation is extracted from the amplitude and phase images by using a Fast Fourier Transform image processing technique. This work could be used for vein localization for perfusion or for the early diagnosis of vein diseases such as primitive varicose and deep vein thrombosis (DVT). A hand vein signature database for identification purposes is also possible.

This paper describes the design of a semi-automated heating and scanning system and analytic method for potato characterization. Potatoes are heated using lamps in a heating chamber and then transferred on a movable fixture to an imaging chamber. A non-linear model was designed to predict which potatoes have excessive sugar defects and the model was evaluated with good results. Results from this research will benefit potato growers and manufacturers/producers of potato-based products such as chips and fries.

The search for an efficient on-line monitoring system focused on the real-time analysis of the welding quality is an active area of research, mainly due to the widespread use of both arc and laser welding processes in relevant industrial scenarios such as aeronautics or nuclear. In this work, an improvement in the performance of a previously designed monitor system is presented. This improvement is accomplished by the employment of a dual spatial-spectral technique, namely imaging spectroscopy. This technique allows the simultaneous determination of the optical spectrum components and the spatial location of an object in a surface. In this way, the spatially characterization of the plasma emitted during a tungsten inert gas (TIG) welding is performed. The main advantage of this technique is that the spectra of all the points in the line of vision are measured at the same time. Not only are all the spectra captured simultaneously, but they are also processed as a batch, allowing the investigation of the welding quality. Moreover, imaging spectroscopy provides the desired real-time operation. To simultaneously acquire the information of both domains, spectral and spatial, a passive Prism-Grating-Prism (PGP) device can be used. In this paper the plasma spectra is captured during the welding test by means of a near infrared imaging spectroscopic system which consists of input optics, an imaging spectrograph and a monochrome camera. Technique features regarding on-line welding quality monitoring are discussed by means of several experimental welding tests.

This paper presents some difficulties encountered when evaluating information from infrared thermal inspections conducted in uncovered power substations. Procedural, technical and environmental are the main factors of influence identified. Based on field data and in laboratory tests, preliminary mathematical models are derived, which are suitable either to forecast the system behavior under specified conditions or to remove the influence such components.

Power plant-heated lakes are characterized by a temperature gradient in the thermal plume originating at the discharge of the power plant and terminating at the water intake. The maximum water temperature discharged by the power plant into the lake depends on the power generated at the facility and environmental regulations on the temperature of the lake. Besides the observed thermal plume, cloud-like thermal cells (convection cell elements) are also observed on the water surface. The size, shape and temperature of the convection cell elements depends on several parameters such as the lake water temperature, wind speed, surfactants and the depth of the thermocline. The Savannah River National Laboratory (SRNL) and Clemson University are collaborating to determine the applicability of laboratory empirical correlations between surface heat flux and thermal convection intensity. Laboratory experiments at Clemson University have demonstrated a simple relationship between the surface heat flux and the standard deviation of temperature fluctuations. Similar results were observed in the aerial thermal imagery SRNL collected at different locations along the thermal plume and at different elevations. SRNL will present evidence that the results at Clemson University are applicable to cooling lakes.

Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and the standard deviation of the surface temperature field, σ, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm^-2. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and σ exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm^-2. The linear relationship between σ and Q is evident in the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifacts and non-convective thermal gradients. The correlation between σ and Q is improved if a correction to the measured σ is made that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lake images, the correlation coefficients between σ and Q ranged from about 0.8 to 0.9.

Thermography if it is properly used, could evolve into a valuable diagnostic tool for predictive maintenance in buildings. The main objective of this work is to point out the harmonised procedures and the produced guidelines for building thermography in Europe with the intention of maintaining a high standard of work. The proposed thermography approach would be used in the buildings diagnostics and monitoring taking into consideration various climate zones and environmental parameters, according to the new ISO working group that was formed in 2007, with the intention of updating the existing standard and in the next stage to develop other connecting standards, if necessary.

In order to provide a method to control conformity of insulation of buildings after restoration, Protomeres project was launched under Prebat 2005 program. This work deals with the development of an experimental protocol for the diagnostic of multi-layered insulated building walls. In a previous study, a test bench was set up in order to measure front and back side temperatures of standard panels compounded of 1cm of plaster and various thicknesses of polystyrene. The panels considered have insulation thicknesses of 2, 6 and 10cm. In the present work, the panels are fixed on walls in laboratory to test real situations in constructions. The front side is painted in standardized black color and heated by two halogen lamps of 500W. A CEDIP Jade Long wave infrared camera and thermocouples are used to carry out temperature measurements during an exposure time and subsequent cooling. In a second time, a one dimensional model based on thermal quadruples and Laplace transforms was developed under Matlab environment. This model simulates a three-layered wall with a blade of air between polystyrene and concrete. Finally, a method of identification of physical parameters is implemented by performing least square minimization based on Levenberg-Marquardt method. The experimental measurements are compared to theoretical results and by minimization we obtain thermal conductivity and diffusivity as well as thickness of the two layers.

Reinforced concrete beams are designed to allow minor concrete cracking in the tension zone. The severity of cracking in a beam element is a good indicator of how well a structure is performing and whether or not repairs are needed to prevent structural failure. FRP composites are commonly used to increase the flexural and shear capacity of RC beam elements, but one potential disadvantage of this method is that strengthened surfaces are no longer visible and cracks or delaminations that result from excessive loading or fatigue may go undetected. This research investigated thermal imaging techniques for detecting load induced cracking in the concrete substrate and delamination of FRP strengthening systems applied to reinforced concrete (RC). One small-scale RC beam (5 in. x 6 in. x 60 in.) was strengthened with FRP and loaded to failure monotonically. An infrared thermography inspection was performed after failure. A second strengthened beam was loaded cyclically for 1,750,000 cycles to investigate how fatigue might affect substrate cracking and delamination growth throughout the service-life of a repaired element. No changes were observed in the FRP bond during/after the cyclic loading. The thermal imaging component of this research included pixel normalization to enhance detectability and characterization of this specific type of damage.

In this paper a new approach for quantitative non-destructive testing (NDT) of near-surface structures in civil engineering (CE) with active thermography is presented. It adopts the method known as pulsed phase thermography (PPT) for the special requirements of NDT-CE and was developed in a German research project of the Federal Institute for Materials Research and Testing (BAM) in cooperation with the Technical University of Berlin. The new quantitative concept that might be understood as a square pulse thermography in frequency domain or an amplitude-expanded PPT with square pulse heating is based on the thermal diffusivity of the material and the characteristic frequency of the negative maximum phase and amplitude contrast. It aims at complementing the established approaches for defects depth calculation for measurements with long heating and observation times quite usual at active thermography in CE but is easily extendable to other fields of application. After an introduction to the basics of active thermography in CE and the thermography concept of BAM, qualitative results of several case studies will be presented. The main focus of the last section of this contribution is on applications of the new quantitative approach at test specimens of BAM to determine the concrete cover of artificially manufactured defects.

Thermography is excellent for a fast characterisation of building materials, both at laboratory or in situ. A great advantage is the possibility to analyse many samples at the same conditions and time. A technique has been applied for new materials, oriented to radiating floor systems, evaluating different approaches. Samples are submitted to a stepwise, uniform heating. Surface excess temperature is recorded by thermography evaluating thermal inertia. At first, thermal diffusivity has been measured using a modified version of the Flash Method, then applied on a single face, for in situ application. Heat capacity and thermal conductivity have been inferred for each samples by definitions and the independent measure of the volumic mass.

In this paper, active thermography NDT method with active heating is developed for concrete structures. Active heating is effectively employed when temperature fluctuation on structure is small. As an estimation method of defect depth, the Fourier analysis of temperature descent curve after heating is employed. As the results, by using the phase delay distribution obtained from the Fourier analysis, the influence of the irregularity heating was reduced in comparison with the original temperature distribution. The phase delay image was also useful for determination of defect depth. Values of phase difference between delamination area and sound area show peaks at certain values of data processing period. These peaks can be directly related to defect depth. It is shown that three-dimensional shape of delamination defect can be accurately evaluated by the proposed technique.

One of our industrial partners, Assek Technologie, is interested in developing a technique that would improve the drying process of wood floor in basements after flooding. In order to optimize the procedure, the floor structure and the damaged (wet) area extent must first be determined with minimum intrusion (minimum or no dismantling). The present study presents the use of infrared thermography to reveal the structure of (flooded) wood floors. The procedure involves opening holes in the floor. Injecting some hot air through those holes reveals the framing structure even if the floor is covered by vinyl or ceramic tiles. This study indicates that thermal imaging can also be used as a tool to validate the decontamination process after drying. Thermal images were obtained on small-scale models and in a demonstration room.

Two models which can be regarded as extreme simulation cases in thermal nondestructive testing are studied numerically with accent being made on the accuracy issue. Four computer programs (ThermoCalc-2D, ThermoCalc-6L, ThermoModel and Comsol Multiphysics) are compared in calculating both absolute temperatures and thermal NDT parameters, such as differential temperature signal and running contrast.

IR-View, is a free and open source Matlab software that was released in 1998 at the Computer Vision and Systems Laboratory (CVSL) at Université Laval, Canada, as an answer to many common and recurrent needs in Infrared thermography. IR-View has proven to be a useful tool at CVSL for the past 10 years. The software by itself and/or its concept and functions may be of interest for other laboratories and companies working in research in the IR NDT field. This article describes the functions and processing techniques integrated to IR-View, freely downloadable under the GNU license at http://mivim.gel.ulaval.ca. Demonstration of IR-View functionalities will also be done during the DSS08 SPIE Defense and Security Symposium.

In non-destructive testing by Infrared Thermography it is usually needed to locate defects and region of interests suspected to contain defects. The defects cannot always be observed directly from one single IR image taken at a single given time t. Thus, in the case of pulsed thermography, direct course techniques as the Fourier transform process the information of many images recorded for a given duration into one resulting image. Another way to compile the temporal information of a sequence of images into a single one is to compute a correlation image. This paper details an approach to use a statistical correlation operator to help improving defect detection in pulsed infrared thermography.

Inspection of thick composite structures, such as Reinforced Thermosetting Resin (RTR) pipes used in the petroleum industry, using infrared thermography is difficult. This paper investigates the use of step heating thermography to increase the maximum detectable defect depth and describes techniques to quantitatively characterize defect depth and severity in thick composites. A procedure to simultaneously determine defect depth and thermal resistance from the early time surface temperature is described. The procedure is based on fitting the early time surface temperature profile over a defect to a one-dimensional three-layer analytical model. Experimental testing demonstrates the accuracy of the procedure.

The prerequisite for more competent and cost effective aircraft has led to the evolution of innovative testing and evaluation procedures. Non-destructive testing and evaluation (NDT & E) techniques for assessing the integrity of an aircraft structure are essential to both reduce manufacturing costs and out of service time of aircraft due to maintenance. Nowadays, active - transient thermal NDT & E (i.e. thermography) is commonly used for assessing aircraft composites. This research work evaluates the potential of pulsed thermography (PT) and/or pulsed phase thermography (PPT) for assessing defects (i.e. impact damage and inclusions for delaminations) on GLARE and GLARE type composites. Finally, in the case of the detection of inserts - delaminations C-Scan ultrasonic testing was also used with the intention of providing supplementary results.

Optically modulated elastic waves enter the surface of the inspected material by absorption of thermal radiation. An inhomogeneous disturbance in the material causes locally enhanced losses. Such material defects heat up at a different rate than the surrounding more homogenous material and therefore generate differences in thermal contrast. Modulating the amplitude of the optical stimulus turns defects into thermal wave transmitters. The frequency of the stimulus signal must be matched to the specific thermal conductivity and mass density of the inspected material. It is possible to locate defects at different depths below the surface by varying the amplitude of the stimulus wave. Proper detection of thermal waves resulting from material defects near the surface requires a measurement setup that allows the recording of thermal images from an infrared camera. The recorded images can then be compared against the phase of the stimulus signal. This photo-thermal lock-in thermography method not only allows the evaluation of the amplitudal thermal wave information but more importantly it also allows for the extraction of the phase information. The phase shift between the stimulus signal and the captured thermal wave is directly correlated to the thermal propagation time.

In ultrasound excitation thermography, the injected ultrasound to an object is transformed to heat by thermo-structure effect and internal friction. The advantage of this technique is selectively sensitive to thermally active defects. The appearance of defects, which can be visualized by thermography camera, depends strongly on the method of excitation. In preliminary studies, ultrasonic excitation horns of ultrasonic manufacturing process are widely adopted for a polymer structure. However, it is needed that these horns are modified for improving the defect detection capability. This paper proposes a new ultrasonic excitation horns with tuning fork shape in NDT of wood material. Geometric conditions are optimized by FEA and application results by the developed horn are described and compared with those by a previous horn.

Structural components subjected to high frequency vibrations, such as those used in vibrating parts of gas turbine engines, are usually required to avoid resonance frequencies. Although the operating frequency is designed at more than resonance frequencies, the structure, when a vibrating structure starts or stops, has to pass through a resonance frequency, which results in large stress concentration. This paper applies thermography to analyze transient stress variation of a circular holed plate. In experiment, the finite element modal (FEM) analysis of the specimen was performed and the surface temperature measured by infrared camera is calculated to the stress of the nearby hole, based on thermoelastic equation. Stress distributions between 2nd and 3rd vibration mode are investigated with thermography and also dynamic stress concentration factors according to the change of vibration amplitude are estimated at resonance frequency.

Characteristics of heat transfer and signal evolution in thermal nondestructive testing (TNDT) in aluminum adhesively-bonded structures were studied by computer simulation based on the finite element method (FEM). The TNDT mathematical model of bonded structures was constructed in cylindrical coordinates. The evolutions of TNDT informative parameters versus defect size and depth were simulated by using the FEM analysis software ANSYS. Some simple regression expressions were obtained for the relations between the informative parameters and the defect parameters. It is shown that, at a fixed defect depth, the four informative parameters including the maximum differential temperature, maximum contrast, differential temperature peak time and best observation time, are linearly proportional to defect radius respectively. However, if defect radius is fixed, the maximum differential temperature and maximum contrast become a non-linear function of defect depth, and the differential temperature peak time and best observation time are linearly proportional to defect depth. It is believed that the obtained results may be of help in developing an inspection strategy for aviation aluminum panels.

We develop a dimensionless heat transfer model to analyze pulsed thermography data for non-destructive testing (NDT) of materials. Simulated thermographic sequences are used in order to evaluate the performance of the inspection technique. Also, we inspect organic and inorganic samples, including a layered plate and two dental pieces, in search of internal defects and structural inhomogeneities. We detect cavities and the inner structure of the samples by means of reconstructed thermograms and a modified version of the differential absolute contrast (DAC). Moreover, we develop an effective data compression method that reduces a thermographic video with m frames of p × q pixels to two matrices of p × q elements. In this data reconstruction process, precision and compression ratio are independent parameters. Finally, we find that partial translucency of dental enamel, in infrared, permits imaging of the internal structure of a tooth. This inspection technique does not require a priori knowledge about a reference defect-free area.