Papers by Keyword: Infrared Thermography (IRT)

Abstract: The focus of this research is the investigation of the Ocular Surface Temperature (OST) in both healthy and pathological (e.g. age-related macular degeneration, eye dry syndrome and choroidal lesions) eyes by using Infrared Thermography (IR). Specifically, the temperature of different anatomical areas (or points) of the eye is measured by applying image processing procedures on the infrared images recorded. It is known that the pathogenesis of some ocular pathology is related to the variation of ocular blood perfusion, and thus to the temperatures of the anterior segment of the eye. Results demonstrated that thermography can provide quantitative documentation of these temperature measurements. Furthermore, thermography is a non-invasive, cheap, harmless and portable technique. The challenge is to make ocular thermography part of the daily diagnostic procedure by providing more and more reliable experimental data.

Abstract: This work is devoted to theoretical and experimental study of energy dissipation and storage processes in titanium alloys under quasistatic loading. The specimen surface temperature was measured by infrared camera FLIR SC 5000 (a spectral range of 3-5 micron). Extending previous results of the research group in Perm, we coupled the experimental investigation of temperature evolution with a statistical description of the mesodefect ensemble. It allowed us to propose a thermodynamic internal variable model of heat dissipation in metals.

Abstract: In this paper, the results of the first-stage research devoted to infrared thermographic detection of cracks in titanium alloys are presented. In application to the inspection of bottom-hole defects in 9.6 mm-thick Ti6Al4V titanium alloy samples, it has been found that a minimum detected defect should have diameter from one to two times greater than its depth. Images of phase are more noise-resistant and able to reveal deeper defects compared to images of amplitude. The test results obtained show that the Fourier analysis is a convenient data processing technique in active thermal NDT.

Abstract: The online temperature detections of fiber along the spinning line should be the important means for the precise controlling of fiber higher order structures as well as fiber-final performance. In this paper, a method of measurement fiber temperature has been introduced which mainly use the instrument of monochromatic infrared thermometer to measure fiber temperature in the melt-spinning processes. Due to the probe field of view of monochromatic infrared thermometer being much larger than the fiber diameter, monochrome infrared thermometers can't be used to measure temperature of fibers directly, the measurement results is an average between the fiber and backgrounds, which can't be used to indicate the temperature of fibers directly and have to calibrated. The calibrated results of monochromatic infrared thermometer are compared to the measurement results of infrared thermography. It has been found that the on-line measurement with infrared thermometer could promise high-speed and highly reliable temperature testing for the fibers.

Abstract: This paper proposes a method based on the spectra response of IR detectors mounted on thermographic camera for emissivity measurement at various target surface temperatures, while the reflected temperature istaken into account, and also studies on the effect of surface roughness on the emissivity value. The emissivity (ε8-14μm) of general engineering material such as iron, stainless steel, brass, copper and aluminum obtained in this paper are in agreement with other literatures. Finally, results found that the roughness and emissivity of equipment increases with increasing of the operating time.

Abstract: Active thermal NDT is a promising technique for the detection of structural defects in solids. In this paper, the results of the first-stage research devoted to infrared thermographic detection of cracks in titanium alloys are presented. The test results obtained show that the Fourier analysis is a convenient data processing technique in active thermal NDT. Images of phase are more noise-resistant and able to reveal deeper defects compared to images of amplitude. In application to the inspection of bottom-hole defects in 9.6 mm-thick Ti6Al4V titanium alloy samples, it has been found that a minimum detected defect should have diameter from one to two times greater than its depth.

Abstract: The emergence recently of a thermoelastic stress analysis (TSA) capability exploiting low-cost, compact and rugged microbolometer detector technology provides a significant opportunity topromote a broader use of this powerful non-contact full-field stress analysis technique. An area whereit has considerable and hitherto unexplored potential is in in-situ structural health monitoring (SHM).The present paper outlines the case for a nexus between SHMand TSA in this new form. It is proposedthat the approach should yield diagnostic and prognostic capabilities surpassing those of some existingSHM modalities. An F/A-18 centre-fuselage full-scale structural fatigue test is employed as a casestudy to illustrate the practical feasibility of the approach and to underscore some of its potential.Although the case study focuses on an aircraft structure, the concept has potential application to awide variety of different engineering assets across the aerospace, civil and maritime sectors.

Abstract: This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm³ can be detected.

Abstract: This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm³ can be detected.

Abstract: The heating distribution assessment on similar and dissimilar friction stir welded joints in AA6082 and AA5754 aluminium alloy sheets was investigated. The FSW experiments were carried out using constant rotational and welding speeds of 1500 rpm and 60 mm/min, respectively. Temperature was locally measured by means of K-type thermocouples inserted into thin grooves located on the bottom side of the sheets, in fixed positions, very close to the welding line. It was observed that the mechanical properties of joints are related to the heat distribution. In order to obtain a completely non intrusive temperature monitoring, that was able to follow the process dynamic, a non-contact measurement system based on infrared thermography was also developed. Such system, used for the experimental evaluation of temperature on the upper surface of the joints, is also able to detect the presence of flow defects with a non-destructive method, demonstrating its effectiveness as a diagnostic instrument for the on-line quality control of welded joints.