1,721,079 research outputs found
On the Thickness Quantification of Composite Materials by Using Lock-In Thermography
No full textMany structural components made of composite materials need an accurate thickness control during fabrication and/or maintenance. In this regard, various non-destructive techniques can be used for the online measuring of thickness of large components such as wings and fuselage in the aerospace industry. In this work, the capabilities of lock-in thermography technique in thickness measurement of glass fiber reinforced plastic material were investigated and a correct procedure has been proposed to ensure the best measurement accuracy. An analytical approach and several tests were carried out on a sample specimen with the aim to study the main test parameters. Finally, the limits of technique have been discussed
Data Correction for Thermoelastic Stress Analysis on Titanium Components
No full textThermoelastic Stress Analysis (TSA) is based on the thermoelastic effect, well described by a linear relationship between change in body temperature and state of stress in the presence of local adiabatic conditions. In TSA material properties are usually considered constant and a peak to peak variation of the state of stress provides a linearly correlated peak to peak temperature variation. For titanium and aluminium alloys thermoelastic properties of materials are not constant and, in fact, the second order effect due to mean stress on thermoelastic signal is not negligible any more. If neglected for these kind of materials, this second order effect could lead to an error that can be higher than 20 %. In this work a new procedure of thermal signal processing is investigated to obtain the corrected thermoelastic data through a new approach based on revised thermoelastic theory
Data Processing Procedures for Defects Evaluation in Composite Materials by Means of Stimulated Thermography
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Metodi termici innovativi per la valutazione dell’integrità strutturale di materiali compositi
No full textQuantitative damage evaluation of composite materials with microwave thermographic technique: feasibility and new data analysis
No full textIn this work microwaves were used as heating source to quantitatively evaluate the extension of damaged areas in composite materials using the thermographic technique. In particular, microwave pulsed thermography was carried out on CFRP damaged specimens. A new procedure was developed to process thermographic data obtained by microwave thermography tests and a new algorithm was used to processing thermography data. The approach used to evaluate the damaged areas is based on the characteristic non-linear heating behaviour and an higher slope of heating and cooling curves respect to undamaged area. The results obtained with new procedure were compared with other NDT techniques such as X-ray and lock-in thermography. Numerical simulations were carried out in order to assess the potential sensitivity of the new procedure. The aim of this work is to develop a quick procedure and data analysis in order to allow the non destructive testing of composite large structures in automatic way with a reduced testing time
Evaluation of the heat dissipated around the crack tip of AISI 422 and CF3M steels by means of thermography
Full text linkThe fatigue crack growth depends on the dissipated energy at the crack tip and in this regard, different analytical and numerical models were proposed by many researchers to describe as the plastic work affect the fatigue material behaviour. Experimental tests can be carried out for evaluating the energy dissipated during the crack growth principally based on the hysteresis loop measurement. However, these techniques need of suitable equipment and set-ups and then find some restrictions if applied in-situ and on real components.
In this work, an experimental approach is used to obtain a thermographic parameter capable of describing the plastic work at the crack tip. The proposed approach is based on the phase shift of the thermal signal that occurs at the crack tip in the plastic area.
Two specimens of two different steels, austenitic and martensitic, were tested and monitored with an infrared camera to collect thermoelastic phase data. A similar correlation to the dissipated energy was obtained with the fatigue crack growth behavior of materials
Damage Investigation in Composite Materials by Means of New Thermal Data Processing Procedures
No full textStimulated thermography is a non-destructive technique capable of detecting and quantifying defects in composite material thanks to the varying thermal behaviour they display if subjected to a thermal stimulation. Although in literature valid and consolidated thermographic techniques (lock-in and pulsed/stepped thermography) are available, the use of stimulated thermography in industry is still not widespread in the case of application of large structures, mainly because of the overall lengthy time required for testing owing to the necessary scanning approach. In this work, the influence of the main set-up parameters of stimulated thermography is assessed, analysing simulated defects on a sample specimen made of Glass Fiber Reinforced Polymer. In particular, the attention was focused on the optimisation of testing parameters for the improvement of signal quality and to reduce testing time. In this regard, a new procedure is proposed based on a least-square fitting algorithm capable of providing various synergic thermal analyses with a modulated heat excitation and within a single test
Thermal Methods for Damage Evaluation of Metallic Materials
Full text linkThermal methods represent a set of techniques and procedures based on the investigation of the thermal phenomena related to damage during static or fatigue stresses, or more in general, to the behaviour of damaged and defected areas [...
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