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Metals
Special Issues
Thermal Methods for Damage Evaluation of Metallic Materials
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Thermal Methods for Damage Evaluation of Metallic Materials

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 March 2019) | Viewed by 27219

Special Issue Editors

Prof. Dr. Umberto Galietti

E-Mail Website
Guest Editor
Department of Mechanics, Mathematics and Management, Politecnico di Bari, Via Edoardo Orabona, n.4, 70125 Bari, Italy
Interests: mechanical engineering; experimental mechanics; stress analysis; nondestructive testing; infrared thermography
Special Issues, Collections and Topics in MDPI journals
Dr. Davide Palumbo

E-Mail Website
Guest Editor
Department of Mechanics, Mathematics and Management, Polythecnic of Bari, 70126 Bari, Italy
Interests: fatigue; fracture mechanics; thermoelastic stress analysis; thermography; heat dissipations; mechanical characterisation of metals; mechanical characterisation of composites
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Thermography is a well-established, non-contacting and full field technique based on detecting of surface temperature of material. Infrared thermography–non-destructive technique (IR-NDT) presents suitable peculiarities for the investigation of large areas, since i) it does not require the coupling with the component, ii) it is easily automated, and iii) the testing time is relatively shorter with respect to other well-established NDT techniques. In view of this, thermal methods have been used in the last few years in many applications to study the fatigue behavior of metallic materials and components, or for evaluating defects that could compromise the mechanical strength of materials.

In the literature, different methods have been developed, considering temperature as a parameter for evaluating the damage of materials. Other methods are based on specific data processing of recorded infrared sequences. In particular, in this case, the infrared signal is processed in the frequency domain in order to obtain information about the second order frequency of thermographic signals, directly correlated to damage phenomena. Metallic materials, such as aluminum alloys, are characterized by a high thermal conductivity coefficient and a high thermal diffusivity; thus, a suitable experimental set-up and procedures are needed to detect damage.

Dr. Umberto Galietti
Dr. Davide Palumbo
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • Thermography
  • Fatigue
  • Fracture Mechanics
  • Metals
  • Thermoelastic Stress Analysis
  • NDT

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Published Papers (7 papers)

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Editorial

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3 pages, 145 KiB  
Editorial
Thermal Methods for Damage Evaluation of Metallic Materials
by Umberto Galietti and Davide Palumbo
Metals 2019, 9(11), 1204; https://doi.org/10.3390/met9111204 - 8 Nov 2019
Viewed by 1627
Abstract
Thermal 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 [...] Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)

Research

Jump to: Editorial

7 pages, 1405 KiB  
Article
Detecting and Monitoring Cracks in Aerospace Materials Using Post-Processing of TSA and AE Data
by Ceri A. Middleton, John P. McCrory, Richard J. Greene, Karen Holford and Eann A. Patterson
Metals 2019, 9(7), 748; https://doi.org/10.3390/met9070748 - 4 Jul 2019
Cited by 9 | Viewed by 3298
Abstract
Thermoelastic stress analysis (TSA) is a non-contact technique for measuring the distribution of stress in the surface of a component subject to cyclic loading by using a sensitive infrared camera. The stress concentrations indicative of a crack can be located and tracked using [...] Read more.
Thermoelastic stress analysis (TSA) is a non-contact technique for measuring the distribution of stress in the surface of a component subject to cyclic loading by using a sensitive infrared camera. The stress concentrations indicative of a crack can be located and tracked using an optical flow method, allowing the position of the crack-tip to be identified at a given time. Acoustic emission (AE) has been used to validate the TSA algorithm. AE events from cracking, located using the Delta-T Mapping method, were detected several seconds before the TSA algorithm first detected cracking; however, TSA provided significantly more accurate location information. Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)
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23 pages, 4755 KiB  
Article
Comparison of Experimental Thermal Methods for the Fatigue Limit Evaluation of a Stainless Steel
by Mauro Ricotta, Giovanni Meneghetti, Bruno Atzori, Giacomo Risitano and Antonino Risitano
Metals 2019, 9(6), 677; https://doi.org/10.3390/met9060677 - 11 Jun 2019
Cited by 43 | Viewed by 4444
Abstract
This paper regards the rapid determination of fatigue limit by using thermal data analysis. Different approaches available in the literature to estimate the fatigue limit of cold-drawn AISI 304L bars are analyzed and compared, namely, temperature- and energy-based methods. Among the temperature-based approaches, [...] Read more.
This paper regards the rapid determination of fatigue limit by using thermal data analysis. Different approaches available in the literature to estimate the fatigue limit of cold-drawn AISI 304L bars are analyzed and compared, namely, temperature- and energy-based methods. Among the temperature-based approaches, the Risitano Method (RM) and the method based on material temperature evolution recorded during a static tensile test were analyzed. Regarding the energy-based approaches, the input mechanical energy density stored in the material per cycle (i.e., the area of the hysteresis loop), the heat energy dissipated by the material to the surroundings per cycle, and the “2nd-harmonic-based” methods were considered. It was found that for the material analyzed, all the considered energy-based approaches provided a very good engineering estimation of the material fatigue limit compared to a staircase test. Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)
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16 pages, 5342 KiB  
Article
A Thermoelastic Stress Analysis General Model: Study of the Influence of Biaxial Residual Stress on Aluminium and Titanium
by Francesca Di Carolo, Rosa De Finis, Davide Palumbo and Umberto Galietti
Metals 2019, 9(6), 671; https://doi.org/10.3390/met9060671 - 10 Jun 2019
Cited by 12 | Viewed by 3430
Abstract
All the studies on the thermoelastic behaviour of materials, including the revised higher order theory on the thermoelastic effect, are based on several assumptions that limit the application of such theory to the cases of isotropic materials in the presence of uniaxial residual [...] Read more.
All the studies on the thermoelastic behaviour of materials, including the revised higher order theory on the thermoelastic effect, are based on several assumptions that limit the application of such theory to the cases of isotropic materials in the presence of uniaxial residual stresses and undergoing uniaxial applied loads. These assumptions lead to some discrepancies in the description of the real thermoelastic behaviour of materials in the presence of residual stresses. In this work, by rewriting the thermoelastic equation in a different way, it was possible to study the behaviour of homogeneous and non-isotropic materials undergoing any loading conditions and residual stresses. Firstly, the error made by the calibration procedures of thermoelastic stress analysis (TSA) data in the presence of residual stresses has been investigated. Then, a statistical analysis was carried out to determine the minimum value of residual stress which would lead to significant and measurable variations in the thermoelastic signal. The simulations involved two non-ferrous metals: AA6082 and Ti6Al4V, which exhibit a specific thermoelastic behaviour. Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)
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16 pages, 5203 KiB  
Article
Assessing the Condition of Gas Turbine Rotor Blades with the Optoelectronic and Thermographic Methods
by Mariusz Bogdan, Józef Błachnio, Artur Kułaszka and Marcin Derlatka
Metals 2019, 9(1), 31; https://doi.org/10.3390/met9010031 - 2 Jan 2019
Cited by 16 | Viewed by 4441
Abstract
Gas turbines and their blades in particular might be damaged in the course of the aviation turbojet engine operation process. The degradation process of the blade microstructure is most evident from the change in the colour of its surface. This is assessed using [...] Read more.
Gas turbines and their blades in particular might be damaged in the course of the aviation turbojet engine operation process. The degradation process of the blade microstructure is most evident from the change in the colour of its surface. This is assessed using the optoelectronic method. The article presents the concept of non-destructive methods, which are used to assess the degree of degradation of the alloy of a gas turbine blade. The proposed optoelectronic method is the basic method for the preliminary determination of color changes in the surface. Appropriate videoscopes or video-analyzers, capable of recording a test object in various electromagnetic wave ranges (infrared radiation, visible range), are used for this purpose. These preliminary results of the diagnosis make it possible to infer further studies of the blade. For accurate investigation of the state of the alloy microstructure, a non-destructive thermographic method (xenon flash pulsed thermography) was used. The results of studies of the degradation of the microstructure with the use of non-destructive methods were verified through the use of metallographic investigations. Appropriate metallographic specimens were created in order to recognize phase γ′ degradation (i.e., the phase strengthening the blade alloy). The results of the presented research allowed for an in-depth assessment of the degree of microstructure degradation of operated blades. Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)
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22 pages, 6587 KiB  
Article
A Quantitative Comparison among Different Algorithms for Defects Detection on Aluminum with the Pulsed Thermography Technique
by Ester D’Accardi, Davide Palumbo, Rosanna Tamborrino and Umberto Galietti
Metals 2018, 8(10), 859; https://doi.org/10.3390/met8100859 - 20 Oct 2018
Cited by 35 | Viewed by 4400
Abstract
Pulsed thermography is commonly used as a non-destructive technique for evaluating defects within materials and components. In the last few years, many algorithms have been developed with the aim to detect defects and different methods have been used for detecting their size and [...] Read more.
Pulsed thermography is commonly used as a non-destructive technique for evaluating defects within materials and components. In the last few years, many algorithms have been developed with the aim to detect defects and different methods have been used for detecting their size and depth. However, only few works in the literature reported a comparison among the different algorithms in terms of the number of detected defects, the time spent in testing and analysis, and the quantitative evaluation of size and depth. In this work, starting from a pulsed thermographic test carried out on an aluminum specimen with twenty flat bottom holes of known nominal size and depth, different algorithms have been used with the aim to obtain a comparison among them in terms of signal to background contrast (SBC) and number of detected defects by analyzing different time intervals. Moreover, the correlation between SBC and the aspect ratio of the defects has been investigated. The algorithms used have been: Pulsed Phase Thermography (PPT), Slope, Correlation Coefficient (R2), Thermal Signal Reconstruction (TSR) and Principal Component Thermography (PCT). The results showed the advantages, disadvantages, and sensitivity of the various thermographic algorithms. Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)
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14 pages, 9654 KiB  
Article
Pattern Deep Region Learning for Crack Detection in Thermography Diagnosis System
by Jue Hu, Weiping Xu, Bin Gao, Gui Yun Tian, Yizhe Wang, Yingchun Wu, Ying Yin and Juan Chen
Metals 2018, 8(8), 612; https://doi.org/10.3390/met8080612 - 6 Aug 2018
Cited by 33 | Viewed by 4764
Abstract
Eddy Current Pulsed Thermography is a crucial non-destructive testing technology which has a rapidly increasing range of applications for crack detection on metals. Although the unsupervised learning method has been widely adopted in thermal sequences processing, the research on supervised learning in crack [...] Read more.
Eddy Current Pulsed Thermography is a crucial non-destructive testing technology which has a rapidly increasing range of applications for crack detection on metals. Although the unsupervised learning method has been widely adopted in thermal sequences processing, the research on supervised learning in crack detection remains unexplored. In this paper, we propose an end-to-end pattern, deep region learning structure to achieve precise crack detection and localization. The proposed structure integrates both time and spatial pattern mining for crack information with a deep region convolution neural network. Experiments on both artificial and natural cracks have shown attractive performance and verified the efficacy of the proposed structure. Full article
(This article belongs to the Special Issue Thermal Methods for Damage Evaluation of Metallic Materials)
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