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Rosado, LS, Santos TG, Piedade M, Ramos PM, Vilaça P.  2010.  Advanced technique for non-destructive testing of friction stir welding of metals, 2010. Measurement: Journal of the International Measurement Confederation. 43(8):1021-1030. AbstractWebsite
Almeida, G, Gonzalez J, Rosado L, Vilaça P, Santos TG.  2013.  Advances in NDT and materials characterization by eddy currents, 2013. 46th CIRP Conference on Manufacturing Systems, CIRP CMS 2013. 7:359-364., Setubal Abstract
Santos, T, Vilaça P, Reis L, Quintino L, De Freitas M.  2008.  Advances in NDT techniques for friction stir welding joints of AA2024, 2008. TMS 2008 Annual Meeting Supplemental: Materials Processing and Properties. 3:27-32., New Orleans, LA Abstract
Santos, TG, Fernandes FB, Bernardo G, Miranda RM.  2013.  Analyzing mechanical properties and nondestructive characteristics of brazed joints of NiTi shape memory alloys to carbon steel rods, 2013. International Journal of Advanced Manufacturing Technology. 66(5-8):787-793. AbstractWebsite
Santos, TG, Vilaça P, Quintino L, dos Santos J, Miranda RM.  2011.  Application of Eddy Current techniques to inspect friction spot welds in aluminium alloy AA2024 and a composite material, 2011. Welding in the World. 55(9-10):12-18. AbstractWebsite
Santos, TG, Faria J, Vilaça P, Miranda RM.  2013.  Application of eddy currents in processed materials structural evaluation, 2013. 6th International Materials Symposium, Materiais 2011. 730-732:715-720., Guimaraes AbstractWebsite
Duarte, VR, Rodrigues TA, Machado MA.  2021.  Benchmarking of Nondestructive Testing for Additive Manufacturing. 3D Printing and Additive Manufacturing. AbstractWebsite

Defect detection in additive manufacturing (AM) is of paramount importance to improve the reliability of products. Nondestructive testing is not yet widely used for defect detection. The main challenges are a lack of standards and methods, the types and location of defects, and the complex geometry of many parts. During selective laser melting (SLM), several types of defects can occur such as porosity, cracking, and lack of fusion. In this study, several nondestructive tests were conducted in a highly complex shaped part in AISI 316L stainless steel with real defects manufactured by SLM. Two additional artificial defects (one horizontal and one flat bottom hole) were produced and the defect detectability was evaluated. The techniques used were as follows: dye penetrant, infrared thermography, immersion ultrasonic, eddy current, and X-ray microcomputed tomography to assess different types of defects in the as-built part. We conclude that no single technique can detect every type of defect, although multiple techniques provide complementary and redundant information to critically evaluate the integrity of the parts. This approach is fundamental for improving the reliability of defect detection, which will help expand the potential for using AM to produce parts for critical structural applications.

Gomes, JF, Albuquerque PC, Miranda RM, Santos TG, Vieira MT.  2012.  Comparison of deposited surface area of airborne ultrafine particles generated from two welding processes, 2012. Inhalation Toxicology. 24(11):774-781. AbstractWebsite
Santos, T, Vilaça P, Quintino L, dos Santos J.  2009.  Computational tools for modelling FSW and an improved tool for NDT, 2009. Welding in the World. 53(5-6):R99-R108. AbstractWebsite
Machado, MA, Antin K-N, Rosado LS, Vilaça P, Santos TG.  2019.  Contactless high-speed eddy current inspection of unidirectional carbon fiber reinforced polymer. Composites Part B: Engineering. 168:226-235. AbstractWebsite

This paper presents the development and the results of a customized eddy current (EC) non-destructive testing (NDT) system for highly demanding online inspection conditions. Several planar eddy current array probes were designed, numerically simulated and experimentally compared for the inspection of low conductivity unidirectional carbon fibre reinforced polymer (CFRP) ropes. The inspections were performed using a dedicated scanner device at 4 m/s with 3 mm probe lift-off where defects under 1 mm were detected with an excellent SNR. Different defect morphologies and sizes, such as broken fibres and lateral cuts, were successful detected and compared to conventional probes.

Costa, FB, Machado MA, Bonfait GJ, Vieira P, Santos TG.  2021.  Continuous wave terahertz imaging for NDT: Fundamentals and experimental validation. Measurement. 172(108904) AbstractWebsite

Continuous wave terahertz (CW THz) imaging, is a variant of terahertz imaging that has been gaining scientific
and technological relevance in multiple areas. In this paper the fundamental phenomena of CW THz were
studied and a mathematical model was developed that successfully describes the Fabry–Perot interference for
such a system, opening the possibility for measurement of thicknesses and surface curvatures. The capabilities
of the system were tested using different types of defects, such as voids, water infiltrations and thin metallic
wires. The interactions between different materials, features and the radiation beam were numerically studied
using finite element method and the results agreed with the experiments. By comparing the results with other
Non-Destructive Testing methods, it was found that CW THz imaging is particularly interesting to image water
infiltrations and composite materials that incorporate conductive wires.

Machado, MA, Rosado L, Pedrosa N, Miranda RM, Piedade M, Santos TG.  2017.  Customized Eddy Current Probes for Pipe Inspection. Studies in Applied Electromagnetics and Mechanics. :283-290.: IOS Press Ebooks Abstract

A novel Eddy Current (EC) probe configurations were developed to detect millimeter defects with any orientation on inner or outer pipe surfaces. The probes were designed and experimentally validated in different materials where the defects tested were identified with a high sensitivity and good signal-to-noise ratio.

Dos Santos, TG, Silva BS, Dos Santos Vilaça P, Quintino L, Sousa JMC.  2008.  Data fusion in non destructive testing using fuzzy logic to evaluate friction stir welding, 2008. Welding International. 22(12):826-833.: Taylor and Francis Ltd. AbstractWebsite
Santos, TG, Miranda RM, Vieira TM, Farinha RA, Ferreira TJ, Quintino L, Vilaça P, de Carvalho CCCR.  2016.  Developments in micro- and nano-defects detection using bacterial cells. NDT & E International. 78:20-28. AbstractWebsite

This paper describes improvements to the Nondestructive Testing (NDT) technique recently proposed, based on the use of bacterial cell suspensions to identify micro- and nano-surface defects. New bacterial strains were used with magnetic fields to improve bacteria mobility. Different materials and defect morphologies were tested, including nanoindentation defects, micro-powder injection moulding components and micro-laser welding. Nanoindentations with 0.6 µm depth and 5.3 µm side length were successfully detected. Bacterial cells allow identifying different topographic attributes of the surfaces, such as roughness. Cracks of about 0.5 µm wide and 10 µm depth in a reference test block Type 1 were successfully detected.

Santos, T, Vilaça P, Quintino L.  2009.  Developments in NDT for detecting imperfections in friction stir welds in aluminium alloys, 2009. Rivista Italiana della Saldatura. 61(1):65-72. AbstractWebsite
Santos, T, Vilaça P, Quintino L.  2008.  Developments in NDT for detecting imperfections in friction stir welds in aluminium alloys, 2008. Welding in the World. 52(9-10):30-37. AbstractWebsite
Rosado, LS, Santos TG, Ramos PM, Vilaça P, Piedade M.  2012.  A differential planar eddy currents probe: Fundamentals, modeling and experimental evaluation, 2012. NDT and E International. 51:85-93. AbstractWebsite
Machado, MA, Silva MI, Martins AP, Carvalho MS, Santos TG.  2021.  Double active transient thermography, nov. NDT & E International. :102566. AbstractWebsite


Santos, TG, Vilaa P, Miranda RM.  2011.  Electrical conductivity field analysis for evaluation of FSW joints in AA6013 and AA7075 alloys, 2011. Journal of Materials Processing Technology. 211(2):174-180. AbstractWebsite
Santos, TG, Miranda RM, Vilaça P.  2011.  Electrical conductivity measurement to assess structural modifications in FSW joints in Aluminium alloys, 2011. Annals of "Dunarea de Jos" University of Galati, Fascicle XII, Welding Equipment and Technology. 22:25-29. AbstractWebsite
Gomes, JF, Miranda RM, Santos TJ, Carvalho PA.  2014.  Emission of nanoparticles during friction stir welding (FSW) of aluminium alloys, 2014. Journal of Toxicology and Environmental Health - Part A: Current Issues. 77(14-16):924-930.: Taylor and Francis Inc. AbstractWebsite
Antin, K-N, Machado MA, Santos TG, Vilaça P.  2019.  Evaluation of Different Non-destructive Testing Methods to Detect Imperfections in Unidirectional Carbon Fiber Composite Ropes. Journal of Nondestructive Evaluation. 38(23) AbstractWebsite

Online monitoring of carbon fiber reinforced plastic (CFRP) ropes requires non-destructive testing (NDT) methods capable of detecting multiple damage types at high inspection speeds. Three NDT methods are evaluated on artificial and realistic imperfections in order to assess their suitability for online monitoring of CFRP ropes. To support testing, the microstructure and electrical conductivity of a carbon fiber rope is characterized. The compared methods are thermography via thermoelastic stress analysis, ultrasonic testing with commercial phased array transducers, and eddy current testing, supported by tailor-made probes. While thermoelastic stress analysis and ultrasonics proved to be accurate methods for detecting damage size and the shape of defects, they were found to be unsuitable for high-speed inspection of a CFRP rope. Instead, contactless inspection using eddy currents is a promising solution for real-time online monitoring of CFRP ropes at high inspection speeds.

Santos, TG, Miranda RM, Vilaça P.  2014.  Friction Stir Welding assisted by electrical Joule effect, 2014. Journal of Materials Processing Technology. 214(10):2127-2133.: Elsevier Ltd AbstractWebsite
Santos, TG, Miranda RM, Vilaça P.  2014.  Friction stir welding assisted by electrical joule effect to overcome lack of penetration in aluminium alloys, 2014. 17th Conference of the European Scientific Association on Material Forming, ESAFORM 2014. 611-612:763-772., Espoo: Trans Tech Publications Ltd AbstractWebsite
Rosado, LS, Gonzalez JC, Santos TG, Ramos PM, Piedade M.  2013.  Geometric optimization of a differential planar eddy currents probe for non-destructive testing, 2013. Sensors and Actuators, A: Physical. 197:96-105. AbstractWebsite