Prof. Alejandro Restrepo-Martínez Profile

Prof. Alejandro Restrepo-Martínez

Associate Professor at Univ Nacional de Colombia Sede Medellin

SPIE Involvement:

Author

Publications (27)

Proceedings Article | 1 October 2024 Poster + Paper

Evaluation of the thermal efficiency of ethylene glycol/magnetite nanofluids for use in direct absorption solar collectors

J. Jose Alcalde, Laura Álvarez-Gil, Alejandro Restrepo-Martínez

Proceedings Volume 13132, 131320H (2024) https://doi.org/10.1117/12.3028098

KEYWORDS: Transmittance, Nanoparticles, Absorption, Iron, Ethylene glycol, Synthetic aperture radar, Solar radiation, Thermal efficiency, Statistical analysis, Quantum experiments

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Proceedings Article | 30 September 2024 Presentation + Paper

Active thermography strategy in phantom models under magnetic induction: a new perspective for the hyperthermia

J. Esteban García, Laura Álvarez, Alejandro Restrepo-Martínez

Proceedings Volume 13136, 131360M (2024) https://doi.org/10.1117/12.3028053

KEYWORDS: Magnetism, Thermography, Thermal modeling, Metals, Temperature distribution, Principal component analysis, Image segmentation, Image processing, Electroluminescence, Statistical analysis

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Proceedings Article | 30 September 2024 Poster + Paper

Open-source 3D-printed microscope with semiautomated liquid crystal polarizer setups: a new opportunity for detecting small phase retards in oocyte meiotic spindles

J. Jose Alcalde, Alejandro Restrepo-Martínez, Giovanni Restrepo Betancur

Proceedings Volume 13136, 131360P (2024) https://doi.org/10.1117/12.3028130

KEYWORDS: Polarization, Liquid crystals, Microscopes, Spindles, Crystals, Biological samples, Polarizers, Prototyping, 3D printing, Linear polarizers

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Proceedings Article | 15 August 2023 Poster + Paper

Non-destructive evaluation of thermal barrier coating thickness using IR thermography in chemical removal processes

Jhonatan Román-Román, Andrés García-Revuelta, Alejandro Restrepo-Martínez, Alejandro Toro-Betancur, Oscar Muñoz-Giraldo

Proceedings Volume 12618, 126182V (2023) https://doi.org/10.1117/12.2673885

KEYWORDS: Coating thickness, Thermography, Coating, Principal component analysis, Statistical analysis

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Active thermography is a non-destructive testing (NDT) technique with great potential for evaluating the integrity, thickness, homogeneity, and structure of thermal barrier coatings (TBCs), which are widely used in the hot gas path of thermoelectric power plants. In this study, active thermography was used as a non-destructive analysis technique to measure the thickness of the YSZ ceramic layer in thermal barrier coatings subjected to a chemical removal process as a function of exposure time to the agent. The TBC samples analyzed consisted of ZrO2-7 wt% Y2O3 atmospheric plasma sprayed with NiCoCrAlY bond coat in nickel-based superalloy. The ablation process consisted of complete immersion of the sample in an aqueous solution of ammonium bifluoride (0 min, 90 min, 240 min, 330 and 420 min), maintaining a temperature of about 60 °C to about 68 °C and subjecting it to an ultrasonic bath. Thermographic evaluation was performed at room temperature using two 600 W flash lamps, one 500 W halogen lamp, and a long-wave infrared camera with an acquisition rate of 30 Hz. Samples were taken for microstructural analysis and thickness measurement using SEM microscopy and eddy currents. Thermographic information was processed using thermal signal reconstruction algorithms and correlated with microstructural characteristics and thickness as a function of immersion time. The results show differences in both the heating and cooling curves of the samples, which can be correlated to differences in the thickness of the coatings. In this study, active thermography was used as a non-destructive analytical technique to measure the thickness of the YSZ ceramic layer in thermal barrier coatings subjected to chemical removal. ZrO2-7 wt% Y2O3 coatings were immersed in an aqueous solution of ammonium bifluoride. Thermographic information was acquired using a 30 Hz infrared camera and two 600 W flash lamps. The results show differences in their heating and cooling curves, which allow them to be correlated with the coating thickness measured by SEM microscopy and eddy currents.

Proceedings Article | 15 August 2023 Poster + Paper

Detection of delaminated areas in thermal barrier coatings by active infrared thermography using different heat sources

Andrés García-Revuelta, Jhonatan Román, Alexander Arboleda, Alejandro Toro, Alejandro Restrepo-Martínez

Proceedings Volume 12618, 126182T (2023) https://doi.org/10.1117/12.2673866

KEYWORDS: Signal to noise ratio, Lamps, Thermography, Principal component analysis, Halogens, Pulse signals, Reconstruction algorithms, Infrared cameras, Matrices, Defect detection, Coating stress, Infrared imaging, Thermographic image processing, Defect inspection

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Proceedings Article | 15 August 2023 Poster + Paper

Photoelastic and Stokes images through deep convolutional neural networks: a comparison of stress fields

Diego Eusse Naranjo, Alejandro Restrepo-Martínez

Proceedings Volume 12618, 1261820 (2023) https://doi.org/10.1117/12.2672129

KEYWORDS: Polarization, Photoelasticity, Image processing, Image quality, Cameras, Neural networks, Deep convolutional neural networks

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Proceedings Article | 10 August 2023 Presentation + Paper

A new three-wavelength chromatic-corrected hybrid phase shifting method for single-camera digital photoelasticity

A. Restrepo-Martínez

Proceedings Volume 12619, 126190C (2023) https://doi.org/10.1117/12.2673726

KEYWORDS: Photoelasticity, Phase shifting, Algorithm development, Phase unwrapping, RGB color model

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