Testing and evaluation

Static and dynamic features of Fourier transform profilometry: A review

The problem of shape control and correction of small displacements in composite structures using piezoelectric actuators glued or embedded was addressed. A finite element model based on Mindlin plate theory was used to characterize the behaviour of the structure and the one of the actuators. Emphasis was put on the development of an efficient and general methodology, based on genetic algorithms, for the determination of the optimal actuation voltages needed to apply to the piezoelectric actuators in such a way that a pre-defined shape of the structure is achieved. The model was investigated numerically and verified experimentally. Measurements were carried out using electronic speckle pattern interferometry. Good agreement was found between simulation results and the optically measured values.

https://paginas.fe.up.pt/~inegi/lome/Artigos/genetic_algorithms.pdf

The application of genetic algorithms for shape control with piezoelectric patches—an experimental comparison

This paper proposed a comprehensive algorithm for building machine learning classifiers for Breast Cancer diagnosis based on the suitable combination of feature selection methods that provide high performance over the Area Under receiver operating characteristic Curve (AUC). The new developed method allows both for exploring and ranking search spaces of image-based features, and selecting subsets of optimal features for feeding Machine Learning Classifiers (MLCs). The method was evaluated using six mammography-based datasets (containing calcifications and masses lesions) with different configurations extracted from two public Breast Cancer databases. According to the Wilcoxon Statistical Test, the proposed method demonstrated to provide competitive Breast Cancer classification schemes reducing the number of employed features for each experimental dataset.

/pdf/improving-the-performance-of-machine-learning-classifiers-w120y1rcqs.pdf

Improving the performance of machine learning classifiers for Breast Cancer diagnosis based on feature selection

We have investigated the technique to detect acoustic emission (AE) signal using a laser interferometer, which can directly detect the surface velocity due to microcracking. Thermal cycle test for Al2O3/NiCrAlY/SUS304 coatings using an infrared image furnace was carried out in order to evaluate the failure process. Laser AE measurement system was improved to increase the sensitivity of AE monitoring for coatings. Microfracture mode during thermal cycle test was analyzed based on the measured AE behavior and a finite element method (FEM) simulation of wave propagation. From the result of waveform analysis, it was found that shear mode microfracture occurred toward the center from one of the edges of the specimen. This result agreed with the propagation direction of delamination determined from AE location results and the observation of the specimen after the thermal cycles were loaded.

Evaluation of Microfracture Mode in Ceramic Coating during Thermal Cycle Test using Laser AE Technique

https://paginas.fe.up.pt/~inegi/lome/Artigos/Mech_of_Mat.pdf

NDI of interfaces in coating systems using digital interferometry

Use of interferometric techniques for measuring the displacement field in the plane of a part-through crack existing in a plate

Apontamentos de Análise Experimental de Tensões

Internal fractures in spherical, paraboloidal, hyperboloidal and elliptical solids subjected to concentrated surface explosive loading are investigated. The initiation and growth of the internal fractures are associated with the focusing effect of P and S wave fronts reflected from the curved boundaries. High speed photography on perspex specimen is used for the verification of predictions of simple methods of geometrical optics and propagation of discontinuities. The speed with which these internal fractures grow are found to depend upon the geometry of the surface of the solid.

https://repositorio-aberto.up.pt/bitstream/10216/64913/2/63485.pdf

Internal Fractures in Solids of Revolution Due to Stress Wave Focussing

/pdf/proceedings-icem15-15th-international-conference-on-3p1ctksotr.pdf

J. F. Silva Gomes

Papers

NDI of interfaces in coating systems using digital interferometry

Use of interferometric techniques for measuring the displacement field in the plane of a part-through crack existing in a plate

Apontamentos de Análise Experimental de Tensões

Internal Fractures in Solids of Revolution Due to Stress Wave Focussing

Proceedings ICEM15 - 15th International Conference on Experimental Mechanics