COMPARATIVE MECHANICAL SPECTROSCOPY BY COMPUTATIONAL GEOMETRY. ACOUSTIC Brandon Farrera Buenrostro, Israel Aguilera Navarrete, Juan Manuel Prado Lázaro, Héctor Javier Vergara Hernández, Francisco Reyes Calderón Vibrations Publicaciones DYNA SL -- c) Mazarredo nº69 - 2º -- 48009-BILBAO (SPAIN) Tel +34 944 237 566 – www.revistadyna.com - email: dyna@revistadyna.com Pag. 1 / 2 ISSN: 0012-7361 eISSN: 1989-1490 / DYNA Vol.98, n.2 DOI: https://doi.org/10.6036/10779 COMPARATIVE MECHANICAL SPECTROSCOPY BY COMPUTATIONAL GEOMETRY. Brandon Farrera-Buenrostro 1 , Israel Aguilera-Navarrete 2 , Juan-Manuel Prado-Lázaro 2 , Héctor J. Vergara-Hernández 1 y Francisco Reyes-Calderón 1 1 CONACYT-TECNM/I.T (México) 2 IIMM/UMSNH (México) DOI: https://doi.org/10.6036/10779 When impacted, it is evident to many that the metals produce a characteristic sound. For centuries, people have struck the coins for the sound that distinguishes the truth from the false. Unfortunately, when the Materials present slight differences, such as heat or mechanical treatments is almost impossible for the human ear to differentiate these modifications. Massara et al. [1] compiled a set of pulse data in different materials using an instrument of its construction to characterize mechanical properties using multivariate statistical analysis. Finally, researchers worldwide use the impulse technique (IET) for a wide range of materials due to their simplicity, cost, high precision, and reproducibility. The IET will probably dominate among the other methods and non-destructive testing techniques, as shown by Wang et al. [2]. Recently Farrera et al. [3] presented a novel technique based on computational geometry that uses the analysis of vector distances to differentiate metallic materials through IET of a metal cylindrical probe y based on the standard ASTM E1876 to obtain frequency spectrum, which through geometry vector analysis are correlated when processing the signal employing programming at SciLab, which despite the diversity of packages of available software, SciLab is a high-level programming language for scientific calculation. The technique in question supports destructive testing used to differentiate the internal state of a material to reduce the response times and costs involved. This note's figure graphically presents the methodology to obtain the frequency spectrum. In which the background is placed frequency domain spectrum; to the left a test representation listing each item main, 1.-Microphone, 2.- Test probe, 3.- Isolated support, 4.- Structure, 5.- Positions for height change and 6.- Impulser; in the center of the figure a frequency spectrum is placed on time domain and to the top right the final result of the methodology, a dendrogram with the clustering of specimens of three different materials. To give more confidence to the methodology is demonstrated experimentally in [3] using a full factorial design that involves Ferrous and non-Ferrous materials, showing that the method can identify differences, independent of the intensity of the impulse provided by changing the drop height, gives the excitatory element. Besides, regardless of the strength of excitation or impact height, the frequency spectrum sequence is the same as long as the force is sufficient to cause a vibration of the material without the specimen being displaced or damaged, demonstrating that the IET assay is an alternative technique to differentiate materials derived from the sensitivity of the test to microstructural in metallic materials. It is crucial to conclude that the natural frequency depends on the modulus of stiffness, which in turn is related to the modulus of elasticity, in such a way that the natural frequency of vibration of a material is unique, as is the module of elasticity. Therefore, it is possible to identify and label different materials through their vibration and, by involving algebra superior, such as the creation of a vector space taken from axes to the frequency spectrum generated by their differences, which makes it possible to expedite the identification of the microstructural state of the materials.