Ultrasonic signal modality: A novel approach for concrete damage evaluation

[EN] In this paper, a new approach for characterizing material damage, using ultrasonic waves, is proposed. Two concrete series with two types of cement with different C3A content and similar mechanical properties were subjected to external sulphate attack (ESA) and evaluated using a novel Recurrence Plot Quantification Analysis (RQA) method. This brand new technique was compared with several methods, such as mechanical tests (compressive and flexural strength determination), dynamic test (dynamic modulus) measurements, and traditional ultrasonic measurements (propagation velocity and ultrasonic wave attenuation). In these experiments, RQA showed a high sensitivity to damage in spoiled series, improving the reliability of damage detection with ultrasonics in non-homogeneous materials compared to other non-destructive techniques. Interesting advantages of this new non-destructive technique are: a) the RQA parameter is normalized (range of 0 to 1); b) a calibration process is not required; c) the values of its standard deviation show the dispersion of the damage. It can contribute greatly to the diagnosis of the degree of damage to a material, when combined with other traditional measures such as the attenuation of the material.This work was supported by the Spanish Government under grants TEC2011-23403, BIA2014-55311-C2-1-P and BIA2014-55311-C2-2-P. This work is protected by the Spanish Patent and Trademark Office (SPTO) under reference P201630212.Carrión García, A.; Genovés, V.; Gosálbez Castillo, J.; Miralles Ricós, R.; Paya Bernabeu, JJ. (2017). Ultrasonic signal modality: A novel approach for concrete damage evaluation. Cement and Concrete Research. 101:25-32. https://doi.org/10.1016/j.cemconres.2017.08.011S253210

Evaluation of Cavitation Erosion Behavior of Commercial Steel Grades Used in the Design of Fluid Machinery

The erosion response under cavitation of different steel grades was assessed by studying the erosion rate, the volume removal, the roughness evolution, and the accumulated strain energy. A 20 kHz ltrasonic transducer with a probe diameter of 5 mm and peak-to-peak amplitude of 50 lm was deployed in distilled water to induce damage on the surface of commercial chromium and carbon steel samples. After a relatively short incubation period, cavitation induced the formation of pits, cracks, and craters whose features strongly depended on the hardness and composition of the tested steel. AISI 52100 chromium steel showed the best performance and is, therefore, a promising design candidate for replacing the existing fluid machinery materials that operate within potential cavitating environments

Numerical modeling of the ultrasonic cavitation field and experimental evaluation of bubble density

6 pages.-- PACS nr.: 43.35 Ei.-- Communication presented at: Forum Acusticum Sevilla 2002 (Sevilla, Spain, 16-20 Sep 2002), comprising: 3rd European Congress on Acoustics; XXXIII Spanish Congress on Acoustics (TecniAcústica 2002); European and Japanese Symposium on Acoustics; 3rd Iberian Congress on Acoustics.-- Special issue of the journal Revista de Acústica, Vol. XXXIII, year 2002.A numerical model of ultrasonic cavitation field is described. It is based on a phenomenological description of a cavitating fluid as a non linear fluid whose characteristics (sound speed, density) depend upon the bubble density. To obtain the constitutive relationship between bubble density and acoustic pressure, a real-time measurement method of the bubble density, relying upon the variation of the electrical resistance of the medium, is proposed. The finite element formulation of the model is derived and implemented in the ATILA code. Computational results on the cavitation field created by a cylindrical concentrator are presented.This work was supported by CNRS and CSIC (French-Spanish cooperation project #7967) and by the European Union (Feder-Retex II).Peer reviewe