Proyectos

Dislocations are at the source of plastic behavior of metals and alloys, yet it is very difficult to quantitatively study their behavior. In order to improve this situation, it is proposed to use their interaction with elastic waves as a nonintrusive probe. The long-term aim of the research presented in this proposal is to enable the development of ultrasound technology as a practical non-intrusive tool for the characterization of plastic behavior of materials. In recent years, proposers have shown, using Resonant Ultrasound Spectroscopy (RUS), that an increase of dislocation density in aluminum by a factor of 6 leads to a change for the speed of shear waves on the order of 1%, a quantity that can be measured with an accuracy on the order of 0.1%. They have also shown that local measurements of the speed of shear waves in aluminum under standard testing conditions in tension provide a quantitative, accurate, nonintrusive and continuous relation between dislocation density and externally applied stress, and that an increase in dislocation density by a factor of ten in copper and aluminum leads to an increase in the value of the (nonlinear) parameter that characterizes second harmonic generation by 20 to 60%. This proposal seeks to go one more step towards a practical implementation of the proposed ultrasonic testing tool for pieces in service. Materials of wide use in industry, 304L steel and TWIP steel, will be used. And in addition to bulk ultrasonic and shear waves, surface Rayleigh waves will be tested, in order to develop techniques that are useful when pieces in service have a geometry that does not lend itself to bulk wave measurement. Both linear (wave propagation velocity and attenuation) and nonlinear (second harmonic generation) acoustics measurements will be performed, using bulk and surface waves, ex situ after mechanical treatment, and in situ under standard testing conditions. In addition, dislocation density will be measured using X-ray diffraction (XRD) , using both the modified Warren-Averbach and Rietveld methods. Additional characterization will be performed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The expected result of the proposed research is a set of measurements that relate acoustics parameters to dislocation density in 304L and TWIP steels. The specific goal is that these measurements will provide a framework for the development of devices to nondestructively measure the dislocation density of pieces in service.

Work on the open problem of proving existence of minimizers in nonlinear elasticity in the paradigmatic neoHookean model. Finite element simulations, modelling, and experiments for swelling of polymer gels bonded to rigid substrates. Finite element simulations, modelling, and asymptotic analysis for Schallamach waves in the detachment of thin hydrogels. Proof that the transition, in elastomers and ductile materials, from multiple independent spherical cavitation to the coalescence stage occurs when the size, in the deformed configuration, of the opened cavities is comparable to the distance, in the reference configuration, between the cavitation singularities.

Nonsmooth dynamical system involving regular structures

-

Fondo de Innovación para la Competitividad - FIC2018 - 6ta región. Gobierno Regional. Proyecto titulado: Laboratorio Biominero para la Región de O’Higgins. Institución patrocinante: Universidad de O’Higgins. Marzo 2019-Diciembre 2020.

The EVE project aims at facilitating the interaction and cooperation between scientists and Civil Protection Agencies (CPs) to timely anticipate to volcanic disasters. Built upon the previous EC ECHO funded project VeTOOLS, the aim of EVE is to combine the knowledge on the past eruptive behaviour of the volcanoes with the analysis of real time monitoring in order to construct the European volcano EWS. EVE will offer an easy and rapid way to forecast in real time how, when and where a new eruption may occur, thus allowing to predict the most probable eruption scenarios and their potential impacts. EVE will facilitate scientific and technical cooperation at regional and international scales by defining common actions and protocols to forecast volcanic scenarios and their potential impacts, in real time during a volcanic crisis.