PhD (M/F) Matrix approach in laser ultrasonic techniques applied to elastic waveguides

  • Paris
  • CDD
  • Temps-plein
  • Il y a 22 jours
Offer DescriptionThis PhD is part of the ANR project NEWCOMERMatrix approach in laser ultrasonic techniques applied to elastic waveguidesNon-contact laser ultrasonic techniques offer a unique tool to generate and measure elastic guided waves in solids. From these waves measurement, mechanical properties can be evaluated in a non-destructive manner. Classical approaches use a focused laser beam that i) generates several guided modes and, ii) is limited in energy by the ablation threshold (to avoid damage). As a result, modes can be difficult to separate and may remain below the noise level. The goal of that PhD is to develop novel matrix approaches in laser ultrasonics to separate and optimize the generation of a particular acoustic mode. As the propagation is linear, the elastic modes can be identified from a measured transmission matrix (TM) [1-3]. Such matrix contains the medium's
responses to any excitation. Its acquisition requires multiple excitations to span the whole wave mode space. In ultrasonic imaging, such matrices are commonly acquired using a transducer array that allows shaping of the acoustic excitation. This permits the TM acquisition in different bases that are adapted to specific cases. With laser ultrasonics, it is more difficult to arbitrarily shape the laser source. Until now, most measurements were accomplished by scanning a point source, thus limiting the level of deposited energy [2]. The first goal of this PhD is to tackle this limitation by tailoring the laser source using a spatial-light-modulator (SLM) [4]. This will allow a wide variety of excitation patterns (e.g., line source arrays, Hadamard patterns, …) and the measurement of the whole sample's TM [3]. In parallel, theory will be built to determine optimal sets of excitations that should be used to measure this matrix.
Measuring specific acoustic modes, such as Zero-Group-Velocity (ZGV) Lamb modes [5], can improve the accuracy of the elastic parameters obtained from the TM measurement. This is the second goal of this work. To this end, the frequency-wavenumber corresponding to the chosen mode in the dispersion curves will be optimized. The frequency can be controlled with a cw-laser while the wavenumber will be controlled by shaping the laser source with the SLM. These complementary approaches will first be tested on well-known materials such as aluminium, and then on more complex ones such as porous silicon [6] or composite materials.
References :
[1] Aubry and Derode, Phys. Rev. Lett., 102, 084301 (2009)
[2] Gérardin et al., Phys. Rev. Lett., 113, 173901 (2014)
[3] Lopez Villaverde et al., IEEE Trans. UFFC 64, 9 (2017)
[4] Mezil et al., Appl. Phys. Lett., 111, 144103 (2017)
[5] Prada et al., Appl. Phys. Lett., 89, 024101 (2006)
[6] Thelen et al., Nat. Commun., 12, 3597 (2021)RequirementsResearch Field Engineering Education Level PhD or equivalentResearch Field Physics Education Level PhD or equivalentLanguages FRENCH Level BasicResearch Field Engineering » Materials engineering Years of Research Experience NoneResearch Field Physics » Acoustics Years of Research Experience NoneAdditional InformationAdditional commentsThe candidate should have good knowledge on wave propagation in acoustics and optics and a strong appetite for experimental work. Website for additional job detailsWork Location(s)Number of offers available 1 Company/Institute Institut Langevin Country France City PARIS 05 GeofieldWhere to apply WebsiteContact CityPARIS 05 WebsiteSTATUS: EXPIRED

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