21th September – Alexandre IMPERIALE: Numerical methods for time domain wave propagation problems applied to ultrasonic testing modelling

Alexandre IMPERIALE Wednesday 21th Sep at 15:00



The Department of Imaging and Simulation for Control (DISC) at CEA – LIST is dedicated to developing Non-Destructive Testing (NDT) methods in advanced industrial contexts (e.g. nuclear energy, aeronautic, or petrochemical industries). Amongst different testing modalities, Ultrasonic Testing (UT) is widespread and plays a major role in numerous industrial processes. It relies on the propagation of mechanical waves in order to probe critical specimens, often formed with complex media – in terms of geometry or material properties. To fully understand the capabilities and performances of UT experiments, the DISC is developing modelling tools for wave propagation, which are bound to incorporate the CIVA platform [1] – a commercial software dedicated to NDT modelling.

When commercializing modelling tools, efficiency and robustness are key features. This talk focuses on numerical methods for wave propagation problems that address these challenges. In particular, we show how the combination of Spectral Finite Elements [2] with the Mortar Element method [3] – a domain decomposition approach – can be tuned to render efficient and robust algorithms [4]. Coupled with high-frequency asymptotic methods [5] (e.g. ray-based algorithms), this combination forms the basis of various advances in the CIVA platform. This approach is typically used to modelling UT experiments relying on bulk wave propagation, e.g. for testing welds (typical nuclear energy industry applications) or composite materials [6] (typical aeronautic industry applications). Additionally, we present some details on ongoing works related to other UT configurations, such as numerical modelling of wave propagation through thin layers – based on effective transmission conditions – or within plate-like geometries – achieved through dedicated time schemes.

[1] http://www.extende.com/civa-in-a-few-words
[2] Cohen, G. C. “Higher-order numerical methods for transient wave equations”. Berlin: Springer, 2002 Vol. 5. [3] F. Ben Belgacem, Y. Maday, “The mortar element method for three-dimensional finite elements”, ESAIM: M2AM 31 (2) (1997)
[4] Imperiale, A., et. al., “A macro-element strategy based upon spectral finite elements and mortar elements for transient wave propagation modeling. Application to ultrasonic testing of laminate composite materials”, Int. J. Numer. Meth. Eng. 119 (10) (2019).
[5] Imperiale, A., et. al., “Coupling Strategies Between Asymptotic and Numerical Models with Application to Ultrasonic Non-Destructive Testing of Surface Flaws”, J. Theor. Comput. Acoust. (2018).
[6] Imperiale, A., et. al. “Numerical modeling of wave propagation in anisotropic viscoelastic laminated materials in transient regime: Application to modeling ultrasonic testing of composite structures”. Int. J. Numer. Methods Eng., 121 (15) (2020).

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