LMA - Laboratoire de Mécanique et d’Acoustique

B. Wattrisse - Measurements of energy in mechanical testing

Amphithéâtre François Canac, LMAAmphithéâtre François Canac, LMA

Le 11 October 2016 de 11h00 à 12h00

Bertrand Wattrisse, Full Professor

Université de Montpellier, LMGC

During a mechanical solicitation, the material transforms the received mechanical energy into different forms of energy (elastic energy, stored energy, heat …). The conversion of mechanical energy into heat has been investigated in a wide range of materials by numerous authors. Naturally, the way the energy is partitioned characterizes the material behavior as a whole. The construction of the energy balance associated with a mechanical loading requires the determination of several “measurable” quantities (overall deformation, temperature) but also of non-measurable ones (stresses). These latter can be “easily” obtained in simple (uniaxial) tests on homogeneous specimens but their estimation is quite more difficult in heterogeneous situations that are far more common in practice (localization, complex loading …).

The combined use of imaging techniques such as Digital Image Correlation and Infrared Thermography allows reaching fields of deformation and temperature measurements even in the presence of highly localized material responses. Apart from the technical difficulties inherent to the simultaneous use of cameras working in different wavelength ranges – which requires temporal (synchronous) and spatial matching, and ad hoc lighting –, it is necessary to develop adapted data processing techniques to extract the relevant thermo-mechanical quantities from the recorded images. These data-processing are often related to inverse problem solving (such as heat equation inversion or mechanical inversion). This presentation will focus on an experimental strategy proposed to reach the local fields necessary to estimate the local mechanical energy developed by the material and the heat sources generated by the mechanical loading. The design of specific mechanical solicitations to activate specific material properties will finally be addressed.

See online : Page personnelle de Bertrand Wattrisse