Assessment of principal strain uncertainties in stereo-DIC due to uncontrollable change of initial boundary conditions during vacuum-assisted thermoforming - Archive ouverte HAL
Communication Dans Un Congrès Année : 2019

Assessment of principal strain uncertainties in stereo-DIC due to uncontrollable change of initial boundary conditions during vacuum-assisted thermoforming

Résumé

Full-field measurement of principal mechanical strains via the stereo-digital images correlation technique (stereo-DIC) during thermoforming of thin thermoplastic sheets was recently reported as a potential method to control the wall-thicknesses under the assumption of material’s incompressibility. The accuracy of mechanical strains during forming thermoplastic sheets are not only dependent of reconstruction and correlation errors of stereo-DIC, but also of the considered reference state of boundary conditions following the temperature-regulation of thermoplastic sheets. This paper introduces an experimental method based on high speed imaging techniques such as IR-thermography and stereo-DIC techniques to detect damped out-of-plane undulations which are associated with the initiation of dynamic inflation operations of thin sheets. The aim is to rely on the characteristic durations of these short-time events to objectively separate between mechanical strains which are affected by the uncontrollable change of boundary conditions from the global pressure-induced strains. An application case is presented to demonstrate that damped out-of-plane undulations are beneficial to avoid ill-posed stereo-DIC problems particularly when the boundary conditions are sensitive to regulation operations of temperature.
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Dates et versions

hal-02175866 , version 1 (06-07-2019)

Identifiants

Citer

A. Ayadi, M.-F. Lacrampe, P. Krawczak. Assessment of principal strain uncertainties in stereo-DIC due to uncontrollable change of initial boundary conditions during vacuum-assisted thermoforming. 22nd International Conference on Material Forming (ESAFORM 2019), May 2019, Vitoria-Gasteiz, Spain. pp.130002, ⟨10.1063/1.5112662⟩. ⟨hal-02175866⟩
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