16:00
Solid Mechanics 2
Chair: Jean-José Orteu
16:00
20 mins
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IDENTIFICATION OF PLASTIC MATERIAL BEHAVIOUR OF THICK HIGH STRENGTH STEEL THROUGH FEMU TECHNIQUES
Kristof Denys, Sam Coppieters, Marc Seefeldt, Dimitri Debruyne
Abstract: A finite element model updating method to identify the strain hardening behaviour of thick high strength steels at large plastic strains (i.e. beyond the point of maximum uniform strain) is presented. The impact of the boundary conditions in the finite element model updating procedure and the chosen cost function are investigated. Numerically deformed speckle patterns have been used to investigate the accuracy of a swift hardening law with different boundary conditions and cost functions. The most accurate boundary conditions and cost function are used to identify a swift hardening law on a real experiment with a perforated 10 mm thick S690QL high strength steel specimen, which gave improved results.
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16:20
20 mins
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EXPERIMENTAL INVESTIGATION OF THE KINEMATICS LINKS BETWEEN SCALES IN A MULTISCALE STRUCTURE
Jeremy Marty, Julien Réthoré, Alain Combescure
Abstract: Multi-scale methods bring new perspectives to obtain detailed information for structures with two scales in particular the methods based on the FE2 techniques. In case of strongly non-linear processes or failure, the kinematics links between the two scales are still unclear. For now the multiscale methods are validated by comparison with a full field simulation. Some experimental works exist but they are related to global macroscopic behaviour or post mortem microscopy at the microscopic scale. In this study, we perform experiments on a multiscale structure with a high resolution camera to obtain the strain fields at both scales. Some aspects of non-linear behaviour like periodicity, higher-order effects or strain localization are then studied.
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16:40
20 mins
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BIAXIAL TESTING OF KNITTED NITI TEXTILES: ADAPTED IMAGE PROCESSING VS DIC
Nathanael Connesson, Francois Tissot, Denis Favier, Ludeck Heller
Abstract: Knitted NiTi textiles are architectured materials that may be used, for example, as flaps reinforcement during facial surgery. An experimental study has been performed to study the textile characteristics impact on its mechanical behavior under biaxial testing. For such an experiment, the data of interest is the textile global displacement and strain fields versus load, the stitches shape evolution, the local sliding between wires and local wire deformation, etc. As a usual DIC would provide only the global displacement and strain fields, an in-house software has been developed. This paper describes the chosen image processing method and the first results obtained while analyzing NiTi textile. For example, the obtained global displacements and associated strain fields obtained with the DIC or the in-house software are identical.
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17:00
20 mins
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LOCAL ANALYSIS OF FRETTING DAMAGE BY MEANS OF FULL FIELD MEASUREMENT
Abdel Rahman Moustafa, Bruno Berthel, Siegfried Fouvry, Jean-François Witz, Eric Charkaluk
Abstract: The improvements in camera technology and image processing have caused full field measurement techniques to become more and more frequently used in the field of experimental mechanics. Nevertheless, few applications can be found in the field of contact mechanics. Therefore, the aim of this work is to present, a novel experimental set-up based on coupled kinematic-thermal measurements to assess fretting damage. A well known 35Ni Cr Mo 16 low-alloyed steel was studied under various plain fretting partial slip conditions. Analysis of the thermal signal have shown the possibility of decoupling thermal effects related to intrinsic dissipation, thermoelastic sources and dissipation due to friction.
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17:20
20 mins
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INTERGRANULAR CREEP CRACK MONITORING IN 316H USING DIGITAL IMAGE CORRELATION
Laurie Podesta, Bertrand Wattrisse, Félix Latourte, Laurent Waltz, Jean-Michel Muracciole
Abstract: ABSTRACT: At elevated temperature (550°C) intergranular creep cracks have been observed in thermally and environmentally aged 316H stainless steel. To improve the understanding of mechanisms responsible of creep cracking, micromechanical experiments are proposed. An identification procedure of the crack tip position based on kinematic measurements is presented. Finite element simulations of intergranular cracks in bycristals have been performed and used as test fields to deform experimental images and to validate the image processing used for the identification.
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17:40
20 mins
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EXTENSIONS TO GLOBAL DIGITAL IMAGE CORRELATION
Johan Hoefnagels, Jan Neggers, Lambert Bergers, Jeroen van Beeck, Salman Shafqat, Marc Geers
Abstract: In the previous edition of the PhotoMechanics conference, a novel Quasi-3D Digital Image Correlation method, based on the Global Digital Image Correlation (GDIC) framework, was presented and it was shown that this technique could eliminate systematic error sources in the well-known Bulge Test method, by directly measure the full-field strain and curvature map. In this PhotoMechanics edition, a number of extensions to the Q3-GDIC method will be presented, including: (i) improvement of the Bulge Test method to buckled membranes, (ii) highly sensitive nano-scale full-field curvature measurements of MEMS structures, and (iii) quantification of three-dimensional surface deformations.
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