Papers by Author: Laurent Orgéas

Abstract: Corrugated boards with small flutes appear as good alternatives to replace packaging folding boards or plastic materials due their small thickness, possibility of easy recycling and biodegradability. Boxes made up of these materials have to withstand significant compressive loading conditions during transport and storage. In order to evaluate their structural performance, the box compression test is the most currently performed experiment. It consists in compressing an empty container between two parallel plates at constant velocity. Usually it is observed that buckling phenomena are localized in the box panels, which bulge out during compression [1]. At the maximum recorded compression force, the deformation localises around the box corners where creases nucleate and propagate. This maximum force is defined as the quasi-static compression strength of the box. The prediction of such strength is the main topic of interest of past and current research works. For example, the box compression behaviour of boxes was studied by Mc Kee et al. [2] and Urbanik [3], who defined semi-empirical formula to predict the box compression strength, as well as by Beldie et al. [4] and Biancolini et al. [5] by finite element simulations. But comparisons of these models with experimental results remain rather scarce and limited.

Abstract: The tension behaviour of initially austenitic NiTi thin wall tubes was investigated using measurements of temperature and strain fields simultaneously. The first specimen was totally superelastic but the unloading was performed before the end of the loading stress plateau. The second specimen loading was performed beyond the stress plateau to allow analyzing the unloading, but was not superelastic and at a faster strain rate. Both tests show homogeneous behaviour at the beginning of the loading. Strong localisations, taking the shape of helical bands, are observed during the loading and unloading stress plateaus. To obtain quantitative energy information, allowing a better recognition of the deformation mechanisms, an estimation of the local heat sources based on image processing of the temperature fields is presented. Two methods of heat sources estimation allowing analysis of deformation mechanisms are proposed in the present paper: first during the homogeneous, then during localized stages.