Search

A uniaxial compression test was performed on a green compacted alumina powder. Using Digital Image Correlation (DIC), displacement fields of two perpendicular surfaces of the specimen were measured showing unavoidable bending effect. A constitutive model was calibrated through three Finite Element Model Updating approaches. First, an analysis was performed using average axial strains assessed via DIC and resultant forces to identify the constitutive model. Then, a plane stress analysis was conducted out using the displacements of the boundaries of the regions of interest for each camera separately to obtain the sought parameters. Last, a 3D analysis was carried out using the multi-point constraint method to link displacement fields of both surfaces. Because of bending, the first two approaches give rise to two sets of different parameters. The analysis that considers the 3D nature of bending leads to the set of parameters with the highest degree of confidence. Unlabelled Image • DIC was applied for two perpendicular surfaces of a uniaxially compressed specimen. • Undesirable (but unavoidable) bending effects were characterized. • A 3D analysis was carried out by coupling the DIC displacements fields on the two faces. • Parameters of a constitutive model were calibrated using three different FEMU approaches. [ABSTRACT FROM AUTHOR]

Abstract Cold uniaxial pressed PTFE compacts were subjected to thermal cycles of increasing maximum temperature below melting temperature, and thermal expansion was followed in both the compaction and transverse directions. The measurements reveal that thermal expansion consists of two distinct contributions: i) an irreversible part that is controlled only by the maximum temperature experienced by the sample, and ii) a reversible, or thermo-elastic, part that is observed while cycling below the maximum temperature. Moreover, both of these thermal strains exhibit marked anisotropy, resulting from the cold oedometric compaction of the sample. A quantitative analysis of these eigenstrains is proposed, following a formal analogy with elasto-plasticity. Finally, it is shown that such behavior is specific to cold-pressed compacts as sintered samples exhibit isotropic and purely reversible thermo-elastic behavior. Highlights • Thermal expansion of cold pressed PTFE compacts contains two anisotropic contributions, one reversible and one irreversible. • Dilatometric measurements during repeated cycles of increasing amplitude allows these two contributions to be distinguished. • The irreversible part of the thermal expansion is controlled solely by the maximum temperature experienced by the sample. [ABSTRACT FROM AUTHOR]