Modeling the effects of friction and geometry on deformation path during hot rolling of aluminum

In this work, a parametric study of hot rolling is conducted. The effect of friction model, friction coefficient, roll gap geometry and temperature on the deformation rate field is demonstrated. This parameter space is restricted to a region which is tractable, yet provides considerable variety in the features of non-uniform deformation developed in rolling. The degree and nature of redundant work (shearing) is contrasted for different stream-line locations within the bite. Recommendations for the application of material models in analysis of rolling is made with consideration of the simulation predictions

Investigation of Preferred Orientations in Planar Polycrystals

More accurate manufacturing process models come from better understanding of texture evolution and preferred orientations. We investigate the texture evolution in the simplified physical framework of a planar polycrystal with two slip systems used by Prantil et al. (1993, J. Mech. Phys. Solids, 41(8), 1357-1382). In the planar polycrystal, the crystal orientations behave in a manner similar to that of a system of coupled oscillators represented by the Kuramoto model. The crystal plasticity finite element method (CPFEM) and the stochastic Taylor model (STM), a stochastic method for mean-field polycrystal plasticity, predict the development of a steady-state texture not shown when employing the Taylor hypothesis. From this analysis, the STM appears to be a useful homogenization method when using representative standard deviations.</p

Mechanisms responsible for texture development in a 5182 aluminum alloy deformed at elevated temperature

The textures that develop in a 5182 aluminum alloy as a result of monotonic high-temperature compression have been investigated. The authors found that the deformation texture was a function of temperature. For compressive deformation at 300 C and below the material formed the classic (101) deformation texture, while the material develops a texture that is a combination of the classical uniaxial compression deformation texture, (101), and static recrystallization texture, (001), as a result of the deformation alone when the deformation temperature was at and above 400 C. The investigation has focused on determining the mechanism responsible for the development of this unusual progression of deformation textures. In addition the authors have performed orientation imaging microscopy (OIM) to identify the shapes of grains with particular orientations and grain-to-grain orientation relationships. The conclusions are summarized as follows: The texture development is not a result of static processes, i.e. static recrystallization at the various hold times altered neither the textures nor the constitutive behavior. Simulation using a crystal plasticity model indicates that the combination of a cube component prevalent in the original texture, slip activity on 011 planes, and increased rate sensitivity leads to a combined (001) and (101) texture. Finally, the microscopic OIM results are consistent with these observations

Une nouvelle méthode de mesure de longueurs segmentaires

Comparaison de la technique proposée au moyen du bras de mesurage articulé FARO et de la méthode classique de l'ISAK pour déterminer plus rapidement des longueurs segmentaires humaine

Simulation of the Portevin-Le Chatelier effect using polycrystal plasticity

A polycrystal plasticity model is used to describe the Portevin-Le Chatelier effect in a velocity controlled tension test. An elastoviscoplastic constitutive model is developed. The resulting fully implicit procedure is introduced into both Taylor (material point) and finite element models. Statistical analysis of the stress drops collected through finite element simulation indicate power law distributions for continuous band propagation, consistent with experimental observations. No “artificial" gradient plasticity formulation is required since spatial gradients exist naturally due to grain incompatibilities

Effects of Size on the Dynamics of Dislocations in Ice Single Crystals

International audienceSingle crystals of ice subjected to primary creep in torsion exhibit a softening behavior: the plastic strain rate increases with time. In a cylindrical sample, the size of the radius affects this response. The smaller the radius of the sample becomes while keeping constant the average shear stress across a section, the softer the response. The size-dependent behavior is interpreted by using a field dislocation theory, in terms of the coupled dynamics of excess screw dislocations gliding in basal planes and statistical dislocations developed through cross slip occurring in prismatic planes. The differences in the results caused by sample height effects and variations in the initial dislocation microstructure are discussed