Three-dimensional yielding in anisotropic materials: validation of Hill's criterion

Abstract

Yielding transition in isotropic soft materials under superposition of orthogonal deformation fields is known to follow von Mises' criterion. However, in anisotropic soft materials von Mises' criterion fails owing to preferred directions associated with the system. In this work we study a model anisotropic yield stress system: electrorheological (ER) fluids that show structure formation in the direction of electric field. We subject the ER fluids to superposition of orthogonal stress fields that leads to different yield stress values. We obtain a yielding state diagram by plotting normalized rotational shear stress against normalized radial shear stress corresponding to yield point for a given electric field. Remarkably, the state diagram validates the Hill's yielding criterion, which is a general yielding criterion for materials having anisotropy along three orthogonal directions, originally developed for metallic systems. Validation of Hill's criterion suggests the universality of its application to anisotropic systems including conventional anisotropic soft materials having yield stress.

Pure elongation flow of an electrorheological fluid: insights on wall slip from electrorheology

“…These dipoles get organized in a preferential manner along the electricfield to form a chain/columnar structure, resulting in a solid-like character in the material. [22][23][24][25][26][27][28] The major advantage of such fluids is that the extent of jamming can be controlled by regulating the electric-field strength at a given concentration. Moreover, these suspensions can achieve a reasonable extent of jamming at moderate particle concentrations under an electric field.…”

“…Moreover, these suspensions can achieve a reasonable extent of jamming at moderate particle concentrations under an electric field. [25][26][27][28] Such external control on fluidity makes these ER fluids a potential candidate for various applications involving electromechanical interfaces, such as shock absorbing devices, damping/breaking systems, clutches. [29][30][31] Therefore, fundamental understanding of flow behavior of such smart fluid in various flow modes is of great importance.…”

Analysis of Plastic Forming Parameters in Aisi 441 Stainless Steel

“…During the analysis is also necessary to consider the impact of previous production process which create dispersion in mechanical properties and which show a character no longer deterministic bust stochastic. The plastic deformation of pipes caused by mechanical processing, leads an anisotropic behavior which must be studied by mathematical models; Von Mises and Johnson-Cook [36,37] criteria for example describe the elastic-plastic behavior of isotropic materials, Hill's criterion instead defines the equations for orthotropic and anisotropic materials [38,39]. In this paper is used a commercial software package adopting Hill's criterion to study the deformation process of ferritic stainless-steel tubes and the results are compared to those resulting from experimental test.…”