Inelastic constitutive equations of polycrystalline metals incorporating rotations and shape changes of grain components

2021 ◽  
pp. 169-175
Author(s):  
Masataka Tokuda ◽  
Frantisek Havlicek ◽  
Jan Kratochvil
Keyword(s):  
Constitutive Equations ◽  
Polycrystalline Metals ◽  
Shape Changes

Plastic Response of Polycrystalline Metals Subjected to Complex Deformation History

1984 ◽  
Vol 106 (4) ◽  
pp. 299-303 ◽  
Author(s):  
Jan Kratochvil ◽  
Masataka Tokuda
Keyword(s):  
Constitutive Equations ◽  
Bauschinger Effect ◽  
Plastic Response ◽  
Deformation History ◽  
Microscopic Mechanism ◽  
Complex Deformation ◽  
Polycrystalline Metals ◽  
Polycrystal Plasticity ◽  
Basic Features ◽  
Good Agreement

We attempt to formulate the elasto-plastic constitutive equations which reflect the basic features of the microscopic mechanism of plastic deformation and at the same time remains sufficiently simple to be applicable in FEM solution of the practical problems. The constitutive equations are based on a simplified verison of polycrystal plasticity. In modeling of the properties of single crystal grains of the polycrystal attention is paid to active and latent hardenings, and especially to the Bauschinger effect. The stress response along three sets of typical examples of complex deformation histories are predicted and compared with precise data of tension-torsion tests. The predictions are in good agreement with the observed behavior.

A Study on a Semimicroscopic Formulation of Inelastic Constitutive Equations of Polycrystalline Metals Subjected to a Large Deformation

1989 ◽  
Vol 111 (3) ◽  
pp. 294-298 ◽  
Author(s):  
M. Tokuda ◽  
K. Yamada ◽  
F. Havlicek
Keyword(s):  
Large Deformation ◽  
Constitutive Equations ◽  
Deformation Process ◽  
Grain Shape ◽  
Shape Change ◽  
Strain Range ◽  
Small Strain ◽  
Polycrystalline Metal ◽  
Polycrystalline Metals ◽  
Hardening Mechanisms

Work-hardening mechanisms of a polycrystalline metal significant in a large deformation range are different from those in a small strain range. That is, a texture development and an effect of grain shape change may be typical and important mechanisms in the large deformation process. In this paper, a set of inelastic constitutive equations incorporating two effects are derived theoretically on the basis of crystal plasticity.

A SMART POLYMER COMPOSITE ACTUATOR WITH THIN SMA STRIPS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 3733-3738 ◽  
Author(s):  
CHEOL KIM
Keyword(s):  
Mathematical Model ◽  
Phase Transformation ◽  
Shape Memory ◽  
Constitutive Equations ◽  
Composite Shell ◽  
Large Strain ◽  
Shell Structures ◽  
Mechanical Behaviors ◽  
Smart Polymer ◽  
Shape Changes

The characteristics of SMA to provide a high force and a large strain make them a good candidate for an actuator for controlling the shape of smart structures. Using a mathematical model that captures the thermo-mechanical behaviors and 2-way shape memory effect (TWSME) of SMA, some smart shell structures were analyzed numerically and experimentally. The deflections of morphing shells to that thin SMA strips are attached were investigated depending on various phase transformation temperatures. SMA strips start to transform from the martensitic into the austenitic state upon actuation through resistive heating, simultaneously recover the prestrain, and thus cause the shell structures to deform three dimensionally. The behaviors of composite shells with SMA strips were analyzed using FEM and 3-D constitutive equations of SMA. Several morphing composite shell structures were fabricated and their experimental shape changes depending on temperatures were compared to the numerical results. That two results show good correlations indicates FEA and 3-D constitutive equations are accurate enough to utilize them for the design of smart shell structures for various applications.

A TEM study of the microstructure of avian eggshells

1992 ◽  
Vol 50 (2) ◽  
pp. 1102-1103
Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer
Keyword(s):  
Electron Microscope ◽  
Calcium Carbonate ◽  
Nucleation And Growth ◽  
Growth Mechanisms ◽  
Shell Surface ◽  
Thin Sections ◽  
Polycrystalline Metals ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.

Sign in / Sign up

Export Citation Format

Share Document