OOF: Finite Element Analysis of Microstructures
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Subsections
damisotropic
This is an isotropic element which can undergo ``damage'' when the
principal stress exceeds a userdefined upper limit or retrocedes
below a userdefined lower limit. The effect of damage is that all
components of the stiffness matrix are multiplied by a userdefined
knockdown value.
The damage does not take place until a mutation command is invoked, either explicitly with mutate (Section 3.1.4) or implicitly with the comp_equil (Section 3.1.3) command. An element can be remutated (i.e, remultiplied by the knockdown factor) if the stress reexceeds its bounds.
Elements which have mutated are drawn in black in the Mesh Drawer (Section 5.1), but are immediately redrawn with the new (unequilibrated) stresses or strains in the Stress Drawers and Strain Drawers. An additional equilibrate step is required to produce equilibrium after any elements incur damage due to a mutate command.
Parameters
 thermoelastic coefficients
 The thermoelastic coefficients young, poisson, and alpha are identical to those defined for the isotropic elements in
Section 4.5.1.
 max_stress
 The upper limit of stress. Elements whose largest principal stress
is greater than max_stress will mutate during a mutate
command (Section 3.1.4). [stress]
 min_stress
 The lower limit of stress. Elements whose smallest principal stress is
less than min_stress will mutate during a mutate command
(Section 3.1.4). Negative stresses are
compressive. [stress]
 max_knockdown
 The factor by which the entire element stiffness matrix is multiplied when
its largest principal stress exceeds max_stress. [dimensionless]
 min_knockdown
 The factor by which the entire element stiffness matrix is multiplied when its smallest principal stress is less than min_stress. [dimensionless]

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