* dislocation flux and internal stress calculation now consistent with new definition of slip system lattice according to paper (polarity of screws inverted)
* now complaining when encountering an unknown nonlocal parameter in material.config
* use same error ID for all material parameters out of bounds
* symmetric flux calculation in side dotState can now be omitted (because of new treatment of periodicity)
* switching back to "local flux balance" (add leaving and entering fluxes at central MP, don't touch neighbor) instead of "flux distribution" (subtract leaving fluxes from central MP and add them at neighboring MP). This has the advantage that there is almost no need for CRITICAL statements in parallelization, so hopefully this results in some speed up.
* need to recalculate dislocation velocity in postResults, otherwise we take values of last perturbed state! So the following outputs were up to now showing the perturbed state: shearrate, dislocation velocity, all density rates!
* also put a call to constitutive_microstructure at the start of each crystallite_integration subroutine like it was before. need that for nonlocal model in case of crystallite cutback
* fluxes are now again calculated and distributed only! by the originating material point. this means that the central MP might change the dotState of its neighbor. have to see whether locks slow down parallel computation
* detection of grain boundary in constitutive_nonlocal_microstructure with the help of transmissivity
* enforce positive densities in constitutive_nonlocal_microstructure (needed because dotState does not create cutbacks for negative densities anymore)
* reset single mobile densities below certain threshold to zero (also done in constitutive_nonlocal_microstructure)
* constitutive_nonlocal_kinetics only gets local state variable as input, no need for the entire array here
* dv_dtau is always positive
* multiplication is only active when there is already some initial density of the respective type
* now remembering stiffness similar to how we do it for Lp etc.; avoids undefined stiffness values for nonconverged stiffness calculation
* non-local stuff:
* changed non-local kinetics (Gilman2002)
* enforce zero shearrate for overall carrrier density below relevant density
* enforce zero density for those states that become negative and were below relevant density before
* dislocation velocity is not limited by V^(1/3) / dt anymore
restructured nonlocal_dotstate, to be able to easily switch on and off particular effects in the microstructure evolution
nonlocal_dotstate now enforces a cutback when single density runs the risk of becoming negative; in the case of a state already below the relevantState dotState is set to zero
introduced two new output variables: rho_dot_edge and rho_dot_screw
beware that crystallite output "orientation" now by default returns the orientation as quaternion. if you want euler angles instead, you have to add "eulerangles" as a crystallite output in your material.config file (see material.config template).
for input of orientations in the texture block of the material.config you still have to specify the rotation in terms of euler angles, quaternions are not yet supported for input.
- flux density interpolation now depends on the position of the interface between ttwo neighboring material points
- simplified flux calculation scheme
- introduced sanity check for dislocation velocity to ensure v*dt< cellsize
- reworked contribution of immobile dislocation density for rate equations
- flux is now calculated on the basis of interpolated velocities and densities at the interface; both incoming and outgoing fluxes are considered, so every material point only changes his own dotState
- dislocation velocity is now globally defined and calculated by subroutine constitutive_nonlocal_kinetics; the subroutine is called inside _LpAndItsTangent as well as _microstructure; therefore, microstructure now needs Tstar_v as additional input; in the future one should perhaps create a subroutine constitutive_kinetics that calls constitutive_nonlocal_kinetics separately, to clearly distinguish between microstructural and kinetic variables
- better use flux density vector as output variable instead of scalar flux values for each interface
- added output variables internal and external resolved stress
crystallite:
- added flag to force local stiffness calculation in case of nonlocal model
- misorientation angle is explicitly set to zero when no neighbor can be found
debug:
- added flag "selectiveDebugger" that is used when debugging statements should only affect a specific element, ip and grain; these are specified with the new variables debug_e, debug_i and debug_g
- debugger can now be used in its original sense
- remobilization of immobile singles immediately increases the mobile single dislocation density and therefore directly affects all other mechanisms in dotState
- changed nomenclature (rho -> rhoSgl) to distinguish precisely between single dislocation density and total dislocation density
- changed material.config accordingly
The calculation of the misorientation is now done once in crystallite init and at the end of every FE increment. This saves a lot of time compared to doing it in dotState for every crystallite subinc.
- corrected flux term
- multiplication is now aware of dislocation type
- corrected change rate for "dipole size" dupper
- corrected term for dipole dissociation by stress change
- added transmissivity term in fluxes which accounts for misorientation between two neighboring grains (yet hardcoded transmissivity according to misorientation angle)
- added more output variables
constitutive:
- 2 additional variables "previousDotState" and "previousDotState2", which are used to store the previous and second previous dotState (used in crystallite for acceleration/stabilization of state integration)
- timer for dotState now measures the time for calls to constitutive_ collectState (used to reside in crystallite_updateState, which is not critical in terms of calculation time anymore)
crystallite:
- convergence check for nonlocal elments is now done at end of crystallite loop, not at the beginning; we simple set all elements to not converged if there is at least one nonlocal element that did not converge
- need call to microstructure before first call to collect dotState for dependent states
- stiffness calculation (jacobian): if there are nonlocal elements, we also have to consider changes in our neighborhood's states; so for every perturbed component in a single ip, we have to loop over all elements; since this is extremely time-consuming, we just perturb one component per cycle, starting with the one that changes the most during regular time step.
- updateState gets a damping prefactor for our dotState that helps to improve convergence; prefactor is calculated according to change of dotState
IO:
- additional warning message for unknown crystal symmetry
in constitutive_nonlocal.f90:
Derivatives of shear rates w.r.t. resolved shear stress HAVE to be positive.
Computation of dgdot_dtauslip is now correct.
Christoph Kords