Hypo-ISA¶
Hypoplasticity combined with Intergranular Strain Anisotropy (ISA). ISA replaces the original intergranular-strain extension with an elastoplastic formulation of the intergranular strain, giving a clean small-strain stiffness, hysteresis and accumulation behaviour. This is the model used in the calibration shown on the home page and is a strong default for cyclic loading. A time integrator parameter selects forward Euler (1) or modified Euler (2).
At a glance
- Class:
ACT.models.hypoplasticity_isa - numgeo name:
Hypo-ISA - Parameters with search bounds: 16
- Imported as:
from ACT.models import hypoplasticity_isa
Default search bounds¶
These are the built-in lower/upper bounds used when a parameter is optimized. Override any of them with set_bounds.
| Parameter | Lower | Upper | Description |
|---|---|---|---|
phic |
0.3491 | 0.62832 | critical-state friction angle (radians) |
ec |
0.5 | 1.5 | critical void-ratio factor e_c0 |
ed |
0.36 | 1.0 | minimum void-ratio factor e_d0 |
hs |
1e-3 | 45 | granulate hardness |
n |
0.1 | 0.5 | compression exponent |
alpha |
0.0 | 0.5 | pyknotropy / fabric exponent |
beta |
0.1 | 6. | barotropy exponent |
R |
1e-4 | 2.5e-4 | size of the elastic / intergranular-strain locus |
mR |
2. | 12. | intergranular-strain stiffness factor (reversal) |
beta_h0 |
0.05 | 1.0 | ISA hardening parameter (initial) |
beta_hmax |
1.0 | 5.0 | ISA hardening parameter (maximum) |
chi0 |
1. | 10. | ISA hardening exponent (initial) |
chi_max |
5 | 50 | ISA hardening exponent (maximum) |
eps_acc |
1e-2 | 0.05 | ISA accumulation parameter |
cz |
100 | 5000 | fabric-evolution parameter |
ei |
1.05 | 1.25 | maximum void-ratio factor e_i0 |
Setting parameters¶
Assign initial / fixed parameter values with set(...):
from ACT.models import hypoplasticity_isa
model = hypoplasticity_isa()
model.set(phic=..., fei=..., ec=..., ed=..., hs=..., n=...)
Full set signature
set(phic=None,fei=None,ec=None,ed=None,hs=None,n=None,alpha=None,beta=None, R=None,mR=None,beta_h0=None,beta_hmax=None,chi0=None,chi_max=None,eps_acc=None,cz=None, phantom_E=None, phantom_nu=None, pmin=None, integrator=None)
Available set parameters: phic, fei, ec, ed, hs, n, alpha, beta, R, mR, beta_h0, beta_hmax, chi0, chi_max, eps_acc, cz, phantom_E, phantom_nu, pmin, integrator.
Choosing free parameters¶
Narrow the search interval of selected parameters, then list the ones to optimize in globals.setup:
model.set_bounds(phic=[0.3491, 0.62832], ec=[0.5, 1.5], ed=[0.36, 1.0], hs=[1e-3, 45])
globals.setup(Model=model, Free_parameter=["phic", "ec", "ed", "hs", "n", "alpha"], ...)
Parameters that accept a set_bounds override: phic, fei, ec, ed, hs, n, alpha, beta, R, mR, beta_h0, beta_hmax, chi0, chi_max, eps_acc, cz.
Reading & updating single parameters¶
model.update("phic", value) # set one parameter
x = model.get_parameter("phic") # read one parameter
See the models overview for the common interface shared by all models, and Optimization for how the free parameters are searched.