====== IRSTH ======
===== Description =====
Elastic-visco-plastic constitutive law with thermal effects for solid elements at variable temperature (to check before use, A-M. HABRAKEN, june 91). 
==== The model ====
Coupled thermo-mechanical analysis of elastic-visco-plastic solids undergoing large strains
==== Files ====
Prepro: LIRSTH.F \\
Lagamine: IRSC2E.F, IRSC2A.F, IRSC2G.F
===== Availability =====
|Plane stress state|NO |
|Plane strain state| YES|
|Axisymmetric state| YES |
|3D state| NO|
|Generalized plane state| YES |
===== Input file =====
==== Parameters defining the type of constitutive law ====
^ Line 1 (2I5, 60A1)^^
|IL|Law number|
|ITYPE| 240|
|COMMENT| Any comment (up to 60 characters) that will be reproduced on the output listing.|
==== Integer parameters ====
^ Line 1 (3I5) ^^
|NTEMP|number of temperature at which material data are given |
|NINTV| number of sub-steps used to integrate numerically the constitutive equation in a time step|
|IENTH|0 to use the classical formulation of the heat problem \\ 1 to use the enthalpy formulation of the heat problem|

==== Real parameters ====
2 lines repeated NTEMP times
^Line 1 (7G10.0)^^
|T|temperature|
|E|YOUNG's elastic modulus at temperature T|
|ANU|POISSON's ratio at temperature T|
|ALPHA|thermal expansion coefficient ($\alpha$) at temperature T|
|AN|strain rate exponent (n) at temperature T|
|B|strain rate coefficient (B) at temperature T|
|AM|hardening exponent (m) at temperature T|
^Line 2 (10X, 4G10.0)^^
|H1|hardening coefficient ($H_1$) at temperature T|
|AQ|recovery exponent (q) at temperature T|
|H2|recovery coefficient ($H_2$) at temperature T|
|AKO|initial yield limit ($K_o$) at temperature T|

===== Stresses =====
==== Number of stresses ====
6 for the 3D state \\ 4 for the other cases
==== Meaning ====
The stresses are the components of CAUCHY stress tensor in global (X,Y,Z) coordinates. \\
For the 3-D state:
|SIG(1)|$\sigma_{XX}$|
|SIG(2)|$\sigma_{YY}$|
|SIG(3)|$\sigma_{ZZ}$|
|SIG(4)|$\sigma_{XY}$|
|SIG(5)|$\sigma_{XZ}$|
|SIG(6)|$\sigma_{YZ}$|
For the other cases:
|SIG(1)|$\sigma_{XX}$|
|SIG(2)|$\sigma_{YY}$|
|SIG(3)|$\sigma_{XY}$|
|SIG(4)|$\sigma_{ZZ}$|
===== State variables =====
==== Number of state variables ====
4
==== List of state variables ====
|Q(1)| = element thickness (t) in plane stress state \\ = 1 in plane strain state \\ = circumferential strain rate $\dot{\varepsilon_\theta}$ in axisymmetric state \\ = 0 in 3D state|
|Q(2)| current yield limit in tension, its initial value is $K_o$ |
|Q(3)| hydrostatic stress ($\sigma_m$) |
|Q(4)| difference between the current temperature and the initial temperature|