2. Possible choices for thermal calculations

The following table specifies the possible models according to the type of analysis.

Modeling	Analysis type		Item type		Example
	Linear	Nonlinear	Linear	Quadratic
3D/3D_ DIAG	Ok	Ok	Ok	Ok	FORMA41
PLAN/PLAN_DIAG	Ok	Ok	Ok	Ok	FORMA21
AXIS/AXIS_DIAG	Ok	Ok	Ok	Ok	FORMA30
COQUE	Ok	Nook	Ok	Ok	HPLA100
COQUE_PLAN	Ok	Nook	Nook	Ok	ZZZZ110
COQUE_AXIS	Ok	Nook	Nook	Ok

Table 2-1 : Possible types of thermal analysis

Remarks:

The 3D_ DIAG , PLAN_DIAG and AXIS_DIAG models*, which correspond to the use of a lumped or diagonalized mass matrix (cf. [R3.06.07]), give more accurate results than conventional models in the presence of thermal shock and for linear elements.

For shells, the temperature variation in thickness is necessarily parabolic (cf. [R3.11.01]).

All loads are not applicable to modelling COQUE, check before use [U4.44.02].

To continue with a mechanical calculation, we recommend:

- to preferentially use linear elements to solve the thermal problem with modelling XXXX_DIAG, and quadratic elements for the mechanical problem that are preferably under-integrated (cf. u2.01.10).

- to check carefully that the law of behavior used takes into account thermal deformation, and that the modeling used accepts control variables and in particular thermal variables. When taken into account, thermal expansion is spherical and is \({\epsilon }_{\mathit{th}}=\alpha \Delta T{I}_{d}\). At present, solid and flat elements, elements DKT and DKTG and multifibre beams ( POU_D_EMetPOU_D_TGM ) support temperature as a control variable.

There is no step model in Code_Aster that specifically describes thermal damage.