.. _R5.03.17-ELAS:

Behavior ELAS
====

Definition
----
In the general case, it is not necessary to assign elastic behavior to the discrete. The STAT_NON_LINE operator does this assignment by default on all the cells in the model. This assignment is then overloaded when the COMPORTEMENT keyword is processed.

On the other hand, if a discrete is affected by a temperature and we want to take into account thermal expansion (only for a "DIS_TR_L"), it is necessary to define the expansion coefficient :math:`\alpha` and this is done by the definition of an elastic material. It is therefore necessary to define :math:`ALPHA=\alpha`, the keyword ``E`` is mandatory but its value will not be taken into account.

The resulting move is :math:`\delta_u = \alpha*(T-T_{ref})*L`.

The corresponding effort is :math:`F_x = K_x*\delta_u`.

Note:
    Unlike other behaviors that exist on discretes, **length has a meaning**.


Internal variables
----
This behavior has no internal variables.