Reference problem
=====================


Geometry
---------

We consider a system composed of a spring fixed at one end and provided with a point mass at the other end.


.. image:: images/10000000000003DB000002249BF4C427AF27020F.png
    :width: 3.4937in
    :height: 1.9398in


.. _RefImage_10000000000003DB000002249BF4C427AF27020F.png:


Material properties
----------------------

Spring stiffness: :math:`k\mathrm{=}10N\mathrm{/}m`

Mass: :math:`m\mathrm{=}1\mathit{kg}`

Wall stiffness: :math:`K\mathrm{=}50N\mathrm{/}m`


Boundary conditions and loads
-------------------------------------

The mass is attached to one end of the spring and the other end is fixed. It moves in the u direction and can impact against the wall which is :math:`e\mathrm{=}0.01m` from its equilibrium position.


Initial conditions
--------------------

For nonlinear mode calculations, the behavior depends on the energy stored in the system.