Introduction
============

The op0070 operator consists of several parts:


1. Reading data;


2. Data initialization;


3. Construction and resolution of a linear system;


4. Updating the fields;


5. Archiving of results, post-treatments.

Everything is encapsulated in three loop levels: time steps, fixed point loops (for contact) and Newton iterations with event-based management.

This document proposes the description of these different areas of the operator, with particular emphasis on the structuring side of SDs (§ :ref:`2 <RefNumPara__32077_1938171266>`), events (§ :ref:`3.3 <RefNumPara__32081_1938171266>`) and on the general algorithm, loop by loop (§ :ref:`4 <RefNumPara__16644_1023021797>`).

Note that to help with debugging, it is possible to save the displacement fields in a file MED, at each Newton's iteration. To do this, you have to overload the dbgcha routine by changing the boolean dbg=.false. to dbg=.true. The movement fields will then be saved in a file in MED format, on the logical unit 80 (do not forget to add a file on this unit as an output in astk).

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