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<a name = "hj-top"> </a><table class = "table1" id = "table11"><tr><td><table class = "DocHeader"><tr><td class = "DocHeader1" colspan = "2"><h1>Loads and Boundary Conditions</h1></td></tr><tr><td class = "DocHeader4" colspan = "2"/></tr><tr><td class = "DocHeader3" colspan = "2"><table class = "DocThemeIntro" id = "table12"><tr><td class = "Intro1Only"><p class = "header"><p class = "abstract">
<span class = "shortdesc">
  <span class = "ph">Abaqus</span>-specific definitions of loads and boundary conditions are discussed.</span>

</p>
<p>This page discusses: </p><ul><li><a href = "#tso-c-usr-solver-abaqus-bcond__tso-c-usr-solver-abaqus-bcond-NodeRestShape" id = "toc_rg" title = "">Node Restrictions for Shape Optimization</a></li><li><a href = "#tso-c-usr-solver-abaqus-bcond__tso-c-usr-solver-abaqus-bcond-contact" id = "toc_rg" title = "">Contact Boundary Conditions</a></li></ul>
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<div class = "section" id = "tso-c-usr-solver-abaqus-bcond__tso-c-usr-solver-abaqus-bcond-NodeRestShape"><h2 class = "title sectiontitle">Node Restrictions for Shape Optimization</h2>

<p>Node restrictions in the <span class = "ph">Abaqus</span>
input file (command <code class = "ph codeph">*BOUNDARY</code>) are imported during the
<span class = "ph">Tosca Structure</span>
preprocessing step if the following command is defined: </p>
<pre class = "codeblock">
<code class = "ph codeph">OPTIONS
</code><code class = "ph codeph"> READ_<span class = "ph">BC</span> = ALL
</code><code class = "ph codeph">END_
</code></pre>
<p>By default, this command is already included in the configuration file
command.ini. Therefore, it must not be defined explicitly in the parameter
file. </p>
<p>Node restrictions defined in the FE-analysis (and maybe not used in
the FE analysis) can be used as restrictions for design variables for
shape and bead optimization (see command <code class = "ph codeph">DVCON_SHAPE, DVCON_BEAD</code>)
to avoid optimization nodal displacements in specified places.</p>
</div>

<div class = "section" id = "tso-c-usr-solver-abaqus-bcond__tso-c-usr-solver-abaqus-bcond-contact"><p><map name = "FPMap1"><area href = "#hj-top" title = "Back to Top" shape = "rect" coords = "416, 0, 435, 10"/></map><span class = "itemsprite"/></p><h2 class = "title sectiontitle">Contact Boundary Conditions</h2>

<p>This behavior can be avoided by the definition of different restrictions in the optimization task
                (casting or minimum member size restrictions)</p>
<p>Sometimes the exact boundary conditions cannot be specified before designing the components.
                Often the exact boundary conditions are unknown early in the design phase. In
                addition, nonlinear boundary conditions such as contact definitions can change
                during designing. Linearized models often require several recalculations and
                reoptimizations with respect to the linearized boundary conditions and are therefore
                time-consuming. Thus, it is more efficient if the contact conditions are directly
                specified in the finite element input file applied for the optimization. </p>
<p><span class = "ph">Tosca Structure</span> is easy to operate for the familiar user of <span class = "ph">Abaqus</span>. You create an analysis model for <span class = "ph">Abaqus</span> with the relevant contact definitions. In addition, you define the design area
                for the optimization and the optimization task. Information for <span class = "ph">Tosca Structure</span> regarding the actual contact problem is not required because <span class = "ph">Tosca Structure</span> is a modular system. The contact problem becomes a part of the optimization
                through the forces of the nodes and the stresses. As a result, you can make full use
                of the capabilities in <span class = "ph">Abaqus</span> for the contact calculations.</p>
<p>Contact conditions are permitted in the analysis model for topology
and shape optimization. Defining a contact surface directly on the edge
of the design space is allowed in topology optimization. The shape optimization
algorithm must be inverted (see command <code class = "ph codeph">OPT_PARAM</code>,
Parameter <code class = "ph codeph">SCALE</code>) if the design edge belongs to a contact
surface in shape optimization. Convergence difficulties in the FE analysis
might arise in cases of complex contact problems due to large changes in
the model during optimization. </p>
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