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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>Summary of Guidelines</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">This section summarizes the guidelines for optimization of
                                    structures with nonlinear behavior. </span>

            </p>
<ul><li><a href = "#tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table" id = "toc_rg" title = "">Check List</a></li></ul>
</p></td></tr></table></td></tr></table>


 
 
<div class = "body conbody"> 
<div class = "section" id = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table"><h2 class = "title sectiontitle">Check List</h2> 
 
<p>The following table contains tips that can be helpful to set up a robust sizing optimization
   problem. </p> 
<table class = "table"><caption/><colgroup><col style = "width:33.33333333333333%"/><col style = "width:33.33333333333333%"/><col style = "width:33.33333333333333%"/></colgroup><thead class = "thead"> 
<tr class = "row"> 
<th class = "entry" id = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__1"> Check case: </th> 
<th class = "entry" id = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__2"> Check before optimization: </th> 
<th class = "entry" id = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__3"> Check after optimization: </th> 
</tr> 
</thead><tbody class = "tbody"> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__1"> Is there geometric or material
nonlinearity in the model? 
</td> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__2"> The following are considered to be stable settings and are set in: <ul class = "ul">
<li class = "li"><span class = "ph">Tosca Structure</span> parameter file:
<pre class = "codeblock"><code class = "ph codeph">
THICKNESS_MOVE    = 0.1
THICKNESS_UPDATE  = CONSERVATIVE
</code></pre> </li>
<li class = "li"><span class = "ph">Abaqus</span> input file:
<pre class = "codeblock"><code class = "ph codeph"> 
*STEP, NLGEOM: YES, INC=10000, extrapolation=NO
*STATIC
0.1, 1.0, 1e-14, 1.0
</code></pre>
</li>
</ul> </td> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">Check if the results are converged.</li> 
<li class = "li">If not, look for warnings in the *.msg and *.dat files
and use the corresponding command: 
<ul class = "ul">
<li class = "li"><span class = "ph uicontrol">Too many attempts made for this
increment.</span> 
<pre class = "codeblock"><code class = "ph codeph">*Controls, parameters=time incrementation
, , , , , , , 50, , ,</code></pre></li> 
<li class = "li"><span class = "ph uicontrol">Time increment required is less than the
minimum specified</span> 
<pre class = "codeblock"><code class = "ph codeph">
*STEP, NAME=&lt;step name=""&gt;, NLGEOM=YES, EXTRAPOLATION=PARABOLIC, INC=1000
</code>
</pre> Or 
<pre class = "codeblock"><code class = "ph codeph">
*Static, stabilize, factor=0.0002, allsdtol=0.05, continue=NO
</code>
</pre> 
</li> 
<li class = "li"><span class = "ph uicontrol">The solution fails to converge in the
maximum number of iterations</span> 
<pre class = "codeblock"><code class = "ph codeph">
*Controls, parameters=time incrementation
, , ,50 , , , , , , , 
</code></pre></li>
</ul>
</li> 
<li class = "li">Alternatively, setting <code class = "ph codeph">*CONTROLS, ANALYSIS=DISCONTINUOUS</code> or <code class = "ph codeph">*STEP,
    UNSYMM=YES</code> can help to improve convergence.</li> 
<li class = "li">If the convergence issue remains, impose additional constraints on the displacement or stiffness
    of the structure to stabilize the optimization procedure.</li> 
</ul> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__1"> Is there contact interaction in the model?</td> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__2"> Make sure that the contact pair is defined
by two surfaces with their normal pointing toward each other. </td> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__3"> To initialize and stabilize contact
interaction, it can be helpful to use the following command: 
<pre class = "codeblock"><code class = "ph codeph">
*CONTACT CONTROL, STABILIZE
</code></pre> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__1"> Is there plasticity in the model? 
</td> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__2"> 
<ul class = "ul"> 
<li class = "li">If possible, use a displacement-controlled load rather
than force-controlled.</li> 
<li class = "li">The elastic-plastic material card needs have a slight slope after the point of yielding, and
    the strain range must cover all strains appearing in the model.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-sizing-NonLin-Summary__tso-c-usr-sizing-NonLin-Summary-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">Check if the results are converged.</li> 
<li class = "li">If not, look for warnings in the *msg and *dat files and
use the corresponding command: 
<ul class = "ul"> 
<li class = "li"><span class = "ph uicontrol">The strain has exceeded fifty times the
strain to cause first yield at ‘n’ points</span> 
<pre class = "codeblock"><code class = "ph codeph">
*STEP, NAME=&lt;step name=""&gt;, NLGEOM=YES, EXTRAPOLATION=PARABOLIC, INC=1000
</code></pre> Or 
<pre class = "codeblock"><code class = "ph codeph">
*Static, stabilize, factor=0.0002, allsdtol=0.05, continue=NO</code></pre> 
</li> 
</ul>
</li> 
</ul> 
</td> 
</tr> 
</tbody></table> 
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