<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html
  SYSTEM "about:legacy-compat">
<html xmlns:mml = "http://www.w3.org/1998/Math/MathML" lang = "en"><head><meta charset = "UTF-8"/><meta name = "copyright" content = "(C) Copyright 2020"/><meta name = "DC.rights.owner" content = "(C) Copyright 2020"/><meta name = "DC.type" content = "concept"/><meta name = "abstract" content = "This guide is meant to help Abaqus users who want to use Tosca Structure for optimization with nonlinear behavior."/><meta name = "description" content = "This guide is meant to help Abaqus users who want to use Tosca Structure for optimization with nonlinear behavior."/><meta name = "DC.format" content = "HTML5"/><meta name = "DC.identifier" content = "tso-c-usr-model-modelguide"/><meta name = "DC.language" content = "en"/><link rel = "stylesheet" type = "text/css" href = "../DSDocUI_XML34.css"/><title>Modeling Guide for Nonlinear Models</title>
<script type = "text/javascript" src = "../DSDocUI_Highlight34.js">
  	/* */
  	</script></head><body onLoad = "highlightSearchTerms();" id = "tso-c-usr-model-modelguide">
<a name = "hj-top"> </a><table class = "table1" id = "table11"><tr><td><table class = "DocHeader"><tr><td class = "DocHeader1" colspan = "2"><h1>Modeling Guide for Nonlinear Models</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 guide is meant to help <span class = "ph">Abaqus</span> users who want to
use <span class = "ph">Tosca Structure</span> for optimization with nonlinear behavior. 
</span>
 
</p>

</p></td></tr></table></td></tr></table>


 
 
<div class = "body conbody"> 
<div class = "section" id = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table"> 
<table class = "table"><caption/><colgroup><col style = "width:25%"/><col style = "width:25%"/><col style = "width:25%"/><col style = "width:25%"/></colgroup><thead class = "thead"> 
<tr class = "row"> 
<th class = "entry" id = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> Topic </th> 
<th class = "entry" id = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> Guideline </th> 
<th class = "entry" id = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> Why? </th> 
<th class = "entry" id = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> Examples and commands </th> 
</tr> 
</thead><tbody class = "tbody"> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> Constraints</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol"> Tie constraints:</span> 
<ul class = "ul">
<li class = "li">When using tie constraints to tie two surfaces based on
shell elements, it is best to exclude the shell section thickness and specify a
position tolerance equal to the average thickness. </li> 
<li class = "li">If possible, choose “Node to surface” as the
discretization method rather than the default “surface to surface.”</li>
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul">
<li class = "li">In sizing optimization the thicknesses of the shell
elements change, which could lead to problems that more elements get into
contact due to the thickness growth or vice versa. In addition, the actual
“surface” might divert from the nodal positions due to interpolation. This could
lead to an unwanted amount of tie in the initial design. </li> 
<li class = "li">This way of determining the tie nodes of the secondary
surface is more efficient and more robust.</li>
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> 
<ul class = "ul"> 
<li class = "li"><code class = "ph codeph">*Tie, no thickness, positiontolerance=&lt;…&gt; 
</code>Or “Exclude shell/ membrane thickness” and specify
the tolerance in <span class = "ph">Abaqus</span>/CAE </li> 
<li class = "li"><code class = "ph codeph">*Tie, Type= Node to surface 
</code> Or “Discretization method set to “Node to
surface” in <span class = "ph">Abaqus</span>/CAE.</li>
</ul> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> </td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol"> Adjustment of secondary nodes:</span> 
<ul class = "ul"> 
<li class = "li"> When working with shell elements: Do not use the
adjustment option because it will move nodes so that they are overlapping with
their corresponding partner node without causing strain. </li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">The geometry of the model will change and that is most
often not wanted since the shell thicknesses will overlap.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> 
<ul class = "ul"> 
<li class = "li"> 
<code class = "ph codeph">*Tie, adjust=no</code> Or Deactivate “Adjust
secondary surface initial position” in <span class = "ph">Abaqus</span>/CAE.</li>
</ul> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> Loading </td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> 
<ul class = "ul"> 
<li class = "li"> If possible, use displacement-controlled load instead of
force-controlled.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">This kind of load is more robust against unstable models
such as buckling or with large plastic regions.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> </td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> General </td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol">Naming:</span> 
<ul class = "ul"> 
<li class = "li">Choose characteristic and unique names for node and
element sets.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">A node and an element set might have identical names or the
name of the design region might be a <span class = "ph">Tosca Structure</span> default name. This would
lead to problems in the optimization. </li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> 
<ul class = "ul"> 
<li class = "li">For example, choose “Design_Elements” instead of “Elements.”</li> 
</ul> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"/> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol">Prerun:</span> 
<ul class = "ul"> 
<li class = "li"> First run your model with deactivated nonlinear
features. Afterward, activate the nonlinear features and run the model again. </li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">This helps to see whether there are problems with
contacts or boundary conditions in the initial model.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> 
<ul class = "ul"> 
<li class = "li"> Deactivate nonlinear geometry: 
<code class = "ph codeph">*Step, NLGEOM=NO</code> Deactivate plasticity:
Delete the plastic material card. </li> 
</ul> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> </td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol">Stabilization:</span> 
<ul class = "ul"> 
<li class = "li">Only use the default settings of any stabilization unless
you are experienced with the effects of any changes.</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li"> Not only will any kind of stabilization method affect
the computation time, but also the accuracy of the simulation. In general, more
stabilization leads to higher inaccuracy. </li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> </td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> Plasticity </td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol">Material law:</span> 
<ul class = "ul">
<li class = "li">The values in the material card for plastic strain should
cover all strain values appearing in the simulation. In addition to this, the
"curve" of the material card should have a positive inclination for larger
strains.</li>
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul">
<li class = "li">When exceeding the maximum plastic strain defined in the
material card, <span class = "ph">Abaqus</span> might extrapolate the data incorrectly, which might lead to
convergence problems.</li>
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> 
<pre class = "codeblock">
*Plastic
400.,      0.0
465., 0.00037
504., 0.02921
599., 0.10357
654., 0.18782
1000.,    1.34
</pre> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> Contact </td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> <span class = "ph uicontrol">Contact normal:</span> 
<ul class = "ul">
<li class = "li"> Make sure that the contact pair is defined by two
surfaces with their normal pointing toward each other.</li>
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul">
<li class = "li">When defining contacts properties, the penetration direction as well as the correct
surface is important to get the wanted result. </li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> 
</td> 
</tr> 
<tr class = "row"> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__1"> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__2"> 
<span class = "ph uicontrol"> Rigid body motion:</span> 
<ul class = "ul"> 
<li class = "li"> Do not use contact definition to constrain rigid body
motion. Rather use tie constraints or beam connectors.
</li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__3"> 
<ul class = "ul"> 
<li class = "li">At the beginning of the optimization, <span class = "ph">Tosca</span> might not
start computing when two bodies are not connected properly. Such contacts may
be ignored. </li> 
</ul> 
</td> 
<td class = "entry" headers = "tso-c-usr-model-modelguide__tso-c-usr-model-modelguide-Table__entry__4"> </td> 
</tr> 
</tbody></table> 
</div>
 
</div>
 
</td></tr></table><script type = "text/javascript" src = "../DSDocUI_Bottom34.js">/* */</script></body>
</html>
