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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>Maximizing the First Eigenfrequencies</h1></td></tr><tr><td class = "DocHeader4" colspan = "2"/></tr><tr><td class = "DocHeader3"><table class = "DocHeaderIntro" id = "table12"><tr><td class = "Intro1"><p class = "header"><p class = "abstract">
<span class = "shortdesc">You can increase several lowest eigenfrequencies.</span>

<div class = "note"><span class = "run-in.note">Note:
			</span><span class = "notecontent">
It is important to consider more than the first natural eigenfrequency when increasing the natural frequencies
using optimization. At least, the next two first natural frequencies
should be considered in the optimization.
</span></div>

</p>
<p>This task shows you how to:
					</p><ul><li><a href = "#tso-t-user-TopOpt-ModAna-Max1Fr-DefFr-gui" id = "toc_rg" title = "">
Define an Eigenfrequency Design Response in <span class = "ph">Tosca Structure.gui</span>
</a></li></ul>
</p></td></tr><tr><td class = "Intro2"><hr class = "header"/><span class = "run-in-beforeyoubegin">Before you begin: </span>
<ul class = "ul">
<li class = "li">
All natural eigenfrequencies requested in the FE model are applied
in the optimization if the <code class = "ph codeph">ALL</code> option is applied in the
<code class = "ph codeph">LC_SET</code> parameter.
</li>
<li class = "li"> During the optimization, the various natural frequencies are automatically weighted by their
     distance from the lowest natural frequency; that is, when the other natural frequencies approach
     the first natural frequency during the optimization, the more they will be weighted. Generally,
     the first natural frequency is always maximized. </li>
<li class = "li">
The design response is defined using the Kreisselmeier-Steinhauser
formulation.
For more information, see <a class = "xref" href = "tso-c-usr-terms-eigfreqOvw.htm#tso-c-usr-terms-eigfreqOvw" title = "This section describes the theory of eigenfrequency.">Overview of Eigenfrequency</a>.
</li>
<li class = "li">
Any number of natural frequencies in the design response can be specified
using the <code class = "ph codeph">DRESP</code> command.
</li>
</ul>
</td></tr></table></td><td class = "DocHeader2"><table class = "DocTopicsSeeAlso" id = "table13"><tr><td class = "TopicsTitle">See Also</td></tr><tr><td><a title = "This section describes the theory of eigenfrequency." href = "tso-c-usr-terms-eigfreqOvw.htm#tso-c-usr-terms-eigfreqOvw">Overview of Eigenfrequency</a></td></tr></table></td></tr></table>



<div class = "body taskbody">
<div class = "p"><!--xxx--></div>

<section><div class = "li step p">

In this example, all calculated natural frequencies are considered
for the objective function using the Kreisselmeier-Steinhauser formulation and are defined as follows:

<p>
<pre class = "codeblock">
<code class = "ph codeph">
DRESP
 ID_NAME  = all_lowest_eigenfrequencies
 DEF_TYPE = SYSTEM
 TYPE     = DYN_FREQ_KREISSEL
 LC_SET   = MODAL, ALL, ALL
END_
  
OBJ_FUNC
 ID_NAME = maximize_eigenfrequencies
DRESP    = all_lowest_eigenfrequencies
 TARGET  = MAX
END_
</code>
</pre>
<p> If you have requested 10 eigenfrequencies in the finite element input model but only the first 5
      eigenfrequencies are to be used in the optimization definition, the design response for 5
      eigenfrequencies is defined as follows: </p>
<pre class = "codeblock">
<code class = "ph codeph">
DRESP
 ID_NAME  = all_lowest_eigenfrequencies_1_5
 DEF_TYPE = SYSTEM
 TYPE     = DYN_FREQ_KREISSEL
 LC_SET   = MODAL, ALL, 1-5
END_

OBJ_FUNC
 ID_NAME  = maximize_eigenfrequencies_1_5
 DRESP    = all_lowest_eigenfrequencies_1_5
 TARGET   = MAX
END_
</code>
</pre>
</p>
</div></section>
</div>


<div class = "related-links"/>

<article class = "topic task nested1" aria-labelledby = "ariaid-title2" id = "tso-t-user-TopOpt-ModAna-Max1Fr-DefFr-gui">
<h2 class = "title topictitle2">
Define an Eigenfrequency Design Response in <span class = "ph">Tosca Structure.gui</span>
</h2>

<div class = "body taskbody">
<section><ol class = "ol steps"><li class = "li step">
Create a new Design Response.
</li><li class = "li step">

Set <span class = "ph uicontrol">DefType = System, Category = Base</span>
and <span class = "ph uicontrol">Type = DYN_FREQ_KREISSEL</span>.

</li><li class = "li step">
Choose the <span class = "ph">load cases</span> 
     by clicking <span class = "ph uicontrol">Add LC</span> and setting Analysis Type to
     <span class = "ph uicontrol">MODAL</span>, entering the <span class = "ph">load case</span>
	ID and the numbers of eigenmodes (for example, 1-5) in the <span class = "ph uicontrol">Eigenmode/Subcase</span>
     field.<br/><img class = "image" src = "../TsoUserImages/topo_dresp_eigenfreq_dialog.png" width = "450"/><br/>
     
</li></ol></section>
</div>

</article>
	

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