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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>Displacement Check against Elements (CHECK_ELGR)</h1></td></tr><tr><td class = "DocHeader4" colspan = "2"/></tr><tr><td class = "DocHeader3"><table class = "DocHeaderIntro" id = "table12"><tr><td class = "Intro1Only"><p class = "header"><p class = "abstract">
        <span class = "shortdesc">Limit node growth with CHECK_ELGR.</span>

        Element surfaces/lines can be
        defined as limiting surfaces/lines to check node displacements against any contour. This
        option offers more flexibility than the check for the absolute displacement or the check
        against geometric primitives. </p>
<p>This page discusses: </p><ul><li><a href = "#tso-c-usr-bead-restrictions-CheckElgr__section_wsl_qgf_mtb" id = "toc_rg" title = "">Considering Shell Thickness and Offset</a></li><li><a href = "#tso-c-usr-bead-restrictions-CheckElgr__" id = "toc_rg" title = "">Remarks</a></li></ul>
</p></td></tr></table></td><td class = "DocHeader2"><table class = "DocTopicsSeeAlso" id = "table13"><tr><td class = "TopicsTitle">See Also</td></tr></table><table class = "DocTopicsInOtherGuides" id = "table14"><tr><td height = "8px"/></tr><tr><td class = "TopicsTitleNormal">In Other Guides</td></tr><tr><td><a title = "Defines restrictions of the design variables in bead optimization." href = "../TsoCmdMap/tso-r-cmd-dvconBead.htm#tso-r-cmd-dvconBead">DVCON_BEAD</a></td></tr></table></td></tr></table>




<div class = "body conbody">
<p>The limiting surfaces are formed
by beam, shell, or solid structures. The limiting surfaces are generated
in the FE preprocessor and loaded through the interface (<code class = "ph codeph">FEM_INPUT</code>)
in the optimization preprocessor.</p>
<p>The parameter</p>
<pre class = "codeblock">
<code class = "ph codeph">
CHECK_ELGR = elgr_name
</code>
</pre>
<p>specifies an element group whose elements might not be penetrated (contact
condition) by the nodes of the node group (<code class = "ph codeph">ND_GROUP</code>
parameter). </p>
<p>Activation of the element check represents a collision control.
If a node attempts to penetrate an element, the node displacement is
scaled back so that the affected node remains on the side of the element
where it is intended to be. If the element group is not already defined in the input file, it must be
defined with <code class = "ph codeph">GROUP_DEF</code> before it can be referenced
with <code class = "ph codeph">CHECK_ELGR</code>.</p>
<p>Up to six <code class = "ph codeph">CHECK_ELGR</code> parameters can be defined in
every <code class = "ph codeph">DVCON_BEAD</code> command. They are executed in the order
of their declaration within the <code class = "ph codeph">DVCON_BEAD</code> command.</p>

<p> If a node starts exactly on a shell element,
there is a high probability that it is seen on either side of the shell. If the
design nodes have an offset from the element group, the current implementation
works fine. Dependent on which side of the shell element a node is seen by the
algorithm, every one of the four situations can be right or wrong. 
<br/><img class = "image" id = "tso-c-usr-bead-restrictions-CheckElgr__d78e24" src = "../TsoUserImages/tso-c-usr-shape-desArea-dvcCheckP-checkElgr-permeability.png" width = "450"/><br/>
The problem is that, if the node is placed on the shell element,
it cannot be said beforehand on which side the node will be seen. As a solution
to this situation, the element group should get permeability: nodes can
penetrate the element from one side but not from the other side. The new
command 
<pre class = "codeblock">
<code class = "ph codeph">
CHECK_ELGR_BLOCKING = &lt;<span class = "ph uicontrol">BOTH</span> | POS | NEG&gt;
</code>
</pre> 
can have the following values: 
<table class = "table"><caption/><colgroup><col style = "width:50%"/><col style = "width:50%"/></colgroup><tbody class = "tbody"> 
<tr class = "row"> 
<td class = "entry">BOTH</td> 
<td class = "entry">(Default) element group is not penetrable from any side. Like current behavior with the known problems.</td> 
</tr> 
<tr class = "row"> 
<td class = "entry">POS</td> 
<td class = "entry">Element group is penetrable in negative normal direction and blocking in positive normal direction.</td> 
</tr> 
<tr class = "row"> 
<td class = "entry">NEG</td> 
<td class = "entry">Element group is penetrable in positive normal direction and blocking in negative normal direction.</td> 
</tr> 
</tbody></table> 
</p>

<div class = "section" id = "tso-c-usr-bead-restrictions-CheckElgr__section_wsl_qgf_mtb"><h2 class = "title sectiontitle">Considering Shell Thickness and Offset</h2>
            
            <p>During the optimization, the geometry can be changed to such an extend that, taking
                into account the shell thickness leads to penetration of the constraining geometry
                    (<code class = "ph codeph">CHECK_ELGR</code> item). In order to avoid this, <span class = "ph">Tosca Structure</span> can consider the shell thickness and offset in penetration checks. The image
                below demonstrates the effect of this feature. </p>
            <br/><img class = "image" id = "tso-c-usr-bead-restrictions-CheckElgr__image_tso-c-usr-shape-desArea-dvcCheckP-checkElgr-permeability.png" src = "../TsoUserImages/tso-c-usr-shape-desArea-dvcCheckP-checkElgr-shellthickness.png" width = "450"/><br/>
            <p>This behavior can be activated and deactivated using the command item</p>
            <pre class = "codeblock">
<code class = "ph codeph">
DVCON_BEAD
...
CONSIDER_SHELL_THICKNESS = &lt;<span class = "ph uicontrol">YES</span> | NO&gt;
...
END_
</code></pre>
            <p>
                <table class = "Remark" id = "table132"><tr><td class = "Remark"><span class = "run-in.important">Important:
				</span><span class = "notecontent">
                    <ul class = "ul">
                        <li class = "li">Thickness and Offset values taken into account only on design
                            elements</li>
                        <li class = "li">Offset definitions only supported with <span class = "ph">Abaqus</span> and <span class = "ph">ANSYS®</span>.<ul class = "ul">
                                <li class = "li">
                                    <span class = "ph">Abaqus</span>
                                    <p>Supported offset definition:</p><p><code class = "ph codeph">*SHELL SECTION,
                                            ..., OFFSET = &lt;numeric&gt; | SPOS |
                                        SNEG</code></p><p>No distribution definitions are
                                        supported.</p></li>
                                <li class = "li"><span class = "ph">ANSYS®</span><p>Supported offset definition:</p><p><code class = "ph codeph">SECOFFSET,
                                            &lt;numeric&gt; | BOT | TOP | MID</code></p></li>
                            </ul></li>
                    </ul>
                </span></td></tr></table>

            </p>
        </div>

<div class = "section"><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">Remarks</h2>

<table class = "Remark" id = "table132"><tr><td class = "Remark"><span class = "run-in.tip">Tip:
				</span><span class = "notecontent">To simplify the definition of the contact check, it is useful to divide
the limiting surfaces by assigning various element property numbers (or
materials). This simplifies the selection and assembly of groups in
the optimization preprocessor.</span></td></tr></table>

<p><table class = "Remark" id = "table132"><tr><td class = "Remark"><span class = "run-in.important">Important:
				</span><span class = "notecontent"><ol class = "ol" id = "tso-c-usr-bead-restrictions-CheckElgr__ol_62B6E380AAA64BE0ACA817DCE96048E4">

<li class = "li">All nodes of the selected node group are checked against all elements
of the element group, <code class = "ph codeph">elgr_name</code>. To keep the number of control
conditions within limits, only those nodes and elements that have the
potential for penetration should be checked against one another. The
groups should be correspondingly defined.</li>
<li class = "li">The nodes (<code class = "ph codeph">ND_GROUP</code> parameter) and the elements
(<code class = "ph codeph">CHECK_ELEM</code> parameter) should have a definite minimum
distance in the initial model in order to verify on which side of the
element a node must remain.</li>
<li class = "li">If the elements being used in the check are loaded with the <code class = "ph codeph">ADD_FILE</code>
parameter (FEM_INPUT),
take care that node or element IDs are not used twice as <span class = "ph">Tosca Structure</span>
cannot process duplicated IDs.</li>
</ol></span></td></tr></table>
</p>
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