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      <title>CGAP</title>
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      <div class="title_refTopic" id="xps10_pagetitle">CGAP </div>
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      <h4 class="refClassification">Gap Element Connection </h4>
      <p class="para_refTopic">Defines a gap or friction element. </p>
      <div class="title_refCategory">Format: </div>
      <div class="refCategoryContent">
         <table border="1" width="100%" align="center">
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                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">1 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">3 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">4 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">5 </p>
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                     <p class="para_td">6 </p>
                  </td>
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                     <p class="para_td">7 </p>
                  </td>
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                     <p class="para_td">8 </p>
                  </td>
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                     <p class="para_td">9 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">10 </p>
                  </td>
               </tr>
            </thead>
            <tbody>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CGAP </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">EID </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">PID </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">GA </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">GB </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">X1 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">X2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">X3 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">CID </p>
                  </td>
                  <td align="center" bgcolor="gray" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Example:</div>
      <div class="refCategoryContent">
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            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CGAP </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">17 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">110 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">112 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">5.2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">0.3 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">-6.1 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Alternate Format and Example: </div>
      <div class="refCategoryContent">
         <table border="1" width="100%" align="center">
            <colgroup span="1">
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               <col span="1" width="10*">
            </colgroup>
            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CGAP </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">EID </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">PID </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">GA </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">GB </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">GO </p>
                  </td>
                  <td align="center" bgcolor="gray" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" bgcolor="gray" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">CID </p>
                  </td>
                  <td align="center" bgcolor="gray" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br><table border="1" width="100%" align="center">
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            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CGAP </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">17 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">110 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">112 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">13 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Fields:</div>
      <div class="refCategoryContent">
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                     <p class="para_th"><b class="uiTerm">Field </b></p>
                  </th>
                  <th align="left" colspan="1" rowspan="1">
                     <p class="para_th"><b class="uiTerm">Contents </b></p>
                  </th>
               </tr>
            </thead>
            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">EID </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Element identification number.  (Integer &gt; 0) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PID </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Property identification number of a PGAP entry.  (Integer &gt; 0; Default = EID) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">GA, GB </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Connected grid points at ends A and B.  (Integers &gt; 0; GA &ne; GB) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">X1, X2, X3 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Components of the orientation vector </p>
                     <p class="para_td"><img align="bottom" src="graphics/bulkc1-ufig11.gif" border="0">, from GA, in the displacement coordinate system at GA.  (Real) 
                     </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">GO </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Alternate method to supply the orientation vector </p>
                     <p class="para_td"><img align="bottom" src="graphics/bulkc1-ufig13.gif" border="0"> using grid point GO.  Direction of <img align="bottom" src="graphics/bulkc1-ufig11.gif" border="0"> is from GA to GO.  (Integer &gt; 0) 
                     </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CID </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Element coordinate system identification number.  CID must be specified if GA and GB are coincident (distance from GA to GB&lt;10<sup class="superscript">−4</sup>). See Remark <a class="links" href="javascript:void(0)" onclick="top.openFile('QRG/13topic_27.html#refp6tWp152lori');return(false);">34-6</a>. (Integer &ge; 0 or blank) 
                     </p>
                  </td>
               </tr>
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         </table><br></div>
      <div class="title_refCategory">Remarks: </div>
      <div class="refCategoryContent">
         <ol type="1" start="1">
            <li>
               <p class="para_item">The CGAP element is treated as a nonlinear gap element when used in the nonlinear solution sequences 106, 129, 153, and 159, in which the gap conditions update as the nonlinear solution iterates. </p>
               <p class="para_item">For SOL 101 with linear contact defined (BCSET card exists), CGAP elements are treated as linear contact elements if the system cell (412) OLDGAPS is set to 0 (default). (See the chapter on surface contact in the <em>NX Nastran User&rsquo;s Guide</em> for more information.) 
               </p>
               <p class="para_item">If linear contact is defined for SOL 101, and the system cell OLDGAPS is set to 1, the CGAP will be treated the same as a linear spring element (as described below). </p>
               <p class="para_item">For SOL 101 without linear contact defined, and for all other solution sequences, the CGAP will be treated the same as a linear spring element, and remains linear with the initial stiffness. This stiffness depends on the value for the initial gap opening (U0 field in the PGAP entry). </p>
            </li>
            <li>
               <p class="para_item">The gap element coordinate system is defined by one of two following methods: </p>
               <ul>
                  <li>
                     <p class="para_item">If the coordinate system (CID field) is specified, the element coordinate system is established using that coordinate system, in which the element x-axis is in the T1 direction and the y-axis in the T2 direction.  The orientation vector <img align="bottom" src="graphics/bulkc1-ufig11.gif" border="0"> will be ignored in this case. 
                     </p>
                  </li>
                  <li>
                     <p class="para_item">If the CID field is blank and the grid points GA and GB are not coincident (distance from A to B &ge; 10<sup class="superscript">−4</sup>), then the line AB is the element x-axis and the orientation vector <img align="bottom" src="graphics/bulkc1-ufig11.gif" border="0"> lies in the x-y plane (like the CBEAM element). 
                     </p>
                  </li>
               </ul>
            </li>
            <li>
               <p class="para_item">The element coordinate system does not rotate as a result of deflections. </p>
            </li>
            <li>
               <p class="para_item">Initial gap openings are specified on the PGAP entry and not derived from the separation distance between GA and GB. </p>
            </li>
            <li>
               <p class="para_item">Forces, which are requested with the STRESS Case Control command, are output in the element coordinate system. <em>F<sub class="subscript">x</sub></em>  is positive for compression. 
               </p>
            </li>
            <li><a name="refp6tWp152lori"></a><p class="para_item">If CID is being used to define the element coordinate system and the CID refers to either a cylindrical or spherical coordinate system, then grid GA will be used to locate the system.  If grid GA lies on the z-axis of the cylindrical or spherical coordinate system it is recommended that a different coordinate system be used for this element. </p>
            </li>
            <li>
               <p class="para_item">See PARAM,CDITER for an alternative approach. </p>
            </li>
         </ol>
      </div>
      <div class="title_refCategory">Remarks related to SOLs 601 and 701: </div>
      <div class="refCategoryContent">
         <ol type="1" start="1">
            <li>
               <p class="para_item">CGAP is simulated with a nonlinear spring element in SOLs 601 and 701, i.e., the transverse properties of this element are ignored. Please see SOL 601 and 701 remarks in the PGAP entry. </p>
            </li>
            <li>
               <p class="para_item">X1, X2, and X3 are ignored. </p><a name="ref58734"></a><div class="figure">
                  <p align="center"><img align="bottom" src="graphics/bulkc1-fig20.gif"></p>
               </div>
               <div class="title_figure">Figure. CGAP Element Coordinate System </div>
            </li>
         </ol>
      </div>
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