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      <title>CHEXA</title>
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      <div class="title_refTopic" id="xps10_pagetitle">CHEXA </div>
      <hr noshade="true">
      <h4 class="refClassification">Six-Sided Solid Element Connection </h4>
      <p class="para_refTopic">Defines the connections of the six-sided solid element with eight to twenty grid points. </p>
      <div class="title_refCategory">Format: </div>
      <div class="refCategoryContent">
         <table border="1" width="100%" align="center">
            <colgroup span="1">
               <col span="1" width="10*">
               <col span="1" width="10*">
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               <col span="1" width="10*">
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               <col span="1" width="10*">
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               <col span="1" width="10*">
            </colgroup>
            <thead>
               <tr>
                  <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>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">6 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">7 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">8 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">9 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">10 </p>
                  </td>
               </tr>
            </thead>
            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CHEXA </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">G1 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G3 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G4 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G5 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G6 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G7 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G8 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G9 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G10 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G11 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G12 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G13 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G14 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G15 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G16 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G17 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G18 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G19 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">G20 </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" 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">
         <table border="1" width="100%" align="center">
            <colgroup span="1">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
               <col span="1" width="10*">
            </colgroup>
            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CHEXA </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">71 </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">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>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">6 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">7 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">8 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">9 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">10 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">0 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">0 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">30 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">31 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">53 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">54 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">55 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">56 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">57 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">58 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">59 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">60 </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">
         <table cellpadding="10" width="100%" align="center">
            <colgroup span="1">
               <col span="1" width="16*">
               <col span="1" width="51.76*">
               <col span="1" width="20.49*">
               <col span="1" width="11.74*">
            </colgroup>
            <thead>
               <tr>
                  <th align="left" colspan="1" rowspan="1">
                     <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>
                  <th align="left" colspan="1" rowspan="1">
                     <p class="para_th"><b class="uiTerm">Type </b></p>
                  </th>
                  <th align="left" colspan="1" rowspan="1">
                     <p class="para_th"><b class="uiTerm">Default </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. </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Integer &gt; 0 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Required </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 aPSOLID or PLSOLID entry. </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Integer &gt; 0 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Required </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Gi </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Grid point identification numbers of connection points. </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Integer &ge; 0 or blank </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Required </p>
                  </td>
               </tr>
            </tbody>
         </table><br><a name="ref33176"></a><div class="figure">
            <p align="center"><img align="bottom" src="graphics/bulkc1-fig29.gif"></p>
         </div>
         <div class="title_figure">Figure. CHEXA Element Connection </div>
      </div>
      <div class="title_refCategory">Remarks: </div>
      <div class="refCategoryContent">
         <ol type="1" start="1">
            <li>
               <p class="para_item">Element identification numbers should be unique with respect to all other element identification numbers. </p>
            </li>
            <li>
               <p class="para_item">Grid points G1 through G4 must be given in consecutive order about one quadrilateral face.  G5 through G8 must be on the opposite face with G5 opposite G1, G6 opposite G2, etc. </p>
            </li>
            <li>
               <p class="para_item">The edge points G9 to G20 are optional.  Any or all of them may be deleted.  If the ID of any edge connection point is left blank or set to zero (as for G9 and G10 in the input example), the equations of the element are adjusted to give correct results for the reduced number of connections.  Corner grid points cannot be deleted.  The element is an isoparametric element (with shear correction) in all cases. </p>
            </li>
            <li>
               <p class="para_item">Components of stress are output in the material coordinate system except for hyperelastic elements, which are output in the basic coordinate system.  The material coordinate system is defined on the PSOLID entry. </p>
            </li>
            <li>
               <p class="para_item">The second continuation is optional. </p>
            </li>
            <li>
               <p class="para_item">For nonhyperelastic elements, the element coordinate system for the CHEXA element is defined in terms of the three vectors R, S, and T, which join the centroids of opposite faces. </p>
               <p class="para_item">R vector joins the centroids of faces G4-G1-G5-G8 and G3-G2-G6-G7. </p>
               <p class="para_item">S vector joins the centroids of faces G1-G2-G6-G5 and G4-G3-G7-G8. </p>
               <p class="para_item">T vector joins the centroids of faces G1-G2-G3-G4 and G5-G6-G7-G8. </p>
               <p class="para_item">The origin of the coordinate system is located at the intersection of these vectors.  The X, Y, and Z axes of the element coordinate system are chosen as close as possible to the R, S, and T vectors and point in the same general direction.  (Mathematically speaking, the coordinate system is computed in such a way that if the R, S, and T vectors are described in the element coordinate system a 3 x 3 positive-definite symmetric matrix would be produced.) </p><a name="ref94915"></a><div class="figure">
                  <p align="center"><img align="bottom" src="graphics/bulkc1-fig30.gif"></p>
               </div>
               <div class="title_figure">Figure. CHEXA Element R, S, and T Vectors </div>
            </li>
            <li>
               <p class="para_item">It is recommended that the edge points be located within the middle third of the edge. </p>
            </li>
            <li>
               <p class="para_item">For hyperelastic elements, the plot codes are specified under the CHEXAFD element name in <a class="links" href="javascript:void(0)" onclick="top.openFile('QRG/09ref75809_1.html');return(false);">&ldquo;Item Codes&rdquo;</a>. 
               </p>
            </li>
            <li>
               <p class="para_item">If a CHEXA element is referenced by a PSET or PVAL entry, then a p-version formulation is used and the element can have curved edges. </p>
               <ul>
                  <li>
                     <p class="para_item">If a curved edge of a p-element is shared by an h-element without midside nodes, the geometry of the edge is ignored and set straight. </p>
                  </li>
                  <li>
                     <p class="para_item">Elements with midside nodes cannot be p-elements and edges with midside nodes cannot be shared by p-elements. </p>
                  </li>
               </ul>
            </li>
            <li>
               <p class="para_item">By default, all twelve edges of the element are considered straight unless: </p>
               <ul>
                  <li>
                     <p class="para_item">For p-elements there is an FEEDGE or FEFACE entry that contains the two grids of any edge of this element.  In this case, the geometry of the edge is used in the element. </p>
                  </li>
                  <li>
                     <p class="para_item">For h-elements, any of G9 through G20 are specified. </p>
                  </li>
               </ul>
            </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">For SOL 601, only elements with 8 or 20 grid points are allowed, i.e., either all edge points G9 to G20 are specified or no edge points are specified. For SOL 701, only elements with 8 grid points are allowed. </p>
            </li>
            <li>
               <p class="para_item">For SOL 601, 20-node CHEXA elements may be converted to 27-node CHEXA elements (6 additional nodes on the centroid of the six faces and 1 additional node at the centroid of the element) by specifying ELCV=1 in the NXSTRAT entry. 27-node CHEXA elements are especially effective in the analysis of incompressible media and inelastic materials, e.g., rubber-like materials, elasto-plastic materials, and materials with Poisson&rsquo;s ratio close to 0.5. 27-node CHEXA elements also perform better than 20-node elements in contact analysis. </p>
            </li>
         </ol>
      </div>
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