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      <title>Creating the Model Geometry</title>
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      <div class="title_topic2" id="xps10_pagetitle">Creating the Model Geometry</div>
      <hr noshade="true">
      <div class="title_division">Coordinate System</div>
      <p class="para_division">NX Nastran has a default rectangular coordinate system called the basic system.  Therefore, no special effort is required to orient our model.  We will choose to define the model&rsquo;s coordinate system as shown in Figure<a class="links" href="javascript:void(0)" onclick="top.openFile('get_start/02topic_5.html#gsprelim_9537');return(false);">1-</a>.  The beam&rsquo;s element x-axis will be parallel to the basic system&rsquo;s x-axis by our choice of X1, X2, and X3 (x, y, and z) on the GRID entries.
      </p><a name="gsprelim_9537"></a><div class="figure">
         <p align="center"><img align="bottom" src="graphics/gsprelim23.gif"></p>
      </div>
      <div class="title_figure">Figure. Model Coordinate System</div>
      <div class="title_division">GRID Points</div><a name="gsprelim_9608"></a><p class="para_division">GRID points are defined in the Bulk Data Section of the input file.  The format of the GRID entry is:      </p>
      <table border="1" cellpadding="2" cellspacing="1" width="100%" align="center">
         <colgroup span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
         </colgroup>
         <thead>
            <tr>
               <td align="center" colspan="1" rowspan="1">
                  <p class="para_td">1</p>
               </td>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">2</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">3</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">4</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">5</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">6</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">7</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">8</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">9</p>
               </th>
               <th align="center" colspan="1" rowspan="1">
                  <p class="para_th">10</p>
               </th>
            </tr>
         </thead>
         <tbody>
            <tr>
               <td align="center" colspan="1" rowspan="1">
                  <p class="para_td">GRID</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9634"></a><p class="para_td">ID</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9636"></a><p class="para_td">CP</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9638"></a><p class="para_td">X1</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9640"></a><p class="para_td">X2</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9642"></a><p class="para_td">X3</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9644"></a><p class="para_td">CD</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9646"></a><p class="para_td">PS</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9648"></a><p class="para_td">SEID</p>
               </td>
               <td colspan="1" rowspan="1"></td>
            </tr>
         </tbody>
      </table><br><table cellpadding="8" width="100%" align="center">
         <colgroup span="1">
            <col span="1" width="55*">
            <col span="1" width="144*">
         </colgroup>
         <tr>
            <th align="left" colspan="1" height="45" rowspan="1">
               <p class="para_th">Field</p>
            </th>
            <th align="left" colspan="1" height="45" rowspan="1">
               <p class="para_th">Contents</p>
            </th>
         </tr>
         <tr>
            <td colspan="1" rowspan="1"><a name="gsprelim_9657"></a><p class="para_td">lD</p>
            </td>
            <td colspan="1" rowspan="1"><a name="gsprelim_9659"></a><p class="para_td">Grid point identification number. (0 &lt; Integer &lt; 1000000)</p>
            </td>
         </tr>
         <tr>
            <td colspan="1" rowspan="1"><a name="gsprelim_9661"></a><p class="para_td">CP</p>
            </td>
            <td colspan="1" rowspan="1"><a name="gsprelim_9663"></a><p class="para_td">Identification number of coordinate system in which the location of the grid point is defined. ((Integer &ge;0 or blank)</p>
            </td>
         </tr>
         <tr>
            <td colspan="1" rowspan="1"><a name="gsprelim_9668"></a><p class="para_td">X1, X2, X3</p>
            </td>
            <td colspan="1" rowspan="1"><a name="gsprelim_9670"></a><p class="para_td">Location of the grid point in coordinate system CP. (Real; Default = 0.0)</p>
            </td>
         </tr>
         <tr>
            <td colspan="1" rowspan="1"><a name="gsprelim_9672"></a><p class="para_td">CD</p>
            </td>
            <td colspan="1" rowspan="1"><a name="gsprelim_9674"></a><p class="para_td">Identification number of coordinate system in which the displacements, degrees of freedom, constraints, and solution vectors are defined at the grid point. (Integer &ge;-1 or blank)</p>
            </td>
         </tr>
         <tr>
            <td colspan="1" rowspan="1"><a name="gsprelim_9679"></a><p class="para_td">PS</p>
            </td>
            <td colspan="1" rowspan="1"><a name="gsprelim_9681"></a><p class="para_td">Permanent single-point constraints associated with the grid point. (Any of the Integers 1 through 6 with no embedded blanks, or blank)</p>
            </td>
         </tr>
         <tr>
            <td colspan="1" rowspan="1"><a name="gsprelim_9683"></a><p class="para_td">SEID</p>
            </td>
            <td colspan="1" rowspan="1"><a name="gsprelim_9688"></a><p class="para_td">Superelement identification number. (Integer &ge;0  ; Default = 0)</p>
            </td>
         </tr>
      </table><br><a name="gsprelim_9689"></a><p class="para_division">The default basic coordinate system is defined by leaving field 3 (CP) blank (the basic coordinate system&rsquo;s ID number is zero).</p><a name="gsprelim_9690"></a><p class="para_division">The values of X1, X2, and X3 (in our rectangular system these mean x, y, and z) in fields 4, 5, and 6 are as follows:      </p>
      <table border="1" cellpadding="5" width="100%" align="center">
         <tr>
            <th colspan="1" rowspan="1">
               <p class="para_th">GRID</p>
            </th>
            <th colspan="1" rowspan="1">
               <p class="para_th">X</p>
            </th>
            <th colspan="1" rowspan="1">
               <p class="para_th">Y</p>
            </th>
            <th colspan="1" rowspan="1">
               <p class="para_th">Z</p>
            </th>
         </tr>
         <tr>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9701"></a><p class="para_td">1</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9703"></a><p class="para_td">0.</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9705"></a><p class="para_td">0.</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9707"></a><p class="para_td">0.</p>
            </td>
         </tr>
         <tr>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9709"></a><p class="para_td">2</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9711"></a><p class="para_td">10.0</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9713"></a><p class="para_td">0.</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9715"></a><p class="para_td">0.</p>
            </td>
         </tr>
         <tr>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9717"></a><p class="para_td">3</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9719"></a><p class="para_td">20.0</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9721"></a><p class="para_td">0.</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9723"></a><p class="para_td">0.</p>
            </td>
         </tr>
         <tr>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9725"></a><p class="para_td">4</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9727"></a><p class="para_td">30.0</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9729"></a><p class="para_td">0.</p>
            </td>
            <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9731"></a><p class="para_td">0.</p>
            </td>
         </tr>
      </table><br><a name="gsprelim_9732"></a><p class="para_division">Field 7 (CD) is left blank since we want grid point displacements and constraints to be defined in the basic coordinate system.  The constraints for this problem could be defined on field 8 (PS) of grid points 1 and 4.  Instead, we will use SPC1 entries and leave field 8 blank.</p><a name="gsprelim_9733"></a><p class="para_division">Finally, field 9 is left blank since superelements are not part of this problem.</p><a name="gsprelim_9835"></a><p class="para_division">The completed GRID entries are written as follows:      </p>
      <table border="1" cellpadding="2" cellspacing="1" width="100%" align="center">
         <colgroup span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
            <col span="1">
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         <thead>
            <tr>
               <td align="center" colspan="1" rowspan="1">
                  <p class="para_td">1</p>
               </td>
               <th colspan="1" rowspan="1">
                  <p class="para_th">2</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">3</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">4</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">5</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">6</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">7</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">8</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">9</p>
               </th>
               <th colspan="1" rowspan="1">
                  <p class="para_th">10</p>
               </th>
            </tr>
         </thead>
         <tbody>
            <tr>
               <td align="center" colspan="1" rowspan="1">
                  <p class="para_td">GRID</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9758"></a><p class="para_td">1</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9762"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9764"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9766"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td colspan="1" rowspan="1"></td>
            </tr>
            <tr>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9776"></a><p class="para_td">GRID</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9778"></a><p class="para_td">2</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9782"></a><p class="para_td">10.0</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9784"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9786"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td colspan="1" rowspan="1"></td>
            </tr>
            <tr>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9796"></a><p class="para_td">GRID</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9798"></a><p class="para_td">3</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9802"></a><p class="para_td">20.0</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9804"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9806"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td colspan="1" rowspan="1"></td>
            </tr>
            <tr>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9816"></a><p class="para_td">GRID</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9818"></a><p class="para_td">4</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9822"></a><p class="para_td">30.0</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9824"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"><a name="gsprelim_9826"></a><p class="para_td">0.</p>
               </td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td align="center" colspan="1" rowspan="1"></td>
               <td colspan="1" rowspan="1"></td>
            </tr>
         </tbody>
      </table><br><a name="gsprelim_9836"></a><p class="para_division">Or, in free field format, the GRID entries are written</p><a name="gsprelim_9837"></a><pre class="indent">
    GRID,1,,0.,0.,0. 
    GRID,2,,10.,0.,0. 
    GRID,3,,20.,0.,0. 
    GRID,4,,30.,0.,0.</pre></body>
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