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      <title>TSTEP</title>
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      <div class="title_refTopic" id="xps10_pagetitle">TSTEP </div>
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      <h4 class="refClassification">Transient Time Step </h4>
      <p class="para_refTopic">Defines time step intervals at which a solution will be generated and output in transient analysis. </p>
      <div class="title_refCategory">Format: </div>
      <div class="refCategoryContent">
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                     <p class="para_th">1 </p>
                  </th>
                  <th align="center" colspan="1" rowspan="1">
                     <p class="para_th">2 </p>
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                  <th align="center" colspan="1" rowspan="1">
                     <p class="para_th">3 </p>
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                     <p class="para_th">4 </p>
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                     <p class="para_th">5 </p>
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                     <p class="para_th">6 </p>
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                     <p class="para_th">7 </p>
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                     <p class="para_th">8 </p>
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                  <th align="center" colspan="1" rowspan="1">
                     <p class="para_th">9 </p>
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                     <p class="para_th">10 </p>
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            <tbody>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">TSTEP </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">SID </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">N1 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">DT1 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">NO1 </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>
                  <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">&nbsp; </p>
                  </td>
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                     <p class="para_td">&nbsp; </p>
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                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">N2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">DT2 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">NO2 </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>
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                  <td align="center" bgcolor="gray" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
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                     <p class="para_td">&nbsp; </p>
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                     <p class="para_td">&nbsp; </p>
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                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">-etc.- </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>
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                  <td align="center" bgcolor="gray" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
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                     <p class="para_td">&nbsp; </p>
                  </td>
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                     <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">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Example: </div>
      <div class="refCategoryContent">
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                     <p class="para_td">TSTEP </p>
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                     <p class="para_td">101 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">9000 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">.001 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">9000 </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>
                  <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">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">1000 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">.001 </p>
                  </td>
                  <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">&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>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br><p class="para_refCategory">In the above example, 10000 time steps with increment .001 seconds are computed, the first 9000 time steps are skipped, and time steps 9001 thru 10000 are output. </p>
         <p class="para_refCategory"><img align="bottom" src="graphics/bulktuv-ufig02.gif" border="0"></p>
      </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>
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            </thead>
            <tbody>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">SID </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Set identification number.  (Integer &gt; 0) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Ni </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Number of time steps of value DTi.  (Integer &ge; 1) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">DTi </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Time increment.  (Real &gt; 0.0) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">NOi </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Skip factor for output.  Every NOi-th step will be saved for output.  (Integer &gt; 0; Default=1) </p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Remarks: </div>
      <div class="refCategoryContent">
         <ol type="1" start="1">
            <li>
               <p class="para_item">TSTEP entries must be selected with the Case Control command TSTEP=SID. </p>
            </li>
            <li>
               <p class="para_item">Note that the entry permits changes in the size of the time step during the course of the solution.  Thus, in the example shown, there are 10 time steps of value .001 followed by 9 time steps of value .01.  Also, the user has requested that output be recorded for t=0.0, .005, .01, .02, .03, etc. </p>
            </li>
            <li>
               <p class="para_item">See &ldquo;Guidelines for Effective Dynamic Analysis &rdquo; in the <em>NX Nastran Basic Dynamic Analysis User&rsquo;s Guide</em> for a discussion of considerations leading to the selection of time steps. 
               </p>
            </li>
            <li>
               <p class="para_item">In modal frequency response analysis (SOLs 111 and 146), this entry is required only when TLOADi is requested; i.e., when Fourier methods are selected. </p>
            </li>
            <li>
               <p class="para_item">The maximum and minimum displacement at each time step and the SIL numbers of these variables can be printed by altering DIAGON(30) before the transient module TRD1 and by altering DIAGOFF(30) after the module.  This is useful for runs that terminate due to overflow or excessive run times. </p>
            </li>
            <li>
               <p class="para_item">For heat transfer analysis in SOL 159, use the TSTEPNL entry. </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">TSTEP may be used in a static or transient analysis. In a nonlinear static analysis, TSTEP is frequently used with TLOAD1 to apply incremental loads to achieve better convergence in the solution. </p>
            </li>
            <li>
               <p class="para_item">If no TSTEP is selected with the Case Control command TSTEP, the program assumes 1 time step with time increment of 1.0. </p>
            </li>
            <li>
               <p class="para_item">For SOL 701, the actual time step size used may be determined by the program based on the critical time step size for stability. To request that the program use the time step size DTi here, specify XSTEP=1 in NXSTRAT entry. In all cases, the total solution time is used, i.e., total solution time is the sum of all Ni * DTi </p>
            </li>
            <li>
               <p class="para_item">For SOL 701, please see Section 7.1 in the Advanced Nonlinear Theory and Modeling Guide on the critical time step size and when results are output. </p>
            </li>
            <li>
               <p class="para_item">Note that TSTEPNL is not used in SOLs 601 or 701. </p>
            </li>
         </ol>
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