做优化时报错ERROR #1800，求大神帮忙

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** **
** **
** OptiStruct 11.0 **
** **
** Design and Optimization Software **
** from Altair Engineering, Inc. **
** **
** **
** Windows 7 Workstation SP1 (Build 7601) ADMIN-PC **
** 4 CPU: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz **
** CPU speed 3200 MHz **
** 1111 MB RAM, 8036 MB swap **
** **
** Build tag: 0569251_5533110_Ce64RBW8H11M:61051-000 4000 **
************************************************************************
** COPYRIGHT (C) 1996-2011 Altair Engineering, Inc. **
** All Rights Reserved. Copyright notice does not imply publication. **
** Contains trade secrets of Altair Engineering, Inc. **
** Decompilation or disassembly of this software strictly prohibited. **
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*** OptiStruct defaults set from:
install config file: C:\Program Files\Altair\11.0/hwsolvers/hwsolver.cfg.
*** WARNING 1931: PLOAD4 46 is not referenced by Case Control.
*** WARNING 1931: PLOAD4 105 is not referenced by Case Control.
*** WARNING 1931: PLOAD4 110 is not referenced by Case Control.
*** WARNING # 1884
Default DESMAX=80 is recommended for Casting and/or Symmetric constraints.
Aborting before finishing all iteration phases is likely to
result in sub-optimal designs.
*** ERROR # 1800 ***
Stress/strain/force response is applied to topology or
free-size domain. For stress-constrained topology or
free-size optimization, please use the STRESS option
on the design variable definition card.
Element ID = 23457
This error occurs in module "dppdrv1".
***** ERROR ENCOUNTERED BEFORE COMPLETING THE CHECK RUN *****
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OPTIMIZATION FILE AND PARAMETER INFORMATION :
---------------------------------------------
FEM model file : D:/gongzuo/jixia/work/zhiliang/m/m.fem
Output files prefix : D:/gongzuo/jixia/work/zhiliang/m/m
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FINITE ELEMENT MODEL DATA INFORMATION :
---------------------------------------
Total # of Grids (Structural) : 14794
Total # of Elements : 16104
Total # of Rigid Elements : 2
Total # of Rigid Element Constraints : 12
Total # of Degrees of Freedom : 71412
Total # of Non-zero Stiffness Terms : 2765586
Element Type Information
------------------------
CHEXA Elements : 7416
CQUAD4 Elements : 8688
Load and Boundary Information
-----------------------------
FORCE Sets : 133
SPC Sets : 1
Material and Property Information
---------------------------------
PSOLID Cards : 2
PSHELL Cards : 5
MAT1 Cards : 1
************************************************************************
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***** ERROR ENCOUNTERED BEFORE COMPLETING THE CHECK RUN *****
Current Memory (RAM) : 100 MB
Estimated Minimum Memory (RAM) for the check run : 30 MB
************************************************************************
This error occurs in module "prpdrv".
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RESOURCE USAGE INFORMATION
--------------------------
MAXIMUM MEMORY USED 100 MB
MAXIMUM DISK SPACE USED 0 MB
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COMPUTE TIME INFORMATION
------------------------
EXECUTION STARTED Wed Nov 04 18:49:31 2015
EXECUTION COMPLETED Wed Nov 04 18:49:33 2015
ELAPSED TIME 00:00:01
CPU TIME 00:00:00
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*** PROGRAM STOPPED: FATAL ERROR(s) ENCOUNTERED.
***** END OF REPORT *****
For Useful OptiStruct Tips and Tricks, go to the URL:
http://www.altairhyperworks.com/tips.aspx
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There were 3 error messages during input processing.
The first message is repeated below:
*** ERROR # 1800 ***
Stress/strain/force response is applied to topology or
free-size domain. For stress-constrained topology or
free-size optimization, please use the STRESS option
on the design variable definition card.
Element ID = 23457
***** ERROR ENCOUNTERED BEFORE COMPLETING THE CHECK RUN *****
...
************************************************************************
Errors reported during program execution
hwsolver.mesg output from the solver:
==============================
*** ERROR # 1800 ***
Stress/strain/force response is applied to topology or
free-size domain. For stress-constrained topology or
free-size optimization, please use the STRESS option
on the design variable definition card.
Element ID = 23457
***** ERROR ENCOUNTERED BEFORE COMPLETING THE CHECK RUN *****
***** ERROR ENCOUNTERED BEFORE COMPLETING THE CHECK RUN *****
Solver FAILED
optistruct:: Solver run finished.