自己做的一个模型，拓扑优化时出现以下#ERROR1800，求高手帮忙解决，非常谢谢！

************************************************************************
** **
** **
** OptiStruct 10.0 **
** **
** Design and Optimization Software **
** from Altair Engineering, Inc. **
** **
** **
** Windows XP Professional SP3 (Build 2600) WWW-4B46AD9643E **
** 2 CPU: Pentium(R) Dual-Core CPU T4300 @ 2.10GHz **
** CPU speed 2100 MHz **
** 955 MB RAM, 3935 MB swap **
** **
** Build tag: 0466938_5333O00_Ci3242M-000 4000 **
************************************************************************
** COPYRIGHT (C) 1996-2009 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. **
************************************************************************

*** OptiStruct defaults set from:
install config file: D:\Hyperworks10/hwsolvers/hwsolver.cfg

NOTE # 1929
Created RAM scratch area: total size 200 MB.
*** WARNING # 1848
Topology Optimization without Minimum Member Size Control activated.
Use DTPL card, or DOPTRM,MINDIM is recommended.
*** INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 10529
independent grid id = 14879
a dependent grid id = 207
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.
*** INFORMATION # 742
The dependent rotational d.o.f. of this rigid element is removed.
RBE2 element id = 10530
independent grid id = 14880
a dependent grid id = 234
This is because there is no need to constrain the rotational d.o.f. of
any of the dependent grids.
*** INFORMATION # 743
The total number of rigid elements, whose rotational dependent d.o.f.
are removed because there is no need to constrain those d.o.f., is 2
*** 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 design variable definition card.
Property ID = 1

This error occurs in module "dppdrv1".

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OPTIMIZATION FILE AND PARAMETER INFORMATION :
---------------------------------------------
Optimization parameters from : D:/Hyperworks10/tutorials/hm/3MCJT_opt.fem
FEM model file : D:/Hyperworks10/tutorials/hm/3MCJT_opt.fem
Output files prefix : D:/Hyperworks10/tutorials/hm/3MCJT_opt
************************************************************************

************************************************************************
FINITE ELEMENT MODEL DATA INFORMATION :
---------------------------------------
Total # of Grids (Structural) : 7179
Total # of Elements : 4428
Total # of Rigid Elements : 2
Total # of Rigid Element Constraints : 2577
Total # of Degrees of Freedom : 24114
Total # of Non-zero Stiffness Terms : 809700

Element Type Information
------------------------
CHEXA Elements : 4112
CPENTA Elements : 316
Load and Boundary Information
-----------------------------
FORCE Sets : 1
SPC Sets : 1
Material and Property Information
---------------------------------
PSOLID Cards : 1
MAT1 Cards : 1
************************************************************************

************************************************************************
***** ERROR ENCOUNTERED BEFORE COMPLETING THE CHECK RUN *****
Current Memory (RAM) : 210 MB
This includes ramdisk area allocated in memory : 200 MB
Estimated Minimum Memory (RAM) for the check run : 15 MB
************************************************************************

This error occurs in module "prpdrv".
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RESOURCE USAGE INFORMATION
--------------------------
MAXIMUM MEMORY USED 210 MB
THIS INCLUDES 200 MB RAMDISK AREA ALLOCATED IN MEMORY
MAXIMUM DISK SPACE USED 0 MB
************************************************************************
************************************************************************
COMPUTE TIME INFORMATION
------------------------
EXECUTION STARTED Tue May 29 10:00:43 2012
EXECUTION COMPLETED Tue May 29 10:00:44 2012
ELAPSED TIME 00:00:00
CPU TIME 00:00:00
************************************************************************

*** 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

************************************************************************
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 design variable definition card.
Property ID = 1