Learning Forum

[marshal.andreas.pub]

 The problem is I can do Static Structural on its own, but i don't know why it just can't when i Imported  Temperature from Steady State Thermal. Help me guys 
the error message is follwong guys:

*** ERROR ***                           CP =    8227.219   TIME= 20:39:50

 The value of UY at node 479015 is 423481388.  It is greater than the   

 current limit of 1000000 (which can be reset on the NCNV command).     

 This generally indicates rigid body motion as a result of an           

 unconstrained model.  Verify that your model is properly constrained.  

 

 *** ERROR ***                           CP =    8227.219   TIME= 20:39:50

 *** MESSAGE CONTINUATION ---- DIAGNOSTIC INFORMATION ***               

 If one or more parts of the model are held together only by contact    

 verify that the contact surfaces are closed.  Also make sure that      

 there are constraints (or friction) in the sliding direction even if   

 no load is applied in that direction.  You can use the CNCHECK command 

 to check the initial contact status in the SOLUTION module.        4

Steady State Thermal

Static Structural

    

[peteroznewman]

Part of your structure is not connected in the Y direction. One diagnostic check to find the unconstrained part is to drop a Modal analysis on the Static Structural Model cell.  In Mechanical, drag the Fixed Support from the Static Structural branch and drop it on the Modal branch. Under Analysis Settings for Modal, request 12 modes instead of 6.  Solve the Modal and plot Deformations for all modes.  I expect you will see the frequency for mode 1 is nearly zero.  In the Details window for Deformation plot of mode one is the name of the part with the maximum deformation. You may see it float around in the animation of the Deformation for mode 1. That is the part you have to constrain.

[marshal.andreas.pub]

I performed the modal analysis, yet it just cant get the result:

 *** WARNING ***                         CP =     114.297   TIME= 07:48:18

 The PCG Lanczos eigensolver has detected that the matrix used during    

 the PCG iterations is indefinite.  This will likely result in an        

 increased number of iterations required to reach convergence as well    

 as longer solution times.  It is recommended to switch to another       

 Lev_Diff value on the PCGOPT command (e.g., Lev_Diff = 5) or switch to  

 another eigensolver, such as Block Lanczos (MODOPT,LANB).               

                                                                         

 

 *** WARNING ***                         CP =    8573.484   TIME= 07:59:33

 The PCG solver detects that the out of balance force goes to            

 infinity.The solution has not converged.  Please check for rigid body   

 motions in your model.                                                  

                                                                         

 

 *** ERROR ***                           CP =    8573.500   TIME= 07:59:33

 The PCG Lanczos eigensolver has failed to converge while solving the    

 linear system of equations for the current Lanczos iteration.  Please   

 switch to the Block Lanczos eigensolver (MODOPT,LANB) in order to       

 extract the mode shapes for this model.                                 

                                             

[peteroznewman]

Under Analysis Settings, change the Solver to Direct.

[marshal.andreas.pub]

nope, doesnt work
 the messages as following:

 *** ERROR ***                           CP =     609.781   TIME= 09:07:17

 Size too large for a memory allocation.                                 

 

 *** ERROR ***                           CP =     609.781   TIME= 09:07:17

 Failure in BLOCK LANCZOS eigensolver.  Error code = -1.  Please send    

 the data leading to this operation to your technical support provider,  

 as this will allow ANSYS, Inc to improve the program.                   

 

 *** WARNING ***                         CP =     609.781   TIME= 09:07:17

 Fewer modes than the requested number of modes ( 12 ) were computed.    

 There are only 0 modes beyond the begin frequency of FREQB= 0.          

 

 

 NUMBER OF WARNING MESSAGES ENCOUNTERED=        176

 NUMBER OF ERROR   MESSAGES ENCOUNTERED=          2

 

[marshal.andreas.pub]

fyi, i do still use automatic connection and it works when i do steady state thermal analysis

[marshal.andreas.pub]

i deleted every contact and finally it works for the modal analysis( iuse nonconformal mesh for hexahedral meshing purpose)
so i should constrain this floating part with fixed support or what???

[marshal.andreas.pub]

this is the modal analysis with contact on :

[peteroznewman]

The small text in the screen snapshots is nearly illegible. The software you are using to take them is reducing the screen image resolution. Windows comes with Snipping Tool which does not reduce screen resolution at all. Try using that to paste images into your replies.

If that last image is for Mode 1, the frequency is now non-zero which is required for Static Structural to solve without an error. When you animate that result, does the part with the Maximum deformation move in a way that shows it is connected to other parts in a sensible manner?  What do you mean by "with contact on"?

In the second last image, the frequency is zero so that would mean Static Structural will give an error. The corrective action is to attach that part to whatever that part is supposed to be attached to. A part that floats that is meant to be fixed to ground should have a Fixed Support but if the part that floats is meant to be attached to other parts, then you need Bonded Contact to connect it to other parts so it doesnt float.

[marshal.andreas.pub]

Here is the modal analysis
I don't use shared topology due to easier hexahedral meshing and I use automatic contacts (it works wonder for my steady state thermal)
As u can see, there is no floating part and the part that have maximum deformation still moves in sensible manner
The problem is when i only import the load temperature on static structural, but when i leave the static structural with gravity only, it works

[peteroznewman]

Now that you have a Static Structural model that solves with a gravity load only, show that deformation result.

When you add an Imported Temperature load you get an error, show that error, plot the Imported Load temperature and the Details window.

Under Analysis Settings, try turning on Large Deflection, does that change the error?

What is the Coefficient of Thermal Expansion value for each material used?

[marshal.andreas.pub]

No Large Deflection:

 *** NOTE ***                            CP =    4225.578   TIME= 23:11:31

 The Sparse Matrix Solver is currently running in the in-core memory     

 mode.  This memory mode uses the most amount of memory in order to      

 avoid using the hard drive as much as possible, which most often        

 results in the fastest solution time.  This mode is recommended if      

 enough physical memory is present to accommodate all of the solver      

 data.                                                                   

 Sparse solver maximum pivot= 2.911567527E+21 at node 129856 UY.         

 Sparse solver minimum pivot= -1.831809152E+21 at node 126907 UY.        

 Sparse solver minimum pivot in absolute value= 2485.20108 at node       

 231642 UY.                                                              

 

 *** ERROR ***                           CP =    4297.906   TIME= 23:12:05

 The value of UY at node 238523 is 287245902.  It is greater than the    

 current limit of 1000000 (which can be reset on the NCNV command).      

 This generally indicates rigid body motion as a result of an            

 unconstrained model.  Verify that your model is properly constrained.   

 

 *** ERROR ***                           CP =    4297.906   TIME= 23:12:05

 *** MESSAGE CONTINUATION ---- DIAGNOSTIC INFORMATION ***                

 If one or more parts of the model are held together only by contact     

 verify that the contact surfaces are closed.  Also make sure that       

 there are constraints (or friction) in the sliding direction even if    

 no load is applied in that direction.  You can use the CNCHECK command  

 to check the initial contact status in the SOLUTION module.            

After Large Deflection:

 *** NOTE ***                            CP =    4196.156   TIME= 23:34:03

 The Sparse Matrix Solver is currently running in the in-core memory     

 mode.  This memory mode uses the most amount of memory in order to      

 avoid using the hard drive as much as possible, which most often        

 results in the fastest solution time.  This mode is recommended if      

 enough physical memory is present to accommodate all of the solver      

 data.                                                                   

 Sparse solver maximum pivot= 6.877451288E+21 at node 129856 UX.         

 Sparse solver minimum pivot= -2.370368105E+20 at node 243904 UZ.        

 Sparse solver minimum pivot in absolute value= 5926.59524 at node       

 231167 UY.                                                              

 

 *** ERROR ***                           CP =    4268.984   TIME= 23:34:39

 The value of UY at node 238523 is 287184481.  It is greater than the    

 current limit of 1000000 (which can be reset on the NCNV command).      

 This generally indicates rigid body motion as a result of an            

 unconstrained model.  Verify that your model is properly constrained.   

 

 *** ERROR ***                           CP =    4268.984   TIME= 23:34:39

 *** MESSAGE CONTINUATION ---- DIAGNOSTIC INFORMATION ***                

 If one or more parts of the model are held together only by contact     

 verify that the contact surfaces are closed.  Also make sure that       

 there are constraints (or friction) in the sliding direction even if    

 no load is applied in that direction.  You can use the CNCHECK command  

 to check the initial contact status in the SOLUTION module.