Learning Forum

[fth987]

Hello,

When both stages are exposed to temperature load, the stress and displacement in the interstage boundary between Stage 1 and Stage 2 do not match. This discontinuity problem does not improve when more coupled harmonics are added to the analysis. All harmonic indices were used for Stage 1 and Stage 2.

 In addition, when the setting of large deflection is turned on, we get the following error.

 

*** ERROR ***                           CP =     171.891   TIME= 09:53:22

Stage STAGE325_1 has non-zero harmonic index and Newton-Raphson        

 iterative solution is requested.  The multistage analysis (MSOPT       

 command) cannot be performed. 

 

Does multiharmonic static analysis for Ansys Mechanical 2024 R1 not support accounting for temperature-pressure load and geometric nonlinearity?

[fth987]

 

current issue

 

 

 

 

 

[dlooman]

For the NLGEOM question - within a static analysis, typically the setup will include HI=0 sectors.  If only HI=0 sectors are used, all non-linearities are allowed (NLGEOM, NL Materials, NL Contacts within a stage).  When higher order HI’s are included, to recombine the solutions we are using linear superposition so nonlinearities get blocked.  We are investigating whether we can recombine solutions of multiple HI sectors when nonlinearities are present but there isn’t a timetable yet for when or if this might be allowed.

 

For the temperature question, Im not sure what the issue might be without seeing the model.  We have run a lot of test case models with applied thermal loads (directly applied temps, temps imported from external data sources, temps imported from multistage thermal analyses). One potential thing that could be causing issues is if you are importing temperatures from external sources, you need to have an individual applied temperature object in the tree for each stage, even if the source is from the same data file.  For example here is a generic gas turbine model which has a 2D thermal analysis result for the entire assembly:

 

You can see that there are 7 unique imported body temperature objects even though they all come from the same source result file.  Each of the imported body temperature objects are scoped to just the bodies for that stage.  This model has 7 stages and each has its own temperature object in the tree. 

[fth987]

 

Thanks a lot for your quick reply to my message. I am stating the model details below.

 

[fth987]

 

It is seen that the stress values created from paths in the interstage boundary between Stage 1 and Stage 2 do not match.

 

The image created using the chart object shows that the curves do not have similar shapes and close peak values.

[fth987]

This image shows that the continuity of the model has improved considerably without temperature and pressure loads.

[fth987]

current issue

[dlooman]

Are you able to log a support request so that the model can be studied?

[fth987]

Does multistage multiharmonic cyclic symmetry analysis for Ansys Mechanical 2024 R2 support accounting for geometric nonlinearity?

 

[dlooman]

Cyclic symmetry only supports geometric non-linearity for harmonic index 0.