Pre-stretch membrane simulation error

Hi everyone,

I used CalculiX 2.19 to predict the dynamic responses of a pre-stretched flexible membrane under given forces. It was weird to find that the simulation automatically ends after running for a while. However, the simulation wasn’t finished, and there is no error message in the log file.

I used a two-step approach to model this problem. In step 1, the membrane was
stretched to deserved length. In step 2, the given force was applied on the membrane to predict the deformation. The problem occurs in step 2. Following are the input files:

Step 1:

step1.inp

*INCLUDE, INPUT=all.msh
*INCLUDE, INPUT=fixed.nam
*INCLUDE, INPUT=membrane.nam
*INCLUDE, INPUT=material.inp
*AMPLITUDE,NAME=AMP1
0,1
0.01,1
0.02,0
0.03,0
*NSET,NSET=probe
597
*BOUNDARY
Nfixed,1,3
*STEP, NLGEOM, INC=100000
*STATIC
1e-3, 1
*RESTART,WRITE
*INCLUDE,INPUT=boundary.inp
*NODE PRINT, NSET=Nall, FREQUENCY=1000
U
*NODE FILE
U
*EL FILE
S,E,ENER
*END STEP

The include files in step1.inp can be downloaded here. Everything goes well in step 1.

Step 2:

step2.inp

*RESTART,READ
*STEP,NLGEOM,INC=10000000
*DYNAMIC
1e-3, 5
*BOUNDARY,FIXED
**INCLUDE,INPUT=Solid/boundary-restart.inp
**BOUNDARY,OP=NEW
**Nfixed,1,1,0
**Nfixed,2,2,0
**Nfixed,3,3,0
*CLOAD,AMPLITUDE=AMP1
**CLOAD
Nmembrane, 1, 0.0
Nmembrane, 2, 0.0
Nmembrane, 3, 0.01
*NODE PRINT,NSET=probe
U
**NODE PRINT,NSET=Nfixed
**U
**NODE PRINT,NSET=Nmembrane
**U
*NODE FILE
U
*EL FILE
S
*END STEP

After running for a while, the simulation automatically ends without any errors. However, there is no errors in the log file. Just ending as follows:

 no convergence
 iteration 4
 Using up to 1 cpu(s) for the symmetric stiffness/mass contributions.
 Factoring the system of equations using the symmetric spooles solver

The results can be downloaded here. Does anyone have ideas about it? Many thanks in advance!

Did you change the step1.rout file to step2.rin ?

When I submit this in ccx 2.19, it runs for some time and ends with an error:

Solution contains Nan! 
PaStiX could not converge to a valid result.

Thanks for your reply! I changed the step1.rout file to step2.rin. I have tried many times in ccx 2.19. Step1 finished with no errors, and the computation was completed. Step 2 also finished with no errors, while the computational wasn’t completed. It was weird.