Propagating displacements

FOL

 Hi,

 I'm trying to simulate the stress level of one part,
which is displaced in a first step in -y 12mm and in a second step in +y 4mm. I
have tried to solve this simulation by using two *STEPS (see below). First step
of -12mm is solved successfully but the calculation diverges just after
starting with the second step.

Any help will be very welcome. :+)

*STEP,NLGEOM=YES,INC=1000

*STATIC,DIRECT

0.01,1

*AMPLITUDE,NAME=AMP_1

0,0

1,1

*BOUNDARY,AMPLITUDE=AMP_1

xbiter_disp_nodes,2,2,-12e-3

*NODE FILE,GLOBAL=YES

U,RF

*EL FILE

S,E

*END STEP

*STEP,NLGEOM=YES,INC=1000

*STATIC,DIRECT

0.01,1

*AMPLITUDE,NAME=AMP_2

0,0

1,1

*BOUNDARY,OP=NEW,AMPLITUDE=AMP_2

xbiter_disp_nodes,2,2,4e-3

*NODE FILE,GLOBAL=YES

U,RF

*EL FILE

S,E

*END STEP

 

Sergio

Can you attach the liml file?

Victor

I would use a single step with amplitude like:

*AMPLITUDE,NAME=AMP_1

0,0

1,1

2,-0.333333333

unless you're planning to add more complicated differences between the steps like making one of them linear or different outputs, etc.

It could be a problem that the displacement is changing suddenly from -12 to 0 between the 1st and 2nd steps. It may need a gradual transition, like with

*AMPLITUDE,NAME=AMP_2

0,-3

1,1

FOL

 

Thanks Victor. Yes, the idea was to split the
simulations in two steps and modify the friction and outputs from one step to
the other. By doing the gradual transition that you recommended, the simulation
is has converged. I’m currently analyzing the results. Good recommendation!

Hi Sergio, unfortunately I cannot upload the liml file
since we are evaluating currently the patent filing for the analyzed geometry.
Thanks a lot for your quick response.

 

Sergio

I understand the point, have signed several NDA and also working for a company that not allow us to share to much detailed information.

About the multiple steps simulations, I like also in that way, having different steps for every load rather than working with an stepped amplitud. But for easy models (like loading/unloading) using this stepped allow you to work within the Mecway and avoid the manual editions.

Regards

davefo

I'm curious what this type of analysis is

is it an incremental displacement showing stresses gradually increasing then reducing ?

Sergio

Sometimes I load and unload (but completly) the material (over the yield point) to see how much deformed the part left after the loading.

He says that will change the friction between steps, I'm tring to figurate a situation were this must be needed :-(