Stepped sine simulation on nonlinear component
Stepped sine simulation on nonlinear component
(OP)
Hello,
I have a structure with a lap joint which I tested at different forces and found being nonlinear (stepped sine excitation revealed softening behaviour in the FRF).
Now I would like to be able to predict the forced response of my FEmodel** by extracting the very same FRF I extracted via stepped sine.
In my understanding, I should do the following things:
a) choose a force level
b) perform a time-domain analysis (NL transient) using sine excitation as input
c) cut out the transient and keep just the steady-state response
d) calculate FFTs and produce a single FRF point
e) steps b) to d) covering all the frequency range
f) steps a) to e) covering all the force levels
That seems a HUGE task to me, and I am wondering if there was a better/quicker way of doing it.
**FEmodel has been linearly validated with prestressed normal modes using contact, friction and bolts preload.
Thanks in advance!
I have a structure with a lap joint which I tested at different forces and found being nonlinear (stepped sine excitation revealed softening behaviour in the FRF).
Now I would like to be able to predict the forced response of my FEmodel** by extracting the very same FRF I extracted via stepped sine.
In my understanding, I should do the following things:
a) choose a force level
b) perform a time-domain analysis (NL transient) using sine excitation as input
c) cut out the transient and keep just the steady-state response
d) calculate FFTs and produce a single FRF point
e) steps b) to d) covering all the frequency range
f) steps a) to e) covering all the force levels
That seems a HUGE task to me, and I am wondering if there was a better/quicker way of doing it.
**FEmodel has been linearly validated with prestressed normal modes using contact, friction and bolts preload.
Thanks in advance!





RE: Stepped sine simulation on nonlinear component
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Stepped sine simulation on nonlinear component
The stepped sine excitation is more conservative in this sense - I could stitch together several sinewaves to create a discrete-swept-sine excitation though.
My problem is that either way it would take just too long to retrieve some useful results and I wonder if there is a workaround to extract frequency responses with nonlinear analysis or at least speed up the process.
I can think of a MATLAB script that generates the NASTRAN input files, feeds them to NASTRAN and processes their results, but perhaps you have better ideas.
Thanks again!
RE: Stepped sine simulation on nonlinear component
In the real world that's called a tracking filter.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?