cyclic tensile loading 1

[Me09]

Hi, I am modelling a cyclic tensile loading of a non metallic wire (3D model with elastic material). I need the wire cyclically be loaded in tension between 50 N to 150 N for 100 cycles at 1HZ.
Does anyone have a suggestion for it?

 

[williwang]

how about do 10 cycle and draw a line on your graph since the system is liner?

Forever Young.....

 

[xerf]

Maybe you could use a tabular or periodic amplitude.

 

[Me09]

if i want to used tabular amplitude, i only can define time and amplitude in each line. for example for time step=5 the amp-1 can be:
1-->0
2-->1
3-->0
4-->1
5-->0
how does it change the force from 50 to 150 and how i can apply the frequency of 1Hz?

 

[TGS4]

Unless your particular material model has strain-rate sensitive material properties, it doesn't matter what the "frequency" of your load application is.

Why would you think that the 10th or 60th, or 100th cycle is going to be any different than the first?

The more I think about this, this is pretty rudimentary. Is this for a school project?

 

[Me09]

thanks for your fantastic responds but still it is not clear.
the material i am using is hyper elastic (moony-rivlin) and the load is initially set to 50 N.
this is the simulation of a cyclic loading test which we normally do it in a mechanical workshop.
1- from the experiment we know the result will be different after predefined cycles for example result of 10 cycle is different with 100 cycle in term of the displacement of the wire
2- the frequency is important as it will change the strain rate effect and change the result
so I have to define frequency but how?

 

[bassmanjax]

You can do this easily with a periodic amplitude curve. Look up *AMPLITUDE, DEFINITION=PERIODIC as Xerf suggested. The amplitude curve is used to scale whatever load is applied, so for example;

*AMPLITUDE, DEFINITION=PERIODIC, NAME=Curve-1
...

*CLOAD, AMPLITUDE=Curve-1
1,2,100
..

This will apply a load of 100 units to node 1 in direction 2 that will be scaled by the amplitude 'Curve-1'.

Have a look at section 28.3.1 'Amplitude Curves' in the user manual - covers most of what you need to know.

Regards

Martin Stokes CEng MIMechE

 

[TGS4]

If your material model has strain-rate properties, then you will set the step size (time) based on the inverse of the frequency. I cannot emphasize this enough - if you material model does not have a strain-rate dependency, then you will be wasting your time with this!

My recommendation would be to make 200 steps (odd-steps would be the load of 50N, even-steps would be the 150N load), with the time span of each step equal to 0.5 seconds. Then, in the post processing, you can see if the displacement changes as a function of time.