Cyclic Loading in Abaqus

[Shruzy]

I am trying to apply a cyclic loading (pressure loading) to a simple cube with 27 elements in the form of Asin(wt) in abaqus. Based on what I read on this forum and other forums as well as the manual, I used the Periodic option in Amplitude to do this, with the parameters set as follows - initial amplitude=0, A=0, B=1, and 3 different cases for circular frequency, 2 pi, 10 pi and 100 pi. I then tried to plot this loading by using the Pressure (P) option in field output request while defining the model, and plotted this against time using the element face option for 1 second. I was expecting a sin wave in my plots with different frequencies but what I got doesn't make any sense to me. I have attached the plots here.
I am unsure if I am making an error while defining the amplitude or while plotting it.
Kindly pardon me if I have been unable to make myself clear. I will be glad to provide any more information required.

2 pi

10 pi

100 pi

 

[IceBreakerSours]

You should request pressure as a history output and plot that, not the field output.

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[Shruzy]

Hi IceBreakerSours,

Thanks for your reply. I cannot find any 'Pressure' option under the option 'Forces' when I select the history output option. I found a 'PRESS'(pressure) option under stresses, but I don't think that is the right one as I read on some other thread. I also tried one of the options RF(reaction force) under the option Forces, and I plotted all these for the top layer of elements where I am applying pressure as well as the nodes for these elements. I am only getting a linearly increasing plot or a constant 0-valued plot.
Can you tell me exactly which option is the right one in the history field request? Also, do I need to define a tracer or something like that to capture the pressure? I went through the manual and a lot of other websites, but could not find anything useful.

Thanks!

 

[Shruzy]

Well, I figured out this problem. It turned out to be a stupid mistake, but I'll share here nevertheless, might help another newbie somewhere who may make the same mistake. I didn't know that I was supposed to specify the initial time increment, and my default time increments were too coarse and hence the plots were only showing some points and totally missing out the actual loading profile. You can do this in the tab "Incrementation" by editing your current step under the option Steps in the model tree. The initial increment size must be changed to a smaller step if it is too large for you now.

 

[IceBreakerSours]

Thank you for the posting the resolution.

By the way, you may notice that your new ODB file size is larger when compared with your previous run. This is the problem with field output requests (or frames).

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