Ansys Multiple Load Cases

[Aussiepea]

Hi all,

I am quite new to this software and beginning to run some basic analysis. Currently I am looking at a fatigue case on a rotating disc which is also being pulsed back and forth along its axis. To test this I am looking at setting up two load conditions within the analysis so that I can run solution combination non-proportional fatigue analysis on both the rotating and acceleration forces acting on the disc.

However I am unsure how to get more than a single load case into the analysis. Below is an example picture I found online and you can see there are two "environments" and I am wishing to achieve the same but am not show how to do so. Any advice?

Cheers!

 

[bxtsafe]

Hi Aussiepea,

I read your post but I can't understand what is your question. Could you explain in a different way please?

I'm finishing a Master of Science course in Mechanical Engineering and I've been studying for 2 years Fatigue. I understand that there are non-proportional loading in your problem. If so, you must to use a Multiaxial Fatigue Criterion to do the fatigue assessment of the analyzed structure. Take care about Ansys Workbench Fatigue Modulus. This software is absolutely not able to do multiaxial fatigue assessment. For example, the mean stress correction of Goodman, Soderberg of Gerber is only applicable to UNIAXIAL fatigue problems. The Von Mises Fatigue Criterion is also only applicable to UNIAXIAL fatigue problems.

I hope I have helped in some way.

Chears.

bxtguard

 

[Aussiepea]

Thanks for the reply bxt. I have since figured out how to achieve what I asked in my post however I'm struggling with how to actually set up the problem. I don't want anything overly complicated and all I am really after is a comparative test between two different designs to determine which is at less risk of fatigue damage.

My problem is for a rotating disc which is also being vibrated fore/aft quite quickly and what I am trying to determine is the fatigue at a weak point at a particular section alone the disc. What I have done thus far is set up a problem which has two load conditions, one is a rotational velocity constrained by a cylindrical support which only allows for radial movement and the other load condition is an acceleration acting in the fore/aft direction however I am unsure as to how to constrain this particular force as it must allow the disc to move fore/aft however if I add a constraint allowing this movement in that axis large deformation occurs and the disc simply moves a distance in that direction rather than the force acting as a continuous fore/aft vibration.

My aim is to use a solution combination with these two load conditions to determine a fatigue result and compare two designs the same.

 

[bxtsafe]

First of all, I reread the answer I've posted in 15/Jul and there is a mistake. The correct phrase is:

"For example, the mean stress correction of Goodman, Soderberg of Gerber is only applicable to fatigue problems with PORPORTIONAL LOADING. The Von Mises Fatigue Criterion is also only applicable to PROPORTIONAL LOADING."


Ok. So, if you don't inted to do a complex analysis, you can use the von Mises Fatigue Criterion to compare (as a "rule of thumb") the 2 load conditions. But you have to be aware that this Fatigue Criterion is ONLY applicabe to fatigue problems that have PROPORTIONAL LOADING.

For more information about Proportional Loading and Non-proportional Loading I suggest to look at:

http://www.eng-tips.com/viewthread.cfm?qid=336936

Regards,

BXT