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# Durability Event Sequences

Greetings,

I am setting up a durability analysis within the advanced simulations module based on a linear static analysis of several events. It is on an aluminum cast part for suspension.

I set up a durability solution with one static event and add three excitations based on three sub-cases results in the linear static solution. The durability requirement calls for the three event sequences to be evaluated at 600000 cycles.

Question 1:
Under the fatigue tab do I leave the number of occurrences at 1 and evaluate the fatigue life results to see if the lowest cycle is above 600000 cycles
or
Under the fatigue tab do I input 600000 occurrences and evaluate the fatigue life to see if the lowest cycle is above 600000 cycles or do I evaluate the plotting grid at some other fatigue life because I used the 600K for the number of occurrences.

Question 2:
Am I even setting up the simulation correct. Instead of one durability solution and one static event and three excitations should I be doing one durability solution and three static events with one excitation be static event? If I did it this way I could have more control over each event that rolls up into the solution.

I tried both ways and they give different answers.  Just need to know which way is standard practice for multiple road events.

Question 1 still pertains to Question 2.

Thanks ahead of time for any input.

3 REPLIES
Solution
Solution
Accepted by Ganesh_S (Community Manager)
‎08-26-2015 04:32 AM

## Re: Durability Event Sequences

For question 1, life is expressed in terms of duty cycles. If you define 600,000 occurences and the minimum life computed by the durability solver is 2 duty cycles, this means the structure can survive 1,200,000 occurences, or 1,200,000 full or half cycles as you defined in your load pattern. If on the other hand you define a single occurrence, then the life output from the durability solver should exceed 600,000 duty cycles.

For question 2, you are getting different results because the axis search is finding different directions for the 3 load cases combined, compared to each load case separately. You should have a safety factor on your desired life and this factor should be greater than the difference between both approaches. I'm not aware of a standard practice: If in doubt, I would use the approach that yields the lowest life, and I'm guessing that is the 3-event approach.

Phil

Philippe Tremblay
phillippe.tremblay.ext@siemens.com
www.mayahtt.com

## Re: Durability Event Sequences

Another Question:

I want to run durability on sol 601. However when I go to select the LC it will only allow me the option to pick one time step.  Is this typical?  I picked the one with the highest load and stress?

Any thoughts.

Thanks

## Re: Durability Event Sequences

If you are creating a transient event, the Durability UI will show you a list of subcases, not time steps. All your time steps are in that one subcase. The time step selection can be done by clicking the Data Control tab. By default, all steps are considered. If you change the Time Domain drop down to Specify, then you can select a start and an end step.

Phil

Philippe Tremblay
phillippe.tremblay.ext@siemens.com
www.mayahtt.com