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# NX Durability results

I did a stress analysis on a ball bearing model , got perfect results . Then i did a durablity analysis on it and chose the proper stress models and got strength safety factor and margin of safety values as the results for a million cycles. How to interpret the result? What does these values indicate? I have to basically approximate the life cycle of the product, how many revolutions will it go in the given load , before failing. How will the SSF and margin of safety help me calculate that?

3 REPLIES
Solution
Solution
Accepted by topic author AKMECH
‎10-06-2016 06:49 AM

## Re: NX Durability results

The SSF tells you how close your max stress is to the ultimate or yield strength. If it is above yield, then you should use a strain life approach to estimate fatigue life. Otehrwise, a stress life approach would be suitable.

If you know how many cycles your structure will experience, then enter them as you did and the fatigue  margin of safety expresses the capacity of the structure to withstand that number of cycles: If it is below 0, it cannot.

You can also compute fatigue life, using one of the methods described above (srtess or strain life).

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

## Re: NX Durability results

But, i am having problem with the data input as i cannot find any information on the fatigue strength coeffiecient and cyclic parameters which are required for durability analysis. I have to do the analysis on ABS plastic.

## Re: NX Durability results

S-N data for this type of material is not easily available.

I would suggest you look at the polymer chapter of either one of these ASM books:

http://www.asminternational.org/home/-/journal_content/56/10192/05361G/PUBLICATION/

http://www.asminternational.org/materials-resources/results/-/journal_content/56/10192/06987G/PUBLIC...

In the past, we've adapted curves found in the such books using the ultimate strengths of the materials.

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