UA-69298255-1 How to Combine Different Displacement Cycle Conditions | Calgary, AB

How to Combine Different Displacement Cycle Conditions | Calgary, AB

March 27, 2018

 

The Designer may have more than one thermal expansion or other displacement cycle conditions to consider. Cycles at lower stress ranges are substantially less damaging than cycles at higher stress ranges. ASME B31.3 uses the cycle with the highest stress range (full displacement cycle), SE, to compare to the allowable stress range, SA. However, cycles with lower stress ranges are converted into equivalent numbers of full displacement cycles to determine the /factor. This procedure, described in par. 302.3.5(d), uses the equation

Based on this procedure, the maximum stress range is limited to SA, which satisfies the shakedown limit. Lesser cycles are converted into equivalent, with respect to fatigue damage, numbers of cycles at SE to determine if an/factor less than one is required to protect against fatigue failure
Table 7.1 provides an example of combining several displacement cycle conditions with different stress ranges and numbers of cycles. Note that due to the sensitivity of fatigue damage to stress (the fifth power in the equation), displacement cycles at significantly lower stress ranges than SE produce very little damage or a significantly reduced number of equivalent cycles.

#Little_PEng

Please reload

Rate UsDon’t love itNot greatGoodGreatLove itRate Us

LITTLE P.ENG. FOR ENGINEERS TRAINING

3705 Fonda Way #18 Southeast Calgary, T2A 6G9

Canada

Bay area, California

Stay Connected

  • Yelp Social Icon
  • Facebook Social Icon
  • Twitter Social Icon
  • LinkedIn Social Icon
  • yp-logo-original
  • Yelp Social Icon
  • Google Places Social Icon
  • Pinterest Social Icon