Rainflow Counting Fatigue Analysis

[stiffening_ring]

Hi,

I have strain gauges installed on a vessel with the intention of performing fatigue analysis to predict 'theoretical' end of life. I have multiple cycles of data to analyse and I want to use the curve fit equations from ASME VIII Div. 2 with Miners rule to summate consumed life. I have successfully done this using the maximum stress from each cycle with good results. Obviously this is only half the story as I now need to apply rainflow counting as the stress are irregular throughout the cycle and I understand the basics of the calculation.

My question is how I apply the rainflow counting into excel? The strain data is taken every second and imported into excel so I want to apply the rainflow counting method to the data in excel, rather than graphing and manually applying the method. The aim would be to import the data in blocks say every month and update the consumed life. I am thinking I need to write an algorithm in excel to achieve this?

Does anybody have any experience in this area that could offer assistance? It seems like this is a service that companies offer so I'm wondering if it's even feasible for a relatively inexperienced engineer to accomplish?

Many thanks in advance for any assistance.

Regards,

 

[davefitz]

Try a science citation search on the basis of the following 4 tech papers:

Downing,SD and Soucie, DF "simple rainflow counting algortihms", Int J of fatigue, V4, no 1 (1983) p 206
Dirsh, WF "a simplified rainflow algorithm:modular cycle counting", ASME paper 87-WA/RT-6 (1987)
ASME E 1049-85 "standard practices in cycle counting in fatigue analysis" 1997
MSci thesis of V Stathis ( 2015), with computer program for the rainflow cycle counting algorithm

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick