Real time fatigue data
Real time fatigue data
(OP)
I am looking for help !
I have "accumulation rainflow" data for propshaft torques, and I need to understand the overall "damage" that this would cause. My data is a matrix of Mean Torque and Torque Amplitude, with the individual cells showing the accumulated cycles at each condition.
If all the data was simple bi-directional fatigue (i.e. with mean torque =0), then I think I know how to combine the data following miners rule. But I am not sure how to manage offset torques. Should I use something like the Goodman rule? and if so how do I apply it?
Thanks for any advice !
I have "accumulation rainflow" data for propshaft torques, and I need to understand the overall "damage" that this would cause. My data is a matrix of Mean Torque and Torque Amplitude, with the individual cells showing the accumulated cycles at each condition.
If all the data was simple bi-directional fatigue (i.e. with mean torque =0), then I think I know how to combine the data following miners rule. But I am not sure how to manage offset torques. Should I use something like the Goodman rule? and if so how do I apply it?
Thanks for any advice !





RE: Real time fatigue data
Low cycle fatigue is a different animal.
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
RE: Real time fatigue data
The data I have includes some very low torque / high cycle data, but it also includes some very high torque / low cycle data. That means I have a mix of high and low cycle data, hence the reason I think I need to take the mean torques into account. An example would be something like 20 cycles of 1500Nm mean torque with +/- 200Nm. If the ultimate strength of the part was say 2000Nm, then the max torque of this combination (1700Nm) is getting pretty close. I think this must be more "damaging" than just +/-200Nm with no mean torque offset?
Dave
RE: Real time fatigue data
Looks like the Coffin-Manson Law applies,and use Goodman's rule to account for the offset.
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight
RE: Real time fatigue data
My experience is that a rainflow approach plus commonsense does seem to work.
Cheers
Greg Locock
I rarely exceed 1.79 x 10^12 furlongs per fortnight