01. Fatigue analysis with AutoPIPE Harmonic analysis command


	Applies To

	Product(s):	AutoPIPE
	Version(s):	All
	Environment:	N/A
	Area:	Analysis
	Original Author:	Bentley Technical Support Group
	Date Logged & Current Version	June 2015 09.06.02.06

Fatigue analysis with AutoPIPE Harmonic analysis command :

AutoPIPE does not have cyclic type of stress, therefore need to add a new code combination with H1 by itself for the RPM of the harmonic from a rotation compressor:

Combination Name = H1

Description = Harmonic Load case #1 for RPM = xxx .

Combination method = 1 Sum

Category = Occasional,

Case = H1.

Now, change the default "Allowable Stress" setting from "Automatic" (typical 1.33 *Sa) to 6500 psi. In this case, because a compressor is high cycle fatigue, API-618 mentions using a value of 26000 psi peak to peak. Therefore, use half of that which is 13000 psi peak to peak or to consider some SIF values typically would suggest using 13000/2 = 6500 psi for the Stress allowable.

Therefore, 26000/2 for peak to peak, /2 assuming a weld stress factor = 2, because the piping codes are typically based on SIF while fatigue values are typically based on stress concentration factors and there is a factor of 2 between SIF and stress concentration factors

AutoPIPE nuclear has a full fatigue analysis engine, however AutoPIPE Standard and Advance does not. This shortfall will be fixed in a future version of the application by enhancement CAE-CR-3268: Add fatigue analysis for ASME piping codes.