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#45392 - 10/19/11 08:29 PM [HELP]What is the main points of a fatigue analysis?
cacusies Offline

Registered: 09/18/10
Posts: 11
Loc: China
Dear all,
Here I have a seris of fexible pipes which I have to get a fatigue analysis of.

I confirm to give them a displatement and the frequence to be the boundary condition.

I have the continuous questions to doult with:

1)How could I decide this pipe experience a small deformation to confirm the analysis as a suitable condition.
For example, my pipe is 3,000mm length and the displatement is +&- 5mm. So 5 is enough small as to 3000.
But I have no formula to identify.

2)As I known that in this high frequency consition I have to use the dynamic Harmonic model.
But I can not find how to give the right condition as I say.
My displatement is +&- 5mm around the balance location. However, in the harmonic displatement settings I can`t find that how to set this.

3)How could I get the dynamic response of the force and the moment by the vibration? Does the data of the restrains in the (FAT)load case show the right result?

Hope for your kindly help.


#45423 - 10/21/11 02:04 AM Re: [HELP]What is the main points of a fatigue analysis? [Re: cacusies]
deb j paul Offline

Registered: 11/17/07
Posts: 49
Loc: delhi,india
At first your Idea about doing stress analysis is not clear.
state for which piping system you will be performing it.e.g compressor, pump etc.

then state how the +&- 5 mm displacement comes?
at what frequency range.

knowing the background of the system,only then anyone can give suggestions.
jr. stress engineer

#45425 - 10/21/11 02:42 AM Re: [HELP]What is the main points of a fatigue analysis? [Re: cacusies]
cacusies Offline

Registered: 09/18/10
Posts: 11
Loc: China
thanks to dj

I think I have found the answers about 2) and 3)

ans to 2):In the harmonic anlysis when we put the displatement boundary in the input page, the software will caculate a 18 points to build a cycle.

ans to 3):Acctually we only could get the maximum data of force and displatement in the result.We cannot get the change about the cycle.

still I do not find the 1) answer.

The vibration comes out from the mechanical vibrate which means that the pipes connect a moving equipment and a static equipment, neither a compressor nor a pump.
We use the pipes to conect a vibration grate which is used in boiler to the header.So the +&-5mm displatement comes from the vibration of the grate.


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