Combination of independent vibrations for fatigue analysis

[JianChen]

I am working on the fatigue analysis of a component subjected to combined transportation and machine operating vibrations. I have time signals of fatigue stresses induced by transportation vibration and by machnie operating vibration seperately; but not both simultaneously. Both vibrations are indepnedet to each other. I want to know how to construct a time signal of fatigue stress under both vibrations simultaneously from the time signals I have, because it is difficult to measure it.

Thank you very much. Jian Chen

 

[GregLocock]

I think you'd be safe adding them together, because they are uncorrelated.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[JianChen]

Thank youver very much. But how to add them together? The two vibrations can have random phase difference. Assume that the system is linear. Jianiion Chen

 

[GregLocock]

In the time domain you just add them.

CombinedTimeHistory(t)=transportation(t)+machine(t)



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.