Learning Forum

[Jeone]

Hi,

I'm always confused about this topic, so that I want to ask you. 

I want to do fatigue analysis of landing gear, and as you see there is a figure which is related to Fx,Fy and Fz loads. Although I have time-series input, I do not know how should I static analysis. What should be my force for Fx,Fy and Fz? Should they be 1 N or not?

Sincerely,

[danielshaw]

Which fatigue software are you using?  Typically with time series type loading, the FE stresses are multiplied by the values in the time series file to obtain the total stresses to be used in the fatigue evaluation.  So, commonly the FE stresses are produced from unit loads and the time series file contains the multipliers based on those unit loads. 

 

 

 

[Jeone]

I use nCode DesignLife. 

In addition, I saw an old forum conversation and I recognised that this topic is same with my topic. I decided to apply 1N for every direction (Fx,Fy and Fz). When I do 1N analysis for Fx, nCode DesignLife will multiply (1N Stress x 4097)

/forum/forums/topic/fatigue-analysis-with-time-history-input/

[danielshaw]

Yes, DesignLife will multiply the FE stress by the values in the time series file to obtain the total stresses.  It will then rainflow count the full set of stresses to obtain the approporiate stress ranges and mean stresses to be used in the fatigue evaluation.

[Jeone]

 

Finally, I should do static analysis with 1N load? I'm right, aren’t I?

 

[danielshaw]

Probably.  It depends on how the values in the time series were generated. The key is that the product of the FE stress multiplied by the time series factor is equal to the actual stress.  That goal is most commonly obtained by using a unit load in the FE with a multipliers of the unit load stored in the time series file.

[Jeone]

Thanks a lot