Fatigue life assessment using FEA results

[jeram123]

Hello all, I am new to repair validation of compressor stage fan blades. To validate, I have to model the repair and compare the results with reference model results. As per the methodology document for fatigue life validation, we have to plot the stress values from linear static (on mean stress axis)and modal analyses (on alternating stress axis) of a haigh diagram. Similar plot is made for reference model and if variation in margin is less than 5%, we can report the repair is ok.
Here, what I don't understand is the usage of stress values from a modal analysis (yes,modal analysis stress is scaled down if it falls outside the curve).Can anyone help me out in understanding this. Thanks in advance

 

[Ankit_Pandey]

What do u mean by "stress values from modal analyses". Also could you please mention stress values from static and model analyses.

 

[jeram123]

Ankit, I run a static analysis of the model where I get the max value at critical location (= 90938.7 psi), Now I run a modal analysis and get the stress value for mode-1 at same location (= 133435 psi). I will plot this on a Haigh diagram.