Hi everyone. I'm working with a project about Fatigue Analysis now. I got some questions I'm stuck with at the moment. So I'm wondering if you have any idea about them. The method people usually use to solve the fatigue problem at the moment is like this: The first six plots shows the forces and torques of a wind turbine in x,y,z directions in 600s. From these 6 plot we find out 6 freedoms interact differently at each time step (see the orange line). Then methods resolve combined stress in a plane at each element (In simple terms, this means to combine these 6 vectors into a 3d plane), finally we can get a single stress history plot (which is combined from previous 6 plots). Next thing is using RAINFLOW COUNTING analysis to work out the fatigue using the S-N plot. This method is quite good but the only problem is to combine those 6 plots into the plane take so long time to do, each of the single point combination need about 30 hours to process. So I'm asked to think another mathematical method to solve this problem. At first I was thinking if I can combine the 3 forces and 3 torques in to resultant vector, but then i found that was wrong way. So now I'm thinking can we find out if there is a period exist for those 6 plot, or can we divide the plot into several time domain sections so that each section has its own individual period. If this can be done, instead of doing 600 points (say) combinations, we now only need to do 300 or even less because the periodic property. Or are there some other ideas in your mind at all?