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Found 3 results

  1. Hello everyone: I've been trying to do the optistruct tutorial OS-T: 1340 Fatigue (Stress - Life) Method but I'm new in this area and I have some questions about FATLOAD and its parameters. What exactly is LDM and what realitonship has with the load of the subcase? I've seen that loads for each subcase are respectively 1250 N and 1000 N. However both load histories are between 1 and -1 and with a scale of 3. Why is like that? Shouldn't it be with a scale of 1000 one and 1250 the other? In the case that instead of a punctual load there's a pressure or moment in one subcase, load histories need to be scaled to N to be consistent or they can stay in the units of the subcase load (Nmm or N/mm^2)?. How would you represent in the fatigue analysis static loads that contribute to the stress of the model but don't vary cyclicaly? I appreciate your time answering them.
  2. I am doing the fatigue practice and at my practice file. I don't know what FATLOAD mean exactly. For example if our model today will subject a F=100N At TID I know we need to set the TABLE to input and when I plot the .csv file I seem it look like the Load Time History photo. So it this mean our total time is 2500 sec? And the load have positive and negative for scale 1 and -1? (At here our model will subject 100N & -100N for 2500sec) And the LDM I just can't know about it. Finally what is mean for the SCALE? Because we have load time history we can see our load is for 1 and -1. At here we set 3 so that means out load will scale for 3? (Final it will ill subject 300N & -300N for 2500sec)
  3. Dear all, As I am quite new in fatigue analysis with optistruct I would like to confirm one thing please. We have two loads L1 and L2. Each of them has a FatLoad, so FATLoad1 FATLoad2. And we put them in a Fatseq - fatevn (so fatseq=fatenv=fatload1 + fatload2). Each load has a table (TABFAT) with two points which is: Tabfat1 ---> y1=0, y2=1 and Tafat2 ---> y1=1 and y2=0 So as you can see the two loads are out of phase. When load1=1 then load2=0 and when load1=0 then load load2=1. When we run the analysis, is this phase difference respected?? Basically I do not want to add stresses at the same time, but run fatigue as the two loads are happening on a cycle one after the other. So when we get the life out, we check how many times the part can survive the sequence: Load1-Load2 , load1-load2, load1- load2.......and not (Load1+load2), (Load1+load2), (Load1+load2).... Could someone please confirm if we understand that correctly, and if optistruct will work this way (maintain phase difference)? I hope I explained the problem clearly enough and I would be really grateful for any response.
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