Why ncode rms stress result different from Ansys Random rms result
Why ncode rms stress result different from Ansys Random rms result
(OP)
Hi. I am using ansys ncode design life v 13 and doing vibration fatigue analysis. I modeled a simple beam with tip mass and firstly run a harmonic analysis with unit load that is 1 g. The material of the beam is Al 7075 T651 and I enter 1.6% damping ratio for the results between the 5-500 Hz. I also save the db file for post-processing the results. After harmonic analysis is finished I import the file.rst file directly into designlife and run a fatigue analysis for the 0.025 g^2/Hz 5-500 Hz white noise. I get the most critical node with 1 sigma rms value and stress psd. Then for the same mathematical model in ansys I run a random vibration analysis and get the 1 sigma rms value and stress psd for the same node. 1 sigma result are different from each other and when I compare the stress psd values at each frequency and especially peaks at the natural frequencies are very different from each other. The difference for peaks is not because of the damping ratio as I mentioned above I use the same mathematical model hence the same damping ratios. I have to find the reason please help me!!!!!!





RE: Why ncode rms stress result different from Ansys Random rms result
Do the codes use the same element formulation?
Do you calculate the peaks at the same frequency?
Are the boundary conditions defined in the same way?
Is the damping defined the same way?
Do a Natural frequency calculation first and compare the mode shapes and frequencies. If the element formulation is similar, the natural frequencies and mode shapes are similar, the damping definition is similar then you also should get similar results.
RE: Why ncode rms stress result different from Ansys Random rms result