| Product(s): | SACS |
| Version(s): | All |
| Area: | Fatigue |
what is the relationship between "Stress-DA" on the response spectrum plots vs. the RMS stress in the Fatigue Stress and Damage report from Interactive Fatigue?
Stress-DA is the RMS of the response spectrum normalized by the wave height, whereas RMS stress is normalized using a single amplitude in the Fatigue listing file. The Stress-DA should generally be RMS stress/2. There is also a difference in how the RMS response spectrum is calculated in the Response Spectrum plot which may affect the results. If the transfer function frequency range does not cover the input wave spectrum frequency range, Fatigue will extrapolate the transfer function past that frequency. The response spectrum plot will truncate the response spectrum to the last defined transfer function frequency instead.