The following PowerPoint is from one of PADT’s inhouse experts on linear dynamics, Alex Grishin.
One of the most valuable results that can come from a harmonic response analysis is the predicted alternating stresses in the part. This feeds fatigue and other downstream calculations as well as predicting maximum possible values. Because of the math involved, calculating derived stresses, like Principal Stresses can be done in several ways. This post shows how Ansys Mechanical does it and offers an alternative that is considered more accurate for some cases.
Part 2 on von Misses Stress can be found here.ANSYS-PADT-Alternating-Principal-Stresses-1
Alex also created an example Ansys Workbench archive that goes with the PowerPoint.