Add Event (Constant) PropertyManager

The Add Event (Constant) PropertyManager allows you to define a constant amplitude event for a fatigue study.

You can set up a fatigue event based on a single load case or several load cases from multiple reference studies. The fatigue loads can refer to one or more static studies, or to a particular solution step of a nonlinear or time history linear dynamic study.



Load

noofcycles.png No. of Cycles Sets the number of cycles associated with this event.
Loading Type

Sets the type of fatigue loading to determine the stress peaks and hence the alternating stress. Alternating stress = |maximum stress - minimum stress|/2, where | | denotes the absolute value.

Fully reversed (LR = -1)

The fatigue event is based on one reference study. All the loads, and hence stress components, in the reference study reverse their directions simultaneously for the specified number of cycles in the event.

Zero-based (LR = 0).

The fatigue event is based on one reference study. All loads, and hence stress components, in the reference study change their magnitudes proportionally from their maximum values as specified by the reference study to zero.

Loading ratio

The fatigue event is based on one reference study. Each load, and hence each stress component, in the reference study changes its magnitude proportionally from its maximum value (Smax) to a minimum value defined by R*Smax, where R is the load ratio. A negative ratio indicates reversal of the load direction.

  • Loading ratio loadratio.png. Enter a loading ratio.
    Fatigue loads are said to be proportional when the directions of principal stresses for each node are identical for all the reference studies that you use in defining fatigue events. In all other cases, the fatigue loads are said to be non-proportional.

Find Cycle Peaks

The fatigue event is based on several load cases. The program calculates the alternating stresses for each node by considering the combination of peaks from different fatigue loads. It then determines the combination of loads that produces the largest stress fluctuation.

The fatigue loads can refer to one or more static studies, or to a particular solution step of a nonlinear or linear dynamic time history study.
Study Association Sets the reference studies.

No.

Study counter.

Select Find cycle peaks to continue defining up to 40 load cases. Double-click in the No. cell to add a row. All studies must have the same mesh.

Study.

Sets the reference study. Click in this cell to select a study from the drop-down menu. For a reference study, you can select a static study, or stress results from a particular solution step of a nonlinear or linear dynamic time history study.

The list of studies includes the studies that are associated with the currently active configuration only.

Scale.

This scale factor lets you define a fatigue event based on a reference study with scaled loads. Since the study is linear, the program uses this factor to scale the stresses. You cannot scale loads defined in a nonlinear study.

For example, if the reference study has a pressure load of 50 psi applied to a face and you want to define a fatigue load based on 150 psi on the same face, you should enter a scale factor of 150/50 = 3. The program multiplies the stress results of the reference study by this factor to calculate stress values for use in calculating alternating stresses.

Step.

Sets the solution step for the reference nonlinear or linear dynamic study. The program uses the stress results of this particular step to calculate the alternating stresses.

You can use the same study for defining multiple fatigue events.