Duty cycles

Typically, for automotive durability analysis, a duty cycle or test schedule is composed of different test segments measured on the test track. The number of test segments typically varies between 5 and 50, each of which may be repeated a different number of times. Thus, the duty cycle effectively defines a loading history.

In other industries, test segments may be much shorter "events," and therefore more than 50 events may be used. These events may also be synthetically derived (that is, using numerical methods instead of measurements).

Fatigue background

Fatigue damage depends on loading sequence. Therefore, the manner in which multiple load histories are put together to make a test sequence will have an effect on the fatigue results. There are exact and approximate ways to handle these sequence effects.

If test event S1 is applied before event S2, it leaves a residue of unclosed hysteresis loops, thus changing the way hysteresis loops close during event S2. The significance of the sequence typically increases for shorter events with the number of events, and with events starting at non-zero values. The significance decreases with higher repeat counts and longer events.

To deal with this situation, you can use two different approaches:

• Solve as one case without influence of the order of eventsIn this approach, the damage is computed as once case in one single solver run. This is irrespective of the number of events used to set up the case. There is no influence of the ordering of the events.

• Solve as one case including influence of the order of eventsIn this approach, the damage is computed as one case. This is irrespective of the number of events used to set up the case. While solving with this approach, the non-closed cycles of the previous events are taken into account. Hence, an ordering effect is included.

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Duty cycles, Simcenter 3D 2021.1 Series

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