Components for Fatigue

When you select Fatigue from the Quantity drop-down list, the Component drop-down list displays the components specific to this quantity. Use this drop-down list to further refine your quantity definition. The choices available on this drop-down list depend on the design study, display type, and quantity combination you select.

These options appear on the Component drop-down list if you select Fatigue:

• Log Life—Shows the estimated number of cycles until your model breaks. Because of the exponential nature of fatigue, it is useful to express life as a logarithm.

• Log Damage—Shows the ratio between accumulated fatigue cycles and the total number of cycles to failure. A value greater than unity indicates failure. A value of 0.5, for example, represents a loss of 50% in the useful life of the model. Because of the exponential nature of fatigue, it is useful to express the damage ratio as a logarithm.

• Factor of Safety—Shows the permissible factor of safety on the input load. When the fatigue life calculated for your model is greater than the target design life, the software carries out a back calculation to determine a permissible factor of safety on the input load. This represents the extent to which the amplitude of the load can be increased without compromising the target design life.

If you want the software to calculate the factor of safety, select the check box in the Output area at the bottom of the Fatigue Analysis Definition dialog box.

• Confidence of Life—Shows the ratio between the calculated life and the target design life. Because of the statistical nature of fatigue, the greater the confidence the better. Values below unity indicate failure. Values greater than 3.0 usually reflect an adequate confidence of achieving the desired target life.

You can display Confidence Of Life results in a tri-colored fringe plot to give an overall view of where the model will break first and where the model will last for a greater number of cycles. Red signifies from 0 cycles to the number of cycles entered for Desired Endurance (considered 1x) on the analysis dialog box. Yellow signifies from 1x to 3x (considered the marginal life). Green signifies any number of cycles over the marginal life (3x). The default is 3x, but you can change this by changing the value of sim_fatigue_safety_margin configuration option.

For fatigue analyses, Creo Simulate reports results for all surfaces on your model, but not the interior of your model.