Fatigue Strength Reduction Factor

Several factors have to be taken into account while using the empirical S-N curve for a real-life model. They are, corrosive environment (Kc), surface conditions (Ks), size factor (Ki), mode of loading (Km), temperature factor (Kt), reliability factor (Kr), notch effects (Kf), fretting conditions (Kfret).

Fatigue Strength Reduction Factor =kc* ks* kl* km* kt* kr* kf* kfret

To apply the reduction factors to the fatigue strength of the selected bodies, the FS(component) of the selected components in their working condition is evaluated as

FS (component) = FS (material) x Surface Finish Factor x Loading Factor x Size Factor

The material fatigue strength FS ( material), equals half the material’s tensile strength.

Surface Finish factor: Specifies the correction surface finish factor. A surface finish correction allows the estimate of the fatigue strength of the part in its working condition. Select an appropriate surface finish type from the list or select Other to enter a user-defined value. The range is from 0.1 to 1.

Loading factor : Specifies the correction loading factor. Fatigue limits are usually determined from test specimens under bending. A specimen loaded in tension has a lower fatigue limit. Select a loading type from the list, or select other to enter a user-defined value. The range is from 0.1 to 1.

Size factor: Specifies the correction sizing factor. Based on experimental results, larger parts have lower fatigue limits than smaller parts. The range is from 0.1 to 1.

Rajat Trehan

Product Manager 

Computer Aided Technology Inc.


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