An empirical formula can be used to estimate SN/EN data from ultimate tensile
strength (UTS) and Young's modulus (E).
From the Assign Material dialog, click the My
Material tab and select your created material.
Select Estimate from UTS as the input method.
Click to view the model
description.
Enter a value for UTS and Elastic modulus.
Click Estimate.
SN Properties
* Source: Yung-Li Lee, Jwo. Pan, Richard B. Hathaway and Mark E. Barekey.
Fatigue testing and analysis: Theory and practice, Elsevier, 2005.
Fatigue strength coefficient. It is the stress amplitude intercept of the SN
curve at 1 cycle on a log-log scale.
The first fatigue strength exponent. The slope of the first segment of the
SN curve in log-log scale.
In one-segment SN curves, this is the cycle limit of endurance (See
Nc1 in Figure 2). In two-segment SN curves, this is the transition point
(see Nc1 in Figure 4).
The second fatigue strength exponent.
Empirically, the life of a metal is 1000 when the stress amplitude is approximately
90% of the UTS. (S1000 = 0.9UTS) when loading type is a bending load.
According to "Engineering Considerations of Stress, Strain, and Strength" by Juvinall
RC, 1976, McGraw-Hill, fatigue limit (FL) can be estimated as follows:
For steel that has pearlite microstructure, FL = 0.38UTS at
Nc1 = 1E6
For aluminum alloys whose UTS < 336MPa, FL = 0.4UTS at
Nc1 = 5E8
For Aluminum Alloys whose UTS >= 336MPa, FL = 130MPa at
Nc1 = 5E8
With the above information, two points on the SN curve are known: (1000, S1000) and
(Nc1, FL). Thus, slope can be calculated:
Once b1 is known, SRI1 is calculated by:
(The stress range 2*S1000 is used.) Therefore,
EN Properties
** Source: Anton Baumel and T. Seeger, Materials Data for Cyclic Loading, Elsevier, 1990
Fatigue strength coefficient.
Fatigue strength exponent.
Fatigue ductility exponent.
Fatigue ductility coefficient.
Cyclic strain-hardening exponent.
Cyclic strength coefficient.
Reversal limit of endurance. One cycle contains two reversals.