Fatigue strength exponent

The fatigue strength coefficient is related to the tensile strength. In plain carbon and low-alloy steels, a rule of thumb states cr( = 1.5i m in aluminium and titanium alloys, = 1.67i m holds approximately [113]. The fatigue strength exponent a depends on the material and the specimen geometry in many materials, it takes values between 0.05 and 0.12 if smooth specimens are used [8,113]. 

Figure 9.21. Effect of VGCNF content on the strength coefficient (oy) and the fatigue strength exponent (6) of epoxy-VGCNF iianocomposites [63]...

Morrow [28] found that the fatigue strength exponent b that appears in (5.22) could be expressed as... 

Strain hardening exponent of the material n is needed together with the fatigue strength coefficient a f and the fatigue ductility coefficient f. these last two coefficient have been already calculated in sample problem 1. of Sect. 5.3 and are... 

Equation (8.21) allows to foreseen fatigue strength under conditions of constant stress spectra combined in any fashion if the values of the y and b exponent were known. 

Nevertheless, the most significant deviations pertain the field of nominal stresses higher than the yield strength and that of low values of the strain hardening exponent n. For nominal stress lower than yield strength, ffr/ffy < 1, discrepancies are rather contained. The issue of Neuber s rule application to fatigue has involved many researchers and study [31, 32, 38-43] with questions... 

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