Fatigue ductility exponent

For the fatigue ductility coefficient ej, the true fracture strain in tensile loading can be used as a good approximation. The fatigue ductility exponent b depends on the hardening of the material. Typical values for b are in the range of 0.4 to 0.73 [113,130]. 

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... 

The constant, C, is proportional to the ductility of the material in tension the exponent, b, is near 0.5 for most materials over a wide temperature range. This equation applies usually in the range 1—10 cycles, and typical data are shown in Figure 4a (5). The exponent rises when creep or environmental interactions affect fatigue behavior. 

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