http://dx.doi.org/10.1016/j.ijfatigue.2008.03.004

It is well-known that the empirical Manson-Coffin law tends to over-predict the cyclic life under
extremely low cycle fatigue condition. In the present paper, a new unified expression is proposed to
overcome this shortcoming. By introducing an exponential function, this new expression is capable
of capturing the cyclic life over the entire span of extremely low cycle fatigue to low cycle fatigue
with an additional material parameter to calibrate. Experimental data from existing literature are
used to demonstrate the applicability of the proposed expression for several polycrystalline metals.
The implication of the new expression to monotonic plastic fracture is discussed. It is also identified
that the exponent in the unified expression is sensitive to temperature. Examples are given for the
thermal influence on the material constants.
Keywords: Damage accumulation; Damage plasticity theory; low cycle fatigue; extremely low cycle
fatigue; ductile fracture.