Fatigue Manson-Coffin equation

Coffln-Manson type equations are commonly used to predict the low-cycle fatigue life of solder. The general form of the Coffin-Manson equation is as follows ... 

When subjected to cyclic strains, ductile materials are found to fail either by Low Cycle Fatigue (when the life is given by the well known Coffin-Manson equation) or by Ratcheting Failure (when the life can be estimated by dividing the strain to failure by strain accumulation per cycle). Both LCF and RF act on the same material and so whichever occurs first causes failure. In this competitive mode of failure, the actual... 

Example 5. An example of modeling coupled failure mechanisms is the failure behavior model for components subjected to the coupling of fatigue and creep (Collins et al. 2009). For components subjected to only low-cycle fatigue, a Coffin-Manson model will approximate the failure behaviors quite well (Equation (14)). In equation (14), Ay is the TTF in cycles, A/ is the plastic strain range and both m and C are constants associated with material properties. 

Coffin-Manson predictions and test data. All predictions fall within 25% of the actual failure data. Subsequent creep-based analyses use the same fitting procedures and will produce separate fatigue life prediction equations for a given creep criterion and package type. 

Isothermal fatigue predictions using the Coffin-Manson relationship have also been developed, but categorized according to the plastic strain levels to which the solder is exposed [88]. Guo et al. developed two equations to predict cycles to failure at 0.5 Hz, based upon a 50% load reduction criterion. The equations refer to two, tension-compression plastic strain ranges, Asp (%) ... 

Many empirical relations have been suggested to predict fatigue lifetimes, one of which is the Manson-Coffin equation. This and other relations have been widely used for metals and alloys (J. Pelleg). The Manson-Coffin relation for lifetime... 

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