Manson-Coffin relationship

Once the analytical expression of the hysteresis loop has been derived, the following step is to infer the equation of the entire e-N curve or Wohler s curve. To this purpose, it is necessary to separate the two component of deformation, the elastic and the plastic one, as already done in Eq. (6.1). As to the elastic component Eg, it has been said in Sect. 5.2.2 that in 1910 Basquin [7] found a power law relationship with the cycles to failure N, see Eq. (5.22), so that in a log-log scale the elastic component of the S-N curve is a line. Later in the 50, Manson and Coffin [8-11] independently found that also the plastic component of the cyclic strain was related to life cycles N through a power law function, known as the Manson-Coffin relationship... 

A project has been initiated to study the effect ofTi/C ratio for optimum creep-fatigue interaction properties of indigenously developed Alloy D9. As part of this progranune, baseline LCF data has been generated at 823 and 923 K on this alloy with a Ti/C ratio of 4. The alloy is foimd to obey the Coffin-Manson relationship at both these temperatures. 

Experiments to characterize low-cycle CF life according to the Coffin-Manson relationship (Eq 2) foUow from an ASTM standard for LCF of metals in air, and a classic ASTM manual on laboratory methods (see Ref 37 and ASTM E 606, Practice for Strain-Controlled Fatigue Testing). Low-cycle CF... 

This c an be further simplified to the most cx>mmon form of the Coffin-Manson relationship shown in Eq. 59.8. ... 

Controlled dependent on the testing temperature relative to the alloy transformation tempm ature. Fracture follows e Coffin-Manson relationship ... 

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 (%) ... 

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