The single location strain-life (e-N) module, mclf supports fatigue life and damage anlysis for Grey Cast Irons.

 

 

The material properties for Grey Cast Irons must be stored in an ASCII file with extension .GIM in the local or central directory. The file must adhere to the following format.

 

<keyword> = value

 

NT, Tensile strain hardening exponent

KT, Tensile strain hardening coefficient (Note: this is not to be confused with stress concentration factor)

MT, Tensile secant slope

NC, Compressive strain hardening exponent

KC, Compressive strain hardening coefficient

MC, Compressive secant slope

MU, Unloading secant slope

E0, Tangent modulus at zero

KS, Damage curve coefficient

NS, Damage curve exponent

CUTOFF, Damage curve cutoff (Reversals)

SCATTER, Standard error of log life

 

A sample .GIM file (gray.gim) is available in the central materials directory

 

A series of fully reversed strain controlled fatigue tests are carried out at a number of different strain amplitudes. The procedure is the same as for conventional tests. Stress/strain hysteresis loops are captured at predefined rates. (Typically 2n , and also when load drops by specific amounts, 5% increments say). The life at each strain amplitude is noted and the parameters defined above are determined.

 

The tensile stress strain curve is defined as

 

The total strain amplitude is the sum of secant strain, εs and the residual non-elastic strain, εr i.e.

εt = εs + εr

The unloading modulus Eu is related to the maximum tensile stress as

 

Eu = Mu σmax + E0

 

For each strain amplitude, the unloading modulus is plotted against peak tensile stress. Mu and intercept E0 are obtained by linear regression.