Minimum creep law for 2.25Cr-1Mo steel

Overview

This is a quite complicated minimum creep rate law for 2.25Cr-1Mo (Gr 22) steel, to be documented in a PVP paper at some point in the future.

The creep rate law it implements is:

if $\sigma_{eq}\le 60$ :

$\dot{\varepsilon}^{cr} = \dot{\varepsilon}_{2}$

else if $T\le13.571\sigma_{eq}^{0.68127}-1.8\sigma_{eq}+437.63$

$\dot{\varepsilon}^{cr} = \dot{\varepsilon}_{1}$

else

$\dot{\varepsilon}^{cr} = \dot{\varepsilon}_{2}$

with

$\dot{\varepsilon}_{1}=\frac{10^{6.7475+0.011426\sigma_{eq}+\frac{987.72}{U}\log\sigma_{eq}-\frac{13494}{T}}}{100}$

$\dot{\varepsilon}_{2}=\frac{10^{11.498-\frac{8.2226U}{T}-\frac{20448}{T}+\frac{5862.4}{T}\log\sigma_{eq}}}{100}$

and $U$ a parameter interpolated linearly as a function of temperature from the table:

Because the model is fully parameterized in the C++ implementation it must be used with units of MPa, hours, and Kelvin.

None, all built into class.

class MinCreep225Cr1MoCreep : public neml::ScalarCreepRule 

The hopelessly complicated 2.25Cr minimum creep rate model.

Public Functions

MinCreep225Cr1MoCreep(ParameterSet &params): Parameters: prefector A and exponent n.

virtual void g(double seq, double eeq, double t, double T, double &g) const: See documentation for the hideous formula.

virtual void dg_ds(double seq, double eeq, double t, double T, double &dg) const: Derivative of rate wrt effective stress.

virtual void dg_de(double seq, double eeq, double t, double T, double &dg) const: Derivative of rate wrt effective strain = 0.

Public Static Functions

static std::unique_ptr<NEMLObject> initialize(ParameterSet &params): Setup from a parameter set.