Use stabilized hysteresis strain-controlled data for estimating initial parameters. Refer to the heuristic procedure described in Determining Material Parameters.

Stress-controlled data can be used for estimating initial parameters, but the resulting fit should be carefully compared to the experimental data. When using stress-controlled data, omitting the elastic-plastic transition region helps to limit the effect of isotropic hardening in the experimental data and can result in a better fit for the kinematic hardening parameters.

The experimental data should be arranged such that the first point is the initial (0,0) stress-strain point. Although this value is not required in the experimental data, the fitting algorithm simulates the experimental data starting from the (0,0) stress-strain point.

Smooth noisy experimental data.

Use a small nonzero value for γ₃ for the initial estimate. If stress-controlled ratcheting data are available, γ₃ can be manually adjusted or automatically fit to control the rate of ratcheting.

The initial values of the constants C₁, γ₁, C₂, γ₂, C₃, γ₃ should be of decreasing order.

Compare the results of the fitted model to the experimental data to verify the fit. If the fit is poor, modify the values for the initial parameters and try the fit again.

If the model cannot be made to fit the entire range of experimental data, it may be necessary to sacrifice the fit quality in some regions of the loading history in order to fit other regions of the loading history.

Use caution when extrapolating model predictions to loading histories outside of the available experimental data, as the results may be of limited value.