# strain_life_diagram¶

class reliability.PoF.strain_life_diagram(E, sigma_f, epsilon_f, b, c, K=None, n=None, mean_stress_correction_method='SWT', max_strain=None, min_strain=None, max_stress=None, min_stress=None, print_results=True, show_plot=True)

This function plots the strain-life diagram.

If you do not have the parameters sigma_f, epsilon_f, b, c, but you do have stress, strain, and cycles data then you can use the function ‘stress_strain_life_parameters_from_data’ to find these parameters.

Parameters: E (float, int) – The modulus of elasticity. Ensure this is in the same units for which K and n were obtained (typically MPa) sigma_f (float, int) – The fatigue strength coefficient. epsilon_f (float, int) – The fatigue strain coefficient. b (float, int) – The elastic strain exponent. c (float, int) – The plastic strain exponent. K (float, int, optional) – The cyclic strength coefficient. Optional input. Only required if you specify max_stress or max_strain. n (float, int, optional) – The strain hardening exponent. Optional input. Only required if you specify max_stress or max_strain. mean_stress_correction_method (str, optional) – Must be either ‘morrow’,’modified_morrow’, or ‘SWT’. Default is ‘SWT’. Only used if mean_stress is found to be non-zero. max_stress (float, int, optional) – Specify the max_stress if you want cycles to failure. If specified, you will need to also specify K and n. max_strain (float, int, optional) – Specify the max_strain if you want cycles to failure. min_stress (float, int, optional) – If this is not -max_stress then specify it here. Optional input. min_strain (float, int, optional) – If this is not -max_strain then specify it here. Optional input. print_results (bool, optional) – Default is True. The cycles to failure will only be printed if max_stress OR max_strain is specified. show_plot (bool, optional) – Default is True. The strain-life plot will be generated if show_plot = True. Use plt.show() to show it. cycles_to_failure (float) – The number of cycles until fatigue failure max_stress (float) – The maximim stress max_strain (float) – The maximum strain min_stress (float) – The minimum stress min_strain (float, int, optional) – The minimum strain

Notes

When specifying min and max stress or strain, do not specify both stress and strain as the corresponding value will be automatically calculated. Only specify the min if it is not -max.