% defect-free strain- life graphing software % plots log-log strain amplitude[s] vs. life (in reversals to failure) curve % % clear % TwoNf : 2N_f, number of reversals to failure TwoNf=logspace(0,8,10) % enter material constants: data for SAE 1040 steel (as-forged), taken from % Table 3 of handout E=29000 % Young's modulus (ksi) (given elsewhere) sfprime=270 % fatigue strength coefficient (ksi) efprime= 0.60 % fatigue ductility coefficient b= -.073 % fatigue strength exposnent (Basquin exponent) c= -.70 % fatigue ductility exponent (Coffin Manson exponent) % % Calculate transition life, in # of reversals, where cyclic elastic and % plastic strains are equal TwoNt= (E*efprime/sfprime)^(1/(b-c)) eap=efprime*(TwoNf.^c) ; % contains plastic strain amplitude at lives corresponding to TwoNf eae= (sfprime/E)*(TwoNf.^b); % contains elastic strain amplitude at lives corresponding to TwoNf ea = eae+eap; % contains total strain amplitude at lives corresponding to TwoNf loglog(TwoNf,ea,'-b'); %creates log-log plot of total strain vs. life title('Strain-Life: BLUE; Plastic strain-life: RED; Elastic strain-life: CYAN'); hold on loglog(TwoNf,eae,'-c'); % on same plot, adds elastic strain vs. life loglog(TwoNf,eap,'-r'); % on same plot, adds plastic strain vs. life xlabel(' 2N_f (Reversals to failure)'); ylabel(' \epsilon_a = \Delta \epsilon / 2 (cyclic strain amplitude)'); text(3,1.e-4,'\bf{1045 quench and tempered : UTS= 236 ksi}'); hold off %grid on