PSI - Issue 14

Nikolay A.Makhutov et al. / Procedia Structural Integrity 14 (2019) 199–206 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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range of nominal stresses σ n . Rearranging equations (4-8) and (20) gives the following expression for stress and strains concentration factors:     (1 )/(1 m) 2/(1 ) 0.5(1 )[1 ( 1 )] (1 ) n Y t m m t n Y m K m t Y n K K K                for n Y    ; (22)

2/(1 ) 0.5(1 )[1 ( m t m K   

n Y    ;

K



for

(23)







1 )] (1 ) n Y t K m    

K

t Y n  

 2 /(1 ) m m 

K

n Y    ;

K



t

for

(24)









(1 )/(1 m) m  

0.5(1 )[1 ( m  

1 )] (1 ) n Y t K m    

K

n Y  

t Y n  

2 /(1 ) m m 

K

n Y    .

K



t

for

(25)







0.5(1 )[1 ( m  

1 )] (1 ) n Y t K m    

K

t Y n  

Fig. 3 Functional relationship F(χ) 1- Line F(χ)≡1 according to Neuber rule (15) .2,3 – Relationships F(χ) according to equation ( 19)

Fig.3 demonstrates the dependence of the function F defined by the equation (19) on the parameter χ=K t σ n / σ Y . Points denote results of experiments for the notched specimens with theoretical stress concentration factors that vary within the range K t =2.2 – 96 made of reactor steel 15 Х 2 М F А (Makhutov, 1981). The stress-strain curve was approximated by power hardening law with exponent m =0.08. Nominal stresses are in the range σ n =0.5 σ Y – 0.55 σ Y . It is important to note that for all the values of parameter χ=K t σ n / σ Y >1 the experimentally obtained values of the function F differ from the value F =1 which is determined by Neuber rule according to equation (15). This fugue shows that the proposed model allows predicting plastic behavior of the material at the roots of notches under monotonic loading in a wide range of plastic deformations.