PSI - Issue 22

N. Makhutov et al. / Procedia Structural Integrity 22 (2019) 93–101 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

95

3

Besides, in the plastic region local stress concentration factor K σ decreases with respect to K t and local strain concentration factor K ε increases. For power law approximation of the stress-strain curve the following relation between maximum local stress and strain can be written:

max E   

max    Y

for

(4)

max

m

max (      / ) Y Y max

max    Y

for

(5)

Similar expressions can be written for nominal stresses and strains that describe the cases of nominally elastic and plastic behavior of the structural component:

E   

  

for

(6)

n

n

n

Y

for (7) Processes of deformation of smooth ( K t =1) and notched ( K t >1) components are described on fig.1. n Y n Y      n Y    ( / ) m

Fig.1. Stress-strain curves for smooth specimen ( K t =1) and notched component ( K t >1)

Fig.2. Stress strain conversion rules for different strain ranges 1 – Pseudoelastic states; 2 – Stress-strain curve; Φ N is a Neuber’s mapping according to (15); I – range of elastic strains; II – range of limited plastic strains; III – range of extensive plastic strains

The rearrangement of equations (5) and (7) gives the expression between K σ and K ε .

m

m n        Y

Y    

n Y    , max

for

(8)

Y   

K K  

n

The concepts of pseudoelastic (fictitious) stress σ e-f and strain ε e-f fields are used in notch mechanics. They are calculated using methods of linear elasticity theory in the assumption that material at the notch zone deforms elastically when maximum local stresses accede to yield strength value:

K





t n 

e f 

n Y    .

, for

(9)

K





t n 

e f 