PSI - Issue 39

N.A. Makhytov et al. / Procedia Structural Integrity 39 (2022) 266–272 Makhutov N.A./ Structural Integrity Procedia 00 (2019) 000–000

270

5

(a) Fig. 4. (a ) Micro relief to surfaces of the fracture

/ 2 π β = (x1000); (b) surface of the fracture of the crack

/ 2 π β = (x10); (c)

macro relief to surface of the fracture of the crack / 3 π β = (x10). Survivability of a detail is regulated by achievement of the relative factor of strain intensity

/

e K K α =

σ

the

e

T

α

ec K α , based on deformation criterion of fracture (Makhutov, 2005)

ec e K K α α = , at which the crack

critical value -

starts to be propagate. The value I II III , , = α , is the type of crack (normal, transverse or longitudinal). Thus the connection with force criterion is regulated by dependence ke P e K K α α = . Here α K is relative stress intensity factor, and ke P is the parameter of deformation fracture criteria (Makhutov, 2005). On the basis of results of (Makhutov, 2005; Makhutov and Makarenko and et al, 2019; Makhutov and Makarenko and et al, 2010), the basic equation of development low-cycle fracture, taking into account the varied properties of the material of wide class of steels, which determines the kinetics of a defect during the operation of equation (1), can be represented in the form (2). ec e K K α α = is the relative factor of intensity elasto-plastic strain,

ej n ej ijk dl dN C e = ∆ / , i

(1)

∫ N 0

σ σ

,

2

2

(

− ∆ )(

sin

)

∗

∗

l

a

a e

dN

=

⋅

β

bi

(2)

1

2

ijk

i

Ti

Where: ∗ β is a settlement corner of an inclination of a modeled surface of destruction to the first main stress and ∗ ∆ i e is the range of intensity relative elasto-plastic strain in a concrete local volume of metal on its contour. Factors а 1 and а 2 are the characteristics of the material. In (2) Ti i i e e e / ∗ ∗ ∆ = ∆ is the range of intensity local relative elastic-plastic strain, Ti σ is the local yield stress and bi σ is the local ultimate strength. For calculation of relative factors of intensity of strain for low-cycle inclined superficial semi-elliptic cracks taking