PSI - Issue 40

Vladlen Nazarov et al. / Procedia Structural Integrity 40 (2022) 348–353 Vladlen Nazarov / Structural Integrity Procedia 00 (2022) 000 – 000

350

3

2. Two complex equivalent stresses under consideration

1 eq  Lebedev (1996) and

2 eq  Nazarov (2019)

max 2  and two complex

max  , mises  ,

In this work, three simple

equivalent stresses have been considered

1 eq

(4)

[1  

]

, 0

1



 



1 max  

1   

1

mises

2 eq

[1  

][2

]

, 0

1

(5)



2 





2 max  

  

max

2

As a criterion for choosing the equivalent stress, the total errors of the difference between the experimental and approximating rupture times have been considered. 3. Method for calculating total errors Two types of experimental data have been considered depending on the signs of the principal stresses. Under biaxial tension of the plane specimens or internal pressure and tension of the tubular specimens at 0 1 2     and 0 3   . Under torsion and tension of the tubular specimens at 0 1   , 0 2   and 0 3   . At biaxial tension of an elementary plane element the basic equivalent stresses

2

2 1 2 2

max       , 2

(6)

,





mises  

  

1 

1

1

max

At tension and compression in two mutually perpendicular directions of an elementary plane element the base equivalent stresses

2

2 1 3 3

,

max      , 2





mises  

  

 

 

(7)

max

1

1

1 3

Principal stresses Nazarov (2015) for a tubular specimen under the influence of torque and axial force

2

2

2 2       

2 2       

   

   

2

2

,

0,   



(8)

2

3

1

The power law dependence Norton (1929) and Bailey (1929) with two material parameters have been considered as the dependence of the fracture time on the equivalent stress

m



app rupt

t



  

  

dim eq

,

0, B m 

1

(9)





B



where app rupt t is rupture time in approximation, B and m is material parameters,

1MPa dim   is dimensionless

stress. The difference between the experimental and approximating fracture times have been considered as the total error