PSI - Issue 16

Cristian Alejandro de León Gómez et al. / Procedia Structural Integrity 16 (2019) 265–272 Cristian Alejandro de León Gómez et al. / Structural Integrity Procedia 00 (2019) 000 – 000

270

6

4 1

   

   

2

   

   

   

   

2

2

c a

1 0,08 0,4       t a

1 0,08 0,15       t a

  

  

  



 3

  ; 1 cos 3  

2

2    sin

f

    

cos

;

.

g

g

1 sin

 

1

2

Model No. 6. SIF for the scheme, presented in Fig. 3f, was calculated by the formula from Newman et al. (1983)

a K FF w a    I ,

(5)

where

2

4

  

 

t M M a 2 1    

t M a 3

    

1,65

1

c a

  

  

F w



Q

F

;

;

;

 

1 1,464



   

     2

Q

W c

t a

cos

0,05

0,29

1 1  M ;

;

.

M

M





2

3

2 3

2 3

c a

c a

  

  

0,11

0,23

   

   

It should note that in cases No. 4, 5 and 6, where the crack is set by various ellipse like figures, by changing the relation of ellipse axes of crack like defect of different geometry. In the research corresponding dimensions less dependences for the considered cases form and location on the basis of the given analytical relations and constructed:

da t dK I

  

t F a

   

,

(6)



where t – size of structural element in the direction of crack propagation; σ – applied load, a – depth of the crack, that is variable value as compared with t that is constant. That is why, in further study of the result of research, we will introduce variable parameter ( a / t ) * that characterizes the effective size of the defect. It should be noted that characteristic feature of this dependences is that certain value of the parameter ( a / t ) * , is always observed on them, starting from this value sharp increase of stress intensity coefficient K I change rate takes place. This value ( a / t ) * was considered as characteristic one for assessment of the strength and reliability of structural elements with crack like defects.

5. Results and discussion

For determination of the characteristic values of the crack length in the studies of structural elements experimental base and analytical relation, described by Paris power dependence with Paris (1963), was used

dN dc  

  n C K

,

(7)

where C and n – constant characterizing system "material – environment". Such constants, along with limiting values of SIF are presented in Table 1 for various systems "material – environment".