PSI - Issue 16

Zinovij Nazarchuk et al. / Procedia Structural Integrity 16 (2019) 169–175

174

6 Zinovij Nazarchuk, Olexandr Andreykiv, Valentyn Skalskyi, Denys Rudavskyi / Structural Integrity Procedia 00 (2019) 000 – 000   K K n K n K dn t A K A h n m thc m In CC In t m a CC           0 2 1 2 2 2 1 2 1 2 ( ) ( )] ) [1 ( . (16) In order to determine the t  value from formula (16), it is necessary to have the values of the parameters m , A 2 t ,  , A a , n  , K thc , K CC . We determine the n  value by a formula similar to (7). Other values are found as follows. Let us write the relation (14) as   1 2 2 2 2 3 ( )] [1 ( )      n B K n K K K n CC In m thc m In  , (17)

m

2



t a B A A h K 2 1 3  

. Then with the help of the above mentioned loading scheme (Fig. 2, a), we carry out

where

CC

In n K ~  . In this case, using formula (15), changing the

experimental studies and construct a graphical dependence

specimen load parameters M and the crack length l , we set the stress intensity factor ( ) i ( ) i In K , using the experimental method described in (Andreykiv et al. (2017a)), we determine the SAE intensity n  . Such measurements are made at least four times for different values ( ) i In K and at least three values of t n  should to be got for each value ( ) i In K (Fig. 2, b). In K value within the CC i In thc K K K   ( ) limits. For these values

a

b

In n K ~  scheme.

Fig. 2. (a) beam with a lateral crack load scheme; (b) dependence

The obtained values of ( ) i In K , t n  and formula (17) are entered into the least squares method database to find the characteristics B 3 , K thc , K CC . These characteristics are finally substituted into the formula (17) and the kinetic diagram In n K ~  is obtained that is analytical dependence of the SAE intensity on stress intensity factor for the high-temperature creep crack growth. Such a kinetic diagram constructing scheme is shown at the Fig. 2, b. Along with the kinetic diagrams In n K ~  for determining the high-temperature creep cracks subcritical growth period t = t  , the kinetic diagrams V ~ K I that were used earlier are important. The method for constructing these diagrams is described in (Andreykiv et al. (2017a)). However, the kinetic diagrams V ~ K I direct construction without the AE method use is labor-intensive, due to large time of the experimental research. Therefore, we propose to construct first less time-consuming kinetic diagrams In n K ~  and then, with the help of the according analytical decoder convert them to the kinetic diagrams V ~ K I . The essence of this analytical decoder is as follows. With the help of relations (6) and (15) we can obtain the formula that connects V and n  values

V B h n  1 4 1  

.

(18)