PSI - Issue 13

O. Plekhov et al. / Procedia Structural Integrity 13 (2018) 1209–1214 Author name / Structural Integrity Procedia 00 (2018) 000–000

1212

4

The analysis of experimental data was carried separately for each regime of heat dissipation. Figure 3 presents the two aforementioned regime of crack propagation in different coordinates.

(a) (b) Fig. 3. Two regimes of heat dissipation under crack propagation in the plot of heat dissipation rate versus time (a), in the plot of crack rate versus stress intensity factor range (b). The figure 4 presents the evolution of crack rate versus relative heat flux and crack length. The relative value of heat flux and relative product of crack length on heat flux was determined as follows

min

min

max Q a Q a Q a Q a Q a 1 1 1 1 1 1 1 1 1 1    

max Q Q Q Q Q 2 2 2 2 2    

,

(3)

min

min

The results presented in figure 4 exhibit the linear relation for both regimes of crack propagation. The classical Paris`s regime of crack propagation can be divided into two regimes with different kinetics of energy dissipation. During first regime, the crack rate is linear function of crack length and power of heat dissipation ( 1 1 1 ~ Q a N a   ). Generally expected linear relation between crack rate and power of heat dissipation characterizes the second regime (  ). The similar separation of two stages on the heat flux for biaxial test dependence under biaxial loading is shown in figure 5. 2 2 ~ Q N a 

Этап 1 Stage

-6

Этап 2

Stage 2

-6

1.5 x 10

6 x 10

F amp =2.5kN F amp =3kN

F amp =2.5kN F amp =3kN

1

4

0.5

2

da/dN, м/цикл da/dN, m/cycle

0 da/dN, m/cycle da/dN, м/цикл

0

0

0.5

1

0

0.5

1

(Q 1 *a 1 ) /

Q /

2

(a) (b) Fig. 4. The evolution of crack rate versus relative crack length multiplied by heat flux from the crack tip (a) and crack rate versus relative heat flux from the crack tip (b).