PSI - Issue 2_A

Fabrizio Moroni et al. / Procedia Structural Integrity 2 (2016) 120–127 Author name / Structural Integrity Procedia 00 (2016) 000 – 000

124

5

5Hz. The crack length was monitored by means of the compliance method. The crack opening ( δ ) was measured by means of a clip gauge (Fig. 3). The relationship between the compliance ( δ/P ) and the crack length ( a ) was obtained by means of finite element simulations carried out at different crack lengths (Fig. 4). This relationship was then used to obtain the crack length by tracking the experimental compliance during the test.

Fig. 4. Compliance vs Crack length obtained through finite element simulations.

The test results are presented in terms of crack growth rate as a function of the range of the applied strain energy release rate ( ΔG ). For a DCB joint the strain energy release can be obtained using the relationship proposed by Krenk (1992), and in particular, the maximum value achieved within a load cycle is given by:   2 3 2 2 max max 1 1 12    G (1)

 

  

B E H P a

a

 

S

,

where:

E

6

 



A

(2)

4





2

3 H t E

1





A S

A

.

The range of the strain energy release rate is defined as:

max G G G   

(3)

min

,

therefore by using the load ratio definition,  G can be computed as:



 3

2

2

  

    

12





 2

2 B E H G G R P a S     max 2 max 1

R

1 1 1 

(4)

a

 

.