PSI - Issue 2_A

Abhishek Tiwari et al. / Procedia Structural Integrity 2 (2016) 690–696 Author name / StructuralIntegrity Procedia 00 (2016) 000–000

695

6

To visualize the variation of q W with a/W , values of q W at 100 MPa m 1/2 are compared with fitting parameters of Eq.(2) and T stress . The comparison of fitting parameters Z’ , β and q W is shown against T stress and Δ T stress in Fig. 5.

Fig. 4 Weibull triaxiality calculated for different a/W simulations

(b)

(a)

Fig. 5 Variation of fitting parameters of Eq.(2) q W and absolute q W with (a) Δ T stress and (b) T stress against a/W .

It is evident from Fig. 5 that the fitting parameters obtained by using σ*- V * model captures the constraint effect with great accuracy. Moreover, the Weibull triaxiality also shows a good correlation with standard constraint loss parameter T stress . From Fig. 5(b), it can also be observed that fitting parameter β shows a quadratic variation with a/W unlike T stress . However, in both Fig. 5(a) and 5(b) q W shows better correlation with T stress as well as Δ T stress . This shows the accuracy of new constraint parameter q W , for modelling constraint effect on fracture in DBT region. Using the K JC -V* correlation shown in Fig. 3 and assuming that same amount sampled volume results in equal cleavage failure probability; the fracture data of different crack depths were transformed to 0.5 a/W . By equalizing the sampled active volume for two different crack depth specimens, namely A and B , the transformation of K JC,B to K JC,A can be expressed by Eq. (4).

1

K

JC B ,

B A   ) ]

B JC A K Z V V 0, ,  A ' [( 

) (

 

(4)

0,

A

'

Z

B