PSI - Issue 39

O.N. Belova et al. / Procedia Structural Integrity 39 (2022) 770–785 Author name / Structural Integrity Procedia 00 (2021) 000–000

773

4

( (

) ( ) ( / 2 ( 1) cos / 2 ( / 2) cos( / 2 2) , / 2 ( 1) sin / 2 ( / 2)sin( / 2 2) , k k k k k k θ θ θ θ − − + − / 2 ( 1) sin / 2 ( / 2)sin( / 2 2) , / 2 ( 1) cos / 2 ( / 2) cos( / 2 2) . k k k k k k k θ θ θ θ + − + − ) ( ) ) ( ) ) )

( ) k

( ) ( ) ( ) ( )

g g g g

k k = + + − = − − − = − + − − k = − + − (

θ κ θ κ

1,1

( ) k

1,2

( ) 2,1 ( ) 2,2 k k

θ κ

(

θ κ

m k a are the unknown mode I parameters. The SIFs can be computed from the

The amplitude coefficients

coefficients as Eqs. (2) are valid for pure crack opening loads whereas Eqs. (3) are valid for pure shear loads. The goal of this study is to determine the higher order coefficients m k a in the multi-point series expansion (1) for the double edge notched specimen. 2. Photoelastic experiments: experimental setup and experimental procedure The experimental setup used is shown in fig. 1. The experimental setup consists of a traditional polariscope setup and a digital image camera. All the specimens in this work were made by casting of polycarbonate. Experimental specimens were machined from the sheet to get the test specimens. The study used ten tension strips 120 mm long by 50 mm wide and 5,4mm thick. Material properties of the photoelastic material are Young’s modulus 3 E GPa = , Poisson’s ration 0.3 ν = and the material fringe constant is found to be 10.41 / f Pa m fringe σ = . The geometry of the cracked specimen and schematic representation of the load application are shown in fig. 2. The angle between the crack and the vertical line equals 60 o for all specimens. I K a = π and 2 1 2 II K a = − π . 1 2 a is related to T-stress as 1 2 4 . a 1 o σ = − 1 1 2

Fig. 1. Photograph of the experimental apparatus used to visualize and capturing the fringe patterns.