PSI - Issue 2_A

Shaowei Hu et al. / Procedia Structural Integrity 2 (2016) 2818–2832 S. Hu et al./ Structural Integrity Procedia 00 (2016) 000–000

2827

10

unstable fracture toughness

un IC K and cohesive toughness

c IC K into formula (6), the initial fracture toughness ini IC K will

be obtained. Each specimen’s fracture parameters calculation results as shown in table 3.

Table 3 Calculation results on fracture parameters of each specimen Specimen serial number P ini (kN) P un (kN) a c (mm)

c IC K (MPa·m 1/2 )

ini IC K (MPa·m 1/2 )

un IC K (MPa·m 1/2 )

 a c (mm)

WS-020-1 WS-020-2 WS-020-3 WS-020-4 WS-025-1 WS-025-2 WS-025-3 WS-025-4 WS-030-1 WS-030-2 WS-030-3 WS-030-4 WS-035-1 WS-035-2 WS-035-3 WS-035-4 WS-040-1 WS-040-2 WS-040-3 WS-040-4 Mean Mean Mean Mean

17.35 18.51 18.61 17.10 17.89 10.51 11.86 11.16 19.05 13.14 10.74 13.20 12.17 11.68 11.95 10.17 10.32 9.73 10.95 10.29

25.63 29.51 26.33 24.67 26.53 27.37 21.83 25.34 26.46 25.25 20.71 21.71 21.31 20.52 21.06 19.48 18.12 19.40 21.43 19.61 15.32 15.07 16.51 16.07 15.74

134.15 139.11 173.62 179.53 156.60 181.25 203.77 178.97 169.99 183.50 189.80 202.56 180.90 187.39 190.16 211.86 206.64 178.38 193.73 197.65 215.92 208.48 215.96 215.49 213.96

54.15 59.11 93.62 99.53 76.60 81.25 78.97 69.99 83.50 69.80 82.56 60.90 67.39 70.16 71.86 66.64 38.38 53.73 57.65 55.92 48.48 55.96 55.49 53.96

0.665 0.881 1.060 1.069 0.919 1.537 1.299 1.335 0.966 1.284 1.160 1.297 1.102 1.127 1.172 1.140 0.959 0.846 1.069 1.004 0.853 0.775 0.856 0.793 0.819

0.729 0.778 0.782 0.718 0.752 0.467 0.527 0.496 0.846 0.584 0.433 0.506 0.455 0.430 0.456 0.575 0.583 0.550 0.619 0.582 0.531 0.523 0.637 0.656 0.587

1.394 1.659 1.842 1.787 1.671 2.004 1.826 1.831 1.812 1.868 1.594 1.803 1.557 1.557 1.628 1.715 1.543 1.396 1.688 1.585 1.385 1.298 1.493 1.448 1.406

103.77

8.25 8.12 9.89

10.18

Mean

9.11

 Initial cracking load P ini and unstable fracture load P un According to the calculation results in table 3, curves of initial cracking load P ini and unstable fracture load P un along with initial seam height ratio a 0 / H is shown in Fig.9. As can be seen from Fig.9, along with the initial seam height ratio changes, the trend of initial cracking load P ini and unstable fracture load P un are similar, with the increase of initial seam height ratio, the initial cracking load P ini and unstable fracture load P un of the specimens are gradually decrease, and almost reduced in a linear trend. In addition, from Fig.9, when initial seam height ratio is 0.2, the variation tendency of initial cracking load has a certain difference with other groups. Analysis of the reason is: For the wedge splitting tensile specimen with a relatively small initial seam height ratio, its fracture characteristics is affected by the maximum-tensile-stress failure, and has a certain shear failure role. For the specimen with large height of section, when the ligament length is large, it means the length of the part above crack tip is small, and the failure will be closed to maximum-tensile-stress failure which conforms to material characteristics (Hu and Xu 2015). Because there is a certain shear failure role in the part above crack tip, and the failure is affected by maximum-tensile-stress failure, so there need a bigger external load to make specimen initial crack failure.  Critical effective crack length c a and subcritical crack propagation length c a  Curve of critical effective crack length c a and subcritical crack propagation length c a  along with the change of initial seam height ratio a 0 / H is shown in Fig.10, the subcritical crack propagation length 0 = c c a a a   . As can be seen from Fig.10, in addition to the specimen which initial seam height ratio is 0.2, the critical effective crack length c a of other groups are all have a linear growth trend with the initial seam height ratio increase. It illustrates that except the specimen with a relatively small initial seam height ratio, the critical effective crack length of non-standard wedge splitting tensile specimen has a linear correlation with specimen’s initial seam height ratio.