Answer Happy

6. When a body has more than one crack the stress fields from each crack will affect the other. For example, for a sheet perforated with an array of cracks, each of length 2a, center-to-center spacing 2b, and loaded with uniform, far-field tension, as shown in Figure, ΚΙ = σωπα, 26 na tan πα 26 2b 2a T b Ky increases if the crack tips approach each other: 46 b a +b=K=o EOV However, it is reasonable as well to expect that when the cracks are widely spaced that their interaction will be minimal. To estimate the distance beyond which cracks have little interaction, calculate the minimum value of b/a for which Kį for the array of cracks shown in Fig. differs by less than 5% from that of a single crack, for which Kj = ota. (from Alan T.Zehnder, Fracture Mechanics. Springer, 2012)