5.1. Plate with edge crack We consider a reference problem of a plate (Fig. 5.a) of size l mm mm L 300 2 2 400 with an edge crack of length a2 , with . The material properties are 2.1 10 Pa 11 E , 0.3 and 3 3220Kg/m . With plane strain state and a mesh of 60x120 elements. The plate is under uniaxial dynamic tensile ( , )0 t y of Heaviside step load (Fig. 4.b) with 20 10 Pa 6 0 , We’re going to evaluate the no normalised SIF I ad K at the crack tip and the maximum of y component of normalised stress ad on A point situated at the nearest node to the crack tip defined as: 0 / ( ) I ad I K K a (8) 0 / ad yy (9) Curves on Fig 4.c were found with sliding the void horizontally with a step of (1/7)a. These Figures represent the variation of I ad K and ad versus the relative position x/2w. ad 0,0 0,1 0,2 0,3 0,4 0,5 1,8 2,0 2,2 2,4 2,6 2,8 3,0 3,2 0,0 0,5 1,0 1,5 2,0 2,5 x/2w ad I ad K I ad K (c) (a) (b) Fig.4 (a) considered geometries, (b). Dynamic load Heaviside (c) SIF and maximum stress Fig 4c shows that both I ad K and ad decreases with the distance of the hole to the crack tip; it is like the crack length decreases. The SIF continues to decline up then vanishes when the hole reached the crack tip. That is why holes at the crack tips are considered a very practical solution to stop their growth. 5.2. Plate with central crack We reanalysis the precedent example but with a central crack crossed by a hole of a diameter varying from 2a/10 to 2a/1.1 as shown in Fig 4a. In this example, we are going to evaluate the dimensionless SIF given in relation (8) for different diameters of hole to verify its role to increase the cracking plate resistance. Effectively, from the curves in Figure 5.b, the hole more and more bigger extinct more and more the SIF and therefore the risk of crack growth. / 0.24 a l
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