PSI - Issue 38

Paul Catalin Ilie et al. / Procedia Structural Integrity 38 (2022) 271–282 P. C. Ilie et al./ Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 3. SimModeler’s 3D explicit crack advancement modelling procedure; generic corner crack at a hole is used as an example.

3. Model Verification and Validation 3.1. Single flaw model verification

The crack growth results obtained from the analytical modelling approach implemented in MATLAB are compared to the 3D FE predictions for three crack different geometries in Ti-6Al-4V plates to assess the accuracy of the FE based solution. Material properties for the Ti-6Al-4 alloy is shown in Table 1. The three crack configurations chosen for verification have been studied extensively over the years with numerous proposed approximate analytical solutions [20, 21, 22, 23]. The plate model considered in this verification study measures 96 mm in length, 48 mm along width and is 16 mm thick as shown in Fig. 4. The crack geometry aspect ratio was selected based on the recommendations provided in [7,8]. For all three cases the semi-minor axis of the ellipse was 2 mm and the semi major axis was 3 mm. The crack was positioned in the middle of the plate length wise. For the embedded and corner cracks the position relative to the width and thickness of the plate is given in Figure 2. The semi-elliptical surface model was used for performing fatigue crack growth simulations using far field stress ranges from 50 MPa to 200 MPa in 25 MPa increments (R = 0). The corner quarter-elliptical and embedded elliptical models were tested for a 200 MPa far field load range. The model parameters are shown in Table 2.

Table 1. Plate specimen material properties [24]

Parameter

Value

Alloy

Ti-6Al-4V

Young’s Modulus Poisson’s Ratio C coefficient (Paris) m exponent (Paris)

115 GPa

0.33 1.77e-14 MPa √mm 3.667