PSI - Issue 28

Domenico Ammendolea et al. / Procedia Structural Integrity 28 (2020) 1981–1991 Ammendolea et Al./ Structural Integrity Procedia 00 (2019) 000–000

1987

7

method. Ooi et al. (Ooi et al. (2012)) have gained good prediction using a scaled boundary finite element method (SBFEM) combined with an efficient remeshing algorithm. To assess the reliability of the proposed method, comparisons with both the experimental and numerical data were developed. Fig. 4-b depicts the initial mesh configuration used in the simulation. It comprises 439 triangular elements arranged finely near the crack tip and coarse elsewhere. A displacement-based control strategy is used to compute the intensity of the load during the analysis. In particular, the up-left corner of the beam (i.e., X 1 =0, X 2 =100 mm) was designated as the control point. Fig. 5-a compares the crack path gained by the present method with experimental data of Sumi and Kagohashi (Sumi and Kagohashi (1983)) and numerical predictions of Ventura et al. (Ventura et al. (2002)) and Ooi et al. (Ooi et al. (2012)). Also, Fig. 5-b reports snapshots of the deformed configurations of the beam at different propagation steps, which are marked in the crack path of Fig. 5-a. The results are in good agreement with experimental findings and numerical predictions, thus denoting the accuracy of the present method to predict crack propagation mechanisms. The computational efficiency of the present method is now checked by developing a parametric study in terms of mesh configurations. The main aim consists to analyze the influence of the mesh arrangement on crack propagation predictions. The crack path obtained by using the mesh reported in Fig. 4-b (here identified as M1) is compared with the results achieved by two coarser meshes reported in Fig. 6-a. The new meshes named as Mesh M2 and Mesh M3 comprise 192 and 148 triangular elements, respectively. The results reported in Fig. 6-b show that the mesh structure does not affect the crack path, since no relevant differences in predictions are observed. 4.2 An edge notched plate with one hole Fig. 7 shows a rectangular plate of width 30 mm and height 45.5 mm having an off-center circular hole of radius 15 mm and a lateral pre-crack of 7 mm. The bottom edge of the plate is clamped, while a uniform tension (  ) is applied on the opposite upper edge. This case was designed by Rashid (Rashid (1998)) for developing its approach based on the Arbitrary Local mesh replacement method implemented within a FEM framework. Rashid has found that the hole’s presence highly affected the crack trajectory. In particular, the crack trajectory deflected toward the hole as the distance between the pre-crack and the hole reduces. Unfortunately, no exhaustive information about material properties and fracture parameters has been provided. Then, comparisons with some Rashid’s results ( e.g. critical applied stress vs. crack extension arc-length) are difficult to perform. Ooi et al. (Ooi et al. (2012)) have reproduced the crack path achieved by Rashid assuming E=98 GPa (Young’s modulus),  =0.3 (Poisson’s ratio), and K Ic =1000 N/mm 3/2 (fracture toughness).

Fig. 4. Case 1: A horizontal pre-crack in a double cantilever beam subjected to two vertical and opposite distributed loads at the free extremity. (a) a schematic of the geometry and boundary conditions (b) Initial mesh configuration