Issue 45

G. Gomes et alii, Frattura ed Integrità Strutturale, 45 (2018) 67-85; DOI: 10.3221/IGF-ESIS.45.06 72 The analysis initially set the pre-processor and then continues with the incremental analysis process of the crack growth, whose propagation path is also discretized by short straight segments or elements and, for each increment, the BEM is applied to perform the stress analysis. At each increment, the J-integral is used to compute the SIFs through Eqn. (8), which are then evaluated by Eqn. (9) to adjust and define the crack path growth direction and compute the fatigue life as a function of the crack length using Eqn. (13). Finally, the post-processing analysis allows the visualization of the results. The automation process described above has been done through the implementation of two codes: the BEMLAB2D GUI for pre- and post-processing, written in MATLAB, and the BemCracker2D program for boundary element analysis, written in C++ and based on Object Oriented Programming (OOP) [16]. The following subsections present a brief review of both codes, whose automation scheme is represented by the flowchart in Fig. 3. Figure 3: Flow chart of the automatic crack growth. BemLab2D GUI The BEMLAB2D program is a graphical user interface (GUI) for pre- and post-processing, written in MATLAB and focused on two-dimensional mesh generation and visualization, as well as for visualizing the results of elastostatic analyses produced using the BemCracker2D program. BEMLAB2D GUI is based on user-defined actions through the tool buttons, mouse and dialogs, which modules and features are described below and illustrated in Fig. 4a.  GEOMETRY (Module I): This module is independent and has two purposes, the 2D model construction using drawing tools (POINTS, LINES, ARCS and ZONES), and model identification without / with cracks;  MESH (Module II): This module allows the mesh generation, for the model created in module I, for three different numerical methods (BEM, FEM and Meshless); however, for the last two methods, the interface is limited by the generation, visualization and storage of the mesh geometry;  BOUNDARY CONDITIONS (Module III): This module is specific for analysis with the BemCracker2D program. It has three boundary condition types: Displacements, Tractions and Unknown;  ELASTOSTATIC ANALYSIS (Module IV): This module is specific for analysis with BemCracker2D program and it is responsible for the three analysis types: STANDARD BEM (no cracked structures), WITH NO CRACK GROWTH and WITH CRACK GROWTH (cracked structures). For the latter analysis model, the dialog in Fig. 4b is opened requesting information such as number of increments, increment size (integer multiplier element that contains the crack-tip size) and Paris parameters;  GRAPHICAL RESULTS (Module V): This module is specific for analysis with the BemCracker2D program and it is responsible for previewing the following graphical results: DEFORMED MESH, STRESS MESH, STRESS INTENSITY FACTORS, CRACK GROWTH PATH, FATIGUE LIFE and CRACK GROWTH REALTIME. Fig. 5 illustrates the interface functionality BEMLAB2D hierarchy, which includes all steps involved in the analysis procedure.