2.1 FEA solution process for bonded repair simulation workflow (BRSW)
Our proposed bonded repair effectiveness evaluation methodology is carried out in the following steps:
Aircraft structure geometry, crack geometry, repair patch geometry preparations. In this step, a CAD drawing is first completed based on the aircraft structure geometry and the initial crack geometry. The repair patch geometry is dependent on the repair strategy to be examined, e.g., stop-drill repair and damage-removal repair. An example of the geometry is shown in Figure 1.
  1. Material properties preparation and assignments. In this step, the material properties are assigned for the aircraft structure to be repaired and the patch materials, e.g., boron patch and titanium patch. These material properties are necessary for the evaluation of crack growth and estimations of service life.
  2. Aircraft structure and patch meshing generation, crack meshing generation. The meshing of the geometry is necessary for FEA simulation and analysis.
  3. Aircraft structure loading and boundary conditions setup. This step sets up the loading and boundary conditions. In the case of fatigue tests, the loading is applied as cyclic loading.
  4. Fatigue damage quantification. This step is to evaluate the damage using stress measurements caused by fatigue loading and to assess when crack is initiated.
  5. Fatigue crack propagation simulation and service life quantification. This step is to provide an estimated service life for each type of the crack repair treatment.
The steps listed above is implemented through our proposed Bonded Repair Simulation Workflow (BRSW) with setup stages, shown in Figure 2. The BRSW process consists of three stages with building blocks which utilizes various Ansys software tools to perform designated tasks. The workflow starts from the definition of material properties (structures, patches, adhesives), to the problem setup (geometry preparation, mesh generation, loading and boundary conditions), to FEA solutions that yield fatigue damage evaluation, crack propagation quantification and service life estimation.