Simulating Fatigue Cracks in Healthy Beam Models for Improved Identification

There is need for an automated Structural Health Monitoring (SHM) system capable of fatigue crack detection in bladed disks as current methods are slow, costly and imperfect. Prerequisite for such a system is a fast method for producing the necessary data libraries. In an effort to develop such a method for simulating nonlinear structural response, fatigue cracks in beams have been modeled by modifying the inputs to the structure rather than the structure model itself to produce a closed-form solution for the total response. Although the time savings are enormous, and the method has proven capable of correctly identifying fatigue cracks over an effective region in data generated by a more traditional bilinear model, additional refinement is needed. The method for calibrating the signature profiles used to identify fatigue cracks between methods is revisited and successfully improved. Existing signature profiles for the bilinear model are reproduced with higher resolution, and new features are observed. Different boundary conditions are evaluated with the new method and compared to published results. Although similar, there are still discrepancies that remain and will need to be investigated. Overall, the proposed method for modeling and identifying fatigue cracks in beams has been improved, but will require validation against physical experiments before being used on more complicated structures such as bladed disks.