Experimental Validation of Model Updating and Damage Detection via Eigenvalue Sensitivity Methods with Artificial Boundary Conditions
Naval Postgraduate School Monterey United States
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The use of finite element modeling FEM in design has expanded as computers have become more capable. Despite these advancements, the construction of physical prototypes remains an essential aspect of design and testing. FEM limitations include the inability to accurately account for joints, damping, and geometric complexities. Due to the reality gap between a FEM and the prototype, there may be design deficiencies that cannot be identified until the prototype is tested. Using eigenvalue sensitivities, enhanced by artificial boundary conditions ABC, the gap between simulation and reality can be closed via FEM updating. With an updated FEM, the same eigenvalue sensitivities can be utilized to detect damage in structural systems in use. Damage that produces differences in natural frequencies between the structure and its FEM can be related to the loss in flexural rigidity, as it is usually assumed that mass modeling is correct. This indicator allows adjustment of a FEM to match a prototype or to detect damage in a potentially compromised structure via comparison to an updated FEM. Based on simulation, a combination of multiple pin and spring ABCs is optimal for producing an ideal sensitivity matrix, and thus, ideal damage detection capability. However, in the experimental realm, the synthesis transformation used to apply ABCs to the measured frequency response functions can distort the frequency response function peaks, leading to error. A compromise of a single pin ABC permits both effective model updating and damage detection.
- Numerical Mathematics