No abstract

No abstract

Non-destructive testing of structures involving vibration-based damage detection methods implies knowing the beam’s boundary conditions. For perfect boundary conditions, numerous damage detection methods are developed and ensure more or less accurate estimation of the crack type, position, and severity. On the contrary, for imperfect boundary conditions, which are the real ones, there are only a few dedicated works. This paper presents a methodology that allows the identification of the weak clamping and the crack if both exist. The weak clamping is modelled as a defect that produces an identical relative frequency shift (RFS) for all vibration modes. Therefore, to find the two defects namely the real crack and defect simulating the weakly clamped end, we apply the principle of superposition. The method is implemented as an application written in the Python programming language. Tests show that defects are successfully identified even if there are uncertainties about the fixing of the beam.

In order to place a product on the market that is completely safe for users, the manufacturer must go through certain steps: design, prototyping, execution and prototype validation through experimental methods, obtaining documents that allow to sell the product from certain public or private companies (for example homologation certificate) and series production. One of the most important steps is the validation tests of the prototype because it will depend on them that the prototype corresponds to the design requirements.

Detecting damage in the incipient state is of crucial importance in monitoring the health of engineering structures. Approaching damage detection as an inverse problem is a common method when vibration-based techniques are used. It implies a precise a priori estimation of the modal parameters. We present in this paper a model to predict the frequency changes due to cracks in the side frames of bogies used to detect the welding defects in T-joints. To this aim, we model the structure and perform simulations using the SolidWorks software. The frequencies for the first thirteen modes are derived for the intact structure and the structure with different damage lengths and positions. By these tests, we first desire to find the optimal fixing of the side frame to reduce the number of vibration modes that are not of interest to the damage detection process. After finding the ideal fixing system, we derive patterns, for different defects, in the form of relative frequency shifts. Finally, we conclude about the damages that can be identified using the derived patterns, the conclusions being traced based on the measurability of the frequency changes.