PSI - Issue 17

Pedro J. Sousa et al. / Procedia Structural Integrity 17 (2019) 812–821 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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(c) Displacement along Z

Fig. 2. Measured displacement at 680 rpm using DIC. (Displacements in millimeters)

These results show, for example a maximum displacement of 7 mm along Z, as well as an average Y displacement significantly different from zero, which is compatible with the measured gaps between the hub and the blades.

3. Computational Model

3.1. Problem definition

In order to obtain a representative model of the physical situation, it is necessary to obtain the material properties and the shape of the object. First, the shape of the object was obtained using a commercial laser scanner, Fig. 3a, and, afterwards, this was used as a basis for a parametric model, created in 3D modelling software to simplify the geometry, Fig. 3b. As would be expected, it was possible to smooth the curves in the parametric model, obtaining a shape that is close to the real object’s, Fig. 3c , including the blade’s root, which was not visible to laser scanner.

(a)

(b)

(c)

Fig. 3. (a) Acquired shape of the blade; (b) Reconstructed parametric model; (c) Photograph of the blade

In the RC helicopter, two of these blades are assembled into a hub component and connected using pins. This connection has several degrees of freedom, namely the rotation of the blade relative to the hub, as well as some small gaps between the different parts. Then, it is possible to create an assembly using these components. However, the rotation freedom could not be implemented in the model, which creates differences between it and the experimental setup.