PSI - Issue 17

Pavel Steinbauer et al. / Procedia Structural Integrity 17 (2019) 799–805 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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low cost processors as well. The cheap communication infrastructure is built within initiative INDUSTRY 4.0 and Internet of Things (IoT), although available bandwidth is very low, so transferred data amounts are limited.

3. Introductory experiments

Large sets of lighting poles were investigated. The experimental modal analyses and force-deflection measurement were carried out, together with pole dimension measurement. The deflection was measured using harmonic, low frequency force excitation, which does not require absolute support construction and point ( Steinbauer, P., & Valášek, M. (2010)). Several interesting conclusions could have been drawn. The pole is relatively cheap product. The production tolerances are not set very strictly. In addition, in many cases the production did use completely different materials. Thus the pole dimension variation is large, even among the sets with same manufacturer specification. The measurement conclusions must be drawn with respect to each particular pole separately.

Fig. 2 Pole ’ s FRFs and deflection measurement a and resulting deflection curves b using laser Doppler vibrometer

The pole compliance measurement is reliable method to determine pole deterioration (Fig. 3 b ). Due to the mechanical parameter variations within pole sets, it can be used only to compare repeated measurements of one pole. Comparison between several poles can be done only if the dimensions and other mechanical parameters were verified to be within tolerance. Experimental modal analyses has shown that eigen frequency shift is very small, almost negligible at lower eigen frequencies, even for quite extensive damage. Higher eigen frequencies exhibit still small, but usually measurable change (Fig. 3). The differences in higher eigen frequencies could be clearly determined. That’s why, if the experimental modal analyses or at least one frequency response function could be measured regularly, the change of selected eigen frequency will indicated deterioration of pole state of health.

Fig. 3. Pol e’s frequency response function differences (fixed in concrete a , fixed in sand bed b )