Issue 29

E. Grande et alii, Frattura ed Integrità Strutturale, 29 (2014) 325-333; DOI: 10.3221/IGF-ESIS.29.28 329 to the use of DF and MDF more clearly underline the damaged element n.6, particularly in the case of MDF where for all the accounted sets of modes the most significant BPA just corresponds to the damaged element. In the case of the use of the classical techniques, it is possible to observe that for many sets of modes the damaged element is not identified (it is characterized by a BPA less than the ones corresponding to other undamaged elements) and it seems that more than one of the elements composing the beam is affected by damage. For these cases, although the application of the DF technique leads to an increase of the BPA corresponding to the damaged element, the corresponding bar results the highest one, significant values of the BPA also characterize the other elements. Also in the case of the MDF technique the sets of modes  =[  3 ,  5 ,  7 ],  =[  3 ,  4 ,  6 ] are characterized by a less accurate damage identification although a significant difference characterize the BPA corresponding to the damage element and the BPA of the undamaged ones. This effect clearly underlines the role of the identified modes of vibration before and after the damage. Indeed, the sets characterized by the better identification of damage are the ones composed of the modes of vibration with significant values of the modal participating mass and by the more sensibility to the damage in terms of variation of the frequency.  =[  1 ,  2 ,  3 ]  =[  1 ,  5 ,  7 ]  =[  3 ,  5 ,  7 ]  =[  3 ,  4 ,  6 ] Figure 3 : rdi and MSECRj index vs. DF technique – S6D15 damage case Multiple Damage Case: M6,11D10 In Fig. 5 and 6 are reported the same results considering the multiple damage scenario. Also for this damage scenario it is possible to observe the capability of the DF and MDF in improving the damage detection with respect to traditional techniques, and, also in this case, it is evident the importance of the selected sets of modes. This last effect becomes more important in the case of multiple damage scenarios. Effect of noise The capability of data fusion to improve the damage detection is further assessed by introducing errors in the modes of vibration generally arising when noises affect the signals at the basis of the identification process. In the paper, this effect is simulated by perturbing each mode shape, accounted in the damage identification, as follows:   1 1,.., i i i r i n         (11) 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements rdi 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements MSECR j 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements BPAs DataFusion -DF 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements rdi 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements MSECR j 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements BPAs DataFusion - DF 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements rdi 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements MSECR j 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements BPAs DataFusion -DF 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements rdi 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements MSECR j 1 2 3 4 5 6 7 8 9101112 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 elements BPAs DataFusion -DF