Experimental detection by magnetoelastic sensors and computational analysis with finite elements, of the bending modes of a cantilever beam with minor damage

Contactless Detection of Natural Bending Frequencies using Embedded Metallic-Glass Ribbons inside Plastic Beams made of 3-D Printing

“…It is not clear why the ≤ 4 modes are missing; perhaps they are present but with lesser measured signal strength compared to the noise and thus more accurate experiments are required to reveal them. As it was mentioned above, in the previous work [25,26], the = 1 and = 2 peaks were very weak, and perhaps the additional damping introduced by the plastic beam here causes two more peaks to disappear (to avoid confusion, it must be recorded that in Figure 4 the mode number n corresponds to "peak number" + 4). Also, from Table 4, it can be analyzed that the corresponding values calculated from eq.…”

“…(b) Moreover, in an earlier study [28], the sensor is forced to vibrate longitudinally while our experiment is in the plain bending vibration mode. In this mode, it was observed in the previous work with single aluminum bars as cantilevers [25,26] that the first n = 1 and n = 2 peaks were very weak compared to the higher peaks.…”

“…The anneal temperature was chosen to be below the alloy's Curie temperature of 353 °C (refer to Table 2). For the Metglas attachment on the beam, the double sticky tape was selected in place of epoxy resin since (a) it worked well in the previous work [25,26] and (b) it provided a uniform attachment across the Metglas ribbons without leading to local stresses due to non-uniformity that a badly spread resin can cause during the curing. Similarly, it has a uniform thickness down to the sub-millimeter range, while it would be extremely difficult to create a resin spread of such a small and uniform thickness.…”

“…Following a similar route, our group has been a pioneer in the usage of magneto-elastic ribbons for identifying and localizing the cracks in metal cantilevers [25,26] by recording the shift of their harmonics under bending vibrations. Magnetoelasticity is the change in the magnetic state of these materials due to the application of mechanical stress on them [27].…”

“…As shown earlier [25,26], the produced signal from an aluminum cantilever with Metglas ribbons on it can be Fourier-analyzed to produce the spectrum of the bending modes of the beam when it is subject to bending excitations. This is a unique signature of the mechanical health of this structure, and its recording is of paramount importance in damage detection.…”