Global Mode

Keywords Laser Doppler Vibrometer, Ambient vibration, Forced vibration. Local frequency, Global frequency. Local mode. Global mode... 

Figure 1.57 Improvement of contrast and resolution of a stained 400 nm thick ABS section produced by zero-loss filtering in an EFTEM (b) compared to global mode imaging (a)...

Omega filter used in the global mode (a) and of the same area by zero-loss filtering (b)[l,2],... 

One might think that an initially straight cohesive crack (Fig. 14) would turn (kink) upon the slightest application of However, it turns out that the elastic mismatch that is contained in Eq. 38 allows a straight crack to continue as such for approximately < 0.1AT,° . To see this, we take the common assumption that cracks in homogeneous materials grow in such a way that the local mode II component /fn = 0. This condition, when substituted into Eq. 38 yields a relationship between the location of the crack (c//z) and the global mode-mix as... 

Fig. 21. Resistance curve behavior in a composite-epoxy-composite adhesively bonded joint under globally mode I loading [54].

Statistics of the modal frequencies identified between 31/07/2012 and 02/08/2012 are summarized in columns (2)-(5) of Table 2 through the mean value, the standard deviation, and the extreme values of each modal frequency. It should be noticed that the natural frequencies of all modes exhibit slight but clear variation, with the standard deviation ranging between 0.011 Hz (mode B2) and 0.037 Hz (mode LI). The correlation analysis performed to investigate the possible relationships between natural frequencies and temperature (Saisi et al. 2013) clearly indicated that the natural frequencies of the global modes B1-B3 and T1 increase with increased temperature. This behavior, observed also in previous measurements on masonry structures... 

The identification of the modal frequencies from the datasets collected during the same period provided the frequency tracking shown in Fig. 14b. The inspection of Fig. 14b firstly suggests that the slight fluctuation of the natural frequencies of global modes follows the temperature variation. In order to better explore the temperature effect on the modal frequencies. Fig. 15 presents the first four natural frequencies of the tower plotted with respect to temperature, along with linear best fit lines. The plots in Fig. 15 confirm what already observed in the first dynamic survey the natural frequencies of the global modes tend to increase with increased temperature almost linearly, as a consequence of the temporary increase of the local stiffness due to the thermal expansimi of materials. 

Fenistein, D., van de Meent, J. W., and van Hecke, M. (2006). Core precession and global modes in granular bulk flow. Phys. Rev. Lett., 96,118001/1-4. 

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