An aluminum plate with long machined cracks of different depths. (a) Photograph of aluminum sample. (b) Surface flaws. (c) Subsurface flaws with an aluminum tape layer attached. (d) Subsurface flaws with three aluminum tape layers attached.
saint row 2 crack pcb
The second kind of specimen, which is used for exploring the performance in inspecting crack direction, is a copper film with machined slits on a 30 mm 30 mm printed circuit board (PCB), as described in Figure 7. The eight slits simulating the cracks are made with the different angles of 0, 30, 45, 60, 90, 120, 135, and 150 against the horizontal direction, while the length and width of the slits are constant at 6.5 mm and 0.6 mm, respectively.
The PCB specimen for testing the performance of the EC probe in determining crack orientation: (a) photograph of the PCB with defects, and (b) illustration for the orientation angles of the defects with the defect numbers.
The simulated EC distribution in the unflawed aluminum sample and the flawed sample with a crack of 1.5 mm depth is shown in Figure 11. The EC density is concentrated at positions around the radius of the excitation coil and it drops rapidly for locations away from the radius of the excitation coil. It can be found that the EC density on the flawless aluminum slab in Figure 11a is higher than the EC density on the aluminum plate with the crack in Figure 11b because of disturbance caused by the crack defect. This leads to the variation of the secondary field induced by these ECs with the presence of the crack.
The eddy-current distribution following the depth of (a) a flawless aluminum sample and (b) a flawed sample at the excitation frequency of 40 kHz. The crack used in (b) has a 1.5 mm depth along the y-axis.
The amplitude and phase signals of the vertical component of secondary field when scanning over cracks with different depths of 0.1, 0.3, 0.5, 1.0, 1.5, and 1.8 mm with the 40 kHz excitation frequency. The lift-off distance is 0.2 mm.
The signal change of the proposed probe on a 1.5 mm deep crack with different lift-off distances from 0.2 to 1.3 mm at the 45 kHz excitation frequency: (a) amplitude distribution near the crack, (b) reduction in the peak amplitude with increasing lift-off.
The amplitude and phase response of the EC signals on a crack with a 0.5 mm width and 1.5 mm depth buried at h = 0, 0.095, and 0.285 mm on the aluminum plate with increasing frequencies. (a) Peak amplitude and (b) corresponding phase.
The amplitude and phase response of the EC signals on a crack with a 0.8 mm width and 15 mm length located respectively on the first and second layers of the two- and three-layer PCB samples with increasing frequencies. (a) Peak amplitude and (b) corresponding phase.
To investigate the relationship between the EC signals and the crack depths, the peak values of the amplitude and phase in Figure 16, Figure 17 and Figure 18 are analyzed for various buried depths, as shown in Figure 19. It is found that both the changes in amplitude and phase increase linearly with the crack depth for the surface and buried cracks when the crack depth is less than 1 mm. For both the amplitude and phase signals, the detection of the surface cracks exhibits the highest sensitivity and the sensitivity decreases gradually with the increasing buried depth of 0.095 and 0.285 mm, as shown in Figure 19a,b. The experimental results are qualitatively in agreement with simulated signals based on the design parameters of the proposed probe.
Relation of the amplitude and phase signals to crack depth for flaws buried at h = 0, 0.095, and 0.285 mm on an aluminum specimen. (a) The change in the amplitude signal and (b) the change in the phase signal.
Determining the spatial resolution of the probe. (a) The photograph of the sample with the 23 artificial cracks with the increasing distance between cracks of a 0.3 mm arithmetic progression, (b) the 1D scanning result of the proposed probe, and (c) the 1D scanning result of the coil-based probe.
Most of the remote controls have a screw inside the battery cover. Unscrew it and then separate the two halves of the control (the top and bottom plastic parts) gently. Be careful not to crack any plastic parts. 2ff7e9595c
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