Finally another insulation layer acting as a protection layer to

Finally another insulation layer acting as a protection layer to prevent moisture, which may also sustain temperatures of up to 150 ��C was coated, but not shown in Figure 1.Figure 1.(a) Configuration of FUT array: aperture (AFUT), element size (EFUT), height (HFUT), gap (GFUT) and pitch (PFUT). (b) Top and (c) bottom view of a 1D 16-element FUT array on a 75 ��m thick Ti foil.For the defect detection, another FUT array (element size: 10 mm �� 2 mm, gap: 1 mm) on a Ti foil of 75 ��m was also produced. In addition, the other smaller FUT array (element size: 9 mm �� 2mm, gap: 0.5 mm) on a thinner Ti foil of 35 ��m was also fabricated. The thicknesses of both two PZT-c films are about 80 ��m to tune the center frequency of each element within 7 and 8 MHz.3.?TheoryUsing the FUT array, the pitch-catch modes of the ith transmitter and the jth receiver can be performed for all elements to acquire the A-scan signal Aij(t), as shown in Figure 2. After storage of the full matrix of Aij(t), a post-processing algorithm can be applied to reconstruct the phased-array imaging. Based on the TFM [11,12] or the so-called sampling phased array algorithm [13], the synthesized signal Sj (x, t) captured by the jth receiver, which scatters from a target point x as waves generated by all transmitters with different time delays simultaneously arrive at the target point, is reconstructed as:Sj(x,t)=��iAij(t?tij)(1)where tij is time shift, tij = dij/V, and dij is the distance, dij = |x �C xi| + |x �C xj|. Here v is the longitudinal wave speed in medium, and xi is the position vector of the ith element. We assume Sj (x, t) is the real part of an Enzalutamide MDV3100 analytic signal. Therefore using the Hilbert transform, we can obtain the envelope of the analytic signal, and find the peak value for the jth receiver. Subsequently, the intensity of the response of multi-transmitters with multi-receivers for the target point x is calculated by combining these peak values of all receivers. Sweeping the inspected area, the phased-array imaging can be obtained to indicate the location of defect and bottom. Since the performance of each element is not the same, the calibration and normalization of these signals are necessary prior to the calculation of phased-array imaging.Figure 2.Schematic of TFM for pitch-catch signals of the ith transmitter and the jth receiver.4.?Experimental Results and DiscussionThe schematic of FUT array for ultrasonic measurement is shown in Figure 3(a). Figure 3(b) is the photo of our experimental setup for the ultrasonic measurements carried out at 150 ��C using an ultrasonic pulser-receiver system for the 1D 16-element FUT array 6 mm �� 3 mm and the gap between them is 1 mm (i.e., 4 mm pitch) on 75 ��m thick Ti foil, as shown in Figure 1(b).Figure 3.(a) Schematic and (b) experimental setup for ultrasonic measurements of FUT array on a metal block at 150 ��C.

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