## 3 Experimental Methodology
Figure 5b is the Test Model 2 schematic and the technical description. For carrying the Test Model 2, eight PZTs were used. Five PZTs were glued in an aligned pattern on plate 1 (in green in Figure 6a), and three PZTs were glued in a misaligned pattern on plate 2 (in blue in Figure 6b). Figure 6c shows the red intersection area between the two plates. The misalignment was calculated to impose intersections of 100%, 40%, 12.5%, and 0%, with 100% completely aligned and 0% completely misaligned. Test Models 3 and 4 are the tensile tests, without temperature variation and with temperature variation, respectively. For this reason, two tensile testing machines were used to carry out the tests. Test Model 3 was performed in a robust servohydraulic tensile machine (Instron, model 8502) (Figure 7a), which withstands stresses of up to 100 kN. In this model, it is not possible to couple the climatic chamber due to the large dimensions of the machine and the limited space available in the climatic chamber. Therefore, the test was  
Figure 5: Schematic of the Test Model 2—the misalignment test. (**a**) Photograph of the thermal bath. (**b**) Test Model 2 diagram. (1) The test controller computer; (2) the thermal bath in which the specimen is allocated; and (3) the vector network analyzer which sends and receives signals S21. performed in this tensile machine to observe the UT communication around the specimen yield strength. According to the properties of the material and the stipulated geometry, this value is MPa, i.e., 1460 \(\upmu\)m/m. The maximum load used was 60 kN, generating a stress of 250 MPa, corresponding to 85.8% of the yield stress. This mechanical tension reached a maximum deformation of 1250 \(\upmu\)m/m. These deformations were applied in steps. The deformation was fixed for 2 min at each step due to the stability time of the stress tensor and data ultrasonic signal collection. The deformation values were 0, 125, 250, 375, 500, 625, 875, 1000, 1104, 1208, and 1250 \(\upmu\)m/m. The Test Model 3 diagram and the technical description are detailed in Figure 7b. The second tensile machine used is an Instron (model E10000) with a climatic chamber operating between \(-\)70 \({}^{\circ}\)C and 350 \({}^{\circ}\)C, temperature stability of \(\pm\)2 \({}^{\circ}\)C, and maximum static stress of 7 kN. The Model 4 tests were carried out in this setup, where ultrasonic communication was possible by applying mechanical strain at different temperatures. This machine only accepts loads up to 7 kN; for safety reasons, the maximum load of this test is 6 kN. According to the geometries of the specimen, this force generates a maximum mechanical stress of 25 MPa and a strain of 125 \(\upmu\)m/m, corresponding to 8.62% of the yield strength. As in the Model 3 tests, the stress is also applied gradually during the Model 4 tests. The active strain values were equal to 0, 21, 42, 63, 83, 104, and 125 \(\upmu\)m/m, and the temperatures were 40, 60, 80, 100, 120, and 140 \({}^{\circ}\)C. Figure 8a shows the photograph of the setup for the Model 4 tests. In the Model 3 and 4 tests, in addition to pre-processing,  
Figure 6: Representation of the instrumentation of the specimens for the alignment test. (**a**) The plate on the left, with five PZTs, is lined up in green. (**b**) Right plate, with three unaligned PZTs in blue. (**c**) The left and right plates overlapped, whereas red was the overlapping area. The white dots represented are spacers for centralizers to align the plates. Figure 7: Schematic of the Test Model 3—the tensile test without temperature variation. (**a**) Photograph of the tensile machine Instron, model 8502. (**b**) Test Model 2 diagram. (1) The test controller computer; (2) Instron model 8502; and (3) the vector network analyzer which sends and receives signals S21. the control computer also controls the Instron machine, applying the deformation for the indicated time or changing the temperature in the climatic chamber. Figure 8b summarizes, step-by-step, how this interaction is performed.