## 4 Simulation Analysis of the Designed Probes
### Simulation Analysis of Delamination Eddy Current Testing
#### 4.2.1 Simulation Analysis of Eddy Current Testing for Delamination of Various Dimensions  
In the simulation experiments, the delamination was located in the third layer (0\({}^{\circ}\) layer) of the CFRP sample shown in Figure 5, with the defect centers at x = y = 0. The specific defect parameters are shown in Tables 8 and 9. Eddy current testing was conducted through simulation of the delamination of different lateral dimensions and different thicknesses.  
Based on the previous analysis, the probe scanning mode shown in Figure 9a was selected for simulating the detection of delamination, scanning from both the top and bottom of the sample. The delamination detection results are shown in Figures 13 and 14. The signal variation curve shown in Figure 13 represents the curve of detection voltage difference changes obtained from top scanning, while Figure 14 shows the signal variation curves obtained from bottom scanning. Each point on the curve represents the voltage difference between when the probe detects the presence of a delamination in the CFRP sample along the scanning path shown in Figure 7 and when the probe detects no delamination in the CFRP sample. In the resulting figure, the center of the coil set is at the indicated probe position.  
Comparing the detection results from Figures 13 and 14, it can be observed that the detection voltage difference obtained from top scanning is greater than that from bottom scanning. This is because when scanning defects in Tables 8 and 9 from the bottom, the defects are farther away from the probe. As a result, the eddy currents within the CFRP sample decrease with increasing thickness, leading to smaller detection signals.  
From Figures 13a and 14a, it can be seen that for smaller lateral dimensions of delamination (Delamination 1 and 2), when the probe is directly above the delamination (x = 0 mm), the detection voltage difference reaches a peak. However, for larger lateral dimension delamination (Delamination 3), there is no peak in the detection voltage difference when the probe is directly above the delamination. This is because when the probe size differs significantly from the delamination dimension, it will reduce the probe's detection sensitivity to some extent. For delamination of different lateral dimensions, the relative position of the probe when the detection voltage difference rises and falls is different. The  
Figure 14: Detection voltage differences obtained from bottom scanning for different dimensions of delamination: (**a**) different lateral dimensions; (**b**) different thicknesses.  
Figure 13: Detection voltage differences obtained from top scanning for different dimensions of delamination: (**a**) different lateral dimensions; (**b**) different thicknesses.  
larger the lateral dimension, the closer the probe's position is to the front when the detection voltage difference rises. Therefore, quantitative evaluation of the lateral dimension of delamination can be achieved by calculating the relative position of the probe when the detection voltage difference rises and falls.  
From Figures 13b and 14b, it can be seen that the impact of different thicknesses of delamination on the detection voltage difference varies. When the thickness of the delamination is 0.05 mm, the detection voltage difference peak is the smallest, at 0.1814 V and 0.0284 V. As the thickness of the delamination increases, the peak detection voltage difference increases. When the delamination thickness is 0.15 mm, the detection voltage difference peak rises to 0.4950 V and 0.085 V. These results indicate that it is possible to quantitatively assess the thickness of the delamination by calculating the peak detection voltage difference during the detection process.