Fig. 1. Schematic diagram of method for transfer learning feature mapping

Fig. 2. Data set preprocessed by original images

Fig. 3. Comparison of four groups without and with surface defects, and red dotted line frame is location of defect

Fig. 4. Schematic diagram of construction method for simulation data set

Fig. 5. Comparison of accuracy and convergence of different activation functions on test data sets

Fig. 6. Comparison of accuracy and convergence of different network depths on test data sets

Fig. 7. Structure diagram of improved ResNet18 model

Fig. 8. Schematic diagram of transfer learning method

Fig. 9. Accuracy verification of transfer learning method