Distortion correction method for SEM images based on sampling moiré patterns and its application to characterization of the microscale fatigue crack propagation

Abstract Scanning electron microscopy (SEM) is a crucial technique for characterizing mechanical behavior at micro- and nano-scales. However, image distortions inherent to SEM can undermine the accuracy and reliability of these measurements, and thus, the distortion correction of image is essential for realizing precise measurement. In this study, a correction method for SEM image distortion based on sampled moiré has been developed to achieve high accuracy measurement of the deformation field. This method could effectively correct both time drift and spatial distortion of SEM image. Following the application of distortion correction, the average coordinate virtual displacement caused by spatiotemporal distortion can be corrected by over 80%. On this basis, nickel-based superalloy GH4169 was selected for microscale fatigue propagation experiments. An in-situ fatigue loading platform within the SEM was employed to observe the initiation and propagation of fatigue cracks in real time. The proposed correction method allowed for accurate measurement of microscale fatigue crack propagation parameters and quantitative characterization of the crack closure effect.