Review of Identification Methods for Early-Stage Cracking in Solids

ABSTRACT Cracking is a predominant factor in engineering accidents, often leading to catastrophic failures. The evolutionary process of cracks in materials starts at the microscopic level, expands at the mesoscale, and culminates in failure at the macroscale. Early detecting cracks and monitoring of crack development are crucial for interrupting the sequence of risk propagation and preventing structural accidents. The detection and growth tracking of cracks, both in laboratories and in engineering structures, have garnered extensive research attention. This study provides a systematic review of identification methods for early-stage cracking in solids, encompassing technologies for detecting opening cracks and monitoring their progression. It details the principles and applicable materials of these methods, highlighting the advantages and disadvantages of identifying microcracks or tracking their growth in various materials. In conclusion, the article summarizes microcrack identification methods and outlines future research directions in three key areas: large-area, visual, and intelligent identification capabilities. This review offers valuable insights into the integration of multiple technologies, facilitating efficient identification of microcracks in situ and in laboratory settings.