An Experimental Method for Capturing Cyclic Deformation with Large Elastoplastic Strain Exceeding ±50% in Structural Steel

Abstract

Cyclic deformation with large elastoplastic strain appears in the ultimate behavior of steel structures during earthquakes. Accurate fracture simulation of structural steel components under large deformation is therefore critical for ensuring structural reliability and safety. An experimental method with a novel specimen geometry, composed of SM400 mild steel, was developed aiming to prevent detachment of the speckle‐pattern surface paint. A displacement‐controlled large‐amplitude cyclic loading experiment was conducted to investigate the elastoplastic behavior of the material, and full‐field strain distributions were captured using the digital image correlation (DIC). Experiment results revealed that the specimen experienced peak strain exceeding ±50%, indicating its ability to undergo large plastic deformation with asymmetric plastic flow due to geometric constraints. The observed large‐strain cyclic behavior provides valuable insight into the plastic deformation of SM400 structural steel under extreme loading conditions. These findings are crucial for identifying the material parameters of large‐strain elastoplastic constitutive models and contribute to more accurate, performance‐based evaluations and resilient designs of steel structures.