Characterization and Modeling of Ductile Damage in Structural Steel at Low and Intermediate Strain Rates

In this research, the concept of continuum damage mechanics (CDM) was implemented to evaluate damage initiation and evolution in structural steel rebars at low and intermediate loading rates. The work was divided into experimental and theoretical phases to evaluate the ductile damage behavior. The experimental part involved uniaxial tensile tests for steel bars at the ambient temperature over a range of strain rates between 3.0 x 10(-4) and 0.1 s(-1). Scanning electron microscopy (SEM), coupled with image processing techniques, was utilized to characterize the damage at several loading stages. The theoretical part of this paper introduced a new energy-based isotropic damage model capable of capturing the evolution of damage throughout the deformation process. The proposed damage model was verified via comparisons with the present SEM results and with other data available in the literature. The comparisons showed good agreement, and results from both approaches indicated that cracks and voids intensified significantly with the increase of plastic strain and strain rates. Results proved that the new procedure was satisfactory for damage characterization and offered good simplifications. DOI: 10.1061/(ASCE)EM.1943-7889.0000415. (C) 2012 American Society of Civil Engineers.