Performance of MMFX Steel Rebar at Elevated Temperatures

Corrosion resistant alloy steel (MMFX) reinforcing bar is increasingly utilized in structural engineering applications due to their high yield strength and corrosion resistance. This paper aims to characterize the thermomechanical response of MMFX rebar by examining their elastic and inelastic properties at a wide range of temperatures and strain rates. To achieve that, a series of quasi-static tensile tests at rates of 0.0015, 0.015, and $0.15{\mathrm{s}}^{-1}$ were conducted at a range of temperatures between room temperature and 650°C. In addition, dynamic tests were conducted at room temperature using a drop mass bench at strain rates of up to $500{\mathrm{s}}^{-1}$. Results showed that at room temperature, the flow stress of the MMFX steel alloy observed slight dependence on the quasi-static strain rate. However, the strain rate-sensitivity became more effective as the temperature increases with very active regions of dynamic strain aging encountered at different levels of strains, strain rates, and temperatures. Moreover, the reduction in the elastic properties was less than 18% at temperatures up to 450°C, then followed by a sharp decrease at 650°C. The stress–strain responses were utilized to identify the material constants for constitutive modeling. The Voyiadjis–Abed constitutive model was utilized to describe the material flow stress and was implemented into a finite-element (FE) model that was developed using ABAQUS version 2017. The FE model is capable of reproducing the experimental results and simulating the dynamic hammer-tests at room temperatures.