Thermo-mechanical Behavior of C45 Steel over a Range of Temperatures and Loading Rates

Abstract

This research aims to describe the behavior of C45 structural steel that is increasingly used in the oil and gas industry in environments where high temperatures and strain rates are applied. The primary goal is to introduce a systematic understanding of the thermo-mechanical ductile failure that occurs due to accumulation of micro-cracks and voids along with plastic deformation to enable proper structural design; and hence provide better serviceability. To achieve such a goal, a series of quasi-static tensile tests are conducted on C45 steel at a range of temperatures between 298 °K and 923 °K for strain rates up to 0.15s-1. Drop hammer dynamic tests are also performed considering different masses and heights to study the material response at higher strain rates. The stress-strain results extracted from the experimental tests are utilized to identify the material constants for the Johnson-Cook (JC) constitutive model to describe the flow stress of this type of high strength steel. Scanning electron microscopy (SEM) images are also taken to quantify the density of micro-cracks and voids of each fractured specimens which are needed to define the evolution of internal defects using an energy based damage model. The coupling effect of damage and plasticity is incorporated into the finite element (FE) software ABAQUS to develop a robust FE model that can accurately simulate different structural responses of this material. Good correlation was observed between the proposed models predictions and the experimental observations.