Constitutive Analysis on Deformation Behavior of XF1700 Ultra-high Strength Low Alloy Steel in Perceptive of Adiabatic Temperature Rise and Strain

The deformation behavior of an ultra-high strength low alloy steel (commercial name: XF1700) at strain rates 0.001/s, 0.1/s (quasi-static), 922/s, 5962/s, 6000/s (dynamic) and temperatures 25, 100, 200 and 400 degrees C by using Split-Hopkinson pressure bar (SHPB) compression test have been investigated in the presented work. The results revealed that at 400 degrees C temperature and 6000/s strain rate, the work hardening remains dominant over thermal softening and could be tracked through sample surface which exhibited fractures but didn't lead to failure of sample. Elaborating this deformation behavior, a modified Johnson-Cook (JC) model for elastic-plastic behavior aided by Z parameter had been formulated based on the combined effect of strain and temperature. Furthermore, SEM images of SHPB samples divulged that at different temperatures (100, 200 and 400 degrees C) and 6000/s strain rate, different modes of plastic deformation like slip, twinning and shear bands are operative accordingly however, at 400 degrees C adiabatic temperature rise enabled the occurrence of adiabatic shear bands only. These adiabatic shear bands led to crack initiation and propagation but not failure, thus supporting the role of adiabatic temperature rise. By data comparison of predicted values obtained from modified JC model (MJC) and values from original JC model (OJC) with experimental values, MJC was found to be in better agreement with experimental values than OJC. The overall R value for MJC model is 0.9925 and for OJC is 0.9937, whereas, AARE% for MJC model is 2.33% and for OJC model is 5.27%.

Automated summary

The present work investigates the deformation behavior of an ultra-high strength low alloy steel under different strain rates and temperatures. The results reveal the dominance of work hardening over thermal softening at high temperature and high strain rate. Different modes of plastic deformation, such as slip, twinning, and shear bands, are observed at different temperatures and strain rates. The occurrence of adiabatic shear bands at high temperature leads to crack initiation and propagation. The modified Johnson-Cook model shows better agreement with experimental values compared to the original Johnson-Cook model.