Modification of the MTS model for high strain-rate behavior of TI-6AL-4V

The Mechanical Threshold Stress (MTS) model provides excellent predictive capabilities for the material constitutive response for a wide range of temperatures and strain rates. However, the MTS model fails to capture the rapidly increasing yield stress at high strain rate behavior as the deformation controlling mechanism transitions from thermal activation to drag mechanisms, only capturing the linear behavior. Further, the model typically over predicts the flow stress behavior at yield and post yield due to its use of a constant work hardening rate parameter derived from the stress-strain response at constant saturation stress. An alternative approach to fitting portions of the MTS model is investigated and mathematical models are developed to address these issues. The results show that with appropriate experimental data, the mechanical threshold stress and work hardening rate parameters within the MTS model can quite easily and accurately be modified to extend applicability to high strain rate behavior and more accurately model the initial flow stress behavior at early work hardening rates without modification of the functions core to the MTS model itself.

Automated summary

The Mechanical Threshold Stress (MTS) model is effective in predicting the material constitutive response for a wide temperature and strain rate range. However, it fails to capture the rapidly increasing yield stress at high strain rates and over predicts the flow stress behavior at yield and post yield. To address these issues, an alternative approach to fitting portions of the MTS model is explored and mathematical models are developed. The results show that with appropriate experimental data, the MTS model can be modified to accurately extend its applicability to high strain rate behavior and improve the modeling of initial flow stress behavior without changing its core functions.