Experimental and numerical determination of the temperature of TWIP steel during dynamic tensile testing

Abstract

One of the most important factor affecting properties of TWIP steels is the heat generated from plastic work during deformation. As the significant temperature rise can lead to a reduction or cessation of the main deformation mechanism – twinning. Nevertheless, the determination of the exact temperature value appears to be especially difficult – mainly under dynamic conditions. The state of knowledge in this subject is not extensive, while in the case of deformation under dynamic conditions it is completely limited. That is why this paper presents the attempt to determine the amount of heat generated during deformation of the austenitic high-Mn TWIP steel – Fe–21Mn-2.55Al (wt.%) at the strain rate of 170 s−1. Firstly, the complexity of the issue was discussed. Then, two methods such as IR thermography and FEM were applied to determine this temperature. Moreover, the DIC technique was used to calculate the elongation of the sample and the strain rate obtained with the use of flywheel machine. The investigated steel exhibited a maximum true stress of ca. 1000 MPa, the deformation limit reached over 0.4, while the temperature in the necked region exceeded 200 °C. Similar temperature values in the necked area were obtained by means of FEM. Unfortunately, the IR measurements at relatively high frame rates can only be achieved for sub-window mode (reduced area) and a limited temperature range, while in the FEM necking starts when the sample is artificially narrowed. Both mentioned methods can be applied for determination of the temperature, but awareness of their limitations is essential.

Keywords

• TWIP steels
• IR camera
• Temperature
• Twinning
• Tensile specimen
• FEM