Eur. Phys. J. Special Topics 225, 409-421 (2016)
https://doi.org/10.1140/epjst/e2016-02638-3

Regular Article

Strain rate effects on the mechanical behavior of two Dual Phase steels in tension

¹ DynaMat Laboratory – University of Applied Sciences of Southern Switzerland, 6952 Canobbio, Switzerland
² Department of Mechanical Engineering, National Institute of Technology, Patna 800 005, Bihar, India
³ Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Torino, Italy
⁴ Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi 110016, India

^a e-mail: ezio.cadoni@supsi.ch

Received: 25 August 2015
Revised: 12 February 2016
Published online: 14 March 2016

Abstract

This paper presents an experimental investigation on the strain rate sensitivity of Dual Phase steel 1200 (DP1200) and Dual Phase steel 1400 (DP1400) under uni-axial tensile loads in the strain rate range from 0.001 s⁻¹ to 600 s⁻¹. These materials are advanced high strength steels (AHSS) having high strength, high capacity to dissipate crash energy and high formability. Flat sheet specimens of the materials having gauge length 10 mm, width 4 mm and thickness 2 mm (DP1200) and 1.25 mm (DP1400), are tested at room temperature (20^∘C) on electromechanical universal testing machine to obtain their stress-strain relation under quasi-static condition (0.001 s⁻¹), and on Hydro-Pneumatic machine and modified Hopkinson bar to study their mechanical behavior at medium (3 s⁻¹, and 18 s⁻¹) and high strain rates (200 s⁻¹, 400 s⁻¹, and 600 s⁻¹) respectively. Tests under quasi-static condition are performed at high temperature (200^∘C) also, and found that tensile flow stress is a increasing function of temperature. The stress-strain data has been analysed to determine the material parameters of the Cowper-Symonds and the Johnson-Cook models. A simple modification of the Johnson-Cook model has been proposed in order to obtain a better fit of tests at high temperatures.

Finally, the fractographs of the broken specimens are taken by scanning electron microscope (SEM) to understand the fracture mechanism of these advanced high strength steels at different strain rates.