In the past decades the steel industry has developed Advanced High Strength Sheet (AHSS) steels with improved formability, crashworthiness and high strength-to-weight ratios in response to demands for lighter, fuel efficient cars with improved passenger safety [1]. An important class of these steels are Dual Phase (DP) steels which combine the toughness of ferrite and strength of martensite to produce steel grades with viable mechanical properties. An important aspect in the development and advancement of these steels is to understand the response of DP steels when subjected to high speed forming or crash conditions which expose the sheet steel to high strain rates resulting in dynamic deformation and fracture [2].

The High Strain Rate lab (Dr. Naresh Thadhani) and the Stereology lab (Dr. Arun Gokhale) are currently involved in a joint effort to understand the effects of strain rate and microstructure in the operative fracture mechanisms of commercial DP steels with protective coatings and complex microstructures. The study focusses on employing Streological techniques to quantify fracture surfaces obtained under various loading conditions to reveal mechanistic information regarding the fracture and tying it back to its microstructure. The results of this work will be useful for the design and development of DP steels with superior formability and crashworthiness.

[1] Bhattacharya, Debanshu. “Developments in advanced high strength steels.” The JointInternational Conference of HSLA Steels. 2005.

[2] Huh, Hoon, et al. “Dynamic tensile characteristics of TRIP-type and DP-type steel sheets for an auto-body.” International Journal of Mechanical Sciences 50.5 (2008): 918-931.