Materials deform as external loads such as force or heat are applied. Any material that resists such deformation and is able to regain its original shape, can be said to be “elastic”. Conversely, plasticity refers to the ability of a material to retain its deformed shape after external loads are removed. While the amount of applied force determines whether a material has elasticity or plasticity, as a general rule, plasticity increases proportionately to the extent of external load imposed. Plasticity is a highly complex phenomenon that requires a sophisticated understanding of the multiple phases of a material – all the way from its microscopic atoms to its macroscopic appearance.

The Materials Mechanics Lab (MML), directed by Professor Frederic Barlat, at the Graduate Institute of Ferrous & Energy materials Technology, POSTECH, develops mathematical models to deepen our understanding on the plasticity of metals. Specifically, the Lab focuses on Advanced High-Strength Steel (AHSS) which delivers strength that far exceeds that of ordinary metals. AHSS is widely adopted in the automobile industry as its exceptional strength helps safeguard passengers while reducing the weight of vehicles to improve fuel efficiency and contribute to the mitigation of exhaust gas emissions.

Despite the advantages of AHSS, its very strength can occasionally become its greatest enemy, which makes it all the more difficult to morph AHSS into specified shapes compared to general metal. Conventional metal forming methodologies simply cannot be done with AHSS because it have different mechanical properties compared to conventional metals. This is what prompted the MML to explore the plasticity of AHSS in partnership with academia, research institutes, and businesses the world over by developing innovative experimentation techniques and mathematical models that deploy cutting-edge algorithms.

One of the mathematical models developed by the Lab was recognized as a global standard model used to analyze the plasticity of AHSS. World Auto Steel, the automotive group of the World Steel Association, released a new version of the AHSS Application Guidelines this year, and it introduced ‘Homogenous Anisotropic Hardening (HAH)’, a plasticity analytical model developed by the Lab, as a standard model. The HAH model was first proposed back in 2011, and by last year, it had been revised four times. Nowadays, researchers at the Lab are stepping ahead to perfect it even further.

Also, the Lab has maintained a close partnership with POSCO. Findings generated from scientific research that is deeply rooted in physics, mechanics and thermodynamics are readily applied as a tool to design and manufacture steel products at POSCO. Its quest for basic research goes on to deliver practical value through its industrial application.

“We will continue to work to engineer solutions that are both scientifically rigorous and practically applicable”, Professor Barlat commented, adding “We will also focus on finding solutions for new applications such as EV frames and battery cases, along with fuel cell bipolar plates”.