Public Defence in Mechanical Engineering, M.Sc. Zinan Li

This doctoral dissertation has uncovered why certain advanced high-strength steels (AHSS) are prone to edge cracking during manufacturing. Focusing on two widely used AHSS types from the first and third generation—dual-phase (DP) and Quenching and Partitioning (QP) steels—the research highlights the role of material anisotropy in edge fracture during forming processes. By looking closely at factors including material anisotropy, stress states and strain localization, edge cracks in DP steels are mainly due to strain localization introduced by anisotropy, while QP steels are more influenced by stress distribution and fracture limits. To address these issues, advanced numerical models are proposed, calibrated and validated through experimental data. This study led to the development of new, anisotropic fracture models for AHSS, which allows manufacturers to better predict edge fracture behavior and prevent fractures. This breakthrough offers valuable tools for the automotive industry, paving the way for designing stronger, more reliable materials, improving automotive safety and efficiency.

Doctoral Student: Zinan Li

Opponent: Prof. Sam Coppieters, KU Leuven, Belgium

Custos: Prof. Junhe Lian, Aalto University School of Engineering, Department of Energy and Mechanical Engineering 

The public defense will be organized in Lecture Hall TU2, Maarintie 8.

The thesis is publicly displayed 10 days prior to the defense in the publication archive Aaltodoc of Aalto University. 

Contact information of doctoral student: 

Doctoral theses in the School of Engineering: https://aaltodoc.aalto.fi/handle/123456789/49