Dr. Haifeng Zhai the research focuses on advancing the fundamental and applied understanding of the mechanical behavior of metallic materials, with emphasis on fatigue life prediction, microstructural evolution, and deformation mechanisms under complex loading conditions. The work integrates experimental investigations with high-fidelity computational modeling approaches—including crystal plasticity finite element modeling (CPFEM) and phase-field (PF) simulations—to uncover the interactions between microstructure, defects, and loading history in determining fatigue performance. Significant contributions include developing predictive frameworks for fatigue life in additive-manufactured alloys by examining the role of defects, anisotropy, and overload effects on crack initiation and propagation. The research further establishes rapid fatigue prediction methodologies using phase-field models to capture microstructural evolution under varied laser scanning strategies, enabling improved process–structure–property relationships. Systematic experimental and simulation studies on 316L stainless steel under multiple overload conditions have provided new insights into cyclic deformation behavior and damage evolution pathways. Active involvement in national research projects has supported the formulation of new computational–experimental strategies for modeling fatigue mechanisms with enhanced accuracy and efficiency. Overall, the research advances the scientific understanding of fatigue behavior in engineered materials and contributes to the development of predictive tools essential for structural reliability, durability assessment, and materials design.