http://yetl.yabesh.ir/yetl1/handle/yetl/19062 2026-04-19T13:12:44Z 2026-04-19T13:12:44Z Li, Yafeng Sun, Yulin Li, Jiarui Zhang, Jian Gao, Hongfei Wang, Rongzhen Zhang, Jing http://yetl.yabesh.ir/yetl1/handle/yetl/4310462 2026-02-17T21:40:27Z 2025-01-01T00:00:00Z

Discrete Element Modeling of Fracture Behavior of Thermal Barrier Coatings Under Bending Conditions Li, Yafeng; Sun, Yulin; Li, Jiarui; Zhang, Jian; Gao, Hongfei; Wang, Rongzhen; Zhang, Jing The bending-driven failure test is a reliable and efficient method for evaluating the quality and load-bearing capacity of thermal barrier coatings (TBCs). This study utilizes the discrete element method (DEM) to examine the damage evolution behavior and mechanical properties of TBCs with two different coating thicknesses under four-point bending (4PB) conditions at the microscale. The results reveal that during the bending process, both thin and thick coatings experience tensile instability fractures and the formation of transverse cracks perpendicular to the interface, with crack spacing ranging from approximately one to two times the coating thickness. Thicker coatings exhibit larger crack spacing and a significantly higher delamination damage evolution rate at the interface compared to thinner coatings, displaying more pronounced delamination characteristics. While thick coatings demonstrate stronger deformation resistance, their higher bending modulus and load-bearing capacity lead to the accumulation of more cracks under equivalent strain conditions, increasing the risk of crack propagation and failure. Additionally, the pores in the coating's microstructure promote crack branching and deflection, resulting in an expanded fractured area and a negative impact on the TBC system's lifespan. This study also analyzes variations in the load–displacement curve, particle contact states, strain energy, and acoustic emission counts. By integrating experimental results, it explores the relationship between different load stages and coating damage evolution. These findings provide a theoretical basis for identifying coating failure modes in 4PB tests and offer valuable insights for the design and optimization of TBC performance.

2025-01-01T00:00:00Z Parasiz, Sunal A. http://yetl.yabesh.ir/yetl1/handle/yetl/4310455 2026-02-17T21:40:14Z 2025-01-01T00:00:00Z

A New Model That Considers the Gradual Change in Local Crystalline Geometry to Account for Grain Boundary Hardening Parasiz, Sunal A. In this study, a new model is proposed to account for grain boundary hardening. The gradual change in the local crystalline geometry constrained by grain boundaries, where dislocations glide and are stored within polycrystalline grains during plastic deformation, is considered by subdivision of the grains in the form of crystalline strips. Within this context, the local dislocation densities, corresponding local strengths, and even the local strains developed within polycrystalline grains could be computed for each crystalline segment for a given small amount of plastic strain. For this purpose, the Orowan equation was implemented together with Taylor polycrystalline deformation and Taylor hardening models. It was also assumed that, rather than strain, the deformation within polycrystalline grains is controlled by stress. Based on these, a new model was developed. The model was verified by comparing the predicted results with the experimental results found in the literature for several pure face centered cubic (FCC) materials, and a good agreement was found. In addition, based on the current model, three alternative equations were also derived to compute yield strength in terms of plastic strain and the reciprocal of grain size. Nevertheless, the model proposed in this study provides new insights in terms of understanding grain boundary hardening.

2025-01-01T00:00:00Z Kashiwa, Youta Caputo, Alexander N. Bridges, Alex Shingledecker, John Neu, Richard W. http://yetl.yabesh.ir/yetl1/handle/yetl/4310445 2026-02-17T21:39:45Z 2025-01-01T00:00:00Z

Assessing Creep–Fatigue Interactions in Wrought and LP-DED-Processed 316 Stainless Steel Kashiwa, Youta; Caputo, Alexander N.; Bridges, Alex; Shingledecker, John; Neu, Richard W. This study examines the low-cycle fatigue (LCF) and creep–fatigue (CF) behavior of wrought 316L and 316H stainless steels to develop acceptance criteria for accelerated testing of additively manufactured (AM) stainless steels. New LCF and CF data were generated between 550 and 700 °C, focusing on the impact of temperature, control mode, and hold time on fatigue life. Life assessment methods, including time fraction (TF), ductility exhaustion (DE), and stress-modified DE (SMDE), were evaluated for their applicability to nuclear code cases. Results highlight that conventional accelerated CF tests often lead to fatigue-dominated failures due to insufficient hold times. DE and SMDE models correlated more effectively with experimental data than TF, particularly when non-damaging viscous strains were excluded. Testing laser powder-directed energy deposition (LP-DED) 316H revealed non-conservative life predictions across all models, contrasting with the conservative predictions for wrought 316L and 316H, despite comparable LCF and creep properties. These findings underscore the need to refine accelerated CF test protocols to better capture damage mechanisms in AM materials.

2025-01-01T00:00:00Z Mahesh, S. Anil Chandra, A. R. Ravikumar, L. Manjunatha, C. M. http://yetl.yabesh.ir/yetl1/handle/yetl/4310434 2026-02-17T21:39:23Z 2025-01-01T00:00:00Z

FCGR-Net: A Novel Approach to Predict Fatigue Crack Growth Rate Behavior in Metals Using Machine Learning Mahesh, S.; Anil Chandra, A. R.; Ravikumar, L.; Manjunatha, C. M.

2025-01-01T00:00:00Z