Fatigue & Fracture of Engineering Materials & Structures最新文献

A strain-controlled low-cycle nonproportional multiaxial loading test, including both constant amplitude and variable amplitude loading, was conducted on AISI 304 stainless steel to investigate the load sequence effect on fatigue behavior. Under constant amplitude loading, the cyclic stress response exhibited initial hardening, with additional hardening induced by nonproportional loading. Under variable amplitude loading, the load sequence effect did not alter the hardening behavior but had contrasting effects on fatigue life depending on the loading characteristics. In a high-low loading, the stable stress amplitude during the low-strain stage increased significantly, leading to a reduction in fatigue life. In contrast, in a low-high loading, both the stress response and fatigue life remained unchanged. The load sequence effect under different loading conditions was analyzed in detail based on variations in stress amplitude and nonlinear damage accumulation. The fatigue life evaluation capabilities of various nonlinear damage accumulation models were compared with the linear damage model.

A strain-controlled low-cycle nonproportional multiaxial loading test, including both constant amplitude and variable amplitude loading, was conducted on AISI 304 stainless steel to investigate the load sequence effect on fatigue behavior. Under constant amplitude loading, the cyclic stress response exhibited initial hardening, with additional hardening induced by nonproportional loading. Under variable amplitude loading, the load sequence effect did not alter the hardening behavior but had contrasting effects on fatigue life depending on the loading characteristics. In a high-low loading, the stable stress amplitude during the low-strain stage increased significantly, leading to a reduction in fatigue life. In contrast, in a low-high loading, both the stress response and fatigue life remained unchanged. The load sequence effect under different loading conditions was analyzed in detail based on variations in stress amplitude and nonlinear damage accumulation. The fatigue life evaluation capabilities of various nonlinear damage accumulation models were compared with the linear damage model.

Traditional models such as the equivalent strain model and the critical plane model have been widely applied to predict multiaxial fatigue life but still are continuously improved in practical engineering scenarios. To find better and more universal model, a deep symbolic regression framework is proposed to generate multiaxial fatigue life prediction models that integrate physical interpretability with high predictive accuracy through the use of a recurrent neural network and policy gradient optimization. Compared with the equivalent strain model, the maximum shear strain model, and the critical plane model, the proposed method demonstrates the superior predictive performance for pure titanium, BT9 and TC4 alloys. Furthermore, it also shows strong generalization capability in cross-material validation involving PA38-T6 aluminum alloy, GH4169 alloy, and S460N steel. The proposed framework provides a novel pathway for advancing the development of fatigue modeling.

The durability of additively manufactured below-knee prosthetic sockets is essential for ensuring long-term comfort and functional reliability. This study investigated fatigue behavior through S–N curve analysis, finite element analysis (FEA), and experimental validation. A power-law relationship between alternating stress and cycles to failure was derived from material testing, with constants obtained using nonlinear regression. FEA of a 4-mm thick ABS socket under cyclic loading identified high-stress concentrations in the distal region, indicating susceptibility to fatigue failure. Experimental fatigue testing confirmed these findings, with failure occurring at approximately 250,000 cycles, within 15.08% of the predicted 212,310 cycles. Additional simulations for 3-, 5-, and 6-mm thicknesses demonstrated that increasing wall thickness enhanced fatigue life but introduced added weight. These results highlight the need to balance durability and mass, emphasizing optimization of wall thickness and reinforcement of critical regions to enhance fatigue performance while preserving user comfort.

The durability of additively manufactured below-knee prosthetic sockets is essential for ensuring long-term comfort and functional reliability. This study investigated fatigue behavior through S–N curve analysis, finite element analysis (FEA), and experimental validation. A power-law relationship between alternating stress and cycles to failure was derived from material testing, with constants obtained using nonlinear regression. FEA of a 4-mm thick ABS socket under cyclic loading identified high-stress concentrations in the distal region, indicating susceptibility to fatigue failure. Experimental fatigue testing confirmed these findings, with failure occurring at approximately 250,000 cycles, within 15.08% of the predicted 212,310 cycles. Additional simulations for 3-, 5-, and 6-mm thicknesses demonstrated that increasing wall thickness enhanced fatigue life but introduced added weight. These results highlight the need to balance durability and mass, emphasizing optimization of wall thickness and reinforcement of critical regions to enhance fatigue performance while preserving user comfort.

Traditional models such as the equivalent strain model and the critical plane model have been widely applied to predict multiaxial fatigue life but still are continuously improved in practical engineering scenarios. To find better and more universal model, a deep symbolic regression framework is proposed to generate multiaxial fatigue life prediction models that integrate physical interpretability with high predictive accuracy through the use of a recurrent neural network and policy gradient optimization. Compared with the equivalent strain model, the maximum shear strain model, and the critical plane model, the proposed method demonstrates the superior predictive performance for pure titanium, BT9 and TC4 alloys. Furthermore, it also shows strong generalization capability in cross-material validation involving PA38-T6 aluminum alloy, GH4169 alloy, and S460N steel. The proposed framework provides a novel pathway for advancing the development of fatigue modeling.

Fatigue loading tests coupled with synchronized acoustic emission detection are utilized to systematically reveal the crack initiation, propagation, and coalescence in multiple fissure contained marble. Key findings reveal that fissure angle (α) and rock bridge inclination (β) critically influence volumetric deformation, energy dissipation, damage evolution, and failure patterns. Results demonstrate that higher rock bridge orientations (e.g., β = 135°) enhance fatigue resistance, while lower fissure angles (e.g., α = 30°) accelerate damage accumulation. AE parameters (counts, energy, b-value, amplitude) are influenced by the fissure and rock bridge configuration. The width of high-frequency band increases with increasing rock bridge segments, indicating late instability waring. Post-test morphology description confirms tensile-dominated fractures in low-rock bridge orientation and high fissure angle samples; however, shear-tensile mixed failure occurs in relatively high-bridge orientation specimens. It is suggested that fissure communication is limited and severe fracture at rock bridge segment occurs for a sample having high rock bridge orientation.

Fatigue loading tests coupled with synchronized acoustic emission detection are utilized to systematically reveal the crack initiation, propagation, and coalescence in multiple fissure contained marble. Key findings reveal that fissure angle (α) and rock bridge inclination (β) critically influence volumetric deformation, energy dissipation, damage evolution, and failure patterns. Results demonstrate that higher rock bridge orientations (e.g., β = 135°) enhance fatigue resistance, while lower fissure angles (e.g., α = 30°) accelerate damage accumulation. AE parameters (counts, energy, b-value, amplitude) are influenced by the fissure and rock bridge configuration. The width of high-frequency band increases with increasing rock bridge segments, indicating late instability waring. Post-test morphology description confirms tensile-dominated fractures in low-rock bridge orientation and high fissure angle samples; however, shear-tensile mixed failure occurs in relatively high-bridge orientation specimens. It is suggested that fissure communication is limited and severe fracture at rock bridge segment occurs for a sample having high rock bridge orientation.