Process-performance-prediction integration for fatigue life improvement technologies: An implementation in cold expansion of hole structures

In this work, the process-performance-prediction integration (3P integration) is developed to improve the fatigue life and reveal the strengthening mechanisms of holed structures after a novel cold expansion process (CEP), where a specific dual-scale modelling approach is proposed to refine the close-loop system. In macro-scale simulation, the cyclic deformation behavior is addressed by an isotropic constitutive model, where the resid-ual stress distribution extracted from CEP simulation is set as initial stress field. The local deformation histories in weak region calculated from the macro-scale simulation are supplied to micro-scale simulation as boundary conditions. The micro-scale simulation solves the local damage evolution of holed structures after CEP by using a modified crystal plasticity theory that grain size effect is considered. Excellent agreements between experimental data and predicted results in terms of fatigue life and damage mechanisms prove the robustness and accuracy of the proposed dual-scale modelling approach. Finally, a feedback link in 3P integration is established by the proposed approach combined with different residual stresses and plastic layers. The significant fatigue life improvement is mainly ascribed to residual stress, while plastic layer plays a synergistic role in life performance.

Automated summary

In this work, a process-performance-prediction integration (3P integration) is developed to improve the fatigue life and reveal the strengthening mechanisms of holed structures after a cold expansion process (CEP). A dual-scale modelling approach is proposed to refine the close-loop system. The macro-scale simulation addresses the cyclic deformation behavior using an isotropic constitutive model, while the micro-scale simulation solves the local damage evolution of holed structures after CEP using a modified crystal plasticity theory. Excellent agreements between experimental data and predicted results prove the robustness and accuracy of the proposed dual-scale modelling approach. A feedback link in 3P integration is established by combining the proposed approach with different residual stresses and plastic layers. The significant improvement in fatigue life is mainly attributed to residual stress, while plastic layer has a synergistic role in life performance.