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To assess the contribution of residual stress to the improvement of high‐cycle fatigue (HCF) properties, HCF tests are performed on Ti‐6Al‐4V specimens with different residual stress levels but no other evident surface state modification induced by machining. Results indicate that compressive residual stress induced by machining significantly improves the HCF performance of Ti‐6Al‐4V specimens. Of all the specimens, the fatigue strength of specimens with a surface residual stress level of −400 MPa is increased by approximately 16.4%. Furthermore, to accurately predict the fatigue life based on three mean stress correction equations (e.g., Walker, Goodman, and Smith–Watson–Topper), the method of reducing surface residual stress by a reduction factor and then adding to the mean stress is proposed. A reduction factor of 0.55 is found to be appropriate for the alloy under the test condition, with majority of the predicted data falling within a factor of three scatter band. Highlights: Isolate residual stress from other surface integrity parameters by machining.Compressive residual stress improves both the fatigue life and strength.Effect of residual stress is considered by introducing a reduction factor in mean stress.Develop a life prediction method based on mean stress correction model. [ABSTRACT FROM AUTHOR]

Laser surface texture (LST) technology can be used to increase the adherence of thermal barrier coating (TBC). The primary research method is to conduct a large number of laser experiments to determine the optimal texture parameters. To minimize costs and enhance efficiency, in the current work, five types of circular pit textures were summarized; the plane strain model was established using the transient thermomechanical coupling finite element method; the residual stress field after spraying was used as the prestress field; the influence of different textures on the distribution of the residual stress field after a thermal cycling was analyzed; and the propagation law of cracks in the coating was predicted. The current work focuses on: (1) The two-dimensional cross-sectional morphology of texture; (2) the principal stress s 22 perpendicular to the interface (resulting in mode I interface crack) and the shear stress s 12 parallel to the interface (resulting in mode II interface crack); (3) texture variables—diameter, depth, and spacing. The results revealed that after thermal cycling, the texture in the ceramic top coat (TC) bore tensile stress of around 350 MPa. Both sides of the pit in the metallic bond coat (BC) bore tensile stress, while the bottom bore compressive stress. Among them, the positive tensile stress of the texture with a sinusoidal section was the greatest, whereas the shear stress was the least. The maximum stress in texture increased as the diameter and depth increased, while the minimum principal stress was obtained by adjusting the spacing among the adjacent textures. The stress level in the coating was reduced by selecting the appropriate texture morphology, and the crack propagation was more complex, that is, it took a longer time before reaching failure, which is expected to improve the life. [ABSTRACT FROM AUTHOR]

• The gradient porosity anode is adopted for the design of a planar SOFC. • The gradient porosity anode can reduce the maximum first principal stress of the components by 20.0 % at room temperature and 44.9 % under the operating condition. • The influence of gradient porosity anodes on the residual stress is analyzed for the first time. • The residual stress and thermal stress of the anode-supported SOFC were analyzed, and the effect of porosity change on stress state was analyzed. Residual stresses and thermal stresses in solid oxide fuel cells (SOFCs) are the main factors to induce the reliability degradation including delamination, cracking and damage. Anode porosity is potential controller to the stresses due to the effects on the mechanical compatibility of SOFC components and electrochemical reaction rate. Herein, we establish a three-dimensional SOFC multi-physics field coupling model to explore the electrochemical and mechanical performance of SOFCs employing gradient porosity anode versus uniform porosity anode. The influence of porosity on the carrier conduction, gas flow, gas diffusion and transfer, and heat transfer in porous composite electrodes are considered. The results indicate that the gradient porosity anode significantly enhances the mechanical compatibility of SOFC components while maintaining high electrochemical performance. At room temperature, the dangerous area of residual stress occurs at the anode, and the gradient porosity anode can reduce the maximum first principal stress of the anode by 20.0 %. Under the operating condition, the dangerous area of thermal stress occurs in the electrolyte, and the gradient porosity anode can reduce the maximum first principal stress of the electrolyte by 44.9 %. Additionally, it significantly alleviates stress concentration in the SOFC. This study provides a way to optimize the reliability of SOFCs by controlling the anode porosity. [ABSTRACT FROM AUTHOR]