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To investigate the influence of residual stress on the fracture performance of T-joint welded joints in 6063 aluminum alloy, ABAQUS simulation was utilized to obtain the post-weld residual stress fields for different welding methods. A finite element model for toughness fracture of T-joints was established using the Johnson-Cook constitutive and damage models, aiming to analyze the impact of welding residual stress on fracture performance. The results indicate that under the same tensile rate, residual stress can lead to earlier fracture occurrence in the welded joints, thereby reducing the overall fracture performance. Among the different welding methods, the double-sided corner weld exhibits the best fracture performance, while the butt joint with a backing plate can effectively mitigate the influence of post-weld residual stress on fracture performance. Through the comparison of experiments and simulations, the material constitutive and damage parameters of each welding zone are verified, and the hardness test is carried out. The results indicate that the average hardness in the weld zone is approximately 63.8 HV, which is higher than the average hardness of 60.2 HV in the heat-affected zone. However, both the weld zone and the heat-affected zone have lower hardness values compared to the average hardness value of 81.5 HV in the base metal zone. Furthermore, it is observed that residual tensile stresses are predominantly distributed in the weld zone, which is one of the reasons contributing to the lower hardness at the center of the weld. [ABSTRACT FROM AUTHOR]

As a vital pathway for cellular energy production, mitochondrial fatty acid β-oxidation (FAO) is essential in regulating immune responses to bacterial pathogens and maintaining intracellular homeostasis in vertebrates. However, the specific role of FAO in antiviral innate immune response in macrophages remains insufficiently understood. In this study, virus infection simulated by poly(I:C) inhibited FAO, as indicated by the reduced expression of FAO-related genes and proteins in the head kidney of large yellow croaker, with similar results observed in poly(I:C)-stimulated macrophages. Then, inhibition of FAO by supplementary mildronate in vivo and etomoxir treatment in vitro revealed varying increases in the mRNA expression of antiviral innate immune response genes after stimulated by poly(I:C) in the head kidney and macrophages. Notably, etomoxir significantly facilitated the transcriptional up-regulation of the IFNh promoter by IRF3. Moreover, inhibiting FAO by knockdown of cpt1b promoted antiviral innate immune response triggered by poly(I:C) in macrophages. Conversely, activating FAO through overexpression of cpt1b or cpt2 significantly reduced the mRNA levels of antiviral response genes in macrophages stimulated by poly(I:C). Unlike etomoxir, cpt1b overexpression inhibited the transcriptional up-regulation of the IFNh promoter by IRF3. Furthermore, in vivo dietary palm oil feeding and in vitro exposure to palmitic acid inhibited the antiviral innate immune response triggered by poly(I:C) in the head kidney and macrophages, respectively. These effects were partly associated with FAO activation, as evidenced by etomoxir. In summary, this study elucidates FAO's critical role in regulating antiviral innate immune response in head kidney macrophages. These findings not only deepen insights into the interaction between metabolic remodeling and host immune responses, but also offer valuable guidance for developing nutritional strategies to improve antiviral immunity in aquaculture., (Copyright © 2024. Published by Elsevier Ltd.)