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The damage evolution and failure process of pre-corroded additive manufacturing AlSi10Mg through in-situ tensile experiments under an optical microscope and micro-scale digital image correlation（μ-DIC） were investigates . Combining the microscopic deformation field evolution，material microstructure，three-dimensional corrosion morphology and fracture microscopic morphology to analyze the initiation and propagation of micro-cracks in pre-corroded AlSi10Mg. The results show that the stress concentration around the corrosion pits and subsurface defects（caused by the additive manufacturing process） leads to the initiation of micro-cracks. There are multiple micro-cracks initiating at the same time，and the propagation and coalescence of micro-cracks originated from the key damage regions dominate the final failure of the specimen. Material micro-structure and corrosion morphology have an important influence on crack propagation.

To improve the current density distribution and electromagnetic performance of air-core inductors, a structural optimization method combining back-propagation(BP) neural network and genetic algorithm(GA) is proposed for the study of axial and radial spiral multi-winding inductors. The Monte Carlo method was used to extract the structural size samples of the inductors, and the training dataset was obtained through the finite element calculation of electromagnetic fields. Based on BP neural networks, nonlinear mapping models between the inductance value, volumetric inductance density, current distribution non-uniformity coefficient, and inductor structural parameters were constructed. A sensitivity analysis of the inductor inductance value affected by the structural parameters was conducted using the Sobol index calculation. Using the current distribution non-uniformity coefficient as the fitness function and the volumetric inductance density as the constraint condition, a genetic algorithm was applied to globally optimize the structural parameters of the inductor. The optimization results were verified through a finite element comparison. The results show that, under the requirement of satisfying the volumetric inductance density, the current distribution non-uniformity coefficient of the Axial Helical Inductor (AHI)-type inductor was reduced by 4.57% compared with the best sample in the sampling, while that of the Radial Helical Inductor (RHI)-type inductor was reduced by 5.33%, demonstrating the practicality of the BP-GA joint algorithm in the structural optimization design of inductors. [ABSTRACT FROM AUTHOR]

The fatigue cracking behavior in pre-corroded AA2024-T4 associated with three different levels of maximum stresses and stress ratios via three-dimensional digital image correlation (3D-DIC) was investigated. The spatial-temporal characteristic of crack initiation and propagation was visually displayed through strain field evolution, while the fracture morphology of determined key damage regions was further examined. Experimental results show that localized corrosion penetrated in the edges of specimens promotes fatigue crack initiation and affects crack nucleation location, accompanied with hydrogen embrittlement. Identified crack orientations (range 60°-68° from the loading direction) reveal that the early growth of fatigue crack can be described by KⅠ/KⅡ-mixed mode. Four typical failure modes (single crack fracture, multi-crack coalescence, multi-crack competition and multi-crack parallel growth) are observed and discussed.

Olivine, the most abundant mineral in the upper mantle, plays a key role in controlling the thermodynamic properties in the Earth's and planetary interiors, like the temperature distribution along the adiabatic geotherm. In this study, we conducted simultaneous high-pressure (P) and high-temperature (T) Raman measurements on a San Carlos olivine sample in an externally heated diamond-anvil cell (DAC). The intrinsic anharmonic parameters, ai, are calculated as functions of both pressure and temperature, and the isochoric (CV) and isobaric (CP) heat capacities are computed at various P-T conditions with the anharmonic correction. The harmonic heat capacities are CV = 807.7 J/kg/K and CP = 815.4 J/kg/K at ambient conditions, with anharmonic contribution of ΔC = 7.9 J/kg/K. Relative to the previous vibrational measurements conducted at high-P or high-T conditions, this simultaneous high-P-T experiment indicates that the anharmonic contribution to heat capacities is overestimated if the anharmonic parameters (ai) are treated as constants, as done previously. The pressure effect is marginal on the intrinsic anharmonic contribution to thermodynamic properties, whereas it has a much more significant effect on the external anharmonicity (thermal expansivity). The pressure dependence of CP (dCP/dP, in J/kg/K/GPa) increases from –3.14 at 300 K to –1.94 at 700 K, and then decreases smoothly to –5.03 at 1800 K. Combining the derived high-P-T capacity with a reliable P-V-T equation of state (EoS) for olivine, we further modeled the thermodynamic Grüneisen parameter, γ(P-T). The Grüneisen parameter is important for the connection between isothermal and adiabatic compressions of minerals, which can be decreased by approximately 5% with the anharmonic correction at high temperatures. The modeled adiabatic bulk modulus and bulk sound velocity can be expressed as: KS(T,P) (GPa) = 127.5(1) + 4.32(5)·P – 0.018(1)·(T – 300) and VΦ(T-P) (km/s) = 6.22(2) + 0.069(3)·P – [3.74(15)–0.075(13)·P]·10–4·(T – 300). The adiabatic temperature gradient, dTS/dP, which is almost independent of pressure, equals 13.40(16) and 12.35(16) K/GPa in the harmonic and anharmonic models, respectively. This study provides a useful example for modeling the radial temperature distribution in adiabatic planetary mantles. [ABSTRACT FROM AUTHOR]

This paper is concerned with environmental corrosion during service of load‐bearing aluminum alloys fabricated by additive manufacturing (AM) with a focus on damage evolution characterization and identification of dominated failure mechanisms of pre‐corroded selective laser melted aluminum alloy. An experimental strategy for analysis of the damage and failure process is presented, combining 3D surface measurement, 3D digital image correlation, and scanning electron microscopy, to provide a multi‐source experimental characterization of corrosion morphology, strain field evolution, and fracture morphology. Statistics and machine learning methods were employed to process the measured multi‐source experimental data, showing that local average roughness has a strong influence on macro‐crack initiation position. The analysis focuses on four primary types of fatigue micro‐crack initiation, namely, internal defect, diffuse corrosion, corrosion micro‐pit, and corrosion jut; internal defect and diffuse corrosion are unique features for powder bed fusion (PBF) AlSi10Mg. The micro‐crack initiation mechanisms for all four types are (i) local stress concentrations due to adjacent material micro‐structural defects, (ii) interaction of underlying alloy microstructure and corrosion‐induced stress/strain, and (iii) local stress/strain concentration at corrosion micro‐pit and jut, respectively. Highlights: Fatigue damage and failure mechanism of pre‐corroded SLM AlSi10Mg were investigated.Experimental strategy was proposed to provide associated multi‐source information.Effect of corrosion morphology characteristics on macro‐crack initiation was evaluated.Main fatigue micro‐crack initiation forms and corresponding mechanisms were analyzed. [ABSTRACT FROM AUTHOR]

This paper presents characterization for fatigue failure analysis of precorroded AA7075‐T651 under air and exfoliation corrosion (EXCO) environments, with respect to damage accumulation, macrocrack and microcrack behavior via 3D digital image correlation (DIC), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). It is shown that that corrosion pits induce fatigue cracking with different nucleation times, and locations. It is furthermore shown that while the corrosive environment accelerates crack formation, it significantly hinders fatigue crack propagation at low stress amplitudes due to crack closure and tip passivation. Five dominant fatigue microcrack initiation types (pit bottom, corrosion tunnel, corrosion micropit, corrosion jut‐in, and chapped feature) and relevant mechanisms were identified, related to corrosion pit macro–micro morphology, material microdefect, local material grain structure, and loading condition. [ABSTRACT FROM AUTHOR]