Chinese Journal of Mechanical Engineering: Additive Manufacturing Frontiers最新文献

These instructions are guidelines for preparing papers for Journal of Additive Manufacturing Frontiers (CJEE:AMF). The length of your paper are at least 7 pages (The review length should be more than 10 pages). Please do not be less than these limitations. Use this document as a template if you are using Word 2013 or later. Or, use this document as an instruction set. The manuscript of yours will be formatted further at Formatting guidelines. (Note:Abstract should include all key elements like background, objective, methods, results, and conclusions. Define all symbols used in the abstract. Do not cite references, nor use formulas, figures and tables in the abstract.)

A metal additive manufacturing process results in a nearly net-shaped fabrication of parts directly from digital data. A local heat source melts the deposited material, and a part is built layer-by-layer. Residual stress and deformation are critical issues experienced by additively manufactured parts. Modeling the additive manufacturing process provides important insights and can help determine an optimal build plan so as to minimize residual stress formation. Various approaches have been used for modeling of residual stresses, ranging from high-fidelity models to simplified models, for quicker results. This paper provides a state-of-the-art review of the approaches used to numerically model residual deformation and stresses in structures built using additive manufacturing. Furthermore, it describes the physical causes of residual-stress generation in an additively manufactured structure.

The geometry of the phase interface in co-continuous piezoelectric composites is critical in improving their piezoelectric properties. However, conventional co-continuous piezoelectric composites are mostly simple structures such as wood stacks or honeycombs, which are prone to stress concentrations at the joints, thus reducing the fatigue service performance and force–electric conversion efficiency of piezoelectric composites. Such simple structures limit further improvements in the overall performance of co-continuous piezoelectric composites. In this study, based on the digital light processing 3D printing method, we investigated the influence of three different structures–the gyroid, diamond, and woodpile interfaces–on the piezoelectric and mechanical properties of co-continuous ceramic/polymer piezoelectric composites. These findings demonstrate that the gyroid and diamond interfaces outperformed the ceramic skeleton of the woodpile interface in terms of both mechanical and electrical properties. When the ceramic volume percentage was 50%, the piezo-composite of the gyroid surface exhibited the greatest hydrostatic figure of merit (HFOM), reaching 4.23×10⁻¹² Pa⁻¹, and its piezoelectric coefficient ($d_{33}$) and relative dielectric constant (${\epsilon }_r$) reached 115 pC/N and 748, respectively. The research results lay the foundation for the application of co-continuous piezoelectric composites in underwater communication and detection.

Metal additive manufacturing, especially laser powder bed fusion (L-PBF), is increasingly being used to fabricate complex parts with fine features. Emerging L-PBF systems have large build volumes and several lasers that operate simultaneously. Hence, they can produce large and complex parts at reduced costs and short build times. However, the thermal distortion remains a critical challenge. Hence, a thorough understanding of the impact of multiple lasers on part distortion in multi-laser PBF (ML-PBF) is imperative. Although experimental investigation is possible, a more conducive approach is to design and create suitable predictive models to understand the impact of multiple lasers consolidating a part into layers. To fulfill this goal, in this study, a commercially available and widely used thermo-mechanical model, Netfabb, was used to investigate the effects of multiple lasers for complex scan patterns such as raster, spiral, and Hilbert on the temperature distribution and thermal distortion. The results show that the thermal distortion is minimal for the spiral scan pattern. Additionally, multiple lasers were found to decrease the build time (as expected) while maintaining or reducing the thermal distortion compared with their single-laser counterparts for all scan patterns (except Hilbert). Therefore, the newly developed ML-PBF predictive model is capable of providing critical insights into the effects of using multiple lasers, thereby opening new possibilities for the faster production of complex parts. In the future, small-scale computational models will be expanded to include large-scale parts, and probabilistic models will be developed to establish correlations.

Inconel 718 is a nickel-based superalloy of high interest in high temperature applications such as turbine parts. To be used in such applications, heat treatments are commonly applied to dissolute Laves phase and to achieve γ′′ phase. However, conventional heat treatment methods for wrought Inconel 718 may not be suitable for Inconel 718 fabricated by laser directed energy deposition (LDED) due to its unique microstructure formed during the rapid solidification process. There has been a lack of investigation in heat treatments for Inconel 718 fabricated by this process, specifically around the impact of aging parameters on this alloy. In this study, the effects of aging parameters were studied by performing seven different heat treatments, including solutionising and aging treatments. Our results indicate that for LDED Inconel 718, a high temperature solution treatment of 1100 ℃ for 1 h followed by single aging at 650 ℃ for 20 h achieved a tensile strength and elongation of 1247 MPa and 23%, respectively. Further, results indicated that even with a shorter aging time of 10 h, γ′′ phase was found to be of comparable size to the standard double aged treatment.

With recent advances in power electronic packaging technologies, liquid-cooled ceramic heat sinks have been considered as a promising solution for further improving the performance of power electronic devices. In this study, several aluminum oxide heat sinks were fabricated and tested using the digital light processing-based additive manufacturing method, to verify their practical performance. The results showed that the complex cooling structures inside the heat sinks can be completely formed and exhibited high surface quality. The experimental thermal and hydraulic performances of the heat sinks were consistent with the numerically modeled predictions. Furthermore, by exploiting the advantages of additive manufacturing, a direct manifold microchannel (MMC) configuration was designed to reduce the vertical flow of the traditional MMC configuration and achieve an improved cooling efficiency. At a constant volumetric flow rate of 1 L/min, the direct MMC configuration achieved a 19.8% reduction in pressure drop and an 11.8% reduction in thermal resistance, as well as a more uniform temperature distribution.

Oxide melt growth ceramics (OMGCs) exhibit excellent performance and microstructure stability near their melting point and are expected to become a new structural material for long-term stable service in extremely high-temperature water-oxygen environments. Owing to its unique advantages of high efficiency, flexible manufacturing, and near-net shaping, laser directed energy deposition (LDED) has become a promising technology for the rapid preparation of high-performance OMGCs. However, owing to the limited understanding of the cracking mechanism, the severe cracking problem that hinders OMGCs-LDED towards engineering applications has not been resolved. Alumina/aluminum titanate (Al₂O₃/Al_xTi_yO_z, A/AT) ceramics are prepared using an LDED system and their cracking characteristics are investigated. Subsequently, numerical simulations are conducted to reveal the dominant factors and influencing mechanisms of the cracking behavior. The results demonstrate that the cracking nucleation process is mainly controlled by solidification defects, whereas the cracking propagation process is determined primarily by both the microstructure and stress level. This study provides a theoretical basis for the development of appropriate cracking suppression methods for OMGCs-LDED.

Kaolin/metakaolin-insulating ceramic components fabricated using direct ink writing (DIW) have important application prospects in architecture and aerospace. The accuracy of the entire process including the forming and sintering accuracy of ceramics greatly limits the application scope, and high-accuracy ceramic samples can meet the usage requirements in many scenarios. The orthogonal experiment was designed with four process parameters, including nozzle internal diameter, filling rate, printing layer height/nozzle internal diameter, and printing speed, to investigate the evolution of the DIW forming accuracy, sintering shrinkage rate and surface roughness of metakaolin-based ceramics with different process parameters. The influence of each process parameter and its mechanism were analyzed to obtain the DIW parameters for high-accuracy metakaolin ceramics. Multiple linear regression models between the dimensional change rate, surface roughness, and process parameters of the ceramic samples were established and validated. The results show that comprehensively considering the forming accuracy of the ceramic green bodies, sintering shrinkage rate and surface roughness, the optimal DIW process parameters were a 0.41 mm nozzle internal diameter, 100% filling rate, 50% printing layer height/nozzle internal diameter, and a 15 mm/s printing speed. Multiple linear regression models were developed for the process parameters and the printing accuracy, sintering shrinkage rate and surface roughness. The error rates between the theoretical results obtained by substituting the optimal process parameters into the multiple linear regression models and the actual results obtained by printing the samples with the optimal parameters were extremely small, all less than 0.8%. This verified the correctness and predictability of the multiple linear regression models. This work provides a reference basis for rapid fabrication of high-accuracy ceramics via DIW and accuracy prediction with different process parameters.

This paper systematically investigates the effects of process parameters, such as exposure time and slice thickness, on the polymerization kinetics of a Si₃N₄ ceramic slurry. The higher the CC conversion rate in the SLA process, the faster the polymerization rate in the slurry during the initial exposure. However, when the UV exposure time is increased from 5 to 20 s, the solidified gel in the slurry hinders the diffusion of free radicals, causing the CC conversion rate to stop. The slurry achieves a CC conversion rate of up to 81% and a curing dimensional accuracy of up to IT7 level at an exposure time of 10 s. When the penetration depth of the slurry is equal to the slice thickness, the difference in CC conversion rates between the ends of the blank is at least 21%. Furthermore, the Si₃N₄ ceramics processed by stereolithography exhibit no defects, such as warpage or holes.