查看更多>>摘要：Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,under-standing the compression behavior and failure mechanism of such structures under loading remains a challenge.In this study,considering the correlation between the strut angle and bearing capacity,body-centered tetragonal(BCT)lattice structures with varying angles are designed based on a body-centered cubic(BCC)structure.BCT Al2O3 ceramic lattice structures with varying angles are fabricated by vat photopolymerization.The mechanical properties,deformation process,and failure mechanism of the Al2O3 ceramic lattice structures are characterized through a combination of ex-and in-situ X-ray computed tomography(X-CT)compression testing and analyzed using a finite element method(FEM)at macro-and micro-levels.The results demonstrate that as the angle in-creases,the stress concentration gradually expands from the node to the strut,resulting in an increased load-bearing capacity.Additionally,the failure mode of the Al2O3 ceramic lattice structures is identified as diagonal slip shear failure.These findings provide a greater understanding of ceramic lattice structure failures and design optimization approaches.
查看更多>>摘要：In this study,to improve the unsatisfactory mechanical properties of polyamide-12 materials formed via selective laser sintering,an independent soaking and rapid cooling device is developed to improve the internal microstruc-tural defects of the materials via sintering.The maximum tensile strength of the material after heat treatment is 57.3±0.5 MPa at the optimum temperature.Meanwhile,its elongation at break is 293％-297％and 22％-25％at-80 ℃ and+80 ℃,respectively.At+80 ℃,its fracture strength and elongation at break are 53.5±3.2 MPa and 539％-582％,respectively.After heat treatment,its maximum bearing capacity of the triply periodic minimal surface(TPMS)in the elastic stage increased significantly by 106％-119％.Among them,the D-type TPMS after heat treatment shows the best comprehensive bearing capacity;the maximum bearing capacity in the elastic stage is 7.2 kN,which is accompanied by favorable thermal insulation.At lower-surface temperatures of+80 ℃ and-80 ℃,the equivalent thermal conductivities are 0.02975 and 0.01592 W/(m·K),respectively.
查看更多>>摘要：The advent of laser powder bed fusion(LPBF)has provided an effective solution for fabricating lightweight structures with intricate designs that cannot be realized using other manufacturing methods.Lattice structures,however,which feature unique characteristics,pose greater challenges in the LPBF process than solid structures and exhibit more significant distortion.The underlying mechanisms and influencing factors of this distortion re-main unclear,presenting a significant research gap.This study investigates the generation mechanism of residual stress in Ti-6Al-4V lattice structures during LPBF and examines how process and geometric parameters influence residual distortion.Lattice-type cantilever structures with various arm thicknesses and strut diameters were fab-ricated using different laser powers and scan patterns.The residual distortion after removal from the building substrate was measured using a non-contact coordinate-measuring machine.The results suggest that increas-ing the arm thickness,reducing the strut diameter,and employing a scanning pattern with interlayer rotation effectively reduce residual distortion.Among these factors,the scanning pattern had the most distinct impact,differing significantly from those affecting solid structures.P2(45°)scanning pattern resulted in the greatest residual distortion,approximately twice that of the least distorted pattern.Meanwhile,the laser power exerted a minor influence on the distortion of the lattice structures.These findings provide insights and guidance for fabricating lattice structures using the LPBF process,broadening its applications in aerospace,automotive,and other weight-sensitive industries.
查看更多>>摘要：Recently,the application of wire-arc additive manufacturing(WAAM)for the production of metallic products is gaining traction.WAAM is associated with the direct energy deposition technique and therefore has a higher deposition rate(approximately 4 kg/h).For this reason,it is of greater interest than powder-based additive manufacturing techniques.Industrial applications such as marine and offshore structures and pressure vessels for space programs commonly utilize high-strength low-alloy(HSLA)steel.HSLA steel components produced by casting methods exhibit defects due to oxidation.Therefore,cold metal transfer(CMT)-WAAM was adopted in this study to fabricate HSLA steel components.The metallurgical properties were analyzed using microscopic and diffraction techniques.The effects of the evolved microstructures on mechanical properties,such as strength,microhardness,and elongation to fracture,were evaluated.To analyze and test the structure,two regions were selected,namely,top and bottom.Microstructural analyses revealed that both regions were primarily composed of acicular ferrite,polygonal ferrite,and bainitic structures.The bottom region exhibited superior mechanical properties compared with the top region.The improved strength at the bottom region can be ascribed to the formation of a high density of dislocations and finer grains.
查看更多>>摘要：The static coarsening behavior of laser powder directed energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy and its effects on the alloy's tensile properties were investigated.The static coarsening kinetics of the crab-like primary a(ap)and secondary a(as)were satisfied by the Lifshitz-Slyozov-Wagner relationships.For the coarsening of the crab-like ap,the coarsening efficiency(n)was satisfied at 0.25-0.35 for 910 ℃,whereas it was satisfied at 0.45-0.50 for 950 and 990 ℃.For the coarsening of the αs,the n was satisfied at 0.45-0.50 for 950 ℃and 990 ℃.Compared to the as-built sample,the samples heat-treated at 910 ℃/2 h/air cooled and 950 ℃/2 h/air cooled exhibited good yield strength(930-1005.5 MPa),the highest elongation(14.5％-16.6％),and the lowest anisotropic ductility(0.6％)among all samples.The crab-like αp and αs increased the crack growth resistance and decreased the fracture difference in two different directions in the samples.
查看更多>>摘要：Catalysts are widely used in the chemical industry because of their environmental friendliness and low energy consumption.However,integrated fabrication of catalytic reactors(CRs)remains challenging.In this study,we propose the integrated manufacturing of a palladium-carbon(Pd/C)CR for the first time.The outer shell ink com-prises Al2O3 powder and aluminum dihydrogen phosphate(AP),whereas the inner core ink consists of activated carbon powder,AP,and polymethylmethacrylate(PMMA).By integrating with the coaxial 3D printing strategy,the Pd/C CR can be freeform-designed with different core thicknesses,lengths,and shapes(W-type,L-type,and U-type).Based on this,a CR with excellent catalytic properties was further developed by loading palladium(Pd)particles.Typically,the resultant Pd/C CR with a length of 2.5 cm exhibits a catalytic efficiency of up to 97.6％after 60 min.This method of preparing Pd/C CR using coaxial 3D printing combines multimaterial 3D print-ing,integrated molding,and complex biomimetic structure fabrication.This offers a feasible and cost-effective solution that uses a simple fabrication process.
查看更多>>摘要：Laser three-dimensional(3D)printing offers significant advantages in integrating the shape and function of regen-erative tissues through biomimetic manufacturing.However,its effectiveness is limited by the lack of specialized biopolymer powders—while solvent methods that use residual solvents produce powders with poor biocompati-bility,mechanical methods result in irregularly shaped crystals.In this study,a biopolymer powder spheroidiza-tion and shaping technology,which utilizes the evolution of irregular powders into spheres with minimal surface free energy in the molten state,is proposed based on the thermodynamic principle of minimum energy.Initially,the motion trajectory and temperature field of the poly(L-lactic acid)(PLLA)powder during spheroidization were quantitatively assessed and optimized using Stokes'law and Fourier's principle.Subsequently,the cohesive forces and aggregation kinetics of the polymer chains were calculated using molecular dynamics.Finally,based on these calculations,a phase-field model was constructed to simulate the evolution of the spheroidization rate and deduce the optimal parameters for the process.This precise approach enhances PLLA spheroidization control for laser 3D printing,improves part densification and surface quality,and offers a clean and efficient path for preparing high-quality PLLA spheroidized powder for laser 3D printing.
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