Material Design & Processing Communications最新文献

As one of the additive manufacturing (AM) methods, fused deposition modeling (FDM) technology is widely adopted but involves some limitations in lacking surface quality and mechanical properties due to the use of only planar layers. This review will explore the novel FDM approach, curved layer FDM (CLFDM) where a nonplanar slicing technique is introduced to improve on these shortcomings. Recently, this technique has gained more and more traction in the industry and among consumers owing to not only its great potential to overcome several manufacturing limitations of conventional FDM method such as the “staircase effect” and poor bonding strength of curved surfaces or shells but also enhanced mechanical properties of CLFDM printed parts. The present review mainly focuses on the toolpath generation, process adaptations, mechanical properties of the printed part, and novel applications in the CLFDM method.

Austempered ductile iron (ADI) is one of the most widely used types of ductile iron produced by austempering heat treatment. ADI heavy section parts are employed in different industries owing to their unique mechanical properties.

Cooling rate in thick parts is significantly low, so heavy section ductile iron parts should have an adequate austemperability for preventing pearlite formation in the middle of the casting. In order to achieve the proper austemperability and fully ausferritic structure, alloying elements like nickel are added to the melt.

The objective of this work is to study the role of austempering parameters on nickel alloyed ADI specimens fabricated from 75-mm-thick Y-block. Austempering temperature and time as main parameters in the austempering process are taken as the control variables. The heat treatment of austempering was performed at 320°C and 380°C for 60, 120, 180, and 240 min. It was possible to determine the best austempering conditions among those investigated in the paper, and the results showed that austempering at a higher temperature contributes to higher strength and hardness compared to lower austempering temperature. Furthermore, specimens that were austempered at 320°C for 120 min had better mechanical properties among other samples.

Many rocks, metals, and concrete are porous, in fact most materials are porous. This would then imply that their properties depend on the density. In this report, we develop a constitutive relation to describe the response of elastic bodies that are linear in both the stress and the linearized strain with the material moduli depending on the density. Such a model is not possible within the context of the classical theory of linearized elasticity but is possible within the context of the implicit theory for elastic bodies that has been developed. The constitutive relations discussed in this paper can be useful to describe the response of porous elastic bodies in the small displacement gradient regime. Using these constitutive relations, we study the stress concentration due to the presence of a circular hole in a plate due to uniaxial extension. We find that the stress concentration factor can be significantly different from that in the case of the classical linearized elastic solid.

In this study, nano-LiFePO4 as the cathode material of lithium battery was prepared by different processes, and its micromorphology, crystal structure, and electrochemical performance were tested. Lithium iron phosphate was prepared by the high-temperature solid-state method and gel–sol method. The micro morphology of the product was detected by an electron microscope. The crystal structure of the product was detected by an X diffractometer. The electrochemical performance of the product was tested by charge and discharge. The results showed that the lithium iron phosphate prepared by the gel–sol method had a smaller particle size and more regular shape; the diffraction pattern of the two kinds of lithium iron phosphate was nearly consistent, but the lithium iron phosphate prepared by the gel–sol method had smaller diffraction intensity because of its smaller particle size; the lithium iron phosphate prepared by the gel–sol method were more stable and efficient and had a larger capacity during charging and discharging.

Among the mechanical properties already evaluated in ductile iron, could be mentioned tensile strength, bend, impact Charpy, fracture toughness and fatigue. However, an aspect no longer explored over the mechanical properties of these materials is concerned with the behavior under compressive loads. In this work, compressive properties are evaluated on quenched ductile iron, which is considered at first as an appropriate alternative for mechanical applications with this kind of load. The evaluation was performed by means of compression tests on cylindrical samples. Further application of compressive loads was explored using the tests known as the Brazilian test, which involves the use of a disc compressed along the diameter line. The results obtained are the first attempt of a complete study involving the different choices of ductile iron.

Additive manufacturing allows high complexity of manufactured structures, permitting entirely new design capabilities. In the context of complex design, lattice structures hold the most promise for high complexity, tailorable and ultra-lightweight structures. These unique structures are suitable for various applications including light-weighting, energy absorption, vibration isolation, thermal management amongst many others. This new complexity leads to new manufacturing quality control and metrology challenges. Traditional metrology tools cannot access the entire structure, and the only reliable method to inspect the inner details of these structures is by X-ray computed tomography (CT). This work highlights the challenges of this process, demonstrating a novel workflow for dimensional metrology of coupon lattice samples—using a combination of surface and internal metrology using tactile probe and CT. This dual combined approach uses traditional surface coordinate measurement on exterior accessible surfaces, which is followed by internal lattice measurements. The results show a clear method and workflow for combining these technologies for a holistic dimensional inspection. The confidence gained by inspection of such lattice coupons will support the application of these lattices in end-use parts.

Nodular cast iron contains about 10 vol% of graphite particles, which debond easily and thus act as nucleation sites of voids. When an elastic–plastic porous material is subjected to cyclic loading, voids grow with each load cycle due to so-called void ratchetting until the micro-ligaments between the graphite particles begin to neck. The cyclic necking leads to void coalescence and finally to the formation of a macroscopic crack. This mechanism is modeled in this study to explain fatigue failure under stress-controlled loading. For this purpose, an axisymmetric cell model is developed and cycle by cycle simulations are performed until final failure. From the simulation results, stress-life curves are extracted and compared with experimental data collected from literature. The effects of the shape of graphite particle, type of matrix material hardening, and mean stress on the fatigue life of nodular cast iron are studied.

At present, due to the unclear understanding of the mixed proportion of stone powder in the manufactured sand, the quality of finished concrete is affected. In this study, the concrete was mixed with manufactured sand containing 0%, 5%, 10%, and 15% stone powder and poured into standard models. The compressive strength of the concrete was obtained by measuring the pressure; the dry shrinkage rate of the concrete was obtained by measuring the volume; the impermeability was evaluated by the seepage height method. The results demonstrated that the increase of stone powder content resulted in the enhancement of concrete compressive strength and impermeability, but blindly adding stone powder led to the deterioration of concrete anti-shrinkage performance. Finally, the comparison of the overall experimental data showed that 10% of stone powder could make all aspects of the performance of the concrete optimal.

Through various examples, this short review presents the main X-ray-based techniques that are available to characterize nodular cast iron at the microstructural level. Emphasis is placed on the enormous potential offered by the recent developments in X-ray tomography, X-ray diffraction, and digital volume correlation, which allow collecting microstructural and micromechanical information in 4D (3D plus time) during both casting and subsequent mechanical loading. The goal is to demonstrate that for nodular cast iron, which has an inherently three-dimensional, composite microstructure, X-ray-based techniques provide some significant advantages over conventional microscopy. For this reason, these techniques can be instrumental in unveiling the mechanisms controlling both the formation of the microstructure as well as its micromechanical behavior during in-service loading, thus paving the way to the development of improved process–structure–property relations.

Recent studies on Co–Cr–Fe–Ni–Nb_x (x = molar ratio) high-entropy alloys (HEAs) have revealed that high-pressure torsion (HPT) induced severe straining improves the load-bearing ability of eutectic HEAs. Nanoindentation using a Berkovich indenter was employed to investigate the influence of severe straining on the rate-dependent strength responses in eutectic, proeutectic, and single-phase Co–Cr–Fe–Ni–Nb_x HEAs. The results reveal that the nature of the microstructure evolution after severe straining significantly affects Young's modulus and the yield strength in eutectic Co–Cr–Fe–Ni–Nb_0.65. The excellent combination of high strength with lower Young's modulus is crucial for opening new sights in lamellar eutectics for possible application as next-generation advanced materials.