Material Design & Processing Communications最新文献

This paper analyzes the effect of thin and thick walls on functional properties of 3D printed cell structures, designed from open cell structures inspired by the natural world. Different types of unit cells with the same density are introduced. The cells are studied in morphology and mechanical performance, in particular effective density, compressive stiffness, and energy absorption under cyclic loading. Material extrusion process with thermoplastic polyurethane filament is used as additive manufacturing technique, without any support structure. The designed printed cellular structures are studied numerically, using an advanced hyperelastic material model with hysteretic capacity, and experimentally by uniaxial compression testing for characterization of stiffness and energy absorption. The benefits and limitations of the method are highlighted.

Calcium fluoride solid electrolytes have been identified as a candidate for solid-state fluoride-ion batteries (FIBs). Here, we investigate the doping of CaF₂ with samarium — Ca_1−xSm_xF_2+x (0 ≤ x ≤ 0.15) — obtained by solid synthesis via high-energy ball milling. Structural, morphological, and ionic conductivity studies of the as-prepared materials were examined. It reveals that the fluorite-type structure is dominating with a crystallite size of 12–14 nm. The highest ionic conductivity at room temperature had been obtained for Ca_0.95Sm_0.05F_2.95 with a value of 2.8 × 10⁻⁶ S·cm⁻¹. It proves that a small content of Sm doping can considerably improve the ionic conductivity of CaF₂.

The physical–chemical processes involved in light-induced polymerization (photopolymerization) are widely exploited in additive manufacturing (AM) technologies such as Stereolithography and Digital Light Processing. The influence of the AM process parameters on the physical properties of manufactured components has been often investigated through empirical methods based on the trial and error approach, that is, by collecting and interpreting a large amount of experimental data. However, when desired physical properties are required, accurate modeling of the liquid–solid conversion is necessary. In this work, in order to determine the properties of the resulting material according to the adopted process setup, we present a multi-physics approach to model the physical–chemical transformation taking place in photopolymerization. The role played on the final mechanical properties by the laser light intensity and by its moving speed is considered. Further, the influence of the uncertainty of the process parameters is investigated through a sensitivity analysis. The proposed approach is suitable for investigating the reliability of additively manufactured components as well as for their design according to an optimum printing strategy. From the perspective of making innovative functional materials, the proposed multi-physics model allows tuning the printing process in order to get the desired distribution of mechanical properties.

The flow behaviors of powder metallurgy (PM) Ti-45Al-6Nb-0.3W (at.%) alloy were systematically investigated in the temperature range from1050 to 1200°Cand the strain rates from 0.001 to 0.5 s⁻¹. The effects of the temperature and the strain rate on deformation behaviors were represented by Zener–Hollomon parameter in an exponent-type equation. Microstructural observations revealed that α₂/γ lamellar colonies varied into particle α₂ due to dynamic recrystallization (DRX) at high temperature during the compression. The result indicated that the strain-dependent constitutive equation could lead to a good agreement between the calculated and measured flow stresses in the elevated temperature range for the PM Ti-45Al-6Nb-0.3W alloy. Subsequently, the correlation coefficient (R) and the average absolute relative error (AARE) were introduced to verify the validity of the constitutive equation, and values of R and AARE were 0.99483 and 3.956%, respectively.

High levels of stiffness, strength, and lightweight can be achieved through lattice structures. Many different technologies can be adopted for their construction; among them, additive manufacturing presents high flexibility and the capacity to produce complex shape parts. In this paper, a detailed analysis of the fracture surface was carried out on titanium sandwich panels, having a lattice core and produced through electron beam melting (EBM) process. The specimens were subjected to the three-point bending test; then, the fracture surfaces were observed by means of a scanning electron microscope (SEM). The occurrence of dimples was found on the fracture surface, demonstrating the ductile behavior of the material; moreover, the micrographies showed a different morphology between the core of the struts and the surface.

This work shows a procedure for the mechanical characterization of a new composite for aerospace. Initially, a preliminary test campaign has been carried out to identify the most suitable fabric and resin for the production of the new composite. Subsequently, the production of the composite plaques has been planned. Then, plaques with different orientation of the layers and thicknesses have been obtained. From each of these plaques' coupons for the experimental tests, needed to the mechanical characterization of the composite, have been obtained. The experimental tests have been carried out in a certified laboratory with electromechanical machines and according to ASTM standards. For each experimental test, the trend of the stress–strain curves has shown a typical behavior up to failure. An analysis of the coefficient of variation, based on the statistical mean of parameters calculated with the experimental tests, has been carried out to evaluate the reproducibility of the tests in different laboratories.

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.