Material Design & Processing Communications最新文献

Lattice components manufactured by selective laser melting processes are increasingly employed for producing high performing lightweight parts to be used in several industrial applications. However, the geometry at a submillimeter scale can exhibit not negligible differences with respect to the nominal design due to the high complexity of the manufacturing process. Accordingly, the mechanical behavior of lattice structures is strongly influenced by such process-induced geometrical defects. Therefore, to numerically predict the fatigue behavior of lattice components, the as-built geometry, as acquired, for instance, by means of micro-computed tomography, should be considered. In this work, we employ an immersed boundary method, namely, the finite cell method, to develop a numerical framework suitable to compute fatigue life directly on an as-built lattice geometry.

Thin-walled tubes are widely used as impact absorbers in transportation structures, due to their high efficiency in absorbing longitudinal impact loads. This study focuses on the investigation of the effect of squared lattice infill in the crashworthiness efficiency of thin-walled aluminum tube. The tube and infill were modeled as an additively manufactured integrated part. Impact analysis was performed using finite element method (FEM), considering empty and filled tubes with different combinations of thicknesses for tube walls and lattice structure. The inclusion of lattice infill changed the crashworthiness efficiency of the energy absorber. Filled tubes presented increased energy absorption and higher values of peak and mean force levels. Tube crushing mode and crushing efficiency were also affected by infill configuration.

It has been recognized that parts produced by additive manufacturing with surfaces in the “as-built” state exhibit reduced fatigue properties. On the other hand, post-process surface finishing is expensive and often unfeasible due to the complexity of parts. Therefore, surface quality parameters must be considered when designing as-built parts for structural applications. This work investigates the as-built surface topography of Inconel 718 samples manufactured via laser powder bed fusion (L-PBF) with three different production systems (SLM 280HL, EOS M290, and RENISHAW AM250) and discusses their respective experimental fatigue behavior. The aim of the investigation is to identify a link between the fatigue response of L-PBF IN718 alloy without post fabrication finishing and the surface morphology; a preliminary comparison among the main surface roughness parameters and the fatigue strength is reported and further investigations are planned to find a univocal correlation. Samples with a mean height (S_a) of approximately 20 μm exhibit lower fatigue strength than those with S_a of approximately 5 μm. Skewness (S_sk) and kurtosis (S_ku) are instead found to be discriminating parameters when comparing surfaces with relatively low surface roughness (S_a 5 μm), with higher values of Ssk and Sku associated with inferior fatigue performance.

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.