Material Design & Processing Communications最新文献

Additive manufacturing (AM) is spreading in a wide range of industrial fields. The influence of the printing parameters on the mechanical performance is still an open issue among researchers, particularly when dealing with fatigue loads, which can lead to an unexpected failure. Classical fatigue tests require a large amount of time and materials to be consumed. Compared to the traditional fatigue assessment, the thermographic method (TM) is able to derive in a very rapid way the SN curve and fatigue limit of the material monitoring its energetic release during fatigue tests.

In this work, for the first time, the energetic release during fatigue test has been evaluated in specimens made of AISI 316L, obtained by SLM technique. Compared to literature data, the specimens show premature failure, even at low stress levels, with brittle fracture surfaces. The internal microstructure seems to be strictly related to the energetic release of the material.

Lightweight core topologies have been considered as an advanced alternative to improve the overall performance of sandwich structures in bending. Designed sandwich beams containing 3D printed cores as conventional honeycomb, re-entrant auxetic honeycomb with two positions of the cells, and chiral topologies were created with CATIA V5. The sandwich beams were manufactured from polylactic acid polymer (PLA) by fused deposition modeling (FDM) using the Ultimaker 3 Extended printer. Three-point bending testing was conducted on sandwich beams using an Instron 8872 testing machine and following ASTM C393-20, as to obtain the strength, bending stiffness, and energy absorption of the sandwich beams for these three designed core topologies. Comments on the cores' performance and sandwich beams response are done together with observations concerning their failure.

This paper presents manufacturing, testing, and computing steps for determining the fracture toughness property of polyamide PA 2200 processed by laser sintering using different process parameters. The design of the samples was conducted according to ASTM D5045-99 and ASTM D5528-01, and the fracture tests consist of four-point bending in symmetric and asymmetric configuration and double cantilever beam test. The process parameters selected as variables were in-plane orientation, spatial orientation, energy density of the process, and induced structural defects. The results provide an extended view regarding the variation of fracture properties when the manufacturing conditions in laser sintering are changed.

In this paper, the current state of the art of additive manufacturing (AM) in the construction industry to manufacture on large scales is reviewed. The central concept of AM was defined, and it has been highlighted in the large use in several sectors. The main advantages that AM offers in the construction industry were described with at the same time the most important challenges that need to be addressed for real use. The main AM technologies solutions on large scales were described from more compact solutions like gantry technology to more flexible and free technology solutions. The choice of an AM solution rather than another is closely linked to the materials to be used and the building component to be built. Regarding materials, the research focused on materials based on aggregates, metals, and polymers. The application of AM in the construction field requires more studies and further research.

The goal of the present study is to obtain a new structured material starting from a copper–polylactic acid (PLA) composite filament 3D printed using fused deposition modeling method, followed by a sintering process in vacuum atmosphere. Metal-reinforced filaments made of 80 wt.% copper encased in an environmentally friendly, biodegradable and carbon neutral PLA binder were used as feedstock materials. The thermal stability and the melting temperature of the filaments were evaluated through thermogravimetric analysis. The printing parameters were chosen according to the producer's specifications. Furthermore, the printed samples were submitted to a two-step sintering process in a vacuum furnace, assuring a complete removal of the polymeric material and the diffusion of the copper particles. The post-treatment revealed a porous structured material, similar to a cellular solid. Microstructural analysis and preliminary mechanical testing show that the porosity and hardness of the end product are heavily influenced by the initial polymer content.

The recycling of materials and the efficient use of resources are nowadays fundamental in a circular economy perspective. This concept also applies to additive manufacturing (AM) where waste can be reused to produce new material. Using mostly thermoplastic polymers, fused deposition modeling (FDM) is an AM technique that allows to melt waste materials and, successively, using a suitable extruder, obtain new filament. In the process, polymers are subject to multiple re-melting and polymer orientations by extrusion operations. The aim of this work is to evaluate the influence of the recycling process over polyethylene terephthalate glycol-modified (PETG) mechanical properties by tensile testing of samples produced using pure and recycled material. Furthermore, filament itself has been tested to evaluate recycle process influence before FDM printing.

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.