Fused deposition modelling is a rapidly growing additive manufacturing technology due to its ability to build functional parts having complex geometries. The mechanical properties of a built part ...depend on several process parameters. The aim of this study is to characterize the effect of build orientation, layer thickness and feed rate on the mechanical performance of PLA samples manufactured with a low cost 3D printer. Tensile and three-point bending tests are carried out to determine the mechanical response of the printed specimens.
Due to the layer-by-layer process, 3D printed samples exhibit anisotropic behaviour. Upright orientation shows the lowest mechanical properties. On the other hand, on-edge and flat orientation show the highest strength and stiffness. From a layer thickness and feed rate point of view, it is observed that ductility decreases as layer thickness and feed rate increase. In addition, the mechanical properties increase as layer thickness increases and decrease as the feed rate increases for the upright orientation. However, the variations in mechanical properties with layer thickness and feed rate are of slight significance for on-edge and flat orientations, except in the particular case of low layer thickness. Finally, the practicality of the results is assessed by testing an evaluation structure.
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•The effect of 3D printing process parameters on the mechanical performance of PLA samples is assessed.•On-edge oriented samples show the optimal mechanical performance.•Ductility decreases as layer thickness and feed rate increase.•Low layer thickness and high feed rate values are recommended for the optimal mechanical performance.
► A W–2Y2O3 composite is produced by powder metallurgy method. ► The composite has W grains (1–2μm) and Y2O3 (300nm to 1μm). ► The mechanical properties are studied by nanoindentation and 3-point ...bend tests. ► 3-Point bend test shows that the composite starts ductile behavior at 400°C. ► The composite can be used as diverter application in fusion power reactors.
A W–2Y2O3 composite is produced by powder metallurgy, including the pressing of the mixed elemental powders, their sintering and hot forging. The microstructure of the obtained composite is investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. It appears that the material is composed of W grains having a mean size of 1–2μm and Y2O3 particles having a mean size of 300nm to 1 μm. The W grains contain a high density of dislocations. The mechanical properties of this material are investigated using nanoindentation and 3-point bend test. Berkovich hardness value is found to be 4.9GPa at 10N load, which is similar to that of pure W. 3-Point bend test shows that the composite starts to show ductile behavior approximately at 400°C and the bending stress continuously decreases from 200°C to 1000°C.
Selective laser melting (SLM) technology can manufacture complex lattice structures, which effectively reduces the manufacturing constraint and significantly increases the design freedom for lattice ...structure. In this study, additive manufacturing and topology optimization are combined for designing Face Centre Cube (FCC), Vertex Cube (VC), and Edge Centre Cube (ECC) structures, which are manufactured via SLM technology. Mechanical performance is evaluated, and a Gibson-Ashby model is developed to predict the performance of the three structures including different levels of porosity. The results show that FCC and VC lattice structures have better mechanical behaviour compared with that of the ECC lattice structure; however, their energy absorption efficiency is inferior to that of the ECC lattice structure. Comparisons between various SLM built lattice structures made from 316L stainless steel prove that the performance of topology-optimized lattice structures is superior to the majority of lattice structures. This result verifies the feasibility of lattice structure unit selection via topology optimization technology. Various work conditions are simulated for topology optimization to obtain a lightweight lattice structure with optimal performance under specific conditions.
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•Proposed a lightweight design method for a topology-optimized lattice structure unit based on actual working conditions.•Designed and tested three types of topology-optimized lattice structures.•Created a Gibson-Ashby model for the three topology-optimized lattice unit structures.
Magnetorheological elastomers (MREs) are a class of recently emerged smart materials whose moduli are largely influenced when exposed to an external magnetic field. The MREs are particulate ...composites, where micro-sized magnetic particles are dispersed inside a non-magnetic polymeric matrix. These elastomers are known for changing their mechanical and rheological properties in the presence of a magnetic field. This change in properties is widely known as the magnetorheological (MR) effect. The MR effect depends on a number of factors such as type of matrix materials, type, concentration and distribution of magnetic particles, use of additives, working modes, and magnetic field strength. The investigation of MREs’ mechanical properties in both off-field and on-field (i.e. absence and presence of a magnetic field) is crucial to deploy them in real engineering applications. The common magneto-mechanical characterization experiments of MREs include static and dynamic compression, tensile, and shear tests in both off-field and on-field. This review article aims to provide a comprehensive overview of the magneto-mechanical characterizations of MREs along with brief coverage of the MRE materials and their fabrication methods.
Creep-fatigue experiments have been conducted in nickel-based superalloy GH720Li at an elevated temperature of 650°C with a stress ratio of 0.1, based on which, different dwell times at the maximum ...loading were applied to investigate the effect of dwell time on the creep-fatigue behaviors. The tested specimens were cut from the rim region of an actual turbine disc in the hoop direction. The grain size and precipitates of the GH720Li superalloy were examined through scanning electronic microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses. Experimental data shows creep-fatigue lifetime decreases as the dwell time prolongs. Further, different scattering was observed in the creep-fatigue lifetime at different dwell times. Then a probabilistic model based on the applied mechanical work density (AMWD), with a linear heteroscedastic function that evaluates the non-constant deviation in the creep-fatigue lifetime, was formulated to describe the dependence of creep-fatigue lifetime on the dwell time. Finally, the possible microscopic mechanism of the creep-fatigue behavior has been discussed by SEM with EDS on the fracture surfaces.
In this paper, several low alloying conductive Al alloys Al-0.5Fe-0.2Si, Al-0.5Mg-0.35Si, Al-0.8Fe-0.2Cu were selected as the research objects. According to our study, the combination of boron ...treatment and grain refinement was proved to be an effective method to improve the electrical conductivity and mechanical properties of the alloys. Firstly, 0.12% was chosen as the optimal amount of boron addition and the electrical conductivity of Al-0.5Mg-0.35Si, Al-0.5Fe-0.2Si and Al-0.8Fe-0.2Cu can be improved to 55.0%IACS, 58.3%IACS and 59.8%IACS, improved by 3.8%, 10%, 6.4% respectively. Secondly, based on the former step, boron treatment combined with grain refinement, the electrical conductivities of Al-0.5Mg-0.35Si, Al-0.5Fe-0.2Si and Al-0.8Fe-0.2Cu can be further improved to 56.5%IACS, 60.4%IACS and 61.8%IACS. At the same time, the low alloying conductive Al alloys show excellent mechanical properties.
Graphene nanosheets (GNSs) reinforced pure copper matrix composites were prepared by ball-milling and hot-press sintering. The morphologies and structures of GNSs-Cu powders were studied after ...ball-milling for different time. The effects of the GNSs content on the microstructures, mechanical properties and fracture mechanisms of the composites were also investigated. It is indicated that the GNSs are gradually dispersed into the copper matrix with increasing the ball-milling time and a uniform dispersion is achieved after ball-milling for 5 h. When the content of GNSs in the composite is 0.5 wt%, GNSs distribute randomly in the composite and the interface bonding is good which is benefit to enhance the mechanical properties of composite. With increasing the GNSs contents, the aggregation of GNSs in the composite is apparent, which seriously separates the matrix and results in low mechanical properties. The fracture mechanism of the composites changes from ductile to brittle.
•Graphene reinforced copper matrix composites were prepared by ball-milling and hot-press sintering.•Graphene is uniformly dispersed into copper matrix after ball-milling and the structure of graphene is relatively complete.•Graphene contents significantly affect mechanical properties and fracture mechanisms of the composites.•The UTS and δ of the composites increase initially and decrease later with increasing the graphene contents.
Additive Layer Manufacturing (ALM) process is used in the present investigation to manufacture long fibre reinforced composite parts using the MarkOne® 3D-printer. In ALM, a continuous filament ...(including a tow of fibres) of composite material is injected by the printer, at high temperature, over a plain tool, forming the part while the material is cooled down. The used composite filament is formed by a PA (Nylon™) matrix and carbon or glass fibre reinforcements. Previous works have shown an improvement on the mechanical properties of a part, when some zones include a nylon based composite reinforcement using ALM. Nevertheless, the characterization of fully made nylon-based ALM composite material parts has not been reported. Thus, the aim of this investigation is the experimental characterization of composite nylon-based coupons. The plane strength and stiffness properties of the composites are obtained, both for tensile and compression load states. Results showed that the obtained mechanical properties for ALM composites are not yet comparable to those obtained by traditional methods (pre-pregs). This fact may be explained by the high porosity found in ALM coupons as well as a low fibre volume obtained. Nevertheless, the mechanical properties improvement in comparison to non-reinforced nylon parts is remarkable.
Effects of filler metal on the microstructure and mechanical properties of Ti-6Al-4V joints were investigated. Three specimens were prepared using α, near-α and α+β type filler materials and one ...specimen was welded without filler metal. The microstructural characterizations, hardness and tensile tests were applied to study the welded specimens. For the specimen welded without filler material, a coarse-grained structure of α+β was found in the microstructure of weld metal. Although this specimen showed lower hardness values compared to the base metal; the hardness of other weld metals was higher than that of the base material. The microstructure of other welds was a mixture of α, β and some amount of α´-martensite. Both acicular and basketweave morphologies of α´ were found in the weld metal. The α colonies were grown from the α lamellae which were formed at the β grain boundaries. The highest tensile strength was obtained for the specimen welded with the matching filler metal (about 91% of the base metal).
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