3D Printing and Additive Manufacturing最新文献

A novel shear test method on shear bond behavior of 3D printed interlayer interfaces and interstrip interfaces was proposed in this study. Thereafter, the effect of different replacement ratios of recycled sand, printing intervals, and surface treatments were investigated. The test results showed that under the same printing condition, the interfacial shear strengths of interlayer interface and interstrip interface were similar to each other. The interfacial shear strength slightly decreased with the increase of the replacement ratio of recycled sand, while it sharply decreased with the extension of printing interval time. The interfaces in 3D printed recycled mortar had higher time sensitivity compared with 3D printed natural mortar. Considering that discontinuous construction will introduce inferior interfaces in 3D printed concrete components, effective surface treatments should be conducted. According to the test results, the improvement effect of surface treatments was epoxy paste > cement paste > surface wetting > no treatment.

In this work, we propose a methodology to develop printability maps for the laser powder bed fusion of AISI 316L stainless steel. Regions in the process space associated with different defect types, including lack of fusion, balling, and keyhole formation, have been considered as a melt pool geometry function, determined using a finite element method model containing temperature-dependent thermophysical properties. Experiments were performed to validate the printability maps, showing a reliable correlation between experiments and simulations. The validated simulation model was then applied to collect the data by varying laser scanning speed, laser power, powder layer thickness, and powder bed preheating temperature. Following this, the collected data were used to train and test the adaptive neuro-fuzzy interference system (ANFIS)-based machine learning model. The validated ANFIS model was used to develop printability maps by correlating the melt pool characteristics to the defect types. The smart printability maps produced by the proposed methodology can be used to identify the processing window to attain defects-free components, thus attaining dense parts.

Moisture absorption into hygroscopic/hydrophilic materials used in fused deposition modeling (FDM) can diminish desired mechanical properties. Sensitivity to moisture is dependent on material properties and environmental factors and needs characterization. In this article, moisture sensitivity of four grades of polylactic acid (PLA) filaments and four different ratios of PLA/polybutylene succinate (PBS) blended filaments were characterized through FDM printed American society for testing and materials (ASTM-D638) test samples after conditioning the filaments at different relative humidity levels. The tensile testing and scanning electron microscopy (SEM) of the samples' fracture surfaces revealed that PLA 4043D was the most moisture-sensitive among the chosen grades of PLA filaments. Through filament tension test and melt flow index (MFI) testing it was observed that moisture had a significant detrimental effect (20% reduction in tensile strength and 50% increase in MFI) on PLA 4043D filaments. Samples from moisture-conditioned PLA/PBS 75/25 blended filaments displayed a significant reduction (10%) in tensile strength. Moreover, the MFI of 75/25 filaments was increased with subsequent increases in moisture level. Investigation of tensile properties of ASTM samples made from four grades of PLA filaments exposed to room temperature and humidity conditions for 3 months showed an even more significant decrease in strength (ranging from 24% to 36%).

Three-dimensional (3D) concrete printing technology has been considered promising, attracting extensive attention in the engineering field. Multiwalled carbon nanotubes (MWCNTs) have been used as an additive to reinforce the cement-based material. However, the research on the 3D printed MWCNT-reinforced high-strength concrete is rare. This research is to study the mechanical properties and pore structure of MWCNT-reinforced reactive powder concrete (RPC) for 3D printing. In this research, the workability of the printed RPC mixture with MWCNTs was first tested to pass the criteria of 3D printing. Then, the enhancement effect of MWCNTs on the printed RPC was tested by mechanical properties after hardening. Meanwhile, strength-displacement curves were recorded. In addition, the pore structures of printed RPC were observed and analyzed by X-ray computed tomography (CT) images. The results show that 0.05 wt% MWCNTs have no effect on the workability of the printable RPC slurry. MWCNTs could enhance the mechanical properties of the printed RPC by filling the flaws inside the samples, increasing the viscosity of the RPC slurry and forming bridges between cracks. Besides, 0.05 wt% MWCNTs may cause the failure mode of the printed RPC from brittle failure to ductile failure. In addition, MWCNTs significantly reduced the porosity of the printed RPC by decreasing pores with a volume over 0.01 mm³. As CT images show, the interlayer zone (IZ) of the 3D printed RPC sample is prone to pores, and a higher volume fraction is evident. In particular, within the volume of IZs, the minimum volume fraction at the IZ of 3D printed RPC appears on sample with MWCNTs.

Binder jetting (3DP) is a kind of additive manufacturing at room temperature and atmospheric environment, which can reduce the risk of magnesium alloy forming. Magnesium alloy powder is bonded to a certain structure by a binder, so the appropriate binder is very important in 3DP. In this study, according to the characteristics of magnesium alloy, a simple and easy-to-obtain water-based low-molecular alcohol binder was used to reduce the difficulty of magnesium alloy 3DP. Additionally, we use COMSOL Multiphysics simulation software to establish a simulation model of the movement and deposition process of the binder. The results show that the increase in jet velocity will increase the quality and saturation of droplets. More importantly, the larger the jet velocity is, the larger the spreading width of the binder droplet after impacting the powder bed, which seriously affects the dimensional accuracy of the green part. In addition, lower binder saturation will weaken the formation of interparticle bonding neck and cannot form a stable structure. Furthermore, we analyzed the bond reactants of the binder and magnesium alloy powder, which eventually decompose into MgO, and the experimental results show that the final sintered sample has considerable performance.

Additive manufacturing processes have recently been used more frequently since they offer high design freedom and easy individualization of components. The processes have been optimized to improve mechanical performance of the manufactured parts. Nevertheless, properties of components made by means of injection molding could not be reached yet. In the study at hand, ultrasonic phase spectroscopy (UPS) is used to compare the elastic properties of acrylonitrile butadiene styrene specimens manufactured by injection molding, by fused filament fabrication, and the Arburg plastic freeforming process. UPS allows a nondestructive and prompt determination of the elastic modulus and allows evaluation of the mechanical properties in every direction in space. In the end, results of UPS are compared with properties derived by uniaxial tensile tests to validate UPS as a test method for the determination of the mechanical properties of polymers. Regardless of the manufacturing process, an approximately linear dependence of the elastic moduli on the density can be determined. Furthermore, the quasistatic properties of the injection molded samples consistently exhibit the mechanical properties of the other samples by at least 10%.

Rapid manufacturing of high purity fused silica glass micro-optics using a filament-based glass 3D printer has been demonstrated. A multilayer 5 × 5 microlens array was printed and subsequently characterized, showing fully dense lenses with uniform focal lengths and good imaging performance. A surface roughness on the order of R_a = 0.12 nm was achieved. Printing time for each lens was <10 s. Creating arrays with multifocal imaging capabilities was possible by individually varying the number of printed layers and radius for each lens, effectively changing the lens height and curvature. Glass 3D printing is shown in this study to be a versatile approach for fabricating silica micro-optics suitable for rapid prototyping or manufacturing.

The wide development in biomedical, regenerative medicine, and surgical techniques has ensured that new technologies are developed to improve patient-specific treatment and care. Tissue engineering is a special field in biomedical engineering that works toward cell development using scaffolds. Bone tissue engineering is a separate branch of tissue engineering, in which the construction of bone, functionalities of bone, and bone tissue regeneration are studied in detail to repair or regenerate new functional bone tissues. In India alone, people suffering from bone diseases are extensive in numbers. Almost 15% to 20% of the population suffers from osteoporosis. Bone scaffolds are proving to be an excellent solution for osseous abnormalities or defect treatment. Scaffolds are three dimensional (3D) and mostly porous structures created to enhance new tissue growth. Bone scaffolds are specially designed to promote osteoinductive cell growth, expansion, and migration on their surface. This review article aims to provide an overview of possible bone scaffolding materials in practice, different 3D techniques to fabricate these scaffolds, and effective bone scaffold characteristics targeted by researchers to fabricate tissue-engineered bone scaffolds.