Chinese Journal of Mechanical Engineering: Additive Manufacturing Frontiers最新文献

High-performance/multifunctional metallic components primarily determine the service performance of equipment applied in the aerospace, aviation, and automobile industries. Organisms have developed structures with specific properties over millions of years of natural evolution, thereby providing inspiration for the design of high-performance structures to satisfy the increasing demands of modern industries. From the perspective of manufacturing, the ability of conventional processing technologies is inadequate for fabricating these complex structural configurations. By contrast, laser additive manufacturing (AM) is an effective method for fabricating complex metallic bio-inspired structures owing to its layer-by-layer deposition advantage. Herein, recent developments in the laser AM of bio-inspired cellular, plate, and truss structures, as well as the materials used in laser AM for bio-inspired printing are briefly reviewed. The organisms being imitated include butterfly, Norway spruce, mantis shrimp, beetle, and water spider, which expand the diversity of multifunctional structures for laser AM. The mechanical properties and functions of laser-AM-processed bio-inspired structures are discussed. Additionally, the challenges, possible outcomes, and directions of utilizing laser AM technology to fabricate high-performance/multifunctional metallic bio-inspired structures in the future are outlined.

Laser powder bed fusion (LPBF) is a popular metal additive manufacturing technique. Generally, the materials employed for LPBF are discrete and particulate metal matters. Thus, the discontinuous behaviors exhibited by the powder materials cannot be simulated solely using conventional continuum-based computational approaches, such as finite-element or finite-difference methods. The discrete element method (DEM) is a proven numerical method to model discrete matter, such as powder particles, by tracking the motion and temperature of individual particles. Recently, DEM simulation has gained popularity in LPBF studies. However, it has not been widely applied. This study reviews the existing applications of DEM in LPBF processing, such as powder spreading and fusion. A review of the existing literature indicates that DEM is a promising approach in the study of the kinetic and thermal fluid behaviors of powder particles in LPBF additive manufacturing.

The conventional fabrication process for single-crystal nickel-based superalloy materials is directional solidification, which is classified as casting. With the rapid development of additive manufacturing (AM) technologies, a novel process for fabricating single-crystal superalloys has become possible. This article reviews recent research on the AM of single-crystal nickel-based superalloys. Laser AM technologies, particularly directed energy deposition, are mainly used to repair single-crystal materials. Electron beam powder bed fusion is an innovative method for the direct fabrication of single-crystal materials. Accordingly, the mechanisms of single-crystal formation during AM are analyzed to elucidate the potential of this process route. Furthermore, this article discusses the challenges faced by AM for single-crystal fabrication, and provides perspectives on the trends of future developments.

In this review, we summarize the research activities carried out by our research group at the University of Padova on the additive manufacturing of ceramics from liquid feedstocks. Particularly, we evaluate the use of preceramic polymers, geopolymers, and sol-gel solutions. We mainly focus on processing with liquid feedstocks because they have some advantages with respect to slurry-based feedstocks in which powders are present. Particularly, lower viscosity, enhanced transparency, and lack of scattering and sedimentation are advantageous features for vat photopolymerization processes, whereas the absence of particulates reduces clogging problems at the nozzle for extrusion-based processes. Simultaneously, preceramic polymers and geopolymers have some limitations in terms of the range of ceramic compositions that can be obtained; sol-gel solutions are intrinsically unstable, whereas printed objects suffer from drying issues. Nevertheless, we successfully produced high-quality parts using a variety of additive manufacturing techniques, some of which (e.g., volumetric additive manufacturing) have been proposed for the fabrication of ceramic components for the first time.

Instead of foreseeing and preparing for all possible scenarios of machine failures, accidents, and other challenges arising in space missions, it appears logical to take advantage of the flexibility of additive manufacturing for “in-space manufacturing” (ISM). Manned missions into space rely on complicated equipment, and their safe operation is a great challenge. Bearing in mind the absolute distance for manned missions to the Moon and Mars, the supply of spare parts for the repair and replacement of lost equipment via shipment from Earth would require too much time. With the high flexibility in design and the ability to manufacture ready-to-use components directly from a computer-aided model, additive manufacturing technologies appear to be extremely attractive in this context. Moreover, appropriate technologies are required for the manufacture of building habitats for extended stays of astronauts on the Moon and Mars, as well as material/feedstock. The capacities for sending equipment and material into space are not only very limited and costly, but also raise concerns regarding environmental issues on Earth. Accordingly, not all materials can be sent from Earth, and strategies for the use of in-situ resources, i.e., in-situ resource utilization (ISRU), are being envisioned. For the manufacturing of both complex parts and equipment, as well as for large infrastructure, appropriate technologies for material processing in space need to be developed.

Continuous fiber reinforced polymer composites (CFRPC) have been widely used in the field of automobile, aircraft, and space due to light weight, high specific strength and modulus in comparison with metal as well as alloys. Innovation on 3D printing of CFRPCs opened a new era for the design and fabrication of complicated composite structure with high performance and low cost. 3D printing of CFRPCs provided an enabling technology to bridge the gaps between advanced materials and innovative structures. State-of-art has been reviewed according to the correlations of materials, structure, process, and performance as well as functions in 3D printing of CFRPCs. Typical applications and future perspective for 3D printing of CFRPCs were illustrated in order to grasp the opportunities and face the challenges, which need much more interdisciplinary researches covering the advanced materials, process and equipment, structural design, and final smart performance.