Search

In recent years, additive manufacturing has reached the required reliability to effectively compete with standard production techniques of mechanical components. In particular, the geometrical freedom enabled by innovative manufacturing techniques has revolutionized the design trends for compact heat exchangers. Bioinspired structures, such as the gyroid lattice, have relevant mechanical and heat exchange properties for their light weight and increased heat exchange area, which also promotes the turbulent regime of the coolant. This work focuses its attention on the effect of the relevant design parameters of the gyroid lattice on heat exchange performances. A numerical comparative analysis is carried out from the thermal and fluid dynamic points of view to give design guidelines. The results of numerical analyses, performed on cylindrical samples, are compared to the experimental results on the pressure drop. Lattices samples were successfully printed with material extrusion, which is a low-cost and easy-to-use metal AM technology. For each lattice sample, counter pressure, heat exchange, and turbulence intensity ratio are calculated from the numerical point of view and discussed. At the end, the gyroid lattice is proven to be very effective at enhancing the heat exchange in cylindrical pipes. Guidelines are given about the choice of the best lattice, depending on the considered applications. [ABSTRACT FROM AUTHOR]

In this study, we propose a high-temperature radar-absorbing structure that combines the ceramic material (YSZ, yttria-stabilized zirconia) with a metamaterial (SRR, split-ring resonator) structure without including additional lossy materials. Although metals typically reflect electromagnetic waves, we found that adjusting the shape of the 3D metal structure and placing dielectric materials in between can impart wave-absorption functionality. The shape of the metamaterial pattern structure was designed using the commercial program CST Studio Suite. The SRR structure was fabricated using metal 3D printing, and YSZ was coated onto the fabricated metal structure using thermal spraying techniques. The proposed radar-absorbing structure was verified using free space measurement equipment, demonstrating a reflection loss characteristic of less than −10 dB over a bandwidth of approximately 0.8 GHz within the X-band. [ABSTRACT FROM AUTHOR]

This work investigates the microstructure and manufacturing control of the masked Cold Spray Additive Manufacturing (CSAM) strategy for producing of new bipolar plates (BPPs) for Proton Exchange Membrane (PEM) electrolyzers, using low-cost, lightweight, and machinable materials. CSAM is a solid-state process capable of fabricating 3D patterned parts based on a bottom-up approach using masks with a desired pattern. This study focuses on the dimensional and microstructural characteristics of pin fins fabricated with spherical (Ti-S) and irregular (Ti-I) Ti powders using the masked CSAM technology. Additionally, the performance of both Ti parts for its application in PEM electrolyzers was evaluated in terms of corrosion resistance and interfacial contact resistance (ICR). The results demonstrated that the masked CSAM technology allowed precise control and customization of the dimensions of the 3D-printed pin fins, obtaining porosity values of 6 ± 1 % for Ti-S and 4 ± 1 % for Ti-I. The evaluation of the corrosion resistance of the CSAM Ti patterned parts showed that for both Ti-S and Ti-I powders a stable oxide film at the typical operation potential (1.8 V vs Ag/AgCl) of a PEM water electrolyzer was formed without signs of pitting corrosion. Finally, at a compaction pressure of 150 N/cm2 ICR values of 42 ± 19, 40 ± 13, and 24 ± 7 mΩ·cm2 were obtained for Ti-I, Ti-S, and standard Ti Bulk, respectively. The results suggest than the masked CSAM technology shows great potential for the fabrication of Ti BPPs.

This review explores the critical role of powder quality in metal 3D printing and the importance of effective powder recycling strategies. It covers various metal 3D printing technologies, in particular Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition, and Binder Jetting, and analyzes the impact of powder characteristics on the final part properties. This review highlights key challenges associated with powder recycling, including maintaining consistent particle size and shape, managing contamination, and mitigating degradation effects from repeated use, such as wear, fragmentation, and oxidation. Furthermore, it explores various recycling techniques, such as sieving, blending, plasma spheroidization, and powder conditioning, emphasizing their role in restoring powder quality and enabling reuse. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing technologies such as powder bed fusion (PBF) and direct energy deposition (DED) are experiencing fast development, due to the growing awareness of industries. However, high energy consumption, slow production processes, and high costs of both machines and feedstocks hamper their competitiveness, compared to conventional manufacturing techniques. Metal material extrusion (metal-MEX) can represent a cost- and energy-effective alternative for metal additive manufacturing. This article aims to assess the potential of such technology by addressing uncertainties related to product design and process stability through a preliminary geometric benchmarking study. The geometric tolerances and minimum achievable sizes of some simple geometries produced in 316L stainless steel were evaluated using geometric benchmark test artifacts (GBTAs). Process maps were also proposed to forecast the feasibility of achieving acceptable values of the investigated tolerances, based on the nominal dimensions of the features. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Segmental bone defects of the mandible result in the complete loss of the affected region. We had incorporated the pressure‐reducing device (PRD) designs into the customized mandible prostheses (CMP) and conducted a clinical trial to evaluate this approach. Methods: Seven patients were enrolled in this study. We examined the association among the history of radiotherapy, the number of CMP regions, the number of chin regions involved, and CMP exposure. Results: We included five men and two women with an average age of 55 years. We excised tumors with an average weight of 147.8 g and the average weight of the CMP was 68.5 g. No significant difference between the two weights was noted (p = 0.3882). Three patients received temporary dentures and the CMP remained stable in all patients. Conclusion: The use of PRD in CMP may address the previous challenges associated with CMP, but further research is necessary. [ABSTRACT FROM AUTHOR]

The creation of strong and tight copper and stainless steel joints in mechanical structures and components is an actual challenge in modern engineering. Thanks to unique combination of different properties such joints have many important applications like components of linear particle accelerators, ultra-high vacuum systems (up to 10-8 torr), heat exchangers, even of the international fusion experimental reactor. At the same time, ensuring a reliable joint of immiscible materials such as copper and stainless steel is a technologically challenging problem due to significantly different physical, mechanical and metallurgical properties, including melting points, thermal expansion coefficients, thermal conductivity, etc. Traditional approaches to the production of such joints, based on certain welding methods, impose many technical and geometric limitations due to the need for special preparation of the contact surfaces of the parts to be joined or the uncontrolled formation of new phases when mixing melts of different metals. As for brazing methods, they do not always provide reliable vacuum-tight joints for relatively thick parts and do not guarantee sufficient joint strength. Therefore, it is important to find more technologically flexible ways to solve such problems. This article discusses a new approach to joining copper and stainless steel using the xBeam 3D Metal Printing technology. This novel directed energy deposition (DED) technology uses a profile electron beam and coaxial feeding of copper wire to deposit it upon a precision machined stainless steel substrate. The results of the exploration study of joints made using this method are presented, including the study of vacuum tightness of the joint, density of the deposited material, metallurgy of the interface, electrical conductivity, oxygen content, hardness in different zones, etc. Specialized preheating strategies minimized the thermal deformation of the machined substrate, a key consideration for adding multimaterial functionality to monolith components. [ABSTRACT FROM AUTHOR]

The 3D printing process of Fused Deposition Modelling (FDM) can be used for fabricating metal parts without the need of mold. Metal Material Extrusion uses metal-polymer composite filament in the 3D printer to extrude the green part, then a de-binding process for removing the polymer binder, and eventually, the sintering process under high temperatures for making a metallic part. A comprehensive research is conducted in which sintering parameters including heating rate, dwell time, and sintering atmospheres are varied for metal parts mechanical characteristics including tensile strength, ductility, and density. Moreover, sintering atmospheres including vacuum and argon are taken into consideration in this research study. The metal part is known as silver part which has exhibited a high mechanical strength of 540 MPa, a considerable density of 7.57 g/cm3, and a high hardness of 220 HV under a vacuum sintering atmosphere. Whereas the metal parts produced under argon atmosphere have shown comparatively low mechanical strength 424 MPa, density 7.1 g/cm3 and 177 HV. The results are compared with an industrial benchmark process where catalytic de-binding and sintering are used to achieve 500 MPa tensile strength, density 7.83 g/cm3, and 175 HV. Scanning Electron Microscopy reveals that grains are coarsened in a vacuum, and grains appear peeled off along with small pores in the boundaries. The industrial benchmark part has uniform and finer grains.

In recent years, additive manufacturing has reached the required reliability to effectively compete with standard production techniques of mechanical components. In particular, the geometrical freedom enabled by innovative manufacturing techniques has revolutionized the design trends for compact heat exchangers. Bioinspired structures, such as the gyroid lattice, have relevant mechanical and heat exchange properties for their light weight and increased heat exchange area, which also promotes the turbulent regime of the coolant. This work focuses its attention on the effect of the relevant design parameters of the gyroid lattice on heat exchange performances. A numerical comparative analysis is carried out from the thermal and fluid dynamic points of view to give design guidelines. The results of numerical analyses, performed on cylindrical samples, are compared to the experimental results on the pressure drop. Lattices samples were successfully printed with material extrusion, which is a low-cost and easy-to-use metal AM technology. For each lattice sample, counter pressure, heat exchange, and turbulence intensity ratio are calculated from the numerical point of view and discussed. At the end, the gyroid lattice is proven to be very effective at enhancing the heat exchange in cylindrical pipes. Guidelines are given about the choice of the best lattice, depending on the considered applications.

Material shaping and joining are the two fundamental processes that lie at the core of many forms of metal manufacturing techniques, including additive manufacturing. Current metal additive manufacturing processes such as laser/e-beam powder bed fusion and Directed Energy Deposition predominantly use heat and subsequent melt–fusion and solidification to achieve shaping and joining. The energy efficiency of these processes is severely limited due to energy conversion losses before energy is delivered at the point of melt–fusion for shaping and joining, and due to losses through heat transfer to the surrounding environment. This manuscript demonstrates that by using the physical phenomenon of lowered yield stress of metals and enhanced diffusion in the presence of low amplitude high frequency oscillatory strain, metal shaping and joining can be performed in an energy-efficient way. The two performed simultaneously enable a metal additive manufacturing process, namely Resonance-Assisted Deposition (RAD), that has several unique capabilities, like the ability to print net-shape components from hard-to-weld alloys like Al6061 and the ability to print components with a very high aspect ratio. In this study, we show this process's capabilities by printing solid components using aluminum-based metal alloys. [ABSTRACT FROM AUTHOR]

Occupational settings are increasingly dealing with nanomaterials, leading to significant concerns about health risks. Nanomaterials in occupational settings can be categorized as engineered and incidental nanomaterials. Projections indicate that more than eight million individuals across the globe will be exposed to engineered nanomaterials as part of their occupational activities, by the year 2029 and assessing the associated risks presents challenges to occupational health experts. Incidental nanomaterials exhibit inherent distinctions from their engineered counterparts, which exert a discernible influence on the outcomes of risk assessments. Notably, a pivotal distinction resides in the controlled nature of the manufacturing process for engineered nanomaterials, which enables meticulous regulation of their size, morphology, quantity, and chemical composition. Conversely, incidental nanomaterials do not benefit from such control, leading to inherent variability in these attributes. Distinguishing risk assessment procedures for incidental and engineered nanomaterials is crucial due to the different processes that generate them, leading to differences in parameters needed for risk assessment. Incidental nanomaterial risk assessments face unknown parameters, emphasizing the need for distinct methodologies. [ABSTRACT FROM AUTHOR]

Metal 3D printing is revolutionizing the industry by enabling rapid and cost‐effective production of complex metal 3D products with intricate geometries, attracting significant attention in recent years. Particularly, metal 3D‐printed catalysts have emerged as a cutting‐edge fusion technology that serves as both catalysts and reactors, referred to as self‐catalytic reactors (SCRs). Therefore, this concept article aims to introduce the recent advancements in metal 3D printing technology in the catalyst and reactor field, and illustrate the various aspects for the rational design of self‐catalytic reactors. [ABSTRACT FROM AUTHOR]

Three-dimensional printing is a non-conventional additive manufacturing process. It is different from the conventional subtractive manufacturing process. It offers exceptional rapid prototyping capabilities and results that conventional subtractive manufacturing methods cannot attain, especially in applications involving curved or intricately shaped components. Despite its advantages, metal 3D printing will face porosity, warpage, and surface roughness issues. These issues will affect the future practical application of the parts indirectly, for example, by affecting the structural strength and the parts' assembly capability. Therefore, this study compares the qualities of the warpage, weight, and surface roughness after milling and grinding processes for the same material (316L stainless steel) between rolled steel and 3D-printed steel. The experimental results show that 3D-printed parts are approximately 13% to 14% lighter than rolled steel. The surface roughness performance of 3D-printed steel is better than that of rolled steel for the same material after milling or grinding processing. The hardness of the 3D-printed steel is better than that of the rolled steel. This research verifies that 3D additive manufacturing can use surface processing to optimize surface performance and achieve the functions of lightness and hardness. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) is a metal 3D printing technique that allows large-scale elements to be built in a relatively timely and cost-effective manner, well suited to the cost-sensitive construction sector. Despite the potential of this novel technology, the basic properties of WAAM materials remain elusive. This paper presents a comparative study on the microstructure and corrosion behaviour of WAAM steel plates and the conventionally rolled Q345 steel. The WAAM steel exhibited comparable corrosion performance to the conventionally-produced steel within twelve days exposure in 3.5 wt% NaCl solution, including the corrosion current density, and the characteristics of steel/concrete interface, determined through electrochemical impedance spectroscopy (EIS) analysis. Post-corrosion observations revealed that preferential dissolution occurred at (Si, Mn)-rich oxide inclusions, in addition to the general corrosion of surrounding steel matrix. The much higher content of Si and Mn element in the feedstock material WAAM steel resulted in slightly higher susceptibility to localised corrosion, compared to the Q345 rolled steel.

Compression mold tooling fabrication has been traditionally conducted via machining processes—for example, computerized numerical control machining, mill, or lathe operations. While subtractive manufacturing operations provide high-precision tooling, they have an extended lead time and generate material waste, which increases manufacturing costs. This paper analyzes direct metal laser sintering (DMLS) as a viable alternative to traditional compression mold manufacturing. DMLS is an additive manufacturing process that uses high-powered lasers to fuse metal powders in a layered approach to create high-precision metal components. Through layering materials, DMLS can produce complex geometries which can have features impossible to machine from traditional manufacturing methods. Additionally, DMLS uses less material for parts, reducing material costs and lead times. In this paper, DMLS manufactured mold was computationally studied against a traditional compression mold's thermal and pressure requirements. The DMLS mold was designed with a honeycomb structure to reduce material usage while maintaining structural integrity. Computational analysis showed that the production requirement, "maximum deflection of 0.001 inches," was achieved with the DMLS when pressures and temperatures were similar to those required for the tooling. In addition, DMLS-produced mold utilized 74% less material than a traditionally manufactured mold. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing (AM) is a layer-by-layer process that makes the direct manufacturing of various industrial parts possible. This method facilitates the design and fabrication of complex industrial, advanced, and fine parts that are used in different industry sectors, such as aerospace, medicine, turbines, and jewelry, where the utilization of other fabrication techniques is difficult or impossible. This method is advantageous in terms of dimensional accuracy and fabrication speed. However, the parts fabricated by this method may suffer from faults such as anisotropy, micro-porosity, and defective joints. Metals like titanium, aluminum, stainless steels, superalloys, etc., have been used—in the form of powder or wire—as feed materials in the additive manufacturing of various parts. The main criterion that distinguishes different additive manufacturing processes from each other is the deposition method. With regard to this criterion, AM processes can be divided into four classes: local melting, sintering, sheet forming, and electrochemical methods. Parameters affecting the properties of the additive-manufactured part and the defects associated with an AM process determine the method by which a certain part should be manufactured. This study is a survey of different additive manufacturing processes, their mechanisms, capabilities, shortcomings, and the general properties of the parts manufactured by them. [ABSTRACT FROM AUTHOR]

This review explores the critical role of powder quality in metal 3D printing and the importance of effective powder recycling strategies. It covers various metal 3D printing technologies, in particular Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition, and Binder Jetting, and analyzes the impact of powder characteristics on the final part properties. This review highlights key challenges associated with powder recycling, including maintaining consistent particle size and shape, managing contamination, and mitigating degradation effects from repeated use, such as wear, fragmentation, and oxidation. Furthermore, it explores various recycling techniques, such as sieving, blending, plasma spheroidization, and powder conditioning, emphasizing their role in restoring powder quality and enabling reuse.

Metal additive manufacturing technologies such as powder bed fusion (PBF) and direct energy deposition (DED) are experiencing fast development, due to the growing awareness of industries. However, high energy consumption, slow production processes, and high costs of both machines and feedstocks hamper their competitiveness, compared to conventional manufacturing techniques. Metal material extrusion (metal-MEX) can represent a cost- and energy-effective alternative for metal additive manufacturing. This article aims to assess the potential of such technology by addressing uncertainties related to product design and process stability through a preliminary geometric benchmarking study. The geometric tolerances and minimum achievable sizes of some simple geometries produced in 316L stainless steel were evaluated using geometric benchmark test artifacts (GBTAs). Process maps were also proposed to forecast the feasibility of achieving acceptable values of the investigated tolerances, based on the nominal dimensions of the features.

The methanation of CO2 has been actively pursued as a practical approach to mitigating global climate change. However, the complexity of the catalyst development process has hindered the development of new catalysts for CO2 methanation; as a result, few catalysts are commercially available. Herein, a multifunctional self‐catalytic reactor (SCR) is prepared via metal 3D printing and selective electrochemical dissolution as a method to not only simplify the catalyst development process but also fabricate active catalysts for CO2 methanation. The combination of metal 3D printing and selective electrochemical dissolution is demonstrated as a feasible method to prepare active catalysts for the methanation of CO2 in a short time. In addition, the use of an electrochemical method enables the formation of galvanic cells on the SCR; these cells continuously generate active sites via self‐dissolution during a simple refresh process, resulting in high reusability of the SCR. The proposed method represents a new facile technique to fabricate highly reusable catalysts that exhibit superior performance for CO2 methanation, and the results provide a guideline for preparing metal 3D‐printed catalysts that will satisfy industrial demand. [ABSTRACT FROM AUTHOR]

With the recent development of computer-aided design-computer-aided manufacturing technology and 3D printing technology, and the introduction of various digital techniques, the accuracy and efficiency of top-down definitive prosthetic restoration are increasing. In this clinical case, stable occlusion support was obtained through the placement of a total of 9 maxillary and mandibular posterior implants in patient with anterior-posterior crossed occlusion. The edentulous area of the maxillary anterior teeth, which showed a tendency of high resorption of the residual alveolar bone, was restored with a Kennedy Class IV implant assisted removable partial denture to restore soft tissue esthetics. Computed tomography guided surgery was used to place implants in the planned position, double scan technique was used to reflect the stabilized occlusion in the interim restoration stage to the definitive prostheses, and metal 3D printing was used to manufacture the coping and framework. This clinical case reports that efficient and predictable top-down full mouth rehabilitation was achieved using various digital technologies and techniques. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) is a metal 3D printing technique that has attracted significant interest from the construction industry for its ability to efficiently and rapidly build large‐scale component. However, there is currently limited information on the cyclic performance of WAAM metal materials. To address this gap, an experimental investigation was conducted to study the cyclic behaviour of WAAM carbon steel. The investigation involved the testing of forty specimens with two nominal thicknesses and two surface finishes under ten cyclic loading protocols. Following this, the failure modes, cyclic performance, and elastic modulus degradation were analysed. The results indicate that WAAM carbon steel exhibits excellent ductility under cyclic loading. The phenomenon of Bauschinger effect, cyclic hardening and elastic modulus degradation were observed in the experiment. The cyclic performance of WAAM carbon steel was found to depend on strain amplitude and strain history. [ABSTRACT FROM AUTHOR]

This study utilizes the Taguchi method and sub-model analysis technique to create a novel optimization lattice for the hypo-loading region. The lattice is designed to mimic the mechanical properties of bone and promote the growth of immature bone under appropriate loading to enhance the osseointegration capacity of implants. The Maxillary lattice implant (ML implant) was developed to address the case of Maxillary antral carcinoma. The implant's structural parameters, including Angle of rotation (A), Concave angle (B), Pillar diameter (C), and Fillet radius (D), were analyzed to design and optimize the Hypo-Loading lattice (HL lattice) with various structures. Through the analysis, the optimal structural parameters for the HL lattice were determined, resulting in the creation of the Optimal HL lattice with exceptional Elastic Admissible Strain (EAS), a comparable elastic modulus to bone, and outstanding mechanical robustness. This feature of the Optimal HL lattice improves the bionic performance.

Binder jet is one of the metal additive manufacturing methods. In this method, metal powder is used as a raw material, and a metal part is obtained by sintering a green body produced by jetting a binder on a metal powder bed leveled with a roller. Powders produced by the gas atomization method with an average particle size of around 10 μm is mainly used in the binder jetting method for metal additive manufacturing. The water atomization method used in this study has a higher production yield, so the cost of powder is lower than that of gas atomized powder. It is also possible to produce ultra-fine powders. However, there are few studies on the use of water-atomized powder in the binder jetting method. This paper aims to evaluate the basic characterization using water atomized powder for practical use in the binder jetting method. Three different water atomized powders with average particle sizes ranging from 4 μm to 10 μm and the gas atomized powder with an average particle size of 10 μm for comparison were used in the evaluation. The results confirmed that the flowability of water atomized powder decreased as the average particle size became smaller, and the flowability was lower than that of gas atomized powder due to differences in powder shape even at the same average particle size. The apparent density of the green body was found that tapped density of powder had a significant effect. The sintering process confirmed that the green body with smaller average particle size powder had higher sintering performance. This result is in line with the existing theory in the sintering technology using metal powders. It is clear that tap density and powder flowability are important for the practical use of water atomized powder in the binder jetting method.

Selective laser melting (SLM) as an additive manufacturing (AM) technique shows great potential to produce complex and high-density three-dimensional structures at high speeds. Currently, alloy materials based on aluminum–silicon (AlSi), including AlSi7Mg and AlSi10Mg, are widely used in AM technology. However, the residual stress caused by rapid cooling was one of the critical issues affecting the tensile and yield strength, dimensional accuracy, and reliability of fabricated parts. In this study, we systematically investigated changes in the microstructure, residual stress, and mechanical properties of AlSi7Mg and AlSi10Mg materials after a heat treatment. The changes in electrical properties were also investigated. The heat treatment process reduced the residual stress of the materials. After the heat treatment, the silicon (Si) network structure and Si dissolved in the Al matrix were completely precipitated and existed as an independent fine spherical precipitate. The AlSi7Mg material has a weaker solid-solution hardening effect due to lower volume fraction of Si, resulting in lower tensile strength, lower hardness, and higher elongation than the AlSi10Mg material. After the heat treatment, the tensile and yield strength of both materials decreased, and the elongation increased. On the other hand, the electrical conductivity of the materials was improved after the heat treatment due to the Si which precipitated in the Al matrix, acting as an impurity. The electrical conductivity and mechanical properties of the AlSi alloy depend on the Si content of the materials. Therefore, the electrical and mechanical properties can be enhanced by optimizing the appropriate Si content in the material. [ABSTRACT FROM AUTHOR]

Hemifacial microsomia (HFM), one of the most common congenital facial anomalies, was usually treated with the bilateral sagittal split osteotomy (BSSO) procedure to correct the asymmetric appearance and malocclusion of the mandible. However, the frequent post-operative relapse incidents would lead to the restoration of the mandibular segment to its preoperative position and failure of the BSSO procedure. In this study, a customized asymmetric fixed plate (CAF plate) was developed to resist relapse due to hemifacial microsomia occlusal forces and the different muscular traction forces on both sides of the mandible. For the actual HFM case in this study, the reconstructed mandibular segmental bone model was fixed using BSSO with a rectangular plate (the original CAF plate appearance) in the topology optimization analysis. With the topology optimization technique, the CAF plate was designed with a lightweight profile and excellent structural strength in consideration of the HFM asymmetrical muscle traction and occlusal force. Using biomechanical simulations, the von-Mises stress and CAF plate mandibular segment displacement and the miniplate were compared to evaluate which had superior relapse resistance. In the in-vitro biomechanical test, a fatigue force of 250,000 cycles and a constant muscle traction force were applied to the HFM mandibular model, which was fixed with the CAF plate fabricated using metal 3D printing (selective laser melting, SLM) to obtain the mandibular segment displacement as a relapse assessment. The topology optimization analysis showed that the CAF plate has the best characteristics, light weight and structural strength with 30% volume retention. The biomechanical analysis showed that the maximum von Mises stress of the mini-plate was 2.71 times higher than that of the CAF plate. The relapse displacement of the mandibular segment fixed with the mini-plate was 1.62 times higher than that fixed with the CAF plate. The CAF plate ability to resist relapse was confirmed by the biomechanical testing results so that only 0.29 mm of recurrence displacement was observed in the mandibular segment. The results indicated that the CAF plate structural strength and resistance to relapse was significantly better than that of the mini-plate. This study developed a customized asymmetric fixation plate for hemifacial microsomia, integrating topology optimization, metal 3D printing, and in vitro biomechanical testing to resist occlusal forces and differential muscle traction on both sides of the mandible to reduce relapse and improve fixation stability. [ABSTRACT FROM AUTHOR]

Metamaterials have offered unprecedented potentials for wave manipulations. However, their applications in underwater acoustic wave control have remained largely unexplored. This is because of the limited material choices and the lack of reliable fabrication techniques for the complicated structures. Herein, a metamaterial with microlattice structures as the building blocks is proposed for underwater operations. By designing the building blocks of the metamaterial and assembling them in a layered fashion, anisotropy is embedded in the structure, which results along different effective sound speeds in orthogonal directions. The designed metamaterial is fabricated by metal additive manufacturing using aluminum and steel. Experiments are performed using a resonator tube to evaluate its performance in water. An anisotropy ratio of around 2 is achieved, which is in good agreement with numerical simulations. The proposed metamaterial provides an effective means for underwater sound control with reduced fabrication difficulties and increased service life. [ABSTRACT FROM AUTHOR]

The integration of additive manufacturing technology into the construction sector has attracted considerable interest in recent years. However, despite the increasing demand for large-scale constructions subjected to large forces, the research on the structural behaviour of thick plates fabricated via Wire and Arc Additive Manufacturing (WAAM) technology has been limited. This paper investigated the structural behaviour and design of WAAM carbon steel double-shear bolted connections with thick plates. The experiment examined 30 bolted connections with varying geometric dimensions and print layer orientations, discovering failure modes including net section tension, shear-out, end-splitting, and bearing failure. The research revealed anisotropic behaviours in WAAM steel bolted connections, with different print layer orientations affecting their failure modes and ultimate capacities. It is consistent with the inherent anisotropy observed in WAAM steel materials. Furthermore, the experimental results were analysed and compared with predictions made by existing design approaches for conventional steel bolted connections. While the existing guidelines were found to be applicable to WAAM steel bolted connections, certain limitations were identified. • Ultimate capacities and failure modes of WAAM steel double-shear bolted connections investigated. • Mechanical properties and anisotropic behaviours of the printed material obtained. • Geometric dimensions of WAAM steel plates determined by the 3D laser scanning. • As-built surface undulations and angles to print layer orientations of the WAAM steel bolted connections assessed. • Ultimate capacities compared against existing structural design codes. [ABSTRACT FROM AUTHOR]

Three-dimensional printing is a non-conventional additive manufacturing process. It is different from the conventional subtractive manufacturing process. It offers exceptional rapid prototyping capabilities and results that conventional subtractive manufacturing methods cannot attain, especially in applications involving curved or intricately shaped components. Despite its advantages, metal 3D printing will face porosity, warpage, and surface roughness issues. These issues will affect the future practical application of the parts indirectly, for example, by affecting the structural strength and the parts’ assembly capability. Therefore, this study compares the qualities of the warpage, weight, and surface roughness after milling and grinding processes for the same material (316L stainless steel) between rolled steel and 3D-printed steel. The experimental results show that 3D-printed parts are approximately 13% to 14% lighter than rolled steel. The surface roughness performance of 3D-printed steel is better than that of rolled steel for the same material after milling or grinding processing. The hardness of the 3D-printed steel is better than that of the rolled steel. This research verifies that 3D additive manufacturing can use surface processing to optimize surface performance and achieve the functions of lightness and hardness.

The production of various 3D-printed metal or ceramic parts via fused deposition modeling (FDM) or fused filament fabrication (FFF) is gaining tremendous interest. This is because FDM or FFF are cost-effective and have comparatively faster processability. FDM or FFF are material extrusion-based additive manufacturing processes in which the filament is extruded through a nozzle at a high temperature, and the object is formed by its layer-by-layer deposition. Irrespective of the metal/ceramic precursors, the choice of binder/carrier is crucial for developing 3D-printed parts using FDM of FFF techniques. The optimization of processing parameters determines the perfectness of the binder/carrier chosen for successful 3D printing. In the case of multi-component metal alloy preparation, the binder tightly holds the alloying components close to each other and helps to maintain their stoichiometry. A suitable carrier holds ample alloying components while retaining enough flexibility and strength to the filament for printing. Compatibility between the binder and carrier can synergistically improve the 3D printing. Polyvinyl pyrrolidone (PVP) has been chosen as a highly processable and biocompatible binder in this work, while thermoplastic polyurethane (TPU) is a biocompatible carrier for the PVP-bound metal. The metal powder having a composition of Fe-1.5Ni-1.5Cu (as per the wt.%) has been used to investigate the efficacy of the binder and carrier. The binding of metal powder with PVP dispersion, melt mixing of PVP-bound metal powder with the TPU, extrusion of the TPU/PVP-bound metal (TPM) composite, 3D printing of the extruded filament (containing 40 vol.%, i.e., 82 wt.% of metal) using a low-cost 3D printer, and debinding of the printed product/s at different heating conditions have been thoroughly optimized and successfully standardized. [ABSTRACT FROM AUTHOR]

Copyright of China Rubber Industry is the property of Editorial Office of China Rubber Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a newly developed metal 3D printed waveguide bandpass filter based on a modified deformed elliptical cavity resonator with an additional plate. The modified resonator has excellent design freedom allowing semi-independent control of centre frequency, bandwidth, and transmission zeros. Furthermore, transmission zeros can be placed close and far from the passband to improve frequency selectivity and stopband’s width and rejection, respectively. Theory of the resonator, filter design with an example, and simulated and experimental results with extensive discussion are given. As proof of concept, a 5-pole Ku-band wideband filter was designed and manufactured using Selective Laser Melting, a metal 3D printing technique. Even though the prototypes were tested as-built, i.e. without any surface post-processing, the simulated and measured results have good agreement and consistency between all four printed prototypes. Moreover, the prototypes were manufactured in one piece, significantly improving measured results compared to the previous two-piece prototypes.

Air compressors are widely used in factories to power automation systems and store energy. Several studies have been conducted on the performance of reciprocating and screw compressors. Advancements in design and manufacturing techniques, such as generative design and topology optimization, are leading to improved performance and turbomachinery growth. This work presents a methodology to design and manufacture air compressor pistons using topology optimization and metal additive manufacturing. The existing piston is converted to 3D CAD data and topology optimization is conducted to reduce material in stress concentration regions. Thermal and mechanical loads are considered in boundary conditions. The results show reduced material and improved efficiency, which is validated using ANSYS fluent. The optimized 3D model of the piston is too complex for conventional subtractive manufacturing, so laser sintering 3D printing is proposed. Honeycomb pattern infill patterns are used in 3D printing. This investigation is a step toward researching similar methods in other reciprocating compressor components such as cylinder, cylinder head, piston pins, crankshaft, and connecting rods, which will ultimately lead to improved compressor efficiency.

Three-dimensional (3D)-printed electronic technology is considered to have great potential as it can be utilized to make electronic products with complex 3D shapes. In this study, based on a 3D printer with single UV laser equipment, we continuously performed photo-polymerization (PP) and selective metal powder sintering to fabricate a conductive pattern. For this, 3D structures were printed at a low energy using a 355 nm DPSS laser with a galvanometer scanner, which are widely used in PP-type 3D printing, and then the selective sintering of metal powders was performed with a high energy. In order to obtain a high-conductivity pattern by laser sintering, a circuit pattern that could actually be operated was fabricated by experimenting with various condition changes from mixing the metal composite resin to the laser process. As a result, it was found that the optimal result was to irradiate a 0.8 W UV laser with a beam spot size of 50 µm to 50 vol% aluminum composite resin. At this time, an optimal conductive pattern with a resistance of 0.33 Ω∙cm−1 was obtained by setting the pulse repetition rate, scan path interval, and scanning speed to 90 kHz, 10 μm, and 50 mm/s, respectively. This suggested process may be of great help in the manufacturing of practical 3D sensors or functional products in the future. [ABSTRACT FROM AUTHOR]

A metal-melting direct writing process, using semi-solid isothermal heat treatment to form high-quality semi-solid components, realized the integrated innovation of semi-solid formation and additive manufacturing. An experimental study was carried out on semi-solid isothermal heat treatment for metal-melting direct-writing technology, using 2A12 aluminum alloy as raw material. The semi-solid isothermal heat treatment was carried out over different temperature ranges, and four-stages evolution mechanism of the semi-solid microstructure in the semi-solid melting direct writing process was investigated. The effects of holding temperature and time on the microstructure of the semi-solid isothermal heat treatment of the alloy were put forward. According to the analysis of the results of the semi-solid-melting direct-writing test, the corresponding relationship between semi-solid microstructure and extrusion formability was found. The results show that when the holding temperature is 640–650 °C and the holding time is 20–25 min, the liquid phase rate can reach about 40%, and the direct-writing forming technology can be carried out stably. [ABSTRACT FROM AUTHOR]

Recent disruptive technological advances, including wire arc additive manufacturing (WAAM) and the concept of digital twins, have the potential to fundamentally transform the way in which we design, build and manage structures. WAAM is a method of metal 3D printing that is well suited to the price‐sensitive construction industry and has been used to manufacture the MX3D bridge – the world's first metal 3D printed bridge. The intricate geometry, undulating surface finish and particular material properties rendered the bridge outside the scope of any existing structural design standards; hence, physical testing and advanced numerical modelling were carried out for its safety assessment. The key features of the finite element model of the bridge, and its validation against in‐situ structural tests, are described herein. Subsequent numerical studies undertaken to verify the structural performance of the bridge under various loading scenarios are presented, while the basis for the development of the smart digital twin of the bridge is also introduced. The presented research provides insight into the use of advanced computational simulations for the verification and ongoing assessment of structures produced using new methods of manufacture. [ABSTRACT FROM AUTHOR]

We developed a coupled CALPHAD and finite element-based computational model of the Laser Powder Bed Fusion (LPBF) process for HAYNES230, considering the feedstock composition and packing density. We further used this model to investigate the effect of variation in feedstock composition and print parameters on the quality of the final printed part. Sensitivity of the maximum reached temperature to variations in characteristics of the laser source is also studied considering a single-track laser scan on a layer of metal powder. We analyzed temperature evolution in the powder bed and melt pool geometry along the path of the laser. Our results indicate that the LPBF process of HAYNES230 alloy requires a powder layer thickness of ∼20 μm and laser spot size ∼30 μm radius compared to other alloys. It is essential to achieve sufficient melt pool depth necessary for cohesion with the substrate while avoiding large melt pool width that adversely affects the formation of cracks and residual stresses. We also revealed that reducing the laser power or increasing scan speed drastically reduces peak temperature while less susceptible to solute composition.

Additive manufacturing is growing rapidly in the last decades due to the significant development in the laser technology and metal powder manufacturing. It offers a way to rapidly create near-net-shape engineered parts starting from a digital CAD file without the need for dies or molding. It also offers the ability to manufacture parts designed in a complex geometry and made of metals which are difficult to produce by using the traditional methods. One of the main obstacles in Laser-Powder Bed Fusion (L-PBF) for example is the dissimilarity in the produced parts’ properties. The main reason behind this is the non-stationary nature due to the turbulence formation above the melt-pool area accompanied by weld fumes, metal evaporation, plasma and sparks formation. These effects increase within the individual printer as the fumes suspending and circulating with the inert gas increasing with the time. Also, these effects differ from one printer to another depending on the build chamber size and gas flow arrangement. This article is focused on exploring the (L-PBF) process in a step-by-step principle and present it to the researchers, technicians and even manufacturers especially those who have novice or lack of information about this technology. The study puts the main issues which must be considered and learned in a successful Additive Manufacturing (AM) lab to produce a functioning metal part.