Additive Manufacturing Methods Research Articles

The Influence of Residual Stress on Fatigue Crack Growth Rates in Stainless Steel Processed by Different Additive Manufacturing Methods

The Influence of Residual Stress on Fatigue Crack Growth Rates in Stainless Steel Processed by Different Additive Manufacturing Methods

Effects of Selective Laser Melting Process Parameters on Structural, Mechanical, Tribological and Corrosion Properties of CoCrFeMnNi High Entropy Alloy

AbstractThe structural, tribological, mechanical, corrosion, and other properties of materials produced by laser-based powder bed fusion additive manufacturing methods are significantly affected by production parameters and strategies. Therefore, understanding and controlling the effects of the parameters used in the manufacturing process on the material properties is extremely important for determining optimum production conditions and for saving time and materials. This study aimed to determine the optimal laser parameter values for CoCrFeMnNi high-entropy alloy powders using the selective laser melting (SLM) method. The layer thickness was kept constant during experimentation. 5 different laser powers and 10 varying laser scanning speeds were tested, with hatch spacing from 30 to 90%. After determining the optimal laser parameters for SLM, prismatic samples were fabricated in different build orientations (0°, 45°, and 90°), and subsequently, their structural, mechanical, tribological, and corrosion properties were compared. Melt pool morphology could not be obtained at 20—40 and 60W laser powers and at all laser scanning speeds used at these laser powers. At 100 W laser power, 600 mm/s laser scanning speed, and 70% hatch spacing parameters, an ultimate tensile stress of 550 MPa and elongation of 48% were obtained. Among the samples produced in different build orientations, the sample produced with a 0° build orientation exhibited the highest relative density (99.94%), the highest microhardness (201.2 HV0.1), the lowest friction coefficient (0.7025), and the lowest wear and corrosion rates (0.7875 mpy). Additionally, SLM parameters were evaluated to have a significant impact on the performance of all properties of the samples. Graphical Abstract

Effect of Pre-Heating on Residual Stresses and Deformation in Laser-Based Directed Energy Deposition Repair: A Comparative Analysis

Laser-directed energy deposition (DED), a metal additive manufacturing method, is renowned for its role in repairing parts, particularly when replacement costs are prohibitive. Ensuring that repaired parts avoid residual stresses and deformation is crucial for maintaining functional integrity. This study conducts experimental and numerical analyses on trapezoidal shape repairs, validating both the thermal and mechanical models with experimental results. Additionally, the study presents a methodology for creating a toolpath applicable to both the DED process and Abaqus CAE software. The findings indicate that employing a pre-heating strategy can reduce residual stresses by over 70% compared to no pre-heating. However, pre-heating may not substantially reduce final distortion. Notably, final distortion can be significantly mitigated by pre-heating and subsequently cooling to higher temperatures, thereby reducing the cooling rate. These insights contribute to optimizing DED repair processes for enhanced part functionality and longevity.

On the Dynamic Mechanical Behavior of Wrought and AM 17-4 Precipitation-Hardenable Stainless Steels Under Rapid Heating

On the Dynamic Mechanical Behavior of Wrought and AM 17-4 Precipitation-Hardenable Stainless Steels Under Rapid Heating

Satellite Thermal Management Pump Impeller Design and Optimization

This study presents a numerical approach to the design and optimization of centrifugal impellers used in the pumps of active thermal control systems of spacecraft. Although launch costs have shrunk in the last decade, the performance requirements, such as efficiency and reliability, have increased, as such systems are required to work up to 15 years, depending on the mission. To that effect, our paper deals with the first step in this pump design, namely the hydraulic optimization of the impeller. Constructively, this type of impeller allows for certain balancing systems and labyrinth seals to be applied in a more effective way, as well as allowing for additive manufacturing methods to be used—however, details regarding these aspects are beyond the scope of the current paper. By combining empirical formulas, computational fluid dynamics (CFD) analysis, and artificial neural networks (ANNs), the research focuses on achieving high efficiency and fast manufacturing. A series of geometries have been sized and validated using steady-state RANS (Reynolds Averaged Navier-Stokes) simulations, leading to the identification of the most efficient configuration. Subsequent optimization using an ANN resulted in a refined impeller design with notable improvements in hydraulic performance: a 3.55% increase in efficiency and a 7.9% increase in head. Key parameters influencing impeller performance, including blade number, incidence, and backsweep angles, are identified. This approach offers a comprehensive method to address the evolving requirements of space missions and contributes to the advancement of centrifugal pump technology in the space domain.

Experimental validation of auxetic stent designs: three-point bending of 3D printed Titanium prototypes

Experimental validation of auxetic stent designs: three-point bending of 3D printed Titanium prototypes

Comparative analysis of modern technologies of additive production

In today's conditions, 3D printing is used to create unique models, prototypes, and equipment necessary for conducting experiments and studying various phenomena and processes, for the rapid prototyping of various parts and devices in scientific and engineering research. 3D printing technologies are actively used to create individual medical implants, prostheses, and organ models for training and planning operations, which significantly improves the quality of medical care. In the aerospace and automotive industries, additive manufacturing is used to create lightweight and durable parts helping to reduce weight and improve vehicle efficiency. The use of additive manufacturing methods, technologies, and tools allows you to check and test designs and concepts before mass production. In this work, a detailed analysis of various existing 3D printers is carried out depending on the tasks, and modern technologies of additive manufacturing are investigated depending on the set goals and scientific and applied tasks. Such technologies include Fused Deposition Modeling, Stereolithography, Selective Laser Sintering, Direct Metal Laser Sintering, and Digital Light Processing. In the work, a comparative analysis of these technologies was carried out according to various criteria, such as principle of operation, materials, resolution, surface finish, accuracy, speed, strength, application, cost, complexity of parts, and post-processing. For each technology, the advantages and disadvantages of its use are determined depending on the goals and objectives. It should be noted that some materials may not be suitable for printing complex parts or require additional support during the printing process. This can lead to complexity in the processing of products and increase the time and costs of printing. Improper selection of materials for 3D printing can be harmful to the environment or human health when used incorrectly. For example, some plastic materials may emit toxic elements or have low biodegradability. Also, using excess expensive material unnecessarily can increase the cost of the project. Keywords: additive manufacturing, 3D printing, additive manufacturing technologies, Fused Deposition Modeling, Stereolithography, Selective Laser Sintering, Direct Metal Laser Sintering, Digital Light Processing.

Effect of polymer infiltration and pyrolysis (PIP) on microstructure and properties of high volume fraction SiC/Al composites prepared by a novel hybrid additive manufacturing

High-volume-fraction SiC/Al (HVF-SiC/Al) composites have a wide range of applications in aerospace, optics, automotive and electronic packaging. However, because the hardness, brittleness and wear resistance increase with the increase in the volume fraction, it is difficult for traditional methods such as machining, to process HVF-SiC/Al composites to complex components. Therefore, in this paper, a novel method of the hybrid additive manufacturing is proposed to fabricate complex-structures SiC/Al composite parts. The effect of polymer infiltration and pyrolysis (PIP) on microstructure and properties of HVF-SiC/Al composites is investigated. The results show that the mechanical properties of the SiC preforms can be effctively enhanced by the PIP process, and this enhancement makes the SiC preforms meet the conditions for subsequent vacuum-pressure infiltration. The mechanical property of HVF-SiC/Al composites show a huge increase when in creasing the volume fraction of SiC. In particular, the flexural strength of HVF-SiC/Al composites increased from 202.28 MPa to 380.87 MPa, and the coefficient of thermal expansion (CTE) has also been reduced from 11.80 to 6.28 × 10−6/K, when the volume fraction of SiC increases from 42 to 80 vol%. For optimise the PIP process in the future, three theoretical models are used to predict the relationship between the CTE and the volume fraction of SiC. The results show that the experimental data are more consistent with the predicted values based on the Kerner's model, but deviate from the Rule-of-mixture (ROM) and Turner's models. Importantly, the complex-structures SiC/Al composite parts was successfully fabricated by this hybrid additive manufacturing.

Biolayer-Interferometry-Guided Functionalization of Screen-Printed Graphene for Label-Free Electrochemical Virus Detection.

Additive manufacturing holds promise for rapid prototyping and low-cost production of biosensors for diverse pathogens. Among additive manufacturing methods, screen printing is particularly desirable for high-throughput production of sensing platforms. However, this technique needs to be combined with carefully formulated inks, rapid postprocessing, and selective functionalization to meet all requirements for high-performance biosensing applications. Here, we present screen-printed graphene electrodes that are processed with thermal annealing to achieve high surface area and electrical conductivity for sensitive biodetection via electrochemical impedance spectroscopy. As a proof-of-concept, this biosensing platform is utilized for electrochemical detection of SARS-CoV-2. To ensure reliable specificity in the presence of multiple variants, biolayer interferometry (BLI) is used as a label-free and dynamic screening method to identify optimal antibodies for concurrent affinity to the Spike S1 proteins of Delta, Omicron, and Wild Type SARS-CoV-2 variants while maintaining low affinity to competing pathogens such as Influenza H1N1. The BLI-identified antibodies are robustly bound to the graphene electrode surface via oxygen moieties that are introduced during the thermal annealing process. The resulting electrochemical immunosensors achieve superior metrics including rapid detection (55 s readout following 15 min of incubation), low limits of detection (approaching 500 ag/mL for the Omicron variant), and high selectivity toward multiple variants. Importantly, the sensors perform well on clinical saliva samples detecting as few as 103 copies/mL of SARS-CoV-2 Omicron, following CDC protocols. The combination of the screen-printed graphene sensing platform and effective antibody selection using BLI can be generalized to a wide range of point-of-care immunosensors.

Macroporous polymer-derived ceramics produced by standard and additive manufacturing methods: how the shaping technique can affect their high temperature thermal behavior

Macroporous polymer-derived ceramics produced by standard and additive manufacturing methods: how the shaping technique can affect their high temperature thermal behavior

Hybrid interlayer hot rolling and wire arc additive manufacturing of Al-Mg alloy: Microstructure, mechanical properties and strengthening mechanism

Considering the deformation-strengthening benefits of Al-Mg alloy and the high forming efficiency offered by wire and arc additive manufacturing (WAAM), the microstructure evolution and strengthening mechanism of hybrid interlayer hot rolling and wire arc additive manufacturing (HR-WAAM) samples have been systematically investigated in this study. The results indicate that interlayer hot rolling can effectively reduce the size and number of pores, which diminishes the stress concentration areas. Additionally, rolling deformation significantly enhances the effect of dislocation strengthening. Furthermore, a high density of dislocations can promote recrystallization to refine grain size, while also improving grain orientation, all of which contribute to better stress distribution. Due to these reasons, the strength and toughness of the alloy are notably improved. The average ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) values achieved by HR-WAAM samples were 338 MPa, 276 MPa, and 20.9%, respectively. These values represent increases of 28.5%, 41.5%, and 38.4% compared to conventional WAAM samples. These findings are expected to provide an efficient and cost-effective method for additive manufacturing (AM) of deformation-strengthened aluminum alloys.

Mechanical and corrosion performance of WAAM printed steel structure

Wire plus arc additive manufacturing (WAAM) is rapidly growing into a popular and cost-effective technology for manufacturing medium-large complex structured components. WAAM is a novel metal additive manufacturing method that deposits material layer by layer using an electric arc as a heat source, allowing the creation of metal components with high mechanical characteristics. The procedure allows for the construction of a near-net-shape structure at a rapid pace of production (50–130 gm/min) and material utilization efficiency (80–90 %). The present study mainly focuses on the fabrication of the WAAM structure and a detailed investigation of the mechanical and corrosion performance of multi-layer fabricated wall components. The most versatile and widely applicable stainless steel SS316L material is employed to build multi-layered wall structures. The average micro-hardness of the WAAM-built structure along the building direction was found to be 197.43±1.46 HV0.3 and that of the commercially available counterpart was found to be 187.26±1.17 HV0.3. Moreover, the maximum hardness was observed close to the bottom region (201.86±1.44 HV0.3) which further reduces with the building height. The ultimate tensile strength, and yield strength of the WAAM printed wall obtained as 573.81±2.3 MPa, and 275.41±1.1 MPa respectively found to have improved mechanical strength to that of wrought counter-part however the ductility in the form of percent elongation gets slightly reduced. Furthermore, comparable corrosion resistance was observed for the WAAM fabricated wall structure and conventionally manufactured SS316L structure. The bottom region experiences better corrosion resistance compared to the upper region in both saline environment and acidic corrosion solution with an average corrosion rate of 0.0276 mm/yr, and 0.0366 mm/yr respectively.

Effect of Process Parameters on the Mechanical Behavior of Ti6Al4V Alloys Fabricated by Laser Powder Bed Fusion Method

The parameters used in the production process in laser powder bed fusion (L-PBF) technology, one of the additive manufacturing methods, have a critical effect on the mechanical behavior and density properties of the product and can change the properties of the product. Therefore, this study examined the influence of laser power, scanning speed, hatch spacing and beam rotation angle on the tensile strength, impact energy, surface roughness, and porosity levels of Ti-6Al-4V produced through the L-PBF method. It was observed that the tensile strength changes directly proportional to the laser power. In addition, the tensile strength decreases significantly with a value of 645 MPa obtained at lowest 0.07 mm hatch spacing, 190 W laser power and 900 mm scanning speed. The lowest value of impact energy, with a value of 8.7 J, was reached at a rotation angle of 180°. It has been determined that surface roughness decreases significantly with increasing laser power, while it demonstrates an increase with higher scanning speeds. Surface roughness values of 8.9 μm parallel and 8.35 μm perpendicular to the building direction were achieved at a laser power level of 220 W. Laser power was identified as the most influential factor in determining the porosity ratio, with a high porosity rate 0.48% occurring at 160 W laser power. Furthermore, an increase in scanning speed resulted in a corresponding increase in the porosity rate.

3D printers and their use in prosthetic dentistry

In recent years, the use of computer-aided design and computer-aided manufacturing (CAD/CAM) has increased considerably in addition to the traditional methods used in routine. CAD/CAM technology has many advantages. However, despite these advantages, it has a very important disadvantage such as material waste. Today, the technology that overcomes this problem is the additive manufacturing method with three-dimensional printers. This method has recently replaced the traditional subtractive computer-aided design and manufacturing technology in prosthodontics. The use of 3D printers has been increasing in recent years due to its advantages such as ease of production, time saving and material saving, freedom of design, error-free and faster production. It is also predicted that the use of this technology will increase in the future and will be the main method for digital manufacturing. The aim of this review is to evaluate the production methods of 3D printers, the areas of use in prosthodontics, the advantages and disadvantages of 3D production methods, and to review the purposes of use, materials used and developments in prosthodontics.

Improving the Flexibility of Ship Propellers Additively Manufactured from High-Density Polyethylene/Long Carbon Fiber Composites by Prepreg Coating.

In efforts to achieve the goal of reducing ship emissions in the fight against climate change, reducing fuel consumption by making ships lighter is stated as one of the solutions. In this study, the possibilities of making composite equivalents of propellers, which are the most complex ship elements and traditionally produced from metal materials, are investigated with the advantages of additive manufacturing, which offers a rapid production opportunity for such forms. In this way, a lighter composite propeller and, therefore, a lighter ship will be achieved, and negative environmental impacts, especially harmful emissions, will be reduced. In the study, a 1/14-scale ship propeller was produced through the material extrusion method of additive manufacturing using an HDPE composite containing long carbon fiber with a 15% weight fraction. An attempt to reduce flexibility with an epoxy-carbon fabric prepreg coating was made, as the flexibility has negative effects on the performance of the produced propeller. The propeller tunnel test showed that the applied carbon fabric epoxy prepreg helped to improve the propeller's performance by decreasing the flexibility of the propeller and reducing the deformation at the tips. At the same time, the propeller weight was decreased by 60% compared to its metal counterparts.

Progress and Challenges of Additive Manufacturing of Tungsten and Alloys as Plasma-Facing Materials.

Tungsten (W) and W alloys are considered as primary candidates for plasma-facing components (PFCs) that must perform in severe environments in terms of temperature, neutron fluxes, plasma effects, and irradiation bombardment. These materials are notoriously difficult to produce using additive manufacturing (AM) methods due to issues inherent to these techniques. The progress on applying AM techniques to W-based PFC applications is reviewed and the technical issues in selected manufacturing methods are discussed in this review. Specifically, we focus on the recent development and applications of laser powder bed fusion (LPBF), electron beam melting (EBM), and direct energy deposition (DED) in W materials due to their abilities to preserve the properties of W as potential PFCs. Additionally, the existing literature on irradiation effects on W and W alloys is surveyed, with possible solutions to those issues therein addressed. Finally, the gaps in possible future research on additively manufactured W are identified and outlined.

STRESS, EQUIVALENT STRAIN AND DEFORMATION FOR MACHINING OPERATION UTILIZING EXPLICIT DYNAMIC ANALYSIS FOR VARIOUS MATERIALS

Subtractive and additive manufacturing methods constitute the two main categories of modern manufacturing technology used in the manufacturing sector. The subtractive method is used for material removal and is performed in (Brass, Aluminum and Teflon), the machining process is achieved using CNC (Computer Numerical Method) turn machine. The main objective of the paper is to perform FEA (Finite Element Analysis) over the three material (Brass, Aluminum and Teflon). The CNC machine is used to perform a machining over the three-material stated above, but within the CNC machine there is no provision for achieving the various values of (stress, strain and deformation) during the machining operation. During the machining process, it’s very difficult to get and accurate value of stress for the tool and raw (test) material, so Ansys FEA analysis method is adopted to predict the parameter like stress, strain and total deformation. The analysis part is achieved by the developing the CAD model using Solid work and FEA analysis using Ansys and thereby the output will be helpful to understand the various stress parameters. The results highlight that Teflon has a higher value for total deformation followed by aluminum and brass. The equivalent strain for the Teflon is higher and followed by brass and aluminum. The stress is acting in axial and compressive direction, so brass have a higher value followed by aluminum and Teflon. This method and analysis procedure can be adopted for understanding the deformation, stress and stain acting on any material, which will be highly useful for material of higher with a higher hardness value.

Laser-inherent porosity defects in additively manufactured Ti–6Al–4V implant: Formation, distribution, and effect on fatigue performance

Porosity defects are inherently present in Ti–6Al–4V (Ti6-4) parts produced using additive manufacturing (AM) methods like laser powder-bed fusion (LPBF). This work aims to investigate different laser-inherent porosity defects at various LPBF parameter settings and assess their impact on the fatigue behaviour of Ti6-4 implants processed by LPBF. The presence of LPBF-inherent porosity defects with different shapes and sizes was established using microstructural examination and X-ray micro-CT analysis. These mostly comprise lack-of-fusion porosity (LoFP), gas-entrapped porosity (GeP), and pores-induced microcracks. Volumetric porosity defects were seen to range from 1.9 × 104 to 9.52 × 105 μm3. The L-1 specimen exhibited the lowest defect, while the L-6 specimen displayed the largest number of defects. While LoFP defects predominate in L-6, there was a notable presence of GeP defects in the specimens processed using the factory default condition (L-D). Upon examination of the majority of specimens, GeP and LoFP coalesced to form clusters, leading to the formation of pores-induced microcracks. This ultimately leads to a decrease in fatigue performance. By maintaining the power at the default setting and increasing the scan speed by 8% of the default value, a specimen (L-1) with minimal porosity defects and superior fatigue performance is achieved. L-6 exhibits defects with significant dimensions and irregular form. Consequently, it displays inferior fatigue characteristics.

Hybrid additive manufacturing of aluminum matrix composites with improved mechanical properties compared to extruded counterparts

Great difficulties existed in fabricating large components of SiC particles reinforced aluminum matrix composites with excellent mechanical properties using existing manufacturing procedures. This study demonstrated that the challenges can be addressed by developing a hybrid solid-state additive manufacturing method. The influence of the deposition procedures and the post-processing heat treatment on the microstructure and mechanical properties of the SiC particles reinforced 2009 aluminum ally matrix composites (SiCp/2009Al composites) was systematically investigated using advanced technologies such as spherical aberration corrected transmission electron microscope, atom probe tomography, etc. The results showed that the SiCp/2009Al composites produced by the hybrid solid-state additive manufacturing exhibited enhanced tensile properties and improved isotropy in mechanical properties compared to the extruded feedstock of SiCp/2009Al composites. This was attributed to the formation of dense metal with uniformly distributed SiC particles, high-density of Cu–Mg co-clusters, refined grains and SiC particles, low deformation texture, tightly bonded SiCp/2009Al interface, and sound interfacial bonding between deposited layers.

Review of Luneburg Lens Antenna Designs Manufactured Using 3D Printing

Introduction. The interest in multibeam dielectric lens antenna arrays has been growing in recent years due to the development of millimeter-wave telecommunication and radar systems. Progress in the development of mobile communication systems based on adaptive beamforming technology is increasingly associated with multibeam systems based on lens antenna structures, providing an alternative to hard-to-implement and energy-consuming phased antenna arrays. In recent years, spherical and cylindrical Luneburg lens antennas implemented using additive manufacturing technology have attracted research attention. Despite their complexity of execution, these design exhibit excellent electromagnetic characteristics. This paper provides a review of Luneburg lens antennas manufactured using 3D printing, which can find application in 5G and 6G communication systems.Aim. To review achievements in the design of lens antenna structures manufactured using additive manufacturing.Materials and methods. Materials for analysis, comparison, and systematization were derived from various sources, including research articles, publications in proceedings of Russian and international conferences, and websites of manufacturers of lens antennas over the past 20 years. The material selection mechanism was based on the originality of the presented designs of printed Luneburg lens antennas.Results. A review of Luneburg lens antennas manufactured using 3D printing, which differ from each other in terms of mechanical strength, complexity of execution, and electrodynamic characteristics, was carried out. The results of a comparative analysis of the key characteristics of these antennas are presented, along with examples of their practical implementation.Conclusion. The disadvantage of Luneburg lens antennas has always been the complexity of their manufacture; however, additive manufacturing technologies open up new opportunities for their fast, high-quality, and automated production. Various 3D printing technologies can be used to create dielectric lens antennas, which differ in the resolution of printers, printing speed, and cost. Additive manufacturing methods are constantly developing, having reached the technological possibility of printing Luneburg lens for the sub-THz range with a high level of resolution and accuracy. In addition, 3D printers capable of printing multiple lenses simultaneously have also appeared.