Search Results (12,658)

Inconel 718 (IN718) is a polycrystalline nickel-based superalloy and one of the most widely used materials in the aerospace industry owing to its excellent mechanical performances at high temperatures, including creep resistance. Interest in additively manufactured components in aerospace is greatly increasing due to their ability to reduce material consumption, to manufacture complex parts, and to produce out-of-equilibrium microstructures, which can be beneficial for mechanical behavior. IN718’s properties are, however, very sensitive to microstructural features, which strongly depend on the manufacturing process and subsequent heat treatments. Additive manufacturing and, more specifically, Laser Powder Bed Fusion (LPBF) induces very high thermal gradients and anisotropic features due to its inherently directional nature, which largely defines the microstructure of the alloy. Hence, defining appropriate manufacturing parameters and heat treatments is critical to obtain appropriate mechanical behavior. This review aims to present the main microstructural features of IN718 produced by LPBF, the creep mechanisms taking place, the optimal microstructure for creep strength, and the most efficient heat treatments to yield such an optimized microstructure. Full article

The rise of Industry 4.0 has introduced challenges and new production models like additive manufacturing (AM), enabling the creation of complex objects previously unattainable. However, many polymers remain underutilized due to the need for improved mechanical properties and reduced process-induced anisotropy. ME-based part construction involves successive filament deposition, akin to welding. Upon exiting the nozzle, the polymer solidifies within seconds, limiting the time and temperature available for diffusion and efficient bonding with the adjacent filament. Therefore, optimizing this welding process is essential. The primary objective of this review was to report on the equipment utilized to enhance the bonding between filaments deposited during manufacturing. While higher temperatures improve welding, most equipment cannot endure prolonged high-heat operations, limiting the use of engineering-grade polymers. Modifying polymer matrices by incorporating low-molar-mass molecules can boost welding and mechanical strength. Significant gains in mechanical properties have come from matrix modifications and new in situ welding devices. Reported devices use light (laser, UV IR), electric current, radio frequency and heat collection from the nozzle. The simplest device is a heat collector, while a double laser beam system has achieved the highest mechanical properties without matrix modification. There was an improvement in properties ranging from 20% to 200%. Full article

This study explores the impact of blending polyethylene terephthalate (PET) with polybutylene terephthalate (PBT) on the thermal, structural, and mechanical properties of 3D-printed materials. Comprehensive analyses, including Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and mechanical testing, were conducted to assess the influence of blend composition. FT-IR confirmed that PET and PBT blend physically without transesterification, while TGA showed enhanced thermal stability with increasing PET content. XRD revealed that PET and PBT crystallize separately, with the crystallinity decreasing sharply for blends with more than 50% PET. The DSC results indicated that PET effectively slows down the crystallization kinetics of PBT, promoting cold crystallization. Mechanical tests demonstrated that the elastic modulus remains relatively unchanged, but the strain at break decreases with a higher PET content, indicating increased stiffness and reduced ductility. Overall, incorporating PET into PBT improves 3D-printability and dimensional stability, reducing warpage and enhancing print precision, making these blends advantageous for 3D-printing applications. Full article

Optimization methods tailored for practical engineering applications continue to evolve in order to realize lightweight single-layer reticulated shell structures and maximize node stiffness. This paper takes the minimum amount of steel as the objective function, and divides the rod types into three groups and three corresponding one-to-one optimization schemes. Considering the stress and stiffness of the rod and the displacement and stability constraints of the whole structure, the equal step search method combined with the criterion method is used to optimize the rod size. Then the multi-scale calculation model based on the multi-point constraint method is established. Through calculation and analysis, the boundary load condition of the target node is obtained as the boundary condition of node optimization. Finally, the variable density method is used to optimize the topology of the node domain, and the minimum member size is included in the constraint conditions to obtain the optimized node form that is conducive to additive manufacturing. The research shows that reasonable cross-section value and grouping of members can effectively reduce the steel consumption without compromising the overall stability performance. The amount of steel used in the three optimization plans was reduced by 12%, 23%, and 28%, respectively, compared to before the optimization. The multi-scale model not only takes into account the calculation accuracy, but also can effectively simulate the stress conditions in the node domain. The development of topology optimization and additive manufacturing technology broadens the space for optimization design, and provides new ideas for advanced design to integrate intelligent manufacturing. Full article

Epoxy nanocomposites are widely used in various applications because of their excellent properties. Different types of manufacturing techniques are used to produce epoxy composites based on various fillers, molecular weight, and applications required. The physical properties and chemical structure of epoxy resin help in determining the method for its manufacturing. Coatings and adhesive formulations are prepared using high- molecular-weight epoxies, whereas epoxy nanocomposites require low-molecular-weight epoxies due to ease of manufacturing. A low-molecular-weight epoxy can provide high crosslink density to the epoxy but may also cause inherent brittleness in epoxy nanocomposites. Further, the addition of CNTs may also cause more brittleness in the final product. In this work, the authors have developed a method to process composites based on high-molecular-weight epoxy reinforced with high loading of CNTs (15 wt.%). The high molecular weight will bring lots of challenges during manufacturing. In this paper, a novel manufacturing technique based on separate molding and curing conditions to produce highly concentrated CNT-filled epoxy with high-molecular-weight epoxy resin is described, achieving excellent mechanical properties, good toughness, and high electrical conductivity in an efficient, low-cost, environmentally friendly, and high-volume way. The findings demonstrated improvements in these mechanical properties compared to conventional systems. They also highlight the potential of the novel method to develop advanced composite materials which can revolutionize industrial sectors such as aerospace, automotives, and electronics where structural integrity and thermal stability are important. Full article

An obstacle for many microfluidic developments is the fabrication of its structures, which is often complex, time-consuming, and expensive. Additive manufacturing can help to reduce these barriers. This study investigated whether the results of a microfluidic assay for the detection of the promyelocytic leukemia (PML)-retinoic acid receptor α (RARα) fusion protein (PML::RARA), and thus for the differential diagnosis of acute promyelocytic leukemia (APL), could be transferred from borosilicate glass microfluidic structures to additively manufactured fluidics. Digital light processing (DLP) and stereolithography (SLA) printers as well as different photopolymerizable methacrylate-based resins were tested for fabrication of the fluidics. To assess suitability, both print resolution and various physical properties, serializability, biocompatibility, and functionalization with biological molecules were analyzed. The results show that additively manufactured microfluidics are suitable for application in leukemia diagnostics. This was demonstrated by transferring the microfluidic sandwich enzyme-linked immunosorbent assay (ELISA) for PML::RARA onto the surface of magnetic microparticles from a glass structure to three-dimensional (3D)-printed parts. A comparison with conventional glass microstructures suggests lower sensitivity but highlights the potential of additive manufacturing for prototyping microfluidics. This may contribute to the wider use of microfluidics in biotechnological or medical applications. Full article

Sandwich structures with triply periodic minimal surface (TPMS) cores have garnered research attention due to their potential to address challenges in lightweight solutions, high-strength designs, and energy absorption capabilities. This study focuses on performing finite element analyses (FEAs) on eight novel TPMS cores and one stochastic topology. It presents a method of analysis obtained through implicit modeling in Ansys simulations and examines whether the results obtained differ from a conventional method that uses a non-uniform rational B-spline (NURBS) approach. The study further presents a sensitivity analysis and a qualitative analysis of the meshes and four material models are evaluated to find the best candidate for polymeric parts created by additive manufacturing (AM) using a stereolithography (SLA) method. The FEA results from static and explicit simulations are compared with experimental data and while discrepancies are identified in some of the specimens, the failure mechanism of the proposed topologies can generally be estimated without the need for an empirical investigation. Results suggest that implicit modeling, while more computationally expensive, is as accurate as traditional methods. Additionally, insights into numerical simulations and optimal input parameters are provided to effectively validate structural designs for sandwich-type engineering applications. Full article

Despite the impressive properties of additively manufactured products, their inherent anisotropy is a crucial challenge for polymeric parts made via fused filament fabrication (FFF). This study compared the tensile, thermophysical, smoke density, and toxicity characteristics of Ultem 9085 (a blend of polyetherimide and polycarbonate) for samples printed in various orientations (X, Y, and Z). The results revealed that mechanical properties, such as elastic modulus and tensile strength, significantly differed from the Z printing orientation, particularly in the X and Y printing layer orientations. Thermomechanical analysis revealed that Ultem 9085 had high anisotropic effects in the coefficient of thermal expansion, indicating superior thermal properties along the printing orientation. The smoke density and toxicity test results proved that Ultem 9085 complies with aviation safety standards. Smoke density tests showed that all samples, regardless of print orientation or thickness, stayed well below the regulatory limit, making them suitable for aircraft interiors. Full article

In the last thirty years, tissue engineering (TI) has emerged as an alternative method to regenerate tissues and organs and restore their function by implanting specific lineage cells, growth factors, or biomolecules functionalizing a matrix scaffold. Recently, several pathologies have led to bone loss or damage, such as malformations, bone resorption associated with benign or malignant tumors, periodontal disease, traumas, and others in which a discontinuity in tissue integrity is observed. Bone tissue is characterized by different stiffness, mechanical traction, and compression resistance as a function of the different compartments, which can influence susceptibility to injury or destruction. For this reason, research into repairing bone defects began several years ago to find a scaffold to improve bone regeneration. Different techniques can be used to manufacture 3D scaffolds for bone tissue regeneration based on optimizing reproducible scaffolds with a controlled hierarchical porous structure like the extracellular matrix of bone. Additionally, the scaffolds synthesized can facilitate the inclusion of bone or mesenchymal stem cells with growth factors that improve bone osteogenesis, recruiting new cells for the neighborhood to generate an optimal environment for tissue regeneration. In this review, current state-of-the-art scaffold manufacturing based on the use of polycaprolactone (PCL) as a biomaterial for bone tissue regeneration will be described by reporting relevant studies focusing on processing techniques, from traditional—i.e., freeze casting, thermally induced phase separation, gas foaming, solvent casting, and particle leaching—to more recent approaches, such as 3D additive manufacturing (i.e., 3D printing/bioprinting, electrofluid dynamics/electrospinning), as well as integrated techniques. As a function of the used technique, this work aims to offer a comprehensive overview of the benefits/limitations of PCL-based scaffolds in order to establish a relationship between scaffold composition, namely integration of other biomaterial phases’ structural properties (i.e., pore morphology and mechanical properties) and in vivo response. Full article

Background/Objectives: Rheumatoid arthritis (RA) is one of the most prevalent autoimmune diseases, characterized by an articular and extra-articular involvement, where autoantibodies, such as rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (ACPAs), are important biomarkers for the diagnosis. Autoantibody determination can be carried out using different assays. However, the results obtained are usually expressed in arbitrary units that are not comparable. Therefore, the aim of this study is to improve clinical interpretation of RF and ACPA test results using the likelihood ratio (LR). Methods: RF and ACPA titers were analyzed by turbidimetry and chemiluminescence using Optilite and BIO-FLASH systems, respectively, in 781 samples from patients with RA and in 1970 controls. Results: The higher the antibody titer of RF or ACPA, the higher the LR for RA. The definition of test result interval-specific LR based on predefined specificities for antibody levels provides more information than the use of the cut-off set by the manufacturer for each antibody. Conclusions: The LR for RA increased with an increasing antibody level. In addition, the use of test result interval-specific LR allows better clinical interpretation for RF and ACPA assays compared to the traditional idea of interpreting antibody results in a dichotomous manner, such as negative or positive. Full article

Our study considered porous Bouligand structured polymer, comprising polymer fibres with porous spaces between them. These are more complicated structures than the non-porous Bouligand, since the addition of porosity into the material creates a secondary variable besides fibre pitch. There is currently no analytical model available to predict the modulus of such materials. Our paper explores the correlation between porosity, polymer fibre pitch angle, and flexural modulus in porous Bouligand structured polymers. Our structures were digitally manufactured using stereolithography (SLA) additive manufacturing methods, after which they were subjected to three-point bending tests. Our aim was to simply and parametrically develop an analytical model that would capture the influences of both porosity and polymer fibre pitch angle on the flexural modulus of the material. Our model is expressed as Ef=Eporo(aθf3+bθf2+cθf+d), and we derive this by applying non-linear regression to our experimental data. This model predicts the flexural modulus, Ef, of porous Bouligand structured polymer as a function of both porosity and pitch angle. Here, Eporo is defined as the solid material modulus, Esolid, multiplied by porosity, ϕ and is a linear reduction in the modulus as a function of increasing porosity, while θf signifies the polymer fibre pitch angle. This relationship is relatively accurate within the range of 10° ≤ θ_f ≤ 50°, and for porosity values ranging from 0.277≤0.356, as supported by our evidence to date. Full article

This study investigates the mechanical properties of thermoplastic polyurethane (TPU) 60A, which is a flexible material that can be used to produce soft robotic grippers using additive manufacturing. Tensile tests were conducted under ISO 37 and ISO 527 standards to assess the effects of different printing orientations (0°, 45°, −45°, 90°, and quasi-isotropic) and test speeds (2 mm/min, 20 mm/min, and 200 mm/min) on the material’s performance. While the printing orientations at 0° and quasi-isotropic provided similar performance, the quasi-isotropic orientation demonstrated the most balanced mechanical behavior, establishing it as the optimal choice for robust and predictable performance, particularly for computational simulations. TPU 60A’s flexibility further emphasizes its suitability for handling delicate objects in industrial and agricultural applications, where damage prevention is critical. Computational simulations using the finite element method were conducted. To verify the accuracy of the models, a comparison was made between the average stresses of the tensile test and the computational predictions. The relative errors of force and displacement are lower than 5%. So, the constitutive model can accurately represent the material’s mechanical behavior, making it suitable for computational simulations with this material. The analysis of strain rates provided valuable insights into optimizing production processes for enhanced mechanical strength. The study highlights the importance of tailored printing parameters to achieve mechanical uniformity, suggesting improvements such as biaxial testing and G-code optimization for variable thickness deposition. Overall, the research study offers comprehensive guidelines for future design and manufacturing techniques in soft robotics. Full article

Titanium aluminides, particularly the Ti-48Al-2Cr-2Nb alloy, have drawn significant attention for their potential in high-temperature aerospace and automotive applications due to their exceptional performances and reduced density compared to nickel-based superalloys. However, their intermetallic nature poses challenges such as limited room-temperature ductility and fracture toughness, limiting their widespread application. Additive manufacturing, specifically Electron Beam Melting (EBM), has emerged as a promising method for producing complex-shaped components of titanium aluminides, overcoming challenges associated with conventional production methods. This work investigates the fracture behavior of Ti-48Al-2Cr-2Nb specimens with different microstructures, including duplex and equiaxed, under tensile and high-cycle fatigue at elevated temperatures. Fracture surfaces were analyzed to distinguish between static and dynamic fracture modes. A novel method, employing confocal microscopy acquisitions, is proposed to correlate surface roughness parameters with the causes of failure, offering new insights into the fracture mechanisms of titanium aluminides. The results reveal significant differences in roughness values between the propagation and fracture zones for all the temperatures and microstructure tested. At 650 °C, the crack propagation zone exhibits lower Sq values than the fracture zone, with the fracture zone showing more pronounced roughness, particularly for the equiaxed microstructure. However, at 760 °C, the difference in Sq values between the propagation and fracture zones becomes more pronounced, with a more substantial increase in Sq values in the fracture zone. These findings contribute to understanding fracture behavior in titanium aluminides and provide a predictive framework for assessing structural integrity based on surface characteristics. Full article

In ancient historical ceramics, for various reasons, some problems such as dirt and damage inevitably occur, and necessary repair work must be carried out. Throughout ceramics restoration work, the selection and use of materials are very important. Thus, it is necessary to explore the use of modern intelligent algorithms to assist the selection and application of restoration materials during the whole restoration process, in order to improve the effectiveness of ancient ceramics restoration. In this study, convolutional neural network (CNNs) technology and a machine learning (ML) algorithm were applied to images of ceramics for the defect identification and repair of ancient ceramics, aided by additive manufacturing (AM). The simulation results show that the recall of this algorithm for AM ancient ceramics image recognition was improved by 19.68%. In order to enhance the restoration effects on ancient ceramics, it is necessary to enhance their restoration by expanding the use of digital technology, with the intent to maintain the advantages of traditional handicrafts. Therefore, we should review experiences in the restoration of ancient ceramics, introduce digital technology according to specific needs, and enhance the advanced nature of restoration work. Full article

Smart homes offer promising opportunities for risk prevention in private households, especially concerning safety and health. For instance, they can reduce safety risks by detecting water leakages quickly and support health by monitoring air quality. Current research on smart home technology predominantly focuses on usability, performance expectations, and cyber risks, overlooking the potential importance of risk prevention benefits to prospective users. We address this gap by utilizing data from a recent survey to construct a structural equation model. Our overarching hypothesis is that prevention benefits and comfort considerations positively influence adoption. The results confirm the relevance of comfort, as suggested by previous research. In addition, the results reveal significant prevention benefits in safety and health, which are positively related to technology expectations and the intention to adopt smart homes. Furthermore, newly included variables such as technology affinity and active aging lifestyle emerge as indicators of potential smart home users, extending the knowledge of user characteristics beyond traditional sociodemographic indicators. The findings contribute to filling a gap in the current risk and technology literature and are also relevant for smart home device manufacturers and risk and insurance practitioners looking to evolve their business models. Full article