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Recently, short carbon fiber-reinforced plastic (SFRP) has been selected as a filament material to improve the strength of components fabricated by material extrusion (ME). However, despite the improved material properties, the weak interlayer bonding and voids present in the microstructure constitute defects that cause anisotropy in the SFRP composite and deteriorate its mechanical properties such as the tensile, compressive, and flexural strengths. In this study, warm isostatic pressing (WIP) was investigated as a means to increase the interlayer bonding force and reduce the voids. To increase the efficiency of WIP, vacuum packing was investigated as a means to promote interfacial strength and diffusion between the layers. The WIP process improved the tensile, compressive, and flexural properties, and the anisotropy decreased with increasing interlayer bonding force. In addition, the thermal properties improved with an increase in the degree of crystallinity, and the voids in the microstructure were effectively reduced. These results indicate that WIP is a promising post-processing treatment for ME-fabricated SFRP parts.

Abstract Two-photon stereolithography (TPS) is widely used for the fabrication of various three–dimensional (3D) structures with sub-micron fabrication resolution in a single fabrication process. However, TPS is unsuitable for microstructures with fine-hole patterns. The laser ablation process can be easily drilled, or made holes in various materials. However, in the case of laser ablation, the focal plane of the laser is fixed, which is limited to the processing plane. In this study, a multidirectional ablation process is studied to apply laser ablation to various processing planes of a 3D microstructure fabricated by the TPS process. A 3D hybrid fabrication process with the advantages of both TPS and laser ablation is expected to improve the fabrication efficiency. The 3D hybrid process is proposed based on a single laser source. The microstructure is fabricated using TPS, and the multi-directional ablation process creates a hole in the lateral side of the 3D microstructure. To develop the multidirectional ablation process, the reflecting mirror system should be designed to adaptably rotate the laser focal plane and guide the laser path for the target process plane. Through various examples, we demonstrate the ability of the multi-directional ablation process with various examples.

Binder jetting (BJ) leads to low mechanical properties and high porosity because it uses binders to selectively bind powder materials. To overcome the poor characteristics of BJ parts, infiltration is a generally applied post-process; however, it results in a low infiltration volume and large number of residual voids in the uninfiltrated section. This study aims to effectively improve the mechanical properties, microstructure, and density of polymer-based BJ parts by overcoming limitations of infiltration process via warm isostatic pressing (WIP) that applies heat and pressure. The infiltrated specimens with epoxy are vacuum-packed, and the WIP process is performed at a target temperature of 130 °C and pressure of 8 MPa. Consequently, the infiltration volume increases by up to 195.2%, and the number of residual voids in the uninfiltrated section, where the infiltrants do not reach, is significantly reduced. Further, in terms of the mechanical properties, the tensile strength increases by 1215%, compressive strength by 1280%, and flexural strength by 535%. In addition, the results of transmission, scanning electron microscopy, and microcomputer X-ray tomography reveal a clear decrease in the number of voids.

In this study, we present the energy absorption capabilities achieved through the application of hybrid lattice structures, emphasizing their potential across various industrial sectors. Utilizing Ti-6Al-4V and powder bed fusion (PBF) techniques, we fabricated distinct octet truss, diamond, and diagonal lattice structures, tailoring each to specific densities such as 10, 30, and 50%. Furthermore, through the innovative layering of diverse lattice types, we introduced hybrid lattice structures that effectively overcome the inherent energy absorption limitations of single-lattice structures. As a result, we conducted a comprehensive comparison between single-lattice structures and hybrid lattice structures of equal density, unequivocally showcasing the latter’s superior energy absorption performance in terms of compression. The single-lattice structure, OT, showed an energy absorption of 42.6 J/m3, while the reinforced hybrid lattice structure, OT-DM, represented an energy absorption of 77.8 J/m3. These findings demonstrate the significant potential of hybrid lattice structures, particularly in energy-intensive domains such as shock absorption structures. By adeptly integrating various lattice architectures and leveraging their collective energy dissipation properties, hybrid lattice structures offer a promising avenue for addressing energy absorption challenges across diverse industrial applications.

In this study, a material extrusion (MEX) nozzle for fabricating bond magnets was designed to form a unidirectional magnetic field with a solenoid. The hard magnetic properties of the bonded magnets were enhanced by induced magnetic anisotropy. The magnetic field strength for magnetic alignment was controlled by the current applied to the solenoid, and the magnetic field strength formed at the bottom of the solenoid was approximately 10 mT. When a magnetic field was applied to the magnetic particles in filaments, magnetic spins and domains that existed in spherical magnetic particles were magnetically rotated and preferentially aligned with the induced magnetic field. Subsequently, as the polymer matrix was softened by the heat generated by the current induced in the solenoid, bonded magnets were additively manufactured using MEX with in situ magnetic field, and hard magnetic properties such as coercivity, remanence, and maximum energy product of the manufactured magnets were confirmed to be enhanced. The improvement in hard magnetic properties was attributed to the increased magnetic anisotropy caused by magnetic alignment. Based on the results of this study, we expect MEX with a magnetic field application system to be used in the future for manufacturing complex-shaped bonded magnets with improved magnetic properties.

Owing to the deposition mechanism, parts fabricated by polymer-based powder bed fusion (PBF) contain numerous porosities, which deteriorate mechanical properties. To address this problem, a warm isostatic press (WIP) process was adopted to control the temperature and isostatic pressure in the chamber. When only the temperature was applied (annealing), the tensile strength increased, but the elongation at break decreased in specimens fabricated with powders of polyamide 12 (PA12) because of the increase in crystallinity without a decrease in porosities. However, when temperature and pressure were simultaneously applied, the tensile strength increased compared with tensile strengths of specimens treated with and without post-processing. The elongation at break compensates for the reduced value obtained by annealing. To identify the effect of the WIP process on the specimens fabricated by the PBF process, mechanical properties were quantitatively investigated. Additionally, tightness and injection moulding tests were performed to qualitatively estimate the effect. These tests verified the effectiveness of the WIP process in the PBF process.

This study proposes an eco-friendly (ECO) mold that is fabricated using the laser powder bed fusion (LPBF) method, which utilizes a three-dimensional (3D) cooling channel. Unlike previous studies, we designed surface-type conformal cooling channels (CCC) based on the design concept for additive manufacturing, at a constant depth corresponding to the casting part. Pin fins were installed inside the surface-type cooling channels and aligned through numerical analysis to induce the turbulence of the coolant uniformly through the cooling channel while generating less thermal stress during solidification of the as-cast Al-Si alloy-based product, which increased the cooling efficiency of the proposed ECO mold. Moreover, the ECO mold was utilized to cast an automobile piston to demonstrate its feasibility at an industrial level. The results showed that, the casting process decreased significantly from 133 to 105 s per piston (21% reduction) compared to the conventional mold with a single columnar cooling channel. Additionally, the average grain size of the ECO mold decreased from 502 to 398 µm. The ultimate tensile strength and Rockwell hardness increased by 12.5% and 5.5%, respectively.

In this study, we report a method for the repair of damaged SUS 630 parts by directed energy deposition (DED). Herein, we aim to analyze the variations in the mechanical properties of such parts caused by post-repair heat treatment performed to regain the pre-repair mechanical properties. Before repair, substrates were subjected to solution annealing (SA-wrought) or SA treatment followed by precipitation hardening (SA + PH-wrought). Each substrate was repaired using SUS 630 powder. The repaired region was dominated by BCC-structured ferrite (96.7%). It also contained FCC-structured retained austenite (3.3%). The martensite fraction of the samples treated with SA after repair increased by 3.1%. Although BCC remained dominant after the SA + PH post-repair heat treatment, reverted austenite and a large amount of precipitate were generated along the grain boundaries after sufficient aging time of PH treatment. The repaired region displayed lower hardness than the substrate. However, the post-repair heat treatment increased the hardness. Meanwhile, the tensile test results revealed that the tensile strength decreased from that of the wrought material because of the cracks generated at the interface between the repaired region and substrate. Although the tensile strength was improved by SA and SA + PH post-repair heat treatments, the elongation decreased because of the cracks at the interface and reduction in the FCC content of the repaired part. Although cracks occurred at the interface, tensile characteristics almost similar to those of SA-wrought and SA + PH-wrought were observed owing to SA + PH post-repair heat treatment.

Abstract Background In this study, we tested whether a combination of radiomic features extracted from baseline pre-immunotherapy computed tomography (CT) images and clinicopathological characteristics could be used as novel noninvasive biomarkers for predicting the clinical benefits of non-small cell lung cancer (NSCLC) patients treated with immune checkpoint inhibitors (ICIs). Methods The data from 92 consecutive patients with lung cancer who had been treated with ICIs were retrospectively analyzed. In total, 88 radiomic features were selected from the pretreatment CT images for the construction of a random forest model. Radiomics model 1 was constructed based on the Rad-score. Using multivariate logistic regression analysis, the Rad-score and significant predictors were integrated into a single predictive model (radiomics nomogram model 1) to predict the durable clinical benefit (DCB) of ICIs. Radiomics model 2 was developed based on the same Rad-score as radiomics model 1.Using multivariate Cox proportional hazards regression analysis, the Rad-score, and independent risk factors, radiomics nomogram model 2 was constructed to predict the progression-free survival (PFS). Results The models successfully predicted the patients who would benefit from ICIs. For radiomics model 1, the area under the receiver operating characteristic curve values for the training and validation cohorts were 0.848 and 0.795, respectively, whereas for radiomics nomogram model 1, the values were 0.902 and 0.877, respectively. For the PFS prediction, the Harrell’s concordance indexes for the training and validation cohorts were 0.717 and 0.760, respectively, using radiomics model 2, whereas they were 0.749 and 0.791, respectively, using radiomics nomogram model 2. Conclusions CT-based radiomic features and clinicopathological factors can be used prior to the initiation of immunotherapy for identifying NSCLC patients who are the most likely to benefit from the therapy. This could guide the individualized treatment strategy for advanced NSCLC.

An interfacial microstructural study was carried out to clarify the hardening mechanism of an as-built Co–Cr alloy fabricated by selective laser melting (SLM). Using transmission electron microscopy, we found a unique martensitic lamellar microstructure with a specific orientation relationship between the α-Co and ε-Co phases; specifically, a nanoscale microstructure consisting of (111)α-Co//(0002¯)ε-Co and [01¯1]α-Co//[1¯21¯0]ε-Co was formed on the Co–Cr alloy. The Co–Cr alloy fabricated by SLM with a martensitic microstructure achieved a Vickers hardness value of approximately 369.36 ± 11.86 HV without any secondary-phase particles such as carbides.

The specimens fabricated by material extrusion (ME)-type additive manufacturing (AM) have external notches because of their deposition mechanism. During tensile tests, accurate results cannot be obtained because the external notch causes stress concentration and induces fractures outside the gauge length. In this study, using laser cutting, we removed the notch of specimens without damage to the specimens. By removing the notch and stress concentration in specimens, fractures were induced within the gauge length with a 62% probability, whereas the specimens in which the notch and stress concentration were not removed had a 27% probability. Through this evaluation method, the tensile results of the specimens for various polymers can be compared fairly and quantitatively with a small standard deviation in terms of the tensile strength and elongation at break between the specimens.

In this study, the residual stress reduction through low energy density reheating method in selective laser melting (SLM) process and the correlation between microstructure and mechanical properties were investigated. Inconel 718 superalloy specimens were manufactured via SLM and subjected to reheating (RH) strategies with different energy density, which was based on laser rescanning method. The microstructures were characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The microstructure was observed in the vertical section, parallel to the building direction. With a scanning speed decrease in the RH conditions, the low angle grain boundary (LAGB) and average misoriented region fraction progressively increased. RH conditions exhibited higher Vickers hardness, tensile strength, and yield strength than those of the as-built condition, which increased slightly when the scanning speed was increased. Thermal residual stress was generally higher at z-axis than that at the x-axis. The lowest residual stress value was observed in the highest scanning speed RH condition, and as the scanning speed decreased, it became similar to that of the as-built condition.

The precise shape of a shift block support for the turbine blade of a hovercraft was additively manufactured using 17–4 precipitation-hardened stainless steel (STS 630) powder through laser powder bed fusion (LPBF). Subsequently, heat treatment under the H900 condition increased the yield strength and fracture strain of the shift block to 1313 MPa and 11.5%, respectively, and enhanced its corrosion resistance to seawater. This improvement in mechanical and physical properties is primarily because Cu precipitates were uniformly distributed at the interfacial boundaries along with the simultaneous suppression of the formation of Cr23C6 precipitates with weak corrosion resistance. Furthermore, this was attributed to the phase transformation from the as-built STS 630 comprising a mixture of austenite, ferrite, and martensite to a dual mixture of ferrite and martensite after the heat treatment. Thereafter, we topologically optimised the shift block and adopted a lattice structure to apply the design for additive manufacturing (DfAM).

A refined additive manufacturing system of material extrusion type was developed considering the high-temperature conditions of extruder and chamber. With this setup, a super engineering plastic material, named polyetheretherketone (PEEK), could be printed into three-dimensional (3D) parts without any delamination or warpage. To obtain maximum performance in terms of mechanical strength, experimental studies were conducted considering the thermal process parameters such as nozzle and chamber temperatures. These optimal process settings and carefully controlled heating conditions, incorporated with post-processing of additional heat treatment, could provide a high degree of crystallinity and high tensile strength (i.e., more than 90% compared to original material properties). To demonstrate the feasibility of industrial applications, we fabricated and tested several product prototypes, such as a wafer jig, a lathe chuck part, and plastic injection molds, all of which confirmed the excellent performance of PEEK for chemical resistance, high strength, and heat resistance, respectively.

Material extrusion (ME) using a filament including metal powders has recently attracted considerable attention because it allows the production of metal parts at low cost. However, like other additive manufacturing processes, metal ME suffers from the problem of internal pores. In this study, warm isostatic pressure (WIP)—a post-process used to downsize or remove the pores in polymer ME—was employed in metal ME to improve the mechanical properties of the finished part. It was confirmed experimentally that the tensile strength and the strain at the ultimate tensile strength were increased by WIP. However, from hardness tests, two different results were obtained. On a microscopic scale, there was no change in hardness because the temperature of the WIP process was not high enough to change the microstructure, while on a macroscopic scale, the hardness changed owing to the collapse of the pores within the material under the indenter load. In specimens with relatively large pores, the hardness sensitivity increases with a larger indenter. Finally, factors affecting the WIP process parameters in metal ME were discussed.

Laser powder bed fusion (L-PBF)-processed 17-4 PH stainless steel (SS) generally exhibits a non-equilibrium microstructure consisting mostly of columnar δ-ferrite grains and a substantial fraction of retained austenite and martensite, contrary to 17-4 PH SS wrought with a fully martensite structure and coarse grains. Despite the different microstructures of L-PBF and wrought 17-4 PH SS, post-processing is typically performed using the conventional heat treatment method. The insufficient effect of the heat treatment on the L-PBF product produces a δ-ferrite phase in the microstructure. To obtain improved mechanical properties, the addition of a normalizing treatment to the conventional heat treatment after L-PBF in a nitrogen gas environment was investigated. The fully martensitic matrix developed by adding the normalizing treatment contained homogeneous Cu precipitates and exhibited a similar or improved strength and elongation to failure compared to the wrought SS.

Due to the development of additive manufacturing (AM), lattice structure which cannot be fabricated by the conventional manufacturing process or have shape restriction has attracted much attention. We propose a new lightweight design method using two types of lattice structures considering the manufacturability in the metal selective laser melting (SLM) and structural characteristics. Firstly, the specific procedure for the proposed design method is presented. In order to apply the two lattice structures, relative density criterion is derived by fabricating experiments using metal SLM process and analyzing geometry according to relative density. The optimal relative density distribution is calculated by performing the topology optimization with minimum relative density using a commercial software package. This proposed method is computationally and experimentally validated by a three-point bending test. Simultaneously, the same procedure is applied to uniform lattice for comparison with the proposed method. This proposed design has a 46% increase in stiffness, a relative flexural rigidity of 35% compared to the solid material, and has a deformation mode different from the uniform lattice. This design sets the standard for using two lattice structures and gives a new perspective on lightweight design with lattice structures. Keywords: Lattice structure, Lightweight design, Additive manufacturing, Topology optimization, Selective laser melting (SLM), Sandwich panel

Fused deposition modeling (FDM), one of the archetypal 3D printing processes, typically requires support structures matched to printed model parts that principally have undercut or overhung features. Thus, the support removal is an essential postprocessing step after the FDM process. Here, we present an efficient and rapid method to remove the support part of an FDM-manufactured product using the phenomenon of oxidative degradation of hydrogen peroxide. This mechanism was significantly effective on polyvinyl alcohol (PVA), which has been widely used as a support material in the FDM process. Compared to water, hydrogen peroxide provided a two times faster dissolution rate of the PVA material. This could be increased another two times by applying ultrasonication to the solvent. In addition to the rapidness, we confirmed that amount of the support residues removed was enhanced, which was essentially caused by the surface roughness of the FDM-fabricated part. Furthermore, we demonstrated that there was no deterioration with respect to the mechanical properties or shape geometries of the obtained 3D printed parts. Taken together, these results are expected to help enhance the productivity of FDM by reducing the postprocessing time and to allow the removal of complicated and fine support structures, thereby improving the design capability of the FDM technique.

General anesthetics produce a widespread neurodepression in the central nervous system by enhancing inhibitory neurotransmission and reducing excitatory neurotransmission. However, the action mechanisms of general anesthetics are not completely understood. Moreover, the general anesthetic state comprises multiple components (amnesia, unconsciousness, analgesia, and immobility), each of which is mediated by different receptors and neuronal pathways. Recently, neurotransmitter- and voltage-gated ion channels have emerged as the most likely molecular targets for general anesthetics. The γ-aminobutyric acid type A (GABAA) receptors are leading candidates as a primary target of general anesthetics. This review summarizes current knowledge on how anesthetics modify GABAA receptor function.

Objective: To build a novel classifier using an optimized 3D-convolutional neural network for predicting high-grade small bowel obstruction (HGSBO). Summary background data: Acute SBO is one of the most common acute abdominal diseases requiring urgent surgery. While artificial intelligence and abdominal computed tomography (CT) have been used to determine surgical treatment, differentiating normal cases, HGSBO requiring emergency surgery, and low-grade SBO (LGSBO) or paralytic ileus is difficult. Methods: A deep learning classifier was used to predict high-risk acute SBO patients using CT images at a tertiary hospital. Images from three groups of subjects (normal, nonsurgical, and surgical) were extracted; the dataset used in the study included 578 cases from 250 normal subjects, with 209 HGSBO and 119 LGSBO patients; over 38 000 CT images were used. Data were analyzed from 1 June 2022 to 5 February 2023. The classification performance was assessed based on accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve. Results: After fivefold cross-validation, the WideResNet classifier using dual-branch architecture with depth retention pooling achieved an accuracy of 72.6%, an area under receiver operating characteristic of 0.90, a sensitivity of 72.6%, a specificity of 86.3%, a positive predictive value of 74.1%, and a negative predictive value of 86.6% on all the test sets. Conclusions: These results show the satisfactory performance of the deep learning classifier in predicting HGSBO compared to the previous machine learning model. The novel 3D classifier with dual-branch architecture and depth retention pooling based on artificial intelligence algorithms could be a reliable screening and decision-support tool for high-risk patients with SBO. [ABSTRACT FROM AUTHOR]