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For the fabrication of structures in complex environments and to improve device performance, this paper presents a thermoelastic topology optimization formulation for the design of support structures in layer-by-layer printed additive manufacturing. The formulation is written in the form of structural compliance minimization with two competing constraint functions, one related to mechanical performance (stress) considering mechanical stress and thermal stress and one related to thermal performance (temperature). The optimization problem is solved by applying the p-norm function to handle global stress constraints and overall temperature constraints, separately. The sensitivity information of the objective function and constraints is derived using the adjoint variable method. The design variables are updated using the Method of Moving Asymptotes (MMA). We present several examples that explore the ability of the formulation to obtain optimized support structures for additive manufacturing under different volume constraints, various performance constraints, and print orientations, which addresses the issues of mechanical and thermal stress concentration when considering thermoelastic coupled effect, thus validating the effectiveness of the proposed method. In comparison with previous works, thermal performance-related constraints are introduced in this study, which effectively solves the optimization problem under thermoelastic coupling effect. [ABSTRACT FROM AUTHOR]

In the detection of pipeline defects hidden after the support structure, the energy cannot be effectively transmitted to the defect and reflected to the transducer due to the existence of the support structure, resulting in the missing detection of defects. Torsional mode guided wave has certain advantages in defect detection of support pipelines because of its non-dispersive feature. Hence, a detection method with the torsional mode guided wave of multi-element axial local excitation is proposed to solve the problem. Firstly, the influence of different connection mode, element number, and element spacing on the transducer performance is discussed in detail by both simulations and experiments. Secondly, the performance of the transducer for detecting defects hidden after the support structure is verified by both simulations and experiments. The results show that when the number of elements is 3, the elements spacing is 3 mm, and the connection mode is parallel exciting and series receiving, the amplitude of the defect echo is 2.7 times that of the traditional ultrasonic guided wave detection method. In addition, the designed transducer could detect 3 mm diameter through-hole defect hidden after the support structures. [ABSTRACT FROM AUTHOR]

Even in digital workflows, models are required for fitting during the fabrication of dental prostheses. This study examined the influence of different parameters on the dimensional accuracy of three-dimensionally printed models. A stereolithographic data record was generated from a master model (SOLL). With digital light processing (DLP) and stereolithography (SLA) printing systems, 126 models were produced in several printing runs—SolFlex350 (S) (DLP, n = 24), CaraPrint 4.0 (C) (DLP, n = 48) and Form2 (F) (SLA, n = 54)—and their accuracy was compared with plaster and milled polyurethane models. In addition to the positioning on the build platform, a distinction was made between parallel and across arrangement of the models to the printer's front, solid and hollow models, and printing with and without support structures. For accuracy assessment, five measurement sections were defined on the model (A–E) and measured using a calibrated digital calliper and digital scans in combination with the GOM Inspect Professional software 2021. The mean deviation between the measurement methods for all distances was 79 µm. The mean deviation of the models from the digital SOLL model were 207.1 µm for the S series, 25.1 µm for the C series and 141.8 µm for the F series. While positioning did not have an influence, there were clinically relevant differences mainly regarding the choice of printer, but also individually in alignment, model structure and support structures. [ABSTRACT FROM AUTHOR]

This paper address the performance optimization of the battery heat sink module by analyzing the lattice structure of the battery heat sink module through in-depth modeling and simulation, and combining the laser powder bed fusion (LPBF)-forming technology with mechanical and corrosion resistance experiments for a comprehensive study. It is found that the introduction of the lattice skeleton significantly improves the thermal conductivity of the phase change material (PCM), realizing the efficient distribution and fast transfer of heat in the system. At the same time, the lattice skeleton makes the heat distribution in the heat exchanger more uniform, improves the utilization rate of the PCM, and helps to maintain the stability of the cell temperature. In addition, the melting of PCM in the lattice heat exchanger is more uniform, thus maximizing its latent heat capacity. In summary, by optimizing the lattice structure and introducing the lattice skeleton, this study successfully improves the performance of the battery heat dissipation system, which provides a strong guarantee for the high efficiency and stable operation of the battery, and provides new ideas and references for the development of the battery heat dissipation technology. [ABSTRACT FROM AUTHOR]

Laser beam powder bed fusion (LB-PBF) is an edge additive manufacturing technology that allows complex near-net shape components to be produced. The freedom of design of the LB-PBF process makes it possible to produce optimized geometries, driving the application of this process in sectors in which high performance is fundamental such as aerospace and automotive. However, the building process inherently generates residual stresses in the part and the use of support structures become essential to anchor the part to the building platform and avoid problems in the downfacing surfaces that may warp or collapse during the production process. In this paper, different support densities obtained using different geometries of support structures are investigated to evaluate how they affect the residual stress distribution in the supported part. Two families of support structures were considered, linear-type and volumetric-type, including also a hybrid support structure that combined a massive volume topped by a linear support structure. Results highlighted that the combined choice of support density and geometry influences the magnitude and the distribution of sub-superficial residual stresses near the support-part interface and that appropriate design is essential to prevent excessive distortion or failure. [ABSTRACT FROM AUTHOR]

Expansive soils exhibit directionally dependent swelling that traditional isotropic models fail to capture. This study investigates the anisotropic swelling characteristics of expansive soil with a medium swelling potential through the use of modified oedometric testing. Vertical swelling strains can reach up to 1.71 times that of the horizontal movements, confirming intrinsic anisotropy. A nonlinear elastic constitutive model incorporates vertical and horizontal elastic moduli with respect to matric suction to characterize anisotropy. Three elastic parameters were determined through the experiments, and predictive equations were developed to estimate the unsaturated moduli. The constitutive model and predictive techniques provide practical tools to better assess expansive soil pressures considering anisotropy, offering guidelines for utilization and design. The outcomes advance understanding of these soils' directionally dependent behavior and stress–strain–suction response. [ABSTRACT FROM AUTHOR]

In comparison to conventional manufacturing technologies, additive manufacturing (AM) offers great design freedom, the integration of functions into components, new lightweight design concepts and high material efficiency. In aerospace and turbomachinery, this technology is increasingly coming into focus, especially the laser-based powder bed fusion of metals (PBF-LB/M) process. PBF-LB/M is already used for some aerospace components, which are often exposed to high thermal and mechanical loads. Dependent on the component geometry, support structures are required for AM, which then usually have to be removed by machining. One suitable support structure is the use of material with specifically induced porosity. This ensures good heat dissipation and thus homogeneous component properties, high retention forces and short process times in PBF-LB/M. However, the machinability of porous, additively manufactured material has hardly been researched so far. One preliminary investigation of milling porous, additively manufactured Inconel 718, though, showed significantly poorer machinability of the porous material compared to the dense material. To further examine this phenomenon, this paper presents the results of fundamental machinability studies with porous, additively manufactured Inconel 718 in orthogonal cutting. The investigations with tungsten carbide cutting tools on a special fundamental test rig include the analysis of the cutting force, the chip geometry, the chip temperature and the surface quality. The research results provide explanations for the poorer machinability of the porous material and derived approaches for improving the machinability in future studies. [ABSTRACT FROM AUTHOR]

Purpose: Additive manufacturing has revolutionized the fabrication of complete dentures. However, this process involves support structure, which is a construction part that holds the specimen during printing, and may prove to be disadvantageous. Therefore, this in vitro study compared the effect of support structure reduction on various volume and area distributions of a 3D-printed denture base to determine optimal parameters based on accuracy. Methods: A complete maxillary denture base construction file was used as reference. Twenty denture bases were 3D printed under four conditions (total n=80): no support structure reduction (control), palatal support structure reduction (Condition P), border support structure reduction (Condition B), and palatal and border support structure reduction (Condition PB). Printing time and resin consumption were also recorded. The intaglio surface trueness and precision of all acquired data were exported to a 3D analysis software, and the dimensional changes to the denture base were analyzed using the root-mean-square estimate (RMSE) to assess geometric accuracy and generate color map patterns. Nonparametric Kruskal-Wallis and Steel-Dwass tests (a=0.05) analyzed the accumulated data. Results: Control had the lowest RMSE values for trueness and precision. Nevertheless, it demonstrated a significantly lower RMSE than that of Condition B (P=0.02) in precision. Owing to negative deviation at the palatal region, Conditions P and PB had higher retention than Control and Condition B regarding the color map pattern. Conclusions: Within the limitations of this study, the reduction of palatal and border support structures showed optimal accuracy with resource and cost savings. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute 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.)

Additive manufacturing of PLA parts using wax-based filament as a support structure was investigated by implementing the 2-level 3-factors full factorial design of experiments (DoE). The aim of the experiments was to identify significant FDM factors that affect the surface roughness of the parent part in the PLA/Wax interfacial region. In addition, the important factors influencing bonding strength between PLA and wax were identified using the same full factorial DoE. The printing parameters chosen for the analysis are printing temperature, nozzle speed, and the pattern type at the interfacial area. The findings of the study show that the wax-based filament can be effectively used as support material with the condition that the PLA printing temperature is at its lowest value and the nozzle speed is close to 40 mm/s. With the optimal printing condition, the surface roughness value (Ra) can reach as low as 18 μm value and the bonding strength of 0.27 MPa at the interfacial area. The results of the study have revealed the capability of FDM technology to join materials having considerably dissimilar properties.

Support structures are widely used in laser powder bed fusion (LPBF) for overhanging features. However, the majority of works carried out on support modeling were to obtain the best trade-off between production time, cost, and accuracy. A notable absence in the existing literature pertains to investigate support structure modeling for optimizing heat dissipation and residual stresses for improving the support structure, thus, enhancing the final part quality. In this study, the effects of the support structure on residual stress were investigated systematically. The influences of the support on residual stress in LPBF sample were categorized into the effect of the constraints and heat conduction area. The rigidity and area of the support structure are used to describe the effect of the support structure on the residual stress. The results showed that the constrain of LPBF samples mainly depends on their inherent characteristics, with limited impact from external constraints. The residual stress in the samples increased as the support area increased. Therefore, when designing the support, priority should be given to reduce its thermal conductivity area. In addition, the hardness of the support added sample were lower than that of the sample without the support, but the hardness distribution is uniform along the deposition height regardless of whether the support is added or not. Therefore, the introduction of support does not result in performance irregularities along the sample height direction.

Even in digital workflows, models are required for fitting during the fabrication of dental prostheses. This study examined the influence of different parameters on the dimensional accuracy of three-dimensionally printed models. A stereolithographic data record was generated from a master model (SOLL). With digital light processing (DLP) and stereolithography (SLA) printing systems, 126 models were produced in several printing runs—SolFlex350 (S) (DLP, n = 24), CaraPrint 4.0 (C) (DLP, n = 48) and Form2 (F) (SLA, n = 54)—and their accuracy was compared with plaster and milled polyurethane models. In addition to the positioning on the build platform, a distinction was made between parallel and across arrangement of the models to the printer’s front, solid and hollow models, and printing with and without support structures. For accuracy assessment, five measurement sections were defined on the model (A–E) and measured using a calibrated digital calliper and digital scans in combination with the GOM Inspect Professional software 2021. The mean deviation between the measurement methods for all distances was 79 µm. The mean deviation of the models from the digital SOLL model were 207.1 µm for the S series, 25.1 µm for the C series and 141.8 µm for the F series. While positioning did not have an influence, there were clinically relevant differences mainly regarding the choice of printer, but also individually in alignment, model structure and support structures.

This paper address the performance optimization of the battery heat sink module by analyzing the lattice structure of the battery heat sink module through in-depth modeling and simulation, and combining the laser powder bed fusion (LPBF)-forming technology with mechanical and corrosion resistance experiments for a comprehensive study. It is found that the introduction of the lattice skeleton significantly improves the thermal conductivity of the phase change material (PCM), realizing the efficient distribution and fast transfer of heat in the system. At the same time, the lattice skeleton makes the heat distribution in the heat exchanger more uniform, improves the utilization rate of the PCM, and helps to maintain the stability of the cell temperature. In addition, the melting of PCM in the lattice heat exchanger is more uniform, thus maximizing its latent heat capacity. In summary, by optimizing the lattice structure and introducing the lattice skeleton, this study successfully improves the performance of the battery heat dissipation system, which provides a strong guarantee for the high efficiency and stable operation of the battery, and provides new ideas and references for the development of the battery heat dissipation technology.

AbstractThe monopile-supported offshore wind turbines (OWTs) are subjected to the wave and current loadings. Affected by currents and waves, monopile-supported OWTs are also vulnerable to scour. However, the effect of scour and currents on the dynamic behavior of the monopile are not fully appreciated. This study conducted the model tests to evaluate the effect of scour depth and flow velocity on the lateral responses of support structure. Furthermore, the two-way (T-W) coupling fluid–structure interaction (FSI) method was proposed to evaluate the dynamic responses of piles in sand. The support structure is modeled using ABAQUS, a finite-element models software package, by considering the nonlinear soil–structure interaction effects, STAR-CCM + tools has been employed to model the FSI which are fed into ABAQUS to predict the structure’s dynamic response. Using the proposed method, a parametric study has been conducted to evaluate the effects of scour depths, flow velocities on the dynamic responses of OWTs. The results indicate that scour altered the fundamental frequency of OWT, causing resonance. An increase in scour depth and flow velocity increased the dynamic responses of support structure, which are detrimental for the safety and stability of the OWT system. [ABSTRACT FROM AUTHOR]

A numerical investigation of floating-type substructures for wind turbine generators was conducted by using time-domain simulation. A Tri-Star floater for 8–10 MW generators, which was developed by Samsung Heavy Industries (SHI), was chosen as the floating substructure. To make the anchor system, catenary mooring lines, considering redundancy, were installed on the floater. The main sources of external force on the wind turbine generator are wind, waves, and currents. To consider severe environmental conditions, Design Load Cases (DLCs) 1.6 and 6.1 of the IEC guidelines (IEC 61400-3-1) were chosen. From the measured environmental data for the installation site, the main parameters for the simulation conditions were obtained. The tilt angle and horizontal movement of the floater and the mooring tension for the different mooring systems were checked. The response of the floater during the failure of the mooring was also studied, and the critical failure of the mooring was confirmed. During the failure of the mooring, the redundancy system worked well, in which the movement of the floater was constrained within the criteria for all scenarios. [ABSTRACT FROM AUTHOR]

Bridging in additive manufacturing (AM) parts occur between two points without any support from below. If the material extruded between these points is dangled (i.e., not horizontal), this is called poor bridging. This paper investigates the effects of AM process parameters and distance between supports on not only poor bridging but also mechanical properties of parts manufactured using AM. Two estimated models (EMs) are computed to predict ultimate stress and strain given these design parameters. To do this, central composite design (CCD) experimental design method is employed to obtain experiment sets based on design parameters. The number of tests is then increased using a systematic sampling technique to obtain the EMs with accurate prediction quality. Tensile experiments are then carried out for all the experiments. Finally, the obtained EMs are integrated into a process optimization test case, in which design parameters are automatically determined in order to achieve mechanical constraints based on the ultimate stress or strain of the printed parts. [ABSTRACT FROM AUTHOR]

Additive manufacturing of PLA parts using wax-based filament as a support structure was investigated by implementing the 2-level 3-factors full factorial design of experiments (DoE). The aim of the experiments was to identify significant FDM factors that affect the surface roughness of the parent part in the PLA/Wax interfacial region. In addition, the important factors influencing bonding strength between PLA and wax were identified using the same full factorial DoE. The printing parameters chosen for the analysis are printing temperature, nozzle speed, and the pattern type at the interfacial area. The findings of the study show that the wax-based filament can be effectively used as support material with the condition that the PLA printing temperature is at its lowest value and the nozzle speed is close to 40 mm/s. With the optimal printing condition, the surface roughness value (Ra) can reach as low as 18 µm value and the bonding strength of 0.27 MPa at the interfacial area. The results of the study have revealed the capability of FDM technology to join materials having considerably dissimilar properties. [ABSTRACT FROM AUTHOR]

The underground structures typically require deep excavation involving multiple stages. Each stage can significantly impact excavation support structures and the surrounding environment. The combination of various influencing factors resulting from the excavation stages typically has varying and considerable effects than a single factor. The combination of supporting structure and excavation-induced deformation critically influences soil pressure, significantly impacting the surrounding environment and structures. Currently, research exploring this combined effect is limited. Accordingly, an earth pressure calculation method is developed in this study. The method considers the combined effect of the excavation process and deformation mode of underground diaphragm walls. Different excavation processes result in different deformation modes in the walls, leading to variations in earth pressure distributions. Considering these differences, the proposed method is deemed suitable for engineering practice. The method was verified and improved using five existing practical engineering and numerical simulation cases. Results indicate that the theoretical calculation method accurately reflects the actual earth pressure distribution. [ABSTRACT FROM AUTHOR]

This study aims to comprehensively investigate the reinforcement mechanism of the tunnel support structure and its supporting characteristics in layered and weak rock tunnels. Uniaxial compressive tests were carried out to study the mechanical and deformation characteristics of anchored rock with the system anchor bolt and the steel floral pipe. Besides, a three-point bending test of the steel–concrete composite beam was conducted to investigate the bending capacity of the grilles and I-beams. The experiment showed the following results: (1) The anchor bolt achieved the anchoring effect by improving the stress state and the strength of the surrounding rock. The improvement of the anchorage strength to the surrounding rock was reflected by the effect of the compression zone of preload, the healing effect of the anchorage agent on the surrounding rock, and the reinforcement effect of the anchor bolt on the density and strength of the anchor bolt. (2) By the CT scanning of the anchored samples after the experiment, it was found that the crack was blunted and arrested within the anchorage zone, and the crack-arresting effect was related to the range of the anchorage zone. The larger the anchorage zones, the better the crack-arresting effect. (3) The steel arch could effectively improve the ability of concrete antideformation. Compared with the lattice girder, the coordination ability of steel arch and concrete deformation was relatively weak. Its coordinate deformation stage was shorter than that of the lattice girder and earlier into the debonding stage. However, the stiffness of the steel arch and concrete was greater than that of the lattice girder after debonding and showed a strong bearing capacity. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology 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.)

Warpage deformation inevitably occurs when laser powder bed fusion (LPBF) is applied on an overhanging structure. An effective support added to the system can mitigate warpage and improve the accuracy of formed parts. Four types of support structures are designed, and sheet tensile specimens and overhanging structures with different support structures are fabricated in this study. The tensile failure behavior and warpage suppression ability of different support structures are investigated, with the relation of the support influence to the design of support structure analyzed. The results show that the support with reinforcement can effectively restrain warpage deformation of the overhanging structure. During the process of tension, the main failure area of the support structure is located on the top of the support structure, close to the overhanging solid body. Increasing the change ratio of the support cross-sectional area is helpful to improve the constraint ability of the support. This design provides a new method for accurate forming of overhanging structures via LPBF and evaluating the restrain ability of support structures.

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement 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.)

The production of metals by additive manufacturing is developing rapidly. After production, support structures emerge as waste materials. In this study, Ti6Al4V support structures recycled from the selective laser melting process were consolidated by vacuum hot pressing. Spherical and irregularly shaped Ti6Al4V alloy particles were also used for the comparison as raw materials. All raw materials have been subjected to the same sintering process by hot pressing. The microstructures of the samples were carried out, and their dry sliding wear performance was studied. The samples produced from support structures showed the highest wear performance compared to the powder forms of raw materials. This study showed that the support structures from additive manufacturing could be recycled and transformed into full dense structures by pressure-assisted sintering techniques, and enhanced wear performance can be obtained. [ABSTRACT FROM AUTHOR]

Expansive soils exhibit directionally dependent swelling that traditional isotropic models fail to capture. This study investigates the anisotropic swelling characteristics of expansive soil with a medium swelling potential through the use of modified oedometric testing. Vertical swelling strains can reach up to 1.71 times that of the horizontal movements, confirming intrinsic anisotropy. A nonlinear elastic constitutive model incorporates vertical and horizontal elastic moduli with respect to matric suction to characterize anisotropy. Three elastic parameters were determined through the experiments, and predictive equations were developed to estimate the unsaturated moduli. The constitutive model and predictive techniques provide practical tools to better assess expansive soil pressures considering anisotropy, offering guidelines for utilization and design. The outcomes advance understanding of these soils’ directionally dependent behavior and stress–strain–suction response.

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction 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.)

The harnessing and utilization of tidal current energy have emerged as prominent topics in scientific inquiry, due to their vast untapped resource potential, leading to numerous investigations into the efficacy of hydrokinetic turbines under various operational conditions. This paper delineates the wake field characteristics and performance of horizontal axis tidal stream turbines under the influence of support structures, using a comprehensively blade-resolved computational fluid dynamics (CFDs) model that employs Reynolds-averaged Navier–Stokes (RANS) equations in combination with the RNG k-ε turbulence model. To achieve this, the study utilized experimental tank tests and numerical simulations to investigate the distribution characteristics and recuperative principles of the turbine's wake field. The velocity distribution and energy augmentation coefficient of the wake field showed strong agreement with the experimental results. To further assess the effect of support structures on the flow field downstream of the unit and its performance, the hydrodynamic attributes of the turbine wake field were analyzed with and without support structures. The interference elicited by the support structure modified the velocity distribution of the near-wake flow field, resulting in a 4.41% decrease in the turbine's power coefficient (Cp), significantly impacting the turbine's instantaneous performance. [ABSTRACT FROM AUTHOR]

Wind turbine towers and their flange connections are highly fatigue loaded structures. Previous investigations have shown that initial parallel gaps between L‐flange connections, which are resulting from their respective flatness of the contact surfaces, can increase fatigue loads of the connecting fasteners significantly. Flange flatness and/or gap sizes in between flanges must comply with limitations given in relevant standards and therefore must be measured after the manufacturing process and/or during installation. More than 1900 flatness measurements of several offshore wind projects were collected and used to determine initial gaps between flanges analytically. A statistical evaluation allows to determine the distribution of expected gap sizes. The increase of gap height with increasing gap length can be described with linear correlations. Furthermore, the distributions of gap heights are approximated with log‐normal distributions. Parameters for generic log‐normal distributions are derived considering all performed mating simulations. Following the described methodology, gaps can be determined from any large number of flatness measurements. It is proposed to consider the results for flange design. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology 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.)

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement 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.)

Drawing support is one of the unique equipment for longwall top coal caving (LTCC) technology in coal mine, whose structure has a significant effect on the top coal drawing mechanism. This research systemically investigates the effect of the dip angle of shield beam (α), length ratio of shield beam to tail beam (RL), and rotation angle of tail beam (β) on the top coal recovery, drawing body and top coal boundary by using particle flow code (PFC2D). The results show that the variation of α and β has a greater effect on the top coal drawing mechanism, the ideal α should be about 55°, RL is within the range of 0.8–1.0, and the tail beam rotates at a small angle range, which is beneficial to the top coal drawing in the panel. When α is large while RL is small, the volume of the initial drawing body gradually increases. With the increase of drawing height, volumes of drawing body under different β all plot an increasing trend with an incremental growth ratio. With increasing RL, the initial top coal boundary on the goaf side experiences the change of “upward concave-nearly linear-upward concave”, while that on the support side shows a curve with a fast-changing slope and closes to the vertical central line of drawing opening. The research results have important theoretical and field guiding significance for the selection and design of hydraulic support in LTCC. [ABSTRACT FROM AUTHOR]

In this article, we investigate geometric properties and modeling capabilities of quad meshes with planar faces whose mesh polylines enjoy the additional property of being contained in a single plane. This planarity is a major benefit in architectural design and building construction: If a structural element is contained in a plane, it can be manufactured on the ground without scaffolding and put into place as a whole. Further, the plane it is contained in serves as part of a so-called support structure. We discuss design of meshes under the requirement that one half of mesh polylines are planar ("P meshes"), and we also investigate the geometry and design of meshes where all polylines enjoy this property ("PP meshes"). We work in the space of planes and with appropriate transformations of that space. We also incorporate further properties relevant for architectural design, such as near-rectangular panels and repetitive nodes. We provide geometric insights, give explicit constructions, and show an approach to geometric modeling of both P meshes and PP meshes, in particular, the case of nearly rectangular panels. [ABSTRACT FROM AUTHOR]

Support structure plays an important role on sustaining overhang areas, resistingshape deformation and reducing thermal stress in many additive manufacturing (AM) processes. However, design of support structures in the preparation stage and removing of those structures in the post-processing stage are still time-consuming and costly. To reduce support structure volume, post-processing time and improve the printing quality, this paper proposes a novel enhanced bio-inspired generative design method, integrating parametric L-system rules and lattice structure configuration, to generate lightweight, easy-to-remove and heat-diffusion-friendly biomimetic support structures. A complex dental component with freeform geometries and discontinuous support areas is selected as a case study to compare with existing popular support design methods. The comparison results show the proposed method exhibits a good support performance for complex dental overhang areas. Hence it has potential to be adopted for other AM processes where support structures are required.

Abstract This study proposes an advanced algorithm for predicting the optimal orientation in human manikin 3D printing. We can print the manikin mesh data on any scale depending on the user’s needs. Once the 3D printing scale was determined, the manikin data were dissected based on the 3D printer’s maximal printing volume using our previous work. Then, we applied the newly proposed algorithm, designated as “per-pixel signed-shadow casting,” to each dissected manikin part to calculate the volumes of the object and the support structure. Our method classified the original mesh triangles into three groups—alpha, beta, and top-covering—to eliminate the need for special hardware such as graphic cards. The result is shown as a two-dimensional bitmap file, designated as “tomograph”. This tomograph represents the local support structure distribution information on a visual and quantitative basis. Repeating this tomography method for the three rotational axes resulted in a four-dimensional (4D) box-shaped graph. The optimal orientation of any arbitrary object is easily determined from the lowest-valued pixel in the 4D box graph. We applied this proposed method to several basic primitive shapes with different degrees of symmetry and complex shapes, such as the famous “Stanford Bunny”. Finally, the algorithm was applied to human manikins using several printing scales. The theoretical values were compared with those obtained from analytical or g-code-based experimental volumes.

Dry reforming of methane (DRM) is a prospective technology for efficient utilization of CH 4 and CO 2 , with the essential challenge being the design and synthesis of efficient catalysts. In this research, serial encapsulated Ni-based catalysts (xNi@S-1, x = 5, 7, 10) by silica zeolite (S-1) were prepared successfully. The effects of support structure, preparation method and Ni content upon the catalytic performance for DRM were investigated and diverse characterizations were utilized for revealing structural features of as-prepared catalysts. Encapsulated 7Ni@S-1 catalyst prepared using the one-pot hydrothermal method could acquire more homogeneously dispersed metallic Ni particles and more Ni species including Ni0, NiO, 1:1/2:1 Ni phyllosilicates that could facilitate forming stable Ni0 sites and Ni2+-O2- ion pairs for adsorption and activation of CH 4 and CO 2 , respectively. Hence, 7Ni@S-1 still maintained the highest CH 4 and CO 2 conversions of 57.9% and 88.6% and H 2 /CO molar ratio of 0.90 after 52 h stability tests. [Display omitted] • Silica zeolite (S-1) encapsulated Ni-based catalysts were successfully prepared. • Highly dispersed Ni0 particles were obtained using the one-pot hydrothermal method. • Ni phyllosilicates and S-1 pores enhanced the anchoring of metal Ni sites. • Encapsulated 7Ni@S-1 catalyst exhibited the optimal catalytic DRM performance. [ABSTRACT FROM AUTHOR]

In order to study the bearing safety and influencing factors of the support structures of hydraulic tunnels in cold regions under the action of low-temperature frost heave, a mechanical model of the support structure and surrounding rock was established. Taking a hydraulic tunnel of a hydropower station in Xinjiang as the research object, a combination of field measurement and a numerical simulation method was adopted to study the bearing safety of the support structure during a period of freezing weather. Based on this model, the effects of different thermal expansion coefficients, temperature differences, and surrounding rock porosity on the bearing safety of the support structure in the low-temperature region were studied. From the calculation results, it was concluded that the simulation results of the numerical model established by using the mechanical model in this paper were in good agreement with the actual measurement results of the project. The circumferential freezing and compressive stresses at the arch waist of the supporting structure of the project were the largest, and significant plastic strain was generated near the arch waist. The displacement at the arch of the supporting structure was the largest, while the weak points were at the arch waist and arch top of the supporting structure. The coefficient of thermal expansion, greater temperature difference, and increased porosity of the surrounding rock all led to an increase in the rock freezing and swelling force to varying degrees, thus reducing the load-bearing safety of the supporting structure. The research results could provide a theoretical basis and a reliable mechanical and numerical simulation model for establishing the bearing safety of tunnels in the cold region. [ABSTRACT FROM AUTHOR]

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A numerical investigation of floating-type substructures for wind turbine generators was conducted by using time-domain simulation. A Tri-Star floater for 8–10 MW generators, which was developed by Samsung Heavy Industries (SHI), was chosen as the floating substructure. To make the anchor system, catenary mooring lines, considering redundancy, were installed on the floater. The main sources of external force on the wind turbine generator are wind, waves, and currents. To consider severe environmental conditions, Design Load Cases (DLCs) 1.6 and 6.1 of the IEC guidelines (IEC 61400-3-1) were chosen. From the measured environmental data for the installation site, the main parameters for the simulation conditions were obtained. The tilt angle and horizontal movement of the floater and the mooring tension for the different mooring systems were checked. The response of the floater during the failure of the mooring was also studied, and the critical failure of the mooring was confirmed. During the failure of the mooring, the redundancy system worked well, in which the movement of the floater was constrained within the criteria for all scenarios.

The U.S. Magnet Development Program (MDP) collaboration is designing a utility mechanical structure for testing various high-field superconducting dipole coils. The design uses a shell-based structure concept, which allows applying preload in two steps: During a room temperature assembly and during a cool down to a cryogenic temperature. The structure is designed to accommodate various coil designs - including Nb3Sn Cosine Theta (CT) and Canted CT magnets as well as hybrid magnets with high temperature superconductor cables. Superconducting coils, enclosed by bolted pads to form an octagonal coil pack, will be inserted into a reusable yoke-shell subassembly and precisely preloaded during the assembly using a bladder-and-key technology. Due to a differential thermal contraction between an external aluminum shell and the magnet core, the coil preload increases during the cool down up to level required for 17-T excitation. Such a reusable structure will serve as a testing fixture supporting goals of the MDP program, decreasing cost and simplifying coil performance testing at different preload levels. We present a finite-element analysis of the structure preloading various coil designs and examine the predicted coil stress at each step of the magnet assembly and excitation.

Selective laser melting (SLM) is one of the additive manufacturing (AM) methods which is applicable to metal. This technique makes it possible to form complex internal shapes such as lattice structures. The lattice structure is expected to have weight reduction and vibration suppression effects on the product. In addition, a support structure is essential for the SLM fabrication process, which has the role of supporting the product and dissipating heat from the product. However, steep temperature gradients due to local laser irradiation and non-uniform heat conduction during the process can cause bending and cracking of the product. In particular, the support structure and lattice structure consisting of thin metal struts are greatly affected by process conditions, so it is necessary to select conditions suitable for stable and high-precision modeling. In this study, the influence of laser power and scanning speed on the mechanical characteristics of the support structure and lattice structure formed by SLM is investigated. In the tensile test of the support structure, a positive correlation with the volumetric energy density was confirmed, and suitable laser conditions were examined. In the compression test of the lattice structure, it was clear that the amount of energy absorption changed depending on the laser power, and the condition of 240 W achieved the maximum energy absorption.

Support structure plays an important role on sustaining overhang areas, resistingshape deformation and reducing thermal stress in many additive manufacturing (AM) processes. However, design of support structures in the preparation stage and removing of those structures in the post-processing stage are still time-consuming and costly. To reduce support structure volume, post-processing time and improve the printing quality, this paper proposes a novel enhanced bio-inspired generative design method, integrating parametric L-system rules and lattice structure configuration, to generate lightweight, easy-to-remove and heat-diffusion-friendly biomimetic support structures. A complex dental component with freeform geometries and discontinuous support areas is selected as a case study to compare with existing popular support design methods. The comparison results show the proposed method exhibits a good support performance for complex dental overhang areas. Hence it has potential to be adopted for other AM processes where support structures are required. [ABSTRACT FROM AUTHOR]

Additive manufacturing technologies are considered advanced processes in which it is possible to produce complex shape components layer-by-layer. In these technologies, it is reported that in producing parts with angles higher than 45°, no support is required. Depending on the material below this angle, it is necessary to use the support structures to dissipate the heat and counterbalance the force of the recoding blade. During the building process, it is well documented that there is a risk of part detachment at low angles that can result in failure. On the other hand, a heavy dross formation on the downskin surface will occur if no failure happens, resulting in a surface with scarce quality. Hence, many efforts have been undertaken to face this challenge and study the effect of various parameters, such as layer thickness, laser power, and scan speed, on the quality of the downskin surface of the minimum printable angle without the support requirement. This review offers an overview of the last progress on the effect of process parameters on the surface quality of the downward surfaces in the production of complex parts via the laser powder bed fusion process. This review highlights the best practices that may be considered for future works to find effective parameters for producing complex shape components with low angles without support structures. [ABSTRACT FROM AUTHOR]

A novel swarf substrate is proposed for the additive manufacturing process. It was prepared by compressing waste metal chips obtained from the conventional machining processes into a flat plate or any desired shape. It could be disintegrated after the deposition, ensuring ease of part removal. Fused metal chips on the bottom layer require minimal post-processing. A fibre laser and two other arc-based heat sources were used to demonstrate the swarf substrate viability for additive manufacturing. Low alloy steel (ER70S-6) and Inconel 625 were used in this study. Melt pool penetration in swarf substrate was observed to be unique and typically formed a tree root structure after solidification. This structure provides strength for holding the further layers upright. The working parameters were optimised for uniform and continuous deposition. Material integrity was confirmed by hardness study comparison with similar parts deposited on the conventional solid substrate. The dilution of swarf material (typically mild steel) was observed to be limited within 2–3 mm layer height, as confirmed by the Energy-dispersive x-ray spectroscopy. The cooling rate was found to be decreasing with layer height and saturated after few initial layers of the deposition similar to the conventional solid substrate. Excellent formability of the swarf substrate allowed to utilise it for unique applications such as deposition of curved features and support structure. The presented work demonstrates additive manufacturing of parts using such geometrical features, including coil spring and alloy wheel. • A novel approach to recycle the swarf as substrate for additive manufacturing. • Successfully performed for three heat sources, i.e. laser beam, MIG and TIG. • A unique tree root structure formed by the swarf/chips to hold the beads. • The substrate facilitates overhang and curved feature deposition. • Material and heat source does not affect the performance of the swarf substrate. [ABSTRACT FROM AUTHOR]