Conceptual Structural Design Research Articles

Blade Structure Analysis of 2 MW V-Shaped Vertical Axis Wind Turbine Using Numerical Simulation

The intensive research on large-scale Vertical Axis Wind Turbine (VAWT) couldprovide an alternative to Horizontal Axis Wind Turbine (HAWT) in offshore deployment for the future. Regarding this fact, this article develops a conceptual design of the VAWT blade structure and analyzes its feasibility using numerical simulation. The blade structure is designed for 2 MW Darrieus type V- shaped VAWT. The blade is tapered, 90m long, and inclined at 35° to the vertical axis. Initially, the blade design is tested for ultimate strength test according to IEC 61400-01 standard using aluminum alloy and homogenized composite material. In doing so, maximum aerodynamic loading on the blade is calculated after steady state 3-D RANS CFD simulation of the blade in ANSYS Fluent. The Finite Element Method (FEM) model of the blade is created using shell element in ANSYS Static Structural with structured meshing strategy, and tested with the aerodynamic load using the one-way Fluid-Structure Interaction (FSI) technique, to obtain mesh independent solution. The impact of the using 2, 3, and 4 number of shear webs is then analyzed on the selected mesh model of the blade. Finally, a four-shear web model of the blade is tested under extreme conditions. The thickness of the blade surface and shear web are varied to test maximum deflection at the tip, and maximum allowable strain of the blade. After obtaining the required blade structure, the deformation, maximum equivalent stress, and maximum equivalent strain for the blade are studied at rotation Tip Speed Ratio (TSR) of 5 under aerodynamic and gravitational loading, using both materials. The study showed significant deflection at the tip of the blade for the tower-less V-VAWT blade, suggesting an alternative support mechanism for the blade. Also, the study concluded that better structural robustness is achieved while using a composite material instead of an aluminum alloy. This article provides basis to study structural behavior of the novel V-VAWT blades and contribute to continuing research on obtaining optimized blade structure for such turbine.

Designing chairs for users with high body weight

The relationship between the functional dimensions of the furniture and a user’s anthropometric dimensions is crucial for safety and functionality. The weight and dimensions of the user’s body significantly affect the functional dimensions of the furniture, especially for overweight users. This paper is focused on the concept of chair structural design, which is suitable for bariatric users, including the application of additional reinforcing structural components. Such components are expected to improve the stiffness and strength properties of the chair structure, and it provides the possibilities to a chair design with improved ergonomic parameters. To increase rigidity and reinforce the frame structure of a chair for obese users, the side stretchers, middle braces inserted under seat and armrests are used. The main goal of the different structural designs of chair frames is to minimize internal forces acting in the structural components of the chair. The finite element method (FEM) was used to determine the internal forces and stress-strain state in the structural elements of the chair, starting with the standard design of the chair frame and comparing different design variants. A synergistic effect is obtained, making the bariatric chair durable and ergonomic, without stigmatizing its users.

Investigating the structure–sensitivity relationship of photosensitive polyimide formulated by using a photobase generator

AbstractPhotosensitive polyimides (PSPIs) have been widely used in the buffer coating layer and insulation layer due to their excellent thermal and mechanical stability. In this work, a series of negative‐type PSPIs based on poly(amic acid) (PAA) and a photobase generator (PBG) have been developed. Two diamines of 4,4′‐oxydianiline (ODA), 3,3′‐diaminodiphenyl sulfone (SDA), and four dianhydrides of pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA) and cyclobutene‐1,2,3,4‐tetracarboxylic dianhydride (CBDA) are copolymerized to PAA through polyaddition, and the PAA is further thermally imidized to polyimide (PI). Through scrutinizing the structure–sensitivity relationship of these PIs, we find that the rigidity and transparency of the PAA/PI backbone play an important role in the sensitivity and contrast of PSPI. Accordingly, PSPI (SDA‐ODPA), possessing high optical transparency and a low rigidity represented by the low glass transition point, is capable of providing good photosensitivity of 30 mJ/cm2, a high contrast of 2.46, and an excellent pattern resolution of 4 μm after optimizing the prebaking (100°C for 5 min), exposure dose (380 mJ/cm2), post‐exposure baking (130°C for 7 min), and development parameters. This work provides the concept of structural design for negative‐type PSPI in the microelectronic application.

Multistate spectral-tunable manipulation of mid-infrared emissivity using Sb2S3/GST/VO2

Conventional thermal emission that exhibits spectral selectivity relies on micro/nanostructures, such as gratings, photonic crystals, photonic cavities, nanoantennas, and metamaterials. By utilizing advanced micro/nanofabrication techniques to modify the structural parameters of the micro/nanostructures, it is possible to create wavelength-selective thermal emitters that span from THz to the visible range. Nonetheless, static micro/nanostructures do not offer flexible tunability in terms of thermal emissivity. In this Letter, we report a conceptual design of a multistate multilayered structure using a combination of three phase change materials: VO2, Ge2Sb2Te5, and Sb2S3. By controlling the temperature, the phase change materials will be in different phase states, rendering the multilayered structure six feasible thermal states with tunable spectra in the mid-infrared range. The impact of layer thickness is investigated. Polarization independence and angle insensitivity are exhibited until a large incident angle. This multilayered thermal structure is lithography-free and industrially scalable, showing great potential for programmable photonics and thermal sensors.

Design and Preparation of Flexible Graphene/Nonwoven Composites with Simultaneous Broadband Absorption and Stable Properties

As the world moves into the 21st century, the complex electromagnetic wave environment is receiving widespread attention due to its impact on human health, suggesting the critical importance of wearable absorbing materials. In this paper, graphene nonwoven (RGO/NW) composites were prepared by diffusely distributing graphene sheets in a polypropylene three-dimensional framework through Hummers' method. Moreover, based on the Jaumann structural material design concept, the RGO/NW composite was designed as a multilayer microwave absorber, with self-recovery capability. It achieves effective absorption (reflection loss of -10 dB) in the 2~18 GHz electromagnetic wave frequency domain, exhibiting a larger bandwidth than that reported in the literature for absorbers of equivalent thickness. In addition, the rationally designed three-layer sample has an electromagnetic wave absorption of over 97% (reflection loss of -15 dB) of the bandwidth over 14 GHz. In addition, due to the physical and chemical stability of graphene and the deformation recovery ability of nonwoven fabric, the absorber also shows good deformation recovery ability and stable absorption performance. This broadband absorption and extreme environmental adaptability make this flexible absorber promising for various applications, especially for personnel wearable devices.

Steered photogenerated carrier separation via mixed-crystal-homojunction-mediated permanent negative charge electric field

The chelation between heavy metal ions and small organic molecules limits the prospects of traditional adsorption methods in dealing with the complex water environment, annihilating the non-negligible reutilization value of heavy metal ions. Photocatalysis enables the reduction of heavy metal ions and the mineralization of small molecule pollutants to be accomplished simultaneously, but the enhancement of photogenerated carrier separation efficiency is a technical challenge to be overcome. Herein, a photocatalyst loaded with mixed-crystal titanium dioxide (TiO2) on the surface of montmorillonite (MMT) was prepared, which is reported for the exceptional performance in the recovery of heavy metals Cr(VI) and the mineralization of organic pollutants Rh-B (10 ppm chelate in total) within 60 min. Scientific characterization and theoretical calculations demonstrate that the generation of oxygen vacancies in mixed-crystal homojunctions driven by a permanent negative charge electric field will maximize the adsorption capacity for H2O and O2. The MMT surface is converted into a reduction platform for Cr(VI), and anatase-TiO2 acts as an active site for Rh-B mineralization, under the synergistic effect of permanent negative charge electric field and mixed-crystal homojunctions. The Cr(III) obtained by photocatalytic reduction is collected by cation exchange between the interlayers of MMT with corresponding selective adsorption. This novel structural design concept provides a highly innovative orientation for the application of photocatalytic technology to the remediation of complex aqueous environments.

Structure and interface engineering on polypyrrole-deposited conductive paper originating from nature wood enables high performance flexible all-solid-state supercapacitors

Paper is an ideal substrate for manufacturing flexible electrodes because of its lightweight, inherent mechanical flexibility, and unique structure. However, the traditional bottom-up method of manufacturing paper-based electrode is time-consuming and the active material is easy to fall off. Here, we report a polypyrrole-deposited conductive paper (PCP), which is fabricated by chemical treatment, mechanical compression, and chemical polymerization of natural wood. The post densification process eliminates the vertical arrangement of wood cell cavities, and the formed wood fiber/multi-walled carbon nanotubes hybrid conductive network has high flexibility. The further deposited polypyrrole (PPy) conductive layer can effectively boost the ion transport between electrode/electrolyte interface and increase the active center of interface reaction. Based on the well-designed electrode structure and good interfacial reaction kinetics, the resulting PCP with a PPy mass loading of only 2.4 mg·cm−2 indicates a high areal capacitance of 275.8 mF cm−2 at 20 mV·s−1 and good cycling stability. All-solid-state symmetric supercapacitor exhibits capacitance of 308.3 mF·cm−2. This structure and interface design concept show a promising method for preparing high-performance and scalable biomass-based flexible electronic devices.

Development and Application of a Crossed Multi-Arch Greenhouse in Tropical China

Deep analysis and demonstration of the developed crossed multi-arch greenhouse were conducted from the perspectives of conceptual design, architectural and structural design, functional design, loading parameters, and structural internal forces. The results show that the crossed multi-arch greenhouse combines the ventilation area between the floor-standing round-arch greenhouse and the unsuitable operation area under the arch bars into one to form a multi-span crossed arch structure with good ventilation and heat dissipation, land savings, and fine mechanical behaviors. The main arch structure uses 32.4% less steel and 25% less foundation volume than the control greenhouse under the same load, which can save about CNY 10,184.00/667m2 of investment according to the current cost level. In the meantime, ventilation simulation analysis of the developed crossed multi-arch greenhouse was carried out using the software Design Builder. A comparison shows that, under the condition of no wind and breeze (1 m/s) in summer, the setting of the ventilation channel has obvious advantages for the heat dissipation of the greenhouse, and the average temperature is about 2 °C lower than that of the greenhouse without a ventilation channel; under the breeze condition, the temperature in the crossed multi-arch greenhouse is more evenly distributed than that of an ordinary round-arch greenhouse with ventilation channels. Considering the greenhouse function, building cost, using effect, and other evaluation factors, the crossed multi-arch greenhouse can meet the production environment requirements of tropical coastal areas (rain protection, sunshade, and ventilation), with obvious structural advantages, good typhoon resistance, and low construction costs, which is a preferable choice of greenhouse type.

Controllable rectification on the thermal conductivity of porous YBa2Cu3O7− x superconductors from 3D-printing

Superconducting YBa2Cu3O7−x (YBCO) bulks have promising applications in quasi-permanent magnets, levitation, etc. Recently, a new way of fabricating porous YBCO bulks, named direct-ink-writing (DIW) 3D-printing method, has been reported. In this method, the customized precursor paste and programmable shape are two main advantages. Here, we have put forward a new way to customize the YBCO 3D-printing precursor paste which is doped with Al2O3 nanoparticles to obtain YBCO with higher thermal conductivity. The great rheological properties of precursor paste after being doped with Al2O3 nanoparticles can help the macroscopic YBCO samples with high thermal conductivity fabricated stably with high crystalline and lightweight properties. Test results show that the peak thermal conductivity of Al2O3-doped YBCO can reach twice as much as pure YBCO, which makes a great effort to reduce the quench propagation speed. Based on the microstructure analysis, one can find that the thermal conductivity of Al2O3-doped YBCO has been determined by its components and microstructures. In addition, a macroscopic theoretical model has been proposed to assess the thermal conductivity of different microstructures, whose calculated results take good agreement with the experimental results. Meanwhile, a microstructure with high thermal conductivity has been found. Finally, a macroscopic YBCO bulk with the presented high thermal conductivity microstructure has been fabricated by the Al2O3-doped method. Compared with YBCO fabricated by the traditional 3D-printed, the Al2O3-doped structural YBCO bulks present excellent heat transfer performances. Our customized design of 3D-printing precursor pastes and novel concept of structural design for enhancing the thermal conductivity of YBCO superconducting material can be widely used in other DIW 3D-printing materials.

Design Concepts for Solution and Solid-State Emitters - A Modern Viewpoint on Classical and Non-Classical Approaches.

For a long time, luminescence phenomena were strictly distinguished between the emission of isolated molecules in dilute solutions or close-packed structures such as in powders or aggregates. This changed with the breakthrough observation of dual-state efficient materials, which led to a rapid boost of publications examining the influence of structural features to achieve balanced emission with disregarded molecular surroundings. Some first general structural design concepts have already been proposed based on reoccurring patterns and pivotal motifs. However, we have found another way to classify these solution and solid-state emitters (SSSEs). Hence, this minireview aims to present an overview of published structural features of SSSEs while shining light on design concepts from a more generalized perspective. Since SSSEs are believed to bridge the gap of hitherto known aggregation-sensitive compound classes, we hope to give future scientists a versatile tool in hand to efficiently design novel luminescent materials.

Modal properties of fractal sympodial trees: insights and analytical solutions using a group tree modeling approach

This study examines the intricate relationship between the hierarchical architecture of fractal trees and their dynamic properties, namely modal frequencies and mode shapes. It focuses on idealized sympodial trees under small, linear elastic lateral vibrations. This study proposes a group tree modeling approach that condenses the branches into simple structures, reducing the complexity of the model as appropriate. With the aid of a renormalization technique, the analysis proves that the sympodial tree is characterized by two families of vibration modes, i.e., the “emerging” and the “self-similar” modes. It further shows that the sympodial tree inherits all modes from the previous tree order (i.e., fractal level). Crucially, these inherited modes are self-similar, and beneficial in mitigating the vibration of the trunk by localizing the vibration of the tree at higher order branches. The study derives recursive closed-form solutions for both self-similar modal frequencies and mode shapes. Further, the analysis of sympodial trees with infinite tree order shows that their modal frequencies converge to stable values as the tree order increases. Accordingly, the study proposes analytical formulas to estimate these frequency limits from the fractal parameters of the sympodial trees. Results reveal that the natural frequency of a sympodial tree with infinite tree order and infinite branching number approaches asymptotically to that of a branchless tree. The proposed approach is then validated with numerical simulations and compared with independent studies. These findings are promising towards new bio-mimicking design concepts for civil engineering structures with improved dynamic behaviour.

A novel concept of hierarchical porous structural design on enhancing output performance of piezoelectric nanogenerator

Piezoelectric materials have been deemed as renewable power resources for the applications of harvesting mechanical energy and powering electronics for decades, due to their conspicuous mechanical and piezoelectric properties. Since the piezoelectric voltage is determined by the parameters such as applied force, piezoelectric and dielectric constant, it is crucial to study on tailoring these impact factors to realize a significant performance. In this work, the hierarchical porous PVDF/BaTiO3 foams (PBfs) are designed via salt-template method to modulate those impact factors. The synergistic effect of BaTiO3 and space-charged electret (SCE) formed by pores after poling on enhancing piezoelectric and ferroelectric properties has been firstly explored. The maximum open-circuit voltage and short-circuit current of PBf-30 realize 25.66 V and 677.45 nA after poling under a small applied force of 2 N, respectively. Attributed to the decent mechanical properties and prominent piezoelectric performance, the PBf is applied as the wearable sensor for human body motions and real-time monitor for vehicle movements. This work manifests a novel concept of enhancing output performance by hierarchical porous structural design and paves a way for the potential of piezoelectric nanogenerators in large-scale applications.

Inverse design of shell-based mechanical metamaterial with customized loading curves based on machine learning and genetic algorithm

Triply periodic minimal surfaces (TPMSs) have attracted great attention due to their distinct advantages such as high strength and light weight compared to traditional lattice structures. Most previous works focus on forward prediction of the mechanical behaviors of TPMSs. Inverse design of the configurations based on customized loading curves would be of great value in engineering applications such as energy absorption. Inspired by TPMSs, we propose the concept of the shell-based mechanical metamaterial (SMM) in this work, which possesses the main geometrical features and mechanical properties of TPMSs. A novel approach, combining machine learning (ML) for high efficiency and genetic algorithm (GA) for global optimization, is put forward to inversely design the configuration of SMM. Two strategies are introduced to develop artificial neural networks (ANNs) for the prediction of their loading curves under compression. GA is then employed to design objective configurations with customized loading curves. The connection between the loading curves and deformation modes is also illustrated to demonstrate the values of such inverse design. SMM with a strain-hardening curve tends to exhibit globally uniform deformation, while SMM with a strain-softening curve tends to present layer-by-layer deformation during compression, which is demonstrated by experiments and simulations. This work fills the blanks of inverse design of SMM with customized loading curves and contributes to the concept of structure design combining ML and traditional optimization approaches.

Conceptual design of transfer structures

AbstractA transfer structure (TS) is a structure that alters the load path of the gravity loads, shifting the line of thrust laterally to a different vertical alignment. Transfer structures are introduced in buildings that feature discontinuities in some columns or walls and where a direct load path to the foundations is not possible. They usually represent major elements of the structure and their impact on building cost and construction time can be substantial. This paper presents an overview of existing transfer systems and provides guidance on their design and construction. Extensive research on buildings with transfer structures all over the world was carried out (more than 100 examples were analyzed) with the aim of developing a rational typology of these structures. The results can be broken down into five main types: BEAM, TRUSS, INCLINED STRUT, PLATE, and ARCH & TIE.

Crashworthiness analysis of gradient fractal thin-walled structure

Inspired by the structure of bamboo, this study introduces a gradient fractal structure (GFS) design concept, which can be used in high-performance energy absorber. Crashworthiness performances of GFSs are investigated via numerical simulation. The 4-cell square thin-walled column with the cross-sectional dimensions of 36 mm × 36 mm reported in reference is used for the finite element model verification before the parametric analysis of GFS. Results show that the specific energy absorption (SEA) of 1st and 2nd order GFSs is 15% and 25% higher respectively compared to conventional square honeycombs under the same cell wall length and thickness. The gradient fractal distribution of materials not only increases the average folding number, but also lowers the force–displacement fluctuation and increases the crashworthiness performances of GFS. When the wall thickness increases, the SEA of GFS increases. However, large wall thickness will inevitably deteriorate the force–displacement fluctuation. Increasing the number of the outer components k also has similar tendency for crashworthiness performances. Simulations also suggest that reasonable wall thickness and height-side length ratio are two important factors for designing the GFSs with better energy absorption performances.

Investigation of the Flow Characteristics for Cylinder-in-Ball Valve Due to a Change in the Opening Rate

Ball valves are widely used as flow control devices wherein a hollow, perforated ball pivots to control the liquid flowing through it. Due to a simple structure and only a quarter-turn of the stem required for either a fully open or fully closed state, ball valves are known for being durable with excellent shut-off properties, albeit without offering precise flow control. V-port ball valves are used as an alternative to allow for linear and even equal percentage flow characteristics, but a robust construction is required for higher velocity working fluids in the small end opening of the V-shape; otherwise, the valve could sustain damage. In the present study, a cylinder-in-ball valve is proposed through a structural conceptual design, wherein the opening begins at the center of the flow path. The flow characteristics and flow rates according to the opening rate were quantitatively evaluated via computational fluid dynamic analysis. The results showed that the flow coefficient, CV, with a range of 1.05~109.87, increased exponentially over the opening rates of 20~100%. A numerical analysis for the multi-phase flow was performed to calculate the vapor volume fraction to confirm the effects of cavitation. In addition, an experiment was conducted on the CV values to verify the validity of applying the proposed cylinder-in-ball valve as a flow control valve. Good agreement for the CV values was obtained between the experimental and numerical results.

Exploring a Design Space Of Shell and Tensile Structures Generated by AI from Historical Precedents

This paper presents the development and application of a computational design tool that can be used to explore an AI-generated design space for the conceptual design of shell and tensile structures. An AI model was trained to extract geometric features from a dataset of 40 well-known design precedents of shell and tensile structures and to construct a design space. The trained model was then endowed with an interface to allow the designer to explore the design space within CAD software. Unlike the majority of current approaches to parametric design and optimisation, the exploration of the design space – and therefore the interaction between the designer and the computational model – does not take place via design variables, but through visual input. The potential of this tool to support the conceptual design of shell and tensile structures is examined through an application involving iconic design precedents. The application shows that, unlike form-finding and optimisation, this tool generates design suggestions that are not performance-driven, and do not require the statement of the boundary conditions, which would pre-determine the results. Despite this, such design suggestions can be considered plausible because they embed specific design knowledge resulting from a re-elaborating process of the main geometric features of the precedents used to train the AI model. These features include, for example, the shape of the openings, the number and location of the support points or the inversion of curvature, where present. The application results question the role of computational tools in conceptual design and illustrate an alternative strategy to explore the design space.

Ship weight reduction by parametric design of hull scantling

In this paper, a semi-automatic design procedure for concept and preliminary phases of hull structural design is described. It allows investigating the design of ship structures, consisting of a series of stiffened panels surrounded by primary members, assembled to form the hull girder. The optimal configuration of the structural lay-out and the best scantling of each structural component (i.e. platings, ordinary stiffeners and primary elements) is provided, accounting for interactions among all structural components as well as integration of primary, secondary and tertiary responses. The proposed method allows the minimization of the overall weight of hull blocks intended as the sum of stiffened panels’ weight (shell and stiffeners) plus that of the surrounding primary members. A dedicated application in VBA language (Visual Basic for Applications) has been developed in which scantling checks have been implemented by applying a few rules formulations after a comprehensive analysis of involved variables defining the state of the hull structural system. The proposed scantling design approach is very practical, it follows well-known hull structural design principles and it takes advantage of the nowadays widely available computation means to update the traditional sequence of the scantling checks in a more rational way and to select the optimal lay-out scantling solutions among truly feasible ones.

Diagrid and Bracing System Comparative Structural Performance and Sustainability Concept

Abstract: One of the intriguing structural design concepts for robust tall structures is the diagrid (diagonal grid) structural design. Due to its attractiveness and structural efficiency, Diagrid, a new design trend for tall, complicated structures, has arisen. Using a compact grid of diagonal members, Diagrid's façade structural system resists both lateral loads and gravity loads. As opposed to a traditional steel frame, it employs less structural steel, resulting in a more environmentally friendly building. This research uses ETABS to examine the structural performance of tall structures made of Diagrid steel and tall buildings with various bracing systems. Therefore, the purpose of this study is to contrast the lateral displacement brought on by wind and earthquake load between high-rise structures (buildings) using the diagrid system and those using other bracing systems. The use of diagrid and other bracing systems in relation to the natural frequency of high-rise structures (buildings) is also investigated in this study. A 40-story building model has been taken for analysis in E-Tabs 2016, with a plan area of 1296m2 (36- meters x 36-meters) and 144 meters tall.

Incorporating additive manufacturing constraints into magneto-structural topology optimization

Abstract The sequential using of topology optimization and AM (additive manufacturing) can generate and fabricate superior-performance yet lightweight magneto-structural components. In this paper, a magneto-structural topology optimization method is proposed considering AM constraints to improve the design manufacturability of optimized designs. The design problem is formulated with the weighted combination of magnetic compliance and mechanical compliance as a single objective subjected to two types of manufacturing constraints and the volume fraction constraint. Two important AM constraints are in a sequential manner incorporated into the topology optimization model, in which the overhang angle constraint is followed by the maximum length scale constraint. Corresponding sensitivities of the objective and constraints are derived, and the optimization problem is solved by the method of moving asymptotes. Two numerical examples and a practical conceptual design of linear motor rotor structure are systematically investigated to demonstrate the effectiveness of the proposed method.