3D Void Research Articles

Investigation of additively manufactured metamaterials for load-bearing structural applications

The study explores the potential application of Triply Periodic Minimal Surface (TPMS) metamaterials in structural engineering and architecture. It evaluates parametric design possibilities and analysis approaches while examining the mechanical properties of five TPMS structures (Gyroid, Schwarz, Diamond, Split, and Neovius). Comparisons are made between Additively Manufactured (AM) samples and numerical simulations. Gyroid and Diamond structures, which display advantageous properties, undergo further investigation with parametric design for uniform and non-uniform lattices. The study proposes simplified analytical formulations for metamaterial design, along with Homogenization analysis and detailed FEM analysis. Compression tests reveal distinct failure modes and stress-strain behaviors for each TPMS. The research suggests further investigation into the influence of the 3D printing process, void detection, and thermomechanical analysis. Finally, the study provides insights into tailored applications of these lattice metamaterials in structural engineering.

Failure analysis of unidirectional CFRP composites with the coupled effects of initial fibre waviness and voids under longitudinal compression

This research delves into the failure mechanisms exhibited by unidirectional Carbon Fiber Reinforced Polymer (CFRP) composites under longitudinal compression, while considering the interplay of three types of manufacturing-induced defects: initial waviness of fibres, void volume fraction, and void size. The study employs 3D high-fidelity intact representative volume element (RVE) models, incorporating the initial waviness of fibres and voids based on Micro-CT imaging. A novel algorithm is proposed to generate more accurate 3D void shapes, departing from conventional circular or triangular approximations. The results highlight the substantial influence of the initial waviness angle on the reduction of predicted compressive stiffness and strength. The volume and size of voids play a significant role in determining damage initiation within the composites. The failure mechanisms of the composite under the coupled effects of initial waviness of fibres and voids are discussed, exhibiting reasonable agreement with experimental observations.

The cosmic microwave background lensing imprint of cosmic voids detected in the WISE-Pan-STARRS luminous red galaxy catalog

The cross-correlation of cosmic voids with the lensing convergence (kappa ) map of cosmic microwave background (CMB) fluctuations offers a powerful tool with which to refine our understanding of the dark sector in the consensus cosmological model. Our principal aim is to compare the lensing signature of our galaxy dataset with simulations based on the concordance model and to characterize the results with an $A_ kappa $ consistency parameter normalized to unity. In particular, our measurements contribute to the understanding of the “lensing-is-low” tension of the Lambda CDM model. In this analysis, we selected luminous red galaxies (LRGs) from the WISE- Pan-STARRS dataset, enabling an extended cross-correlation measurement using a 14,200 deg$^2$ sky area, which offers a more precise measurement than previous studies. We created 2D and 3D void catalogs to cross-correlate their locations with the Planck CMB lensing map and studied their average imprint signal using a stacking methodology. Applying the same procedure, we also generated a mock galaxy catalog from the WebSky simulation to serve as a basis for comparison. The 2D void analysis reveals a good agreement with the standard cosmological model, with $A_ kappa 0.08$ amplitude; that is, $S/N=13.3$, showing a higher signal-to-noise than previous studies using voids detected in the Dark Energy Survey (DES) dataset. The 3D void analysis exhibited a lower signal-to-noise ratio and demonstrated worse agreement with our mock catalog than the 2D voids. These deviations might be attributed to limitations in the mock catalog, such as imperfections in the LRG selection, as well as a potential asymmetry between the northern and southern patches of the Pan-STARRS dataset in terms of data quality. Overall, we present a significant detection of a CMB lensing signal associated with cosmic voids, largely consistent with the concordance model. Future analyses using even larger datasets also hold great promise of further sharpening these results, given their complementary nature to large-scale structure analyses.

Towards cosmology with void lensing: how to find voids sensitive to weak-lensing and numerically interpret them

In this work, we present a study of the void lensing signal or the excess surface mass density (ESMD) around cosmic voids. First, we propose a new void-finder algorithm that is designed to capture the ESMD around voids. We compare our algorithm applied to projected slices with the ZOBOV void finder and find significantly deeper weak-lensing profiles for voids defined by our algorithm in the context of a realistic galaxy mock. Then we test the consistency between the measurements of the ESMD as measured through the shear of background galaxies and directly calculated through the dark matter density profiles of the same voids. We found inconsistencies for voids with diameter ≥ 100h -1Mpc along the line-of-sight, but the consistency holds for smaller voids, meaning that we are indeed probing the underlying dark matter field by measuring the shear around these voids. Moreover, we show that voids found in the projected slices, which are highly sensitive to lensing, are correlated to 3D voids exhibiting intrinsic alignments between them.

Integrated geophysical approach for detection and size-geometry characterization of a multiscale karst system in carbonate units, semiarid Brazil

Abstract The karstification of carbonate rocks creates 3D maze voids that are normally controlled by fracture networks and sedimentary bedding. The spatial distribution and density of karst systems are usually complex and difficult to predict, demanding multidisciplinary studies at different scales of investigation to determine the spatial distribution and density of karst features and their possible links with cave systems controlled by the regional structural setting. The present study integrates geophysical datasets (gravity, electrical resistivity tomography - ERT, and ground penetrating radar - GPR) with a digital elevation model to investigate a karst system in the Irecê basin, a semiarid region of Brazil. Morphostructural lineaments reveal a NNW-SSE- and E-W-oriented structural setting of the crystalline basement, which is imprinted on the internal basin architecture, and surface drainage network. Negative gravity anomalies and high-gradient gravity zones indicate the main karstic zone, where karst landforms are concentrated. In addition, 2.5D gravity modeling provides the internal basin geometry, demonstrating that the karst system has evolved in the thickest sector of the basin. ERT profiles delineate the underground passages that connect dolines at depth. Finally, GPR data image shallow subsurface ghost-rock karstification that spread out from the surface to depth and that took advantage of vertical fractures and slightly arched bedding planes. Our results point out the role of the fracture corridors in channelizing hydrodynamic energy at a sufficiently high level to create caves by the total removal of dissolved material, whereas in the surrounding areas under low hydrodynamic conditions, overall shallow ghost-rock karstification took place, creating residual weathered rocks (alterites).

Extended defects-enhanced oxygen diffusion in ThO[formula omitted]

Oxygen self-diffusion is key to understanding stoichiometry and defect structures in oxide nuclear fuels. Experimentally, low activation-barrier oxygen migration was found in ThO2, a candidate nuclear fuel, possibly due to short-circuit diffusion mechanisms. Here, we perform extensive molecular dynamics simulations to show that various types of extended defects can enhance oxygen self-diffusion with a much-reduced activation barrier in ThO2. In this work, we consider extended defects including 1D (dislocation), 2D (grain boundary), and 3D (void) defects. Due to the distinct characteristics of each type of extended defect, the modulation of oxygen diffusion varies. These results provide a quantitative description of oxygen transport, which is significantly enhanced within a close distance (nanometer scale) from the extended defects. Among all these considered defects, grain boundary, particularly the low-energy Σ3 twin boundary, exhibits the strongest effect on increasing oxygen transport.

KOGPSR: A 3D GPSR algorithm using adaptive Kalman prediction for FANETs with omnidirectional antenna

Nowadays, flying ad hoc network (FANET) has captured great attention for its huge potential in military and civilian applications. However, the high-speed movement of unmanned aerial vehicles (UAVs) in three-dimensional (3D) space leads to fast topology change in FANET and brings new challenges to traditional routing mechanisms. To improve the performance of packet transmission in the 3D high dynamic FANETs, we propose a 3D greedy perimeter stateless routing (GPSR) algorithm using adaptive Kalman prediction for FANETs with omnidirectional antenna (KOGPSR). Especially, in data forwarding part of the KOGPSR, we propose a new link metric for greedy forwarding based on a torus-shaped radiation pattern of the omnidirectional antenna of UAVs, and a restricted flooding strategy is introduced to solve the 3D void node problem in geographic routing. In addition, in order to enhance the accuracy of the location information of high dynamic UAVs, we design an adaptive Kalman algorithm to track and predict the motion of UAVs. Finally, a FANET simulation platform based on OPNET is built to depict the performance of the KOGPSR algorithm. The simulation results show that the proposed KOGPSR algorithm is more suitable for the actual 3D high dynamic FANET.

Investigation on Three-Dimensional Void Mesostructures and Geometries in Porous Asphalt Mixture Based on Computed Tomography (CT) Images and Avizo

To investigate the void mesostructure in porous asphalt mixtures (PA), computed tomography (CT) and Avizo were utilized to scan and reconstruct the three-dimensional (3D) void model of PA-16 specimens. The void mesostructure of the specimen was quantitatively characterized through the anisotropy evaluation index. The equivalent pore network model (PNM) was extracted using the medial axis method. Based on the PNM model, the topological structure of the specimen and the morphological characteristics of the connected pores were analyzed. The results showed that the void anisotropy evaluation method can reflect the microscopic morphology of voids in porous asphalt mixtures. The cross-sectional porosity of representative elementary volume (REV) is mainly distributed between 20% and 25%, and about 90% of the macropores have a diameter between 0.5 mm and 3 mm. The distribution of cross-sectional porosity is uneven along the REV height direction. As the smallest cross-section of the seepage path, the equivalent radius of the throat is mainly between 0.1 mm and 1.5 mm, which is much smaller than the equivalent radius of the pore. The topological structure of pores is quite different, and their coordination numbers are mainly concentrated within 18. The pores with coordination numbers 1 to 10 constitute the main body of the pores inside REV, accounting for over 98% of the total number of pores. In addition, the permeability calculation results show that there is a significant difference in the permeability of each axis of REV compared to the total permeability of the superpave gyratory compactor (SGC) specimen, which illustrates that the permeability distribution presents an obvious spatial anisotropy. This study effectively reveals the heterogeneity of the 3D void morphology of porous asphalt mixtures, and it provides a reference for a better understanding of the void flow rules in drainage pavements.

Analysis of the influence of 2D and 3D void distribution characteristics of matrix skeleton on the mechanical properties of semi-flexible pavement: industrial CT scanning and 3D reconstruction

ABSTRACT This study aims to clarify the specific impact of the void distribution characteristics of the matrix skeleton on the mechanical properties of semi-flexible pavement (SFP) and form a targeted control method for the mechanical properties of SFP based on the gradation design of the matrix skeleton. Therefore, based on industrial CT and 3D reconstruction methods, this study comprehensively analyzed the matrix skeleton's two-dimensional and three-dimensional void distribution characteristics and conducted correlation analysis with the mechanical properties such as compression characteristics, tensile characteristics, dynamic modulus characteristics, and cracking characteristics of SFP. Research has found that the strength and rigidity of SFP are mainly positively correlated with the porosity and void's aperture of the matrix skeleton. The toughness of SFP is mainly positively correlated with the uniformity of void distribution and the three-dimensional void relative surface area index. The three-dimensional void relative surface area index is the most critical indicator affecting the mechanical properties of SFP, followed by the uniformity of void distribution, porosity, and the void's aperture.

Thermodynamic Modelling and Experimental Study of Nasicon Sub-Systems for Application as Solid State Electrolyte

Solid state electrolytes are crucial for enhancement of the safety and practicability of batteries. NASICON ( Na Super Ionic Conductor) is proposed as replacement for β″-Al2O3 [1], because of its excellent structural strength and conductivity which is attributed to its structure wherein Na migrates in 3D voids providing ionic conductivity of 0.2 S·cm-1 (300 °C). Furthermore, the processing temperature is relatively low (~700 °C), and high Na abundance makes it cheaper than Li-ion batteries.The NASICON phase with formula Na1+xZr2SixP3-xO12 [0≤x≤3] is found to be conductive and is a part of the complex Na2O-SiO2-P2O5-ZrO2 system. For a successful material design, thermodynamic properties (phase equilibria, heat capacity, stability, etc.) for all subsystems must be known, and for prediction of the properties, a reliable and consistent database is imperative. To accomplish these milestones, a thermodynamic database of the quaternary oxide system including the NASICON phase is being developed using Calculation of Phase Diagrams (CALPHAD) method.As part of this development, underlying binary systems such as Na2O-ZrO2 and ternary systems such as ZrO2-SiO2-P2O5 are studied. After preliminary results, the phase diagram construction is in progress with DTA/TG, XRD, and the experimental data along with literature values after critical analysis will be utilized for generation of Gibbs energies for all phases in the system. Using the thermodynamic dataset obtained, phase equilibria are predicted in agreement with the experimental data. The current state of work will be presented.

Hybrid Biofabrication of Heterogeneous 3D Constructs Using Low-Viscosity Bioinks.

The application of cytocompatible hydrogels supporting extensive cellular activities to three-dimensional (3D) bioprinting is crucial for recreating complex physiological environments with high biomimicry. However, the poor printability and tunability of such natural hydrogels diminish the versatility and resolution of bioprinters. In this study, we propose a novel approach for the hybrid biofabrication of complex and heterogeneous 3D constructs using low-viscosity bioinks. Poly(lactic acid) (PLA) filament is extruded by fused deposition modeling on a micromesh to create PLA-framed micromesh substrates onto which fibrinogen is printed by microextrusion bioprinting. The micromesh supports the printed hydrogel with a capillary pinning effect to enable high-resolution bioprinting. Accordingly, the micromesh-bioink layers are aligned and stacked to form volumetric constructs. This approach, called the 3D micromesh-bioink overlaid structure and interlocked culture (3D MOSAIC) platform, enables the fabrication of complicated and multimaterial 3D structures, including overhangs and voids. Endothelial cells cultured under vasculogenic conditions in the platform self-organize within the biologically functional hydrogel to form vascular networks, and cancer cell migration can be observed across the layers. The multidisciplinary 3D MOSAIC platform is an important step toward the biofabrication of complex constructs with high biological and structural significance and functionality.

Characteristics of Internal Water Flow Conduction within Asphalt Mixtures Based on Real Three-Dimensional Void Structure

This work presents a new approach to investigating water conduction properties in real three-dimensional (3D) voids of asphalt mixtures. Three different molding methods were employed for the same grade of asphalt mixture, and the three asphalt mixture specimens were scanned using X-ray Computerized Tomography (CT) to identify the real 3D void structure distribution inside the mixture. The real 3D behavior of void moisture conduction inside the mixture was simulated using the discrete lattice Boltzmann method and the BGK collision model. Three different molding methods were used to study the behavior of mesoscopic seepage inside the specimen. The results show that water conduction varies substantially in real 3D voids inside diverse molded objects. Regardless of flow and flow velocity, the Superpave Gyratory Compactor (SGC) method is extraordinarily close to the conduction qualities of the actual field core material. It shows that the Marshall molding method is inconsistent with the actual pavement molding method, and the SGC method can not only ensure that the reasonable void ratio is conducive to the thermal expansion and cold shrinkage space of the asphalt mixture but also prevents rainwater from entering the asphalt mixture. This work provides a new perspective for the study of water damage resistance and medium transmission characteristics of asphalt mixtures.

Parameter level set method for identifying 2D and 3D void using boundary displacement information

In this paper, the parameter level set method for 2D and 3D void identification is established uniformly by adopting boundary displacement information. Among them, the level set function is used to describe the evolution of the void interface. To avoid mesh reconstruction during the identification process, the ersatz material model associated with the level set function is developed to solve the forward problem. Simultaneously, considering further improving the optimization efficiency and reducing the identification cost, the compactly supported radial basis function is used to approximately expand the level set function. This scheme transforms the optimization of level set function into the optimization of the expansion coefficients, which reduces the optimization variables to some extent. In addition, the L-M algorithm with a certain regularization capability is employed to optimize the objective function. Finally, voids with various shapes in 2D and 3D structures are uniformly identified including complex multi-void structures such as structures similar to the human face and I-beam. The identification results show that the proposed identification method is effective and reliable even after introducing noise.

In silico quantification of 3D thermal gradients and voids during fused filament fabrication deposition to enhance mechanical and dimensional stability

Fused filament fabrication (FFF) is one of the most widely used additive manufacturing techniques for polymeric materials. However, the mechanical and dimensional quality of the final printed parts are still deviating from the maximal performance, due to the presence of voids, and incomplete inter- and intralayer bond formation implying suboptimal molecular chain entanglement. The current work puts forward a three-dimensional Ansys Polyflow® computational study in which temperature gradients and void formation are analysed for the deposition of up to eight strands, accounting compared to the state of the art for (i) bond formation at the strand interfaces by material deformation; (ii) non-Newtonian viscosity variations; (iii) measured temperature dependent material properties, including conductivity, specific heat capacity and viscosity; and (iv) convection. Selecting acrylonitrile butadiene styrene (ABS) as polymeric material, it is demonstrated that a dynamic heat transfer is obtained with contributions from the heated bed to layers printed above, and from just printed warmer layers to colder layers printed before in both the vertical and transversal direction. These extra heat transfers renew the interlayer contact between two strands, as the temperature at the weld line can be pushed several times above the glass transition temperature. A tuning of this renewable welding is possible based on a variation of the bed and nozzle temperature; the latter more relevant upon increasing the number of layers printed. It is further highlighted that the void shape and size is different close and away from the bed (2.5-8% void percentage variation). Moreover, a novel computational method is put forward to quantify the surface roughness based on edge analysis (80-120 μm variation).

Development of 3D tomosynthesis technique for nondestructive technology application using vertically aligned carbon nanotube-based high-resolution cold cathode electron beam

Nondestructive technology (NDT) is the most popular method for detecting defects inside an object without harming it. A 3D tomography algorithm toolbox and an x-ray imaging system are the essential components of NDT. We fabricated a high-resolution cold cathode electron beam (HRC-beam) based on vertically aligned carbon nanotubes to accomplish this objective. Using an HRC-beam, multiple angle projection images were captured in an x-ray imaging system. This x-ray source's horizontal and vertical focal spot sizes were 0.57 and 0.49 mm, respectively. Using the homemade 3D tomography algorithm toolbox, all the multiple projection images were recreated in a 3D volume. This toolbox employs algorithms such as the radon transform and the inverse radon transform to generate the 3D volume. The matlab r2022b program was used to execute the algorithm. This study explains the development of a three-dimensional volume and the inspection of the 3D volume in a slice view using a high-resolution cold cathode electron beam and the 3D tomography algorithm toolbox. A large phantom cable was used to evaluate 3D reconstruction and void inspection inside the large phantom cable.

Three-Dimensional Sulfonated Graphene Oxide Proton Exchange Membranes for Fuel Cells

During the last decades, graphene oxide (GO)-based materials have been extensively studied as low-cost efficient solid electrolytes for fuel-cell application. However, the observed limited proton conductivity of GO in the out-of-plane directions and associated lower fuel-cell performance largely limit their practical application. Herein, we have demonstrated a sulfate ion-intercalated three-dimensional graphene oxide (3DSGO) showing an exceptionally high out-of-plane proton conductivity of 0.74 S cm–1 at room temperature and 90% RH, and an in-plane proton conductivity of 3.19 S cm–1. Additionally, measurement of cell performance using the prepared membrane as the electrolyte of the proton exchange membrane fuel cell (PEMFC) showed an optimum power density of 112.65 mW cm–2 at 100% RH and 30 °C, which is more than double that achieved for 3DGO (50 mW cm–2). This efficient proton conduction ability and PEMFC performance of the 3DSGO is linked with the 3D interconnected ionic highways and substantial interlayer void space, which provide the higher water retention capacity in the 3D spongy architecture and a facile proton conduction pathway.

Effect of air void structure and mechanical properties of high strength fiber reinforced mortar composed with different construction sand species based on X-CT technology

The significant effect of desert sand on cement-based composites was observed in the previous investigation. However, how the composition of fine aggregate affects the formation of air void structure remains to be investigated. In this paper, mortars composed of five different sand mixtures were prepared, and the specific surface area (SSA) of the sand mixture with different content of fine aggregate was calculated. It was observed that the air void content decreased as the SSA value of the sand mixture increased. A negative-slope linear relation was observed between the SSA values and air void content in the composite construction sand fiber reinforced mortar system. With the increase of SSA, the air void number of every high-strength fiber reinforced mortar decreased from 12,446 to 6652. With the gradual increase of desert sand content, the count of air void number decreased. When the fine aggregate was completely desert sand, the air void content of the fiber-reinforced mortar dropped from 1.21% to 0.98%. Through the analysis of the 3D air void system, it can be concluded that the mixture of fine aggregate with different particle size distributions plays a positive role in optimizing the air void characteristics. Reasonable utilization of desert sand can significantly improve the pore structure characteristics and compressive strength of cement-based composites, which provides an effective theoretical basis for the development and utilization of desert sand resources.

Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement

Limestone calcined clay cement (LC3) has considerable potential for large-scale implementation. We investigated three selected kaolinitic clays at different locations in South Africa. LC3 mortars were compared to Portland cement mortar as control, particularly the hydration phase mineralogy/content, microstructure, compressive strength, and 3D void structure. The investigation indicated that similar pozzolanic oxide (SiO2 + Al2O3) could be obtained from calcined clay of varied kaolinite content. While kaolinite content improves the pozzolanic activity, consistency, and compressive strength of the mortar, the void refinement at the microscale depends on the degree of limestone filling/hydration. The hydration phase contents, microstructure, mineralogy, and porosity of the processed kaolinitic clays were determined to be adequate. However, it is noted that the intrinsic content of limestone (and gypsum) in commercially available Portland cement should be considered for equivalent clinker, limestone, and gypsum contents of 50%, 15%, and 5%, respectively.

Experimental Investigation of Rod Pitch Effect on Void Fraction in 5 × 5 Rod‐bundle under Elevated Pressure Conditions

In the present study, void fraction distributions in 5 × 5 rod-bundle test sections were investigated. Two different rod-bundle test sections with different rod pitch lengths were constructed. Experiments were carried out using unheated rod-bundle test sections equipped with 10 mm rod diameter with rod-pitch lengths of 13 and 12 mm, respectively. The HUSTLE (Hitachi Utility Steam Test Leading Facility) facility supplied steam and water with an inlet mass flux (G) ranging from 75 to 500 kg/m2/s at 5.0 to 7.5 MPa system pressure. These inlet and boundary conditions simulate the prototypic BWR at natural circulation conditions. For the measurement of void fraction, the X-ray CT system was newly developed for the three-dimensional time-averaged void fraction measurement, and 3D void fraction distributions were successfully obtained for various pressure conditions. The volume-averaged void fraction was also measured using differential pressure transmitters. Based on the newly developed void fraction database, the assessment was carried out using state-of-the-art drift-flux correlations applicable for rod-bundle. Existing correlations tend to show good void fraction prediction at high mass flux conditions for both geometries, poorer performance was shown for the narrow rod test sections with low mass flux conditions. Furthermore, the effect of the rod-pitch lengths on void fraction distribution in rod-bundle flow field was assessed. It was observed that narrower rod bundle configuration tends to have higher void fraction at given mass flux. Narrowed pitch-length enhances wall-friction against two-phase flow, which likely suppress the central phase fraction peak tendency. This promotes lower distribution parameter values, results in increased area-averaged void fraction for narrower pitch test section. However, the present study revealed that no existing correlations could clearly capture the void fraction trend for the narrow rod test section.

Data-Constrained Modelling with multi-energy X-ray computed microtomography to evaluate the porosity of plasma sprayed ceramic coatings

Atmospheric plasma spray (APS) deposited ceramic coatings of zirconium boride (ZrB2) and hydroxyapatite (HAp) were inspected using Data-Constrained Modelling (DCM) of X-ray Micro-Computed Tomography (X-ray μ-CT) datasets to evaluate coating porosity. The DCM approach was used to quantify the porosity and void distributions in the coatings. The results from the 3D analysis were compared to 2D porosity and void distributions determined from the image analysis method. The 3D porosity determined from the ZrB2-1 model, 24.7%, agreed well with the 2D porosity estimation of 22.1 ± 2.6%. Additionally, the 3D porosity determined from the HAp-1 model, 22.8%, was marginally greater than the estimated 2D porosity, 19.8 ± 2.1%. However, a comparison of the 2D and 3D void distributions revealed that a 2D assessment poorly predicted the 3D microstructure of coatings and cannot be used to infer properties that depend strongly on the 3D void network. The DCM method has the ability to include the effect of fine-structure details over the 3D scan volume and hence incorporated micropores and cracks that are typically overlooked during traditional porosity inspections. Furthermore, the 3D analysis demonstrated the deficiencies in typical CT segmentation methods applied to data with a moderate CT resolution size, which was 5.4 μm. The superior DCM approach enabled the quantification of pores below the CT resolution limit that would not have been accurately modelled using typical CT segmentation methods.