Structural Strength Research Articles

Compressive behavior of SLA open-cell lattices: A comparison between triply periodic minimal surface gyroid and stochastic structures for artificial bone

This study evaluates the compressive properties of stereolithography (SLA) fabricated open-cell lattices, specifically triply periodic minimal surface (TPMS) gyroid and stochastic structures, for artificial bone applications. Two resins, Standard White and BioMed Amber, were tested across four relative densities (0.2, 0.3, 0.4, 0.5). Mechanical characterization of horse tuber coxae trabecular bone used as a biological comparator showed an average elastic modulus of 0.05 GPa and a yield strength of 3.369 MPa. Gyroid structures exhibited higher elastic modulus and yield strengths, with BioMed Amber gyroid at a density of 0.5, achieving an elastic modulus of 0.623 GPa and yield strength of 14.149 MPa. Stochastic structures showed lower and more variable mechanical properties. The highest yield strength for stochastic structures was observed in BioMed Amber at a density of 0.5 (14.199 MPa). Comparative analysis indicated that high-performing synthetic structures approach the lower bounds of natural bone properties. Using a field-driven design approach, variable relative density structures were developed to emulate the mechanical properties of natural bone. SEM analysis provided insights into failure mechanisms, highlighting the impact of relative density on structural integrity and material ductility. This research supports the development of 3D-printed bone-like structures as viable substitutes for cadaveric specimens in preclinical tests, with implications for material science and orthopedic applications.

Effects of folded fissure properties on tunnel model failure: Experiments and numerical simulations

Natural folded fissures commonly exist rather than simple straight fissures in rock masses surrounding tunnels. The presence of folded fissures significantly affects the fracture processes and failure modes of tunnel structures, thereby affecting their safety and stability. However, the research in this area is limited. Given this, this study fabricates city-gate section tunnel specimens containing folded fissures of various dip angles (α) and orientation angles (β), utilising 3D sand printing with sand and furan resin as matrix materials. Uniaxial compression fracture tests were conducted at a loading rate of 0.3 mm/min on these specimens using a digital image correlation technique to assess the impact of folded fissures on the mechanical properties and failure modes of the tunnel structures. Additionally, the improved smoothed particle hydrodynamics (SPH) method was used for damage evolution simulations during interactions between folded fissures and tunnels, and the simulation results were compared with the experimental results to verify the correctness of the method. The results show that for folded fissures, wing cracks and anti-wing cracks initiate not only from the ends but also from the bends of the fissures, whereas for straight fissures, they appear only at the fissure ends. Except for β = 0°, the interaction between folded fissures and tunnels generally results in the formation of a crack connecting the folded fissure upper end with tunnel, and the connection position varies with β. Different β values of folded fissures also influence the appearance and morphologies of top major cracks, underside major cracks, side cracks, and corner cracks around tunnels. As α increases, the overlap point of the crack and the tunnel moves from the tunnel corner to the tunnel crown. Moreover, folded fissures significantly affected the peak strength of the tunnel structures. As β increases, the peak strength first decreases, then increases, and finally decreases, reaching a minimum of 3.58 MPa at β = 90°. However, the peak strength differences are not evident under different α values. Finally, the influence of folded fissures on the cracking mechanism of the tunnel models is discussed in detail. This study provides insights into the impact of folded fissures on tunnel fracture modes and offers a reference for the application of SPH to reveal the underlying failure mechanisms of tunnel structures.

A deep learning GNSS spoofing and jamming detection method with dual-frequency C/N0 heatmap

Abstract The Global Navigation Satellite System (GNSS) is vulnerable to interference due to the open signal structure and low signal strength, posing a significant threat to the billions of terminals worldwide that rely on GNSS receivers for precise Positioning, Navigation, and Timing (PNT) services. In this paper, we propose a cloud-edge framwork for GNSS spoofing and jamming monitoring, comprising the data acquisition module, GNSS monitoring module, detecting and reporting module. In this framwork, we design a Deep Learning (DL) method for detecting GNSS interference through Dual-frequency Carrier-to-Noise density ratio (C/N0) heatmaps (DD-C/N0). This method involves extracting and correlating features from C/N0 heatmaps of visible navigation satellites operating in the GPS L1 and L2 frequency bands, allowing the identification of anomalous patterns. A U-BLOX receiver was utilized to capture the GNSS satellite signals, while commercial jammers and Software-Defined Radio (SDR) HackRF One kits were employed to simulate the interference sources. Experimental results demonstrate that the proposed method achieves significantly higher performance, with an accuracy of 99% and 98% on the public dataset and real-time testing data, compared to unsupervised, semi-supervised, and supervised detectors that rely solely on single-channel data (L1 frequency band). Integrated with the DD-C/N0 method, the online GNSS monitoring system will be improved and deployed to automate spoofing and jamming detection tasks in the next step.

Assessment of residual bonding performance for bimetallic steel bar-seawater concrete after exposure to high temperature

The bimetallic steel bar (BSB) is a new type of corrosion-resistant reinforcement material composed of carbon steel and stainless steel, which can effectively improve the durability of structures. Reinforced concrete structural strength depends on the bond between steel bars and concrete. This mechanism can be compromised after exposure to a fire, but it has been less considered in research, and is not addressed in concrete design codes. To evaluate the residual bearing capacity of BSB reinforced concrete structures after a fire, it is necessary to clarify the bonding performance between BSBs and concrete after exposure to high temperatures. In this study, 45 BSB-seawater concrete (BSBSC) pull-out specimens were prepared, and the bonding performance of BSBSC after high temperature was studied by heating treatment and pull-out tests. The results showed that the BSBSCs changed from bluish-gray to grayish-yellow with the increase in heat treatment temperature. After exposure to 400 °C, cracks appeared on the surface of BSBSCs. As the heat treatment temperature increased, the slope of the rising and descending stages for the bond stress-strain curve decreased gradually. In addition, as the thickness of the concrete cover increased, the bonding strength of BSBSCs also improved. The higher the heat treatment temperature, the less significant the improvement effect. Based on test results, a predictive model for the bonding performance characteristics of BSBSCs after high temperature was proposed, and a constitutive model for bonding stress-slip relationship was established.

[Translated article] Anatomical and biomechanical factors of osteoporotic vertebral fracture and the occurrence of cascade fractures

Osteoporosis weakens the structural strength of bone to such an extent that normal daily activity may exceed the capacity of the vertebra to bear this load. Vertebral fracture and deformity is a hallmark of osteoporosis. The detriment of trabecular bone properties alone cannot explain the occurrence of osteoporotic vertebral fracture. The ability of the spine to bear and resist loads depends on the structural capacity of the vertebrae, but also on loading conditions arising from activities of daily living or low-energy trauma. This review describes the mechanical properties of the vertebral bone, the structural load-bearing capacity of the various elements forming the spine, the neuromuscular control of the trunk, as well as the biomechanics of the loads to which the spine is subjected in relation to the presence of osteoporosis and the risk of vertebral fracture. A better understanding of biomechanical factors may help to explain both the high incidence of osteoporotic vertebral fractures and their mechanism of production. Consideration of these issues may be important in the development of prevention and management strategies.

The ways and mechanisms of using CFRP materials to strengthen the flexural performance of reinforced concrete beams

Due to the increasing demand for structural strengthening and retrofitting solutions, Fiber-reinforced plastic (FRP) materials has emerged as a promising technology to improve the performance of existing structures. FRP material is a composite material composed of fiber-reinforced plastics, known for its excellent strength and resistance to corrosion. The primary components of this material consists of various fibers, such as glass fiber, carbon fiber, or aramid fiber, along with a resin matrix, such as epoxy resin, polyester resin. FRP materials are commonly employed in construction engineering to enhance the flexural strength of concrete structures. This paper, through methods of literature review and building physical models, investigates the effectiveness of Carbon Fiber Reinforced Polymer (CFRP) materials in enhancing the bending strength of reinforced concrete beams. This study aims to examine the impact of carbon fiber reinforced polymer (CFRP) sheets on the flexural strength of reinforced concrete beams, which aims to establish calculation formulas based on the specific impacts observed. The findings of this study demonstrate the capacity of FRP materials, specifically CFRP materials, to improve the bending strength of reinforced concrete beams. The usage of FRP materials for structural reinforcement offers a durable, corrosion-resistant, and lightweight solution that can prolong the lifespan and improve the structural efficacy of existing infrastructure.

Extreme risk spillovers in international energy markets: New insights from multilayer networks in the frequency domain

This paper constructs multilayer risk spillover networks in the frequency domain, containing short-, medium-, and long-term layers, to explore extreme risk spillovers in international energy markets at different frequency bands. We analyze the topology properties of multilayer networks at the system, region, and country levels. Based on daily data from 20 national energy stock markets spanning 2006–2023, the empirical results show that: (1) The overall topology of multilayer networks, including the edge structure and spillover strength structure, exhibit frequency heterogeneity. With the onset of a major crisis, the frequency heterogeneity of the network topology increases significantly, and international energy risk spillovers tend to concentrate in fewer layers (i.e., over one or two frequency bands). (2) Long-term risk is primarily responsible for the extreme risk spillover behavior between energy markets. (3) Compared to short- and medium-term spillovers, long-term spillovers are more crisis-sensitive. Furthermore, long-term spillovers within different regions vary in their sensitivity to local or global crises. (4) As market conditions fluctuate, the key players driving the short-term layer change, whereas those driving the medium- and long-term layers remain relatively stable. Overall, our findings provide new insights for policymakers and investors to prevent international energy systemic risks and optimize investment strategies.

Effect of bisphosphonate on bone microstructure, mechanical strength in osteoporotic rats by ovariectomy

BackgroundBisphosphonate (BP) can treat osteoporosis and prevent osteoporotic fractures in clinical. However, the effect of BP on microstructure and mechanical properties of cortical and trabecular bone has been taken little attention, separately.MethodsIn this study, BP was used to intervene in ovariectomized female SD rats. The femoral micro-CT images were used to measure the structural parameters and reconstruct the 3D models in volume of interest. The structural parameters of cortical and trabecular bone were measured, and the mechanical properties were predicted using micro-finite element analysis.ResultsThere was almost no significant difference in the morphological structure parameters and mechanical properties of cortical bone between normal, ovariectomized (sham-OVX) and BP intervention groups. However, BP could significantly improve bone volume fraction (BV/TV) and trabecular separation (Tb.SP) in inter-femoral condyles (IT) (sham-OVX vs. BP, p < 0.001), and had no significant effect on BV/TV in medial and lateral femoral condyles (MT, LT). Similarly, BPs could significantly affect the effective modulus in IT (sham-OVX vs. BP, p < 0.001), and had no significant difference in MT and LT. In addition, the structural parameters and effective modulus showed a good linear correlation.ConclusionIn a short time, the effects of BP intervention and osteoporosis on cortical bone were not obvious. The effects of BP on trabecular bone in non-main weight-bearing area (IT) were valuable, while for osteoporosis, the main weight-bearing area (MT, LT) may improve the structural quality and mechanical strength of trabecular bone through exercise compensation.

Deep learning neural networks for monitoring early-age concrete strength through a surface-bonded PZT sensor configuration

Monitoring the immediate evolution of concrete’s strength is essential to ensure structural integrity and construction efficiency, requiring Forecasting to avoid unforeseen and severe failures during construction. The present investigation introduces an Equivalent structural parametric (ESP) study using a surface-bonded piezo sensor and electromechanical impedance (EMI) methodology to monitor and forecast the strength of concrete by implementing machine learning and deep learning methods. The concrete hydration processes are simulated using COMSOL™ 5.5. The concrete cube’s hydration is represented by altering Young’s modulus and damping ratio to show the rate of curing. Concrete strength development is examined in terms of conductance resonant frequency (CRF) and Conductance resonant peak (CRP). Continuous conductance signature monitoring and data analysis show that CRF and CRP increase with compressive strength. The system’s mechanical impedance is measured, and EMI signatures vs. frequency plots within a specific frequency range are compared to healthy impedance graphs. A mass-spring-damper system with identical properties is identified, and relevant structural parameters are computed. Modern ML algorithms include linear regression (LR), interaction LR, fine, medium, and coarse Gaussian SVM, etc. reliably predict strength with an error rate of less than 2%. Convolutional neural networks (CNN) have advanced image-based recognition, but their usage in EMI-based structural strength assessment is still being studied. A unique strategy using 2D CNN, 2D CNN– Long short-term memory (LSTM), and 2D CNN Bidirectional-LSTM to forecast concrete structure compressive strength shows the potential of deep learning. The proposed 2D CNN-Bi-LSTM model excels in compressive strength prediction, obtaining an R2 value of 0.99 and stabilizing loss error over a few epochs.

A Review of Flow Field and Heat Transfer Characteristics of Jet Impingement from Special-Shaped Holes

The jet impingement cooling technique is regarded as one of the most effective enhanced heat transfer techniques with a single-phase medium. However, in order to facilitate manufacturing, impingement with a large number of smooth circular hole jets is used in engineering. With the increasing maturity of additive technology, some new special-shaped holes (SSHs) may be used to further improve the cooling efficiency of jet impingement. Secondly, the heat transfer coefficient of the whole jet varies greatly on the impact target surface. The experiments with a large number of single smooth circular hole jets show that the heat transfer coefficient of the impact target surface will form a bell distribution—that is, the Nusselt number has a maximum value near the stagnation region, and then rapidly decreases exponentially in the radial direction away from the stagnation region. The overall surface temperature distribution is very uneven, and the target surface will form an array of cold spots, resulting in a high level of thermal stress, which will greatly weaken the structural strength and life of the equipment. Establishing how to ensure the uniformity of jet impingement cooling has become a new problem to be solved. In order to achieve uniform cooling, special-shaped holes that generate a swirling flow may be a solution. This paper presents a summary of the effects of holes with different geometrical features on the flow field and heat transfer characteristics of jet impingement cooling. In addition, the effect of jet impingement cooling with SSHs in different array methods is compared. The current challenges of jet impingement cooling technology with SSHs are discussed, as well as the prospects for possible future advances.

The Analysis Of Deterioration Of Village Road: A Case Of Palasah-Majalengka

Raising international issues related to road maintenance and repair. Road damage occurring in various countries, including cracks, potholes, and surface deformation, significantly impacts transportation safety and efficiency. Many roads in certain regions experience damage such as cracks, potholes, and surface deformation due to increased traffic loads and extreme weather conditions. The purpose of this paper is to analyze road damage in Karamat Village according to Bina Marga standards, to identify and understand the causes and effects of such damage. Primary data is the data collected from field observations at the study site, referred to as primary data or first-hand data. The road damage found on Pajaten road in Karamat Village, Majalengka Regency includes patches, cracks, disintegration, potholes, and waves. The purpose of routine maintenance is to improve the surface layer quality without increasing structural strength. The Pajaten road section in Karamat Village, Majalengka Regency, has conditions of loose stones, cracks, patches, potholes, and waves. The Directorate General of Highways states that the calculation results have a priority order of 10, placing it in the priority group &gt; 7. According to Bina Marga, road damage is addressed through a routine maintenance schedule. Patching is the recommended and suggested method for repairing cracks, ruts, and collapses on roads.

Wire-arc-additively manufactured Bi metallic structure: Mechanical properties and microstructural characterization

In this investigation, the fabrication and mechanical properties of Bi metallic structure walls produced using wire-arc-additive manufacturing (WAAM) technique, employing stainless steel (SS) 316L and 304 filler wires, are examined. The findings reveal that SS 304 exhibits superior mechanical attributes compared to SS 316L, notably showcasing impressive tensile strength and exceptional ductility. Bi metallic structure, meticulously constructed using both SS 316L and SS 304 filler wires, effectively replicates these distinctive mechanical properties, rendering it highly desirable for application prioritizing mechanical performance. The observed enhancement in strength is attributed to variations in microstructure resulting from a complex thermal history. Microstructural and crystallographic analyses of Bi metallic structure are conducted using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscattered diffraction spectroscopy (EBSD), and X-ray diffraction spectroscopy (XRD). Additionally, tensile strength (TS) of Bi metallic structure surpasses that of WAAM SS 316L by 3.95%. This comprehensive research not only elucidates the intricate process of material selection in additive manufacturing but also underscores the significant potential of Bi metallic structure in meeting the stringent demands of engineering applications requiring exceptional mechanical properties.

Nano-tentacled interconnected channels organic gel for rapid uranium extraction from seawater

Due to dwindling terrestrial uranium resources and escalating ecological pressures, the long-term viability of uranium supply has become a critical concern. The immense uranium reserves in seawater present a potential solution, yet extraction technology faces dual challenges of efficiency and adaptability to complex marine environments. Current interconnected porous adsorbents, despite their high flux properties, are limited by low specific surface area and weak mechanical strength, which constrain their effectiveness. Here, inspired by the unique hierarchical structures of marine organisms, we describe an organic gel adsorbent with supermacroporous and interconnected channels (10 ∼ 100 µm) adorned with "nano-tentacle" structures. This design significantly enhances the specific surface area by 18 times, increasing adsorption sites and imparting antibacterial properties. Notably, this adsorbent maintains structural integrity and superior mechanical strength (1.32 MPa tensile and 2.44 MPa compressive strength) even when fully saturated. During a 23-day trial in natural seawater, a uranium adsorption rate of 0.332 mg g⁻¹ day⁻¹ was achieved. This work offers a pioneering approach for the design and fabrication of hierarchical structured adsorbents, highlighting the immense potential of extracting uranium from seawater for sustainable energy production.

Construction of foam-templated Antarctic krill oil oleogel based on pea protein fibril and ι-carrageenan

Edible plant-based oleogels with zero trans-fat are promising solid fat substitutes. In this study, Antarctic krill oil (AKO) oleogels prepared from pea protein fibril (PPF) and ι-carrageenan (CG) by foam-templated method were developed for the first time. The modulation of the ratio of PPF and CG concentration on the structure and properties of foam, cryogel and oleogel was investigated and the potential formation mechanism of the foam-templated oleogel was explained. The results demonstrated that the addition of CG significantly decreased the foam size and enhanced the foam stability. The oil absorption and oil holding ability of the dense and reticular porous structure of the cryogel was demonstrated. Fourier infrared spectroscopy confirmed the interaction between PPF and CG involved in the formation of cryogels. With the addition of CG, the network structure and mechanical strength of the cryogel were reinforced, leading to more compact pores and higher capillary suction, which was appropriate for the establishment of good viscoelastic semi-solid oleogels. In addition, the oleogel was effective in masking the fishy odor of AKO. The significance of this study lies in its provision of a novel approach to the preparation of the foam-templated oleogel with PPF and CG as the oleogelators.

Utilizing almond shell filler to improve strength and sustainability of jute fiber composites

AbstractIn recent years, natural fibers have begun to replace synthetic fibers in automotive, building, and marine applications because of their sustainability, renewability, low cost, and availability of raw materials. However, because of their low strength, biocomposites are strengthened by hybridization with stronger synthetic fibers or adding fillers. This study reinforced high‐cellulose jute fiber composites with cellulose‐based almond (Prunus amygdalus) shell filler (ASF). Natural waste almond shells were ground to microparticle size. Hybrid composites were prepared by adding microparticulate ASF to the jute fiber composites at 0%, 1.5%, 3%, 4.5%, and 6% by weight. A comprehensive experimental study included tensile, flexural, Charpy impact (flat and edgewise), and shear tests. The addition of ASF significantly improved the mechanical properties of the jute fiber composites, and the best values were obtained with 3 wt.% ASF addition. Tensile, flexural, impact, and shear properties increased by 48.2%, 63.5%, 24.4%, and 52.2%, respectively. Scanning Electron microscopy (SEM) micrographs used in morphological structural analysis prove that the high mechanical values are achieved by ASF strengthening the interlaminar adhesion. This study contributed to developing a hybrid natural composite material reinforced with natural fillers that is stronger, environmentally friendly, and sustainable.Highlights The organic structure of Almond Shell Filler (ASF) ensured the sustainability of natural composites. Cellulosic ASF significantly contributed to the structural stiffness and strength of jute fiber composites. ASF reduced voids, improved fiber‐matrix bonding, and prevented debonding and delamination. ASF optimized the mechanical performance of jute fiber composites at 3%.

A computational study on buckling strength of pressurised submarine pressure hull structures under combined static load and asymmetric impact load

A computational study on buckling strength of pressurised submarine pressure hull structures under combined static load and asymmetric impact load

Nondestructive testing techniques for investigating mechanical property and porosity disparities in extrusion 3D printed concrete

ABSTRACT Three Dimensional Concrete printing (3DCP) stands at the forefront of modern construction methodologies, also named additive manufacturing, offering unparalleled time, cost, and labour savings compared to conventional approaches. The evaluation of fresh state parameters like extrudability and buildability through a specialised concrete extruder, combined with a methodical layer-by-layer deposition, ensures structural stability by precisely strengthening each layer. Mechanical strength evaluations highlight the printed material’s anisotropic nature, revealing extreme reductions of Fy = 27.94%, Fx = 19.07%, and Fy = 16.33% in compression, flexural, and split tensile strengths, respectively, compared to cast specimens. This emphasises the importance of direction-specific mechanical testing in understanding material behaviour completely. Non-destructive testing (NDT) methods, like Ultrasonic Pulse Velocity (UPV) testing, are crucial for the qualitative assessment of the integrity and mechanical strength of concrete structures, including both printed and cast specimens, by establishing a strong correlation with compressive strength without causing any damage. Limited research indicates that the microstructure of the material plays a significant role in its mechanical strength, particularly in printed specimens. This claim is reinforced by mercury intrusion porosimetry (MIP) results, which reveal that printed specimens have slightly higher overall porosity, concentrated between 1 µm and 0.1 µm, while cast specimens show higher porosity in pores smaller than 0.1 µm.

Viscometric studies of heavy oil in the presence of compositions consisting of amphiphilic compounds and organic solvents

The chemical composition of high-viscosity heavy oil has been studied by IR spectroscopy and X-ray fluorescence spectrometry. It is found that characteristic absorption bands are available and characterize aliphatic structures and aromatic cycles, sulfur- and organophosphorus compounds, and the presence of compounds containing heteroatoms P, V, Ca, Pd, Ni, Ru, Mo, Fe, Cu and Zn in its composition is found. The method of rotational viscometry has established the Newtonian nature of the oil flow in the studied range of the velocity up to 300 s–1. At the same time, according to the densitometry results (ρ = 0.954 g/cm3 ), studied heavy oil belongs to the bituminous type characterized by a complex rheological behavior under long- and high-term deformation conditions. In order to regulate the studied oil viscosity properties, composite additives based on amphiphilic reagents of cationic and amphoteric type and organic solvents have been developed, their influence on dynamic and kinematic viscosity has been examined. It has been established that compositions with surfactants simultaneously containing a large amount of amino and phosphate groups dissolved in a non-polar aromatic solvent (toluene) or an organic mixture (catalytic reforming gasoline) have a maximum modifying effect of the colloidal structure of bituminous oil. The interaction of functional groups of amphiphilic reagents with oil heteroatoms leads to the dispersion of resinous-asphaltene substances, a decrease in the structural and mechanical strength of the system, an increase in the molecular mobility of aggregates, which results in improving the investigated oil quality and viscosity characteristics by 7.0 and 12.6 % according to the composition efficiency index.

Analysis of the overall structural strength and optimization recommendations for ultra-large container ships based on the improved equivalent design wave method

Ultra-large container ships face challenges in structural strength under complex sea conditions. The traditional equivalent design wave method inadequately considers nonlinear wave effects, leading to inaccuracies in strength assessments. This article improves the method by incorporating nonlinear wave effects and optimizing wave spectrum parameters to better simulate structural responses. A study on a container ship, using refined wave load calculations and finite element analysis, focusing on stress distribution in critical hull areas. The findings show that the enhanced method more accurately reflects real loading conditions, confirming the ship’s structural soundness and offering optimization suggestions for improved safety and longevity.

IR-spectroscopic analysis of interaction with multi-layer paper and cardboard containing synthetic fibers with printing inks

An IR spectroscopic analysis of the printing and technical properties of new types of multilayer packaging paper and cardboard containing waste polyacrylonitrile fiber and their interaction with printing inks was carried out. The preference for using multilayer composite paper and cardboard for the printing and paper industries is shown. It has been established that the tensile strength of paper does not depend on the strength of individual components, but on the strength of the paper structure formed during its production. When the paper contained 20% waste modified polyacrylonitrile, maximum optical density was achieved with a minimum thickness of the ink layer, that is, saturated prints were obtained with minimal consumption of printing ink.