Load Transfer Research Articles

In situ anchoring of Cu single-atom sites into porous organic polymers for efficient overall CO2 photoreduction

Single-atom site (SAS) catalysts have been extensively investigated for their remarkable catalytic properties. However, the multistep preparation procedures are complex and difficult to control. Here, we developed a one-step in situ synthesis of Cu single atom sites anchored into two types of alkynyl-linked covalent phenanthroline frameworks (CPFs) using a facile and controllable strategy during the synthesis process, that is Cu-SASs/CPF-DBPhen and Cu-SASs/CPF-TPP. Notably, the phenanthroline ligands in Cu-SASs/CPF-DBPhen have higher opening degree than the porphyrin ligands in Cu-SASs/CPF-TPP. This allows Cu-SASs/CPF-DBPhen to achieve higher metal loading and faster charge transfer efficiency than Cu-SASs/CPF-TPP, suggesting that Cu-SASs/CPF-DBPhen may have better photocatalytic performance. As expected, the CO yield of Cu-SASs/CPF-DBPhen (∼21.1 μmol·g−1·h−1) is about 11.7 times higher than that of CPF-DBPhen (∼1.8 μmol·g−1·h−1) and also exceeds that of Cu-SASs/CPF-TPP (∼8.3 μmol·g−1·h−1). Likewise, similar results were observed during the oxidation process. This work proposes a versatile one-step, in situ growth method for synthesizing catalysts.

Microstructure and properties controlling of Al-xGd alloys for thermal neutron absorbing

A novel lightweight thermal neutron absorbing Al-xGd alloy (x = 2.5, 5, and 10 wt.%) with tunable mechanical properties was fabricated by induction melting followed by a rolling process and an annealing treatment. During solidification, the Al3Gd phase predominantly formed and was distributed along grain boundaries. Cold rolling crushed and redistributed the Al3Gd phase throughout the matrix. Furthermore, the large deformation imposed on the material during cold rolling enhanced the work hardening effect and promoted dynamic recrystallization. The load transfer strengthening effect was influenced by the size, volume fraction, and distribution of the second phase. The spheroidization of the second phase increased rapidly and then remained stable during 5000 h long-term aging at 400°C. The thermal neutron absorbing performance of the Al-5Gd alloy is comparable to the 30%B4C/Al composite evaluated by Monte Carlo simulations. Furthermore, Al-5Gd alloy exhibited higher plasticity (> 20%). This novel Al-xGd alloy is a promising candidate for future lightweight thermal-neutron-absorbing materials.

Improving the mechanical and tribological properties of Cu matrix composites by doping a Mo2BC ceramic

Cu matrix composites (CMCs) are widely employed for tribological applications such as in sliding bearings and electrical contact fields. However, the Cu matrix needs to be modified to improve its mechanical and tribological properties. In this study, CMCs reinforced with Mo2BC ceramic particles (10–30wt.%) are prepared via the spark plasma sintering (SPS) route method. In comparison with the plain Cu sample, when the content of the Mo2BC particles increased to 30wt.%, the Vickers hardness, yield strength, and tensile strength of CMCs increased by 196%, 157%, and 588%, respectively. Fine grain and load transfer strengthening mechanism are considered the main strengthening mechanism. Introducing the Mo2BC ceramic effectively reduces friction and wear as well as the frictional noise vibration of CMCs. Incorporating Mo2BC ceramic into the Cu matrix can elevate the load-bearing ability, inhibiting mechanical and adhesive wear. In addition, the composite exhibits superior friction and wear properties as the content of Mo2BC ceramic increases gradually up to 30wt. %, where the friction coefficient and wear rate are as low as 0.35 and 3.25 × 10−6 mm3/Nm, respectively. A layer of tribo-film containing Fe2O3 derived from the counterparts and induced by the tribo-oxidation reaction can provide a lubricating effect. Considering the superior mechanical and tribological properties, the as-prepared CMCs could be an attractive alternative material for sliding bearing fields.

Research on the load transfer performance of large-span steel truss cable-stayed bridge structures

Since the wave is accompanied by the transfer of energy in the process of transmission, and the energy density at the node directly affects the bearing capacity and service performance of the steel truss cable-stayed bridge members and joints, this paper quantitatively studies the energy density at the key nodes of the long-span steel truss cable-stayed bridge from the perspective of the wave response of the structure. Firstly, according to the drawings of Xiangshan Bridge, a local finite element model of the steel truss cable-stayed bridge is established, and by changing the angle between the cable and the steel truss girder and the bending stiffness of the cable, the variation law of energy density at the connection node between the cable and the steel truss girder is obtained by changing the angle between the cable and the steel truss girder and the bending stiffness of the cableway. Due to the limitations of finite element wave analysis, from the perspective of theoretical analysis, this paper establishes the local scattering matrix at the node, proves the obtained law to a certain extent, and uses the return wave-light matrix method to analyze and solve the energy density at the connection node between the cable bar and the steel truss girder, and the final analytical solution is in good agreement with the numerical solution, which proves that the law obtained by numerical analysis is correct.

Development and Characterization of Ethylene‐Vinyl Acetate‐Graphene Nanocomposites

AbstractThe prospective applications of carbon graphene nanoplatelets (GNPs) reinforced ethylene vinyl acetate (EVA) nanocomposites in flexible electronics, energy storage devices, and thermal management systems have attracted a lot of attention. These nanocomposites offer an effective solution for enhancing the electrical conductivity of interfacing materials in electronic systems and addressing issues related to thermal management. GNPs that possess excellent thermal conductivity of 2000–4000 W m−1 K−1 and an electrical conductivity of 107 S m−1 are utilized in this investigation. The homogeneous dispersion of nanofiller and the effective load transfer between components through strong filler/polymer interfacial interactions are essential for the creation of multifunctional polymer nanocomposites. Particularly, their electrical conductivity and dielectric properties are highlighted in this study, with an emphasis on the synthesis and characterization of nanocomposite materials. This work investigates the utilization of graphene nanocomposites in EVA using a melt‐mixing technique assisted by sonication to fabricate multifunctional composites. Incorporating different weight percentages of GNPs (ranging from 0.1 to 0.4 wt.%) within the polymer matrix is carried out. In the present study, the nanocomposites are characterized by scanning electron microscopy investigation and impedance spectrum analysis. The distinctive characteristics of the AC electrical transport in nanocomposites are investigated between 10 Hz and 1 MHz. Excellent interfacial compatibility has been demonstrated by the homogenous distribution of GNPs within the matrix, confirmed by SEM examination. These EVA nanocomposites demonstrate improved electrical conductivity, thereby rendering them very useful for energy storage applications, such as electronic capacitors, wherein supports with a significant dielectric constant and minimal dielectric loss are required.

Improving strength-ductility synergy of titanium matrix composites containing nitrogen via the introduction of intragranular nano-TiB

We prepared a titanium matrix composite (TMC) with added boron nitride nanosheets (BNNSs) for strength-ductility trade-off issues. The composite, characterized by in-situ nano-TiB intragranular distribution and trace nitrogen solid solution, was prepared using rapid hot press sintering (FHP) and short-duration hot rolling. During pre-rolling heat preservation, the diffusion of boron and nitrogen resulted in the intragranular distribution of nano-TiB and nitrogen solid solution. The nano-TiB demonstrated excellent load transfer, fracture suppression, and dislocation storage capabilities at both room and high temperatures. Coupled with the nitrogen solid solution, the composite exhibited a significant enhancement in strain hardening effect compared to the titanium matrix. The composite outperformed the titanium matrix in strength and ductility at both room and high temperatures, demonstrating a notable strength-ductility synergy. This work provides a reference for designing TMCs with excellent performance at both room and high temperatures.

Bond-slip behavior of Aluminum Alloy (AA) bars for near-surface mounted (NSM) technique

An experimental study consisting of 22 pull-out tests was carried out to investigate the bond-slip performance and load transfer mechanism between near-surface mounted (NSM) Aluminum Alloy (AA) bars and concrete when the AA bars are inserted into pre-cut grooves on the surface of the host structure and bonded with an appropriate bonding agent. The effects of several design parameters were evaluated including bond length, diameter of AA bars, bar surface treatment, and adhesive type. A digital image correlation (DIC) system was used to measure the slips and surface strain and four failure modes were observed in the tests, being concrete splitting failure, epoxy splitting, debonding at the bar-epoxy interface, and AA bar rupture. Results showed that an increase in bond length could make the failure mode more ductile, while AA bars with rough surfaces exhibited a relatively satisfactory bond-slip behavior when a suitable epoxy was used. Finally, the test data from this study were used to examine three bond-slip models based on fiber reinforced polymers (FRP) for the NSM technique. A new bond-slip model considering the influence of the bar external surface was proposed and validated by the test results from both this study and literature.

Dynamic responses of locomotive axle box bearings under varying operating conditions

Axle box bearings (ABBs) are a vital component of a railway locomotive, ensuring their reliable performance requires an in-depth understanding of their dynamic behaviour. This work theoretically derives a locomotive–track longitudinal–vertical coupled dynamics model that takes detailed dynamics of the ABBs into account. The model considers a number of complex interactions, such as non-linear contact and friction forces within the ABB, wheel–rail interactions, and track irregularities. The motions of ABB are coupled with the wheelset and bogie frame, allowing detailed investigation of the ABB dynamic behaviour during operation. The correctness of the proposed model is verified in both the time and frequency domains by comparing with field test. The dynamic characteristics of ABBs under varying operating conditions were comprehensively investigated. The results demonstrate that track irregularities have a non-negligible influence on the dynamic forces of the locomotive ABB. Furthermore, the axle load transfer occurs during loading conditions, which leads to significant differences in vertical and longitudinal dynamic interactions within the ABBs across wheelsets. It is clear that the operating conditions of the locomotive should be suitably considered in the dynamic assessment, operation, and maintenance of ABBs.

Experimental study on rotary inter-module connections with corrosion-resistant metal materials: Under axial tension

Modular construction is an innovative construction technology that has attracted considerable attention for its pronounced advantages in reducing reliance on on-site labor, speeding up construction, enhancing productivity, and ensuring superior quality. To extend the applicability of modular construction to structures in corrosive environments, such as ocean floating structures for exploring renewable energy, a rotary inter-module connection employing corrosion-resistant metal materials was proposed herein. Six full-scale inter-module connection specimens made of grade S30408 austenitic stainless steel, grade S220503 duplex stainless steel, and grade A96061-T6 aluminum alloy were tested under axial tension. The load-displacement relationships of each specimen were recorded to enable a thorough analysis of the strength, stiffness, and ductility of the tested specimens. As compared to the conventional carbon steel counterparts, the stainless steel specimens showed superior load-bearing capacity with improved ductility, while the aluminum alloy specimens experienced brittle fracture at the bolt shank-bottom plate junction with reduced load-bearing capacity. Three typical failure modes were identified in the experimental study, namely, plastification of the connector and lower corner fitting, plastification of the connector and both corner fittings, and fracture of the bolt. The load-strain relationships of each specimen were also discussed to analyze the load transfer mechanism and structural behavior of the connection. In addition, the applicability and accuracy of the simplified calculation methods based on beam bending theory and Navier solution for rectangular thin plates, respectively, were discussed based on the test results.

Numerical and experimental blast response of multilayer laminated glass panels

Laminated glass is used in high-security buildings to mitigate the effects of blasts and ballistic loadings. The multi-layered composition of the laminated glass (LG) panels allows the glass panes to crack and undergo large deflections while preventing glass shards from spalling by mostly remaining attached to the polymeric interlayer. To characterize multilayer LG panels under blast loading, it is essential to develop their static resistance response under uniform loading. A full-scale water chamber was used to experimentally evaluate the quasistatic response to the failure of the multilayer LG panel systems under uniform pressure. The influence of different polymeric interlayer types on the response of multilayer LG panels was studied. Also, the glass breakage patterns and deflections exhibited by various multilayer glass configurations were investigated. The response of LG panels under blast was developed using ANSYS AUTODYN, which was verified using field experiments. LG panels with an Ethylene Vinyl Acetate (EVA) polymeric interlayer experienced the most dynamic deflections, whereas LG panels with an ionoplast SentryGlas® (SG) polymeric interlayer displayed the least dynamic deflections. The results indicated that multilayer LG systems provide higher blast resistance compared to double-layer systems; the additional layers can help reduce glass breakage and maintain structural integrity. Multilayer LG system’s SG interlayer enhanced blast protection by allowing load transfer and ensuring uniform load distribution between glass layers.

Influence of TiC particle size on microstructural evolution and fracture mechanism of TiC/Al-Cu composites

Using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and molecular dynamics simulations, this work investigated the microstructure, texture evolution, strengthening mechanisms, and fracture progression of TiC/Al-Cu composites with various particle sizes following hot extrusion and heat treatment. TiC particles significantly refine grain sizes, shifting the dominant coincidence site lattice (CSL) boundaries from Σ5 to Σ3. The addition of TiC particles alters the preferred grain orientation from (111)/ED to (001)/ED, and modifies the type and intensity of the texture. The primary strengthening mechanisms attributed to TiC include grain boundary strengthening, dislocation strengthening, Orowan strengthening, and load transfer strengthening. However, the strong tendency of smaller TiC particles to agglomerate substantially diminishes these strengthening effects; thus, under a TiC addition of 0.5 wt%, larger TiC particles exhibit better mechanical properties. Fractographic analysis and molecular dynamics simulations revealed that microcracks originate from dissociation at the interfaces between the TiC agglomerates and the Al matrix. The subsequent propagation, expansion, and interconnection of multiple crack initiation sites lead to the formation of macroscopic cracks that result in material failure.

Effect of Silicon Carbide Particulates on Mechanical Behavior of Al5052 Alloy Metal Matrix Composites for Mining Applications

In particular, the impact of Silicon Carbide (SiC) particles on the mechanical properties of stir-cast Al5052 alloy Metal Matrix Composites (MMCs) for rotor blade applications is examined in this work. The goal of integrating SiC particles is to improve mechanical characteristics including wear resistance, tensile strength, and hardness while preserving the ideal weight-tostrength ratio, which is essential for rotor blade performance. The Al5052 matrix was filled with SiC in a variety of compositions (0%, 2%, 4%, 6%, and 8% by weight), and the resultant composites underwent mechanical testing and microstructural examination. Due to the efficient load transfer and reinforcing processes, the results show a considerable improvement in tensile strength and hardness with the addition of SiC particles. Furthermore, microstructural analyses demonstrate a uniform dispersion of SiC in the matrix, which supports the improved performance attributes. Wear resistance of Al5052 alloy is greatly increased when Silicon Carbide (SiC) particles are added as reinforcement. This makes the composite material perfect for applications requiring great durability and longevity to survive hard mining conditions, such as wear plates, conveyor liners, and drill bits in mining machinery components.

Dynamic 3D hydrogen-bond network in siloxene-water system enables efficient moisture-enabled electricity generation

Utilizing ubiquitous moisture as an energy source for moisture-enabled electric generator (MEG) has emerged as a significant technological frontier. The migration process of protons at the water/solid interface is crucial for understanding the mechanism of moisture-to-electricity conversion and efficient energy harvesting. However, the lack of clarity on this scientific question has hindered the substantive development of MEG. Here, a novel dynamic three-dimensional (3D) hydrogen-bond network between the interface of siloxene layers was designed through water molecule intercalation. The spatial bridging effect of this dynamic 3D hydrogen-bond network, formed on the siloxene layers, enhances the load transfer capability of the siloxene-water system, thereby randomizing the direction of proton hopping. Experimental and theoretical calculations demonstrate that the dynamic 3D hydrogen-bond network constructed within and between the siloxene layers facilitates rapid proton conduction. Kinetic simulations further confirm that the strength of the hydrogen-bond network accelerates proton transport rate. The current density of siloxene under high humidity increases significantly, reaching 22.37 µA cm−2, which is 122 times that under low humidity, as well as the open-circuit voltage reaches 0.73 V. This work contributes to understanding the microscopic mechanisms behind efficient moisture-enabled electricity and provides a fresh perspective for enhancing MEG performance.

Integrated Energy System Load Forecasting with Spatially Transferable Loads

Integrated Energy System Load Forecasting with Spatially Transferable Loads

Correlation between sagittal balance and thoracolumbar elastic energy parameters in 42 spines subject to spondylolisthesis or spinal stenosis and 21 normal spines

The curvature of the lumbar spine plays a critical role in maintaining spinal function, stability, weight distribution, and load transfer. We have developed a mathematical model of the lumbar spine curve by introducing a novel mechanism: minimization of the elastic bending energy of the spine with respect to two biomechanical parameters: dimensionless lumbosacral spinal curvature cLS and dimensionless curvature increment along the spine CI. While most of the biomechanical studies focus on a particular segment of the spine, the distinction of the presented model is that it describes the shape of the thoracolumbar spine by considering it as a whole (non-locally) and thus includes interactions between the different spinal levels in a holistic approach. From radiographs, we have assessed standard geometrical parameters: lumbar lordosis LL, pelvic incidence PI, pelvic tilt PT, sacral slope ψ0 and sagittal balance parameter SB = sagittal vertical axis (SVA)/sacrum-bicoxofemoral distance (SFD) of 42 patients with lumbar spinal stenosis (SS) or degenerative spondylolisthesis (SL) and 21 radiologically normal subjects. SB statistically significantly correlated with model parameters cL5 (r = −0.34, p = 0.009) and −CI (r = 0.33, p = 0.012) but not with standard geometrical parameters. A statistically significant difference with sufficient statistical power between the patients and the normal groups was obtained for cLS, CI, and SB but not for standard geometrical parameters. The model provides a possibility to predict changes in the thoracolumbar spine shape in surgery planning and in assessment of different spine pathologies.

Explorations of mechanical and corrosion resistance properties of AA6063/TiB2/Cr2O3 hybrid composites produced by stir casting

Mechanical and Corrosion characteristics of composite materials made from Aluminum alloys (AA) 6063 supplanting as the material of choice for automotive, aerospace, and marine applications by systematically varying ceramic reinforcements developed through controlled stir cast technique ensuring uniform dispersion are explored. The hardness, density, impact and tensile strength, corrosion resistance, and microstructural characteristics of Aluminum Matrix Composites (AMCs) reinforced with titanium diboride (TiB2) at 7.5, 10, and 12.5 wt% and chromium oxide (Cr2O3) at 3, 6, and 9 wt% were assessed according to ASTM standards. The microstructural analysis revealed a reduction in the growth of reinforcement clusters within acceptable limits. The addition of reinforcements to the matrix resulted in improved tensile strength, ranging from 124.6 to 188.7 MPa, and hardness, increasing from 71.5 to 144.32 VHN. This improvement is attributed to the strengthening or load transfer mechanism facilitated by the reinforcements. Additionally, the impact strength of the composites increased from 11.845 to 21.16 J, while the density showed slight variations. Consistent corrosion tests demonstrated that the chemical and interfacial interactions between the matrix material and the reinforcements significantly enhanced the corrosion resistance, reducing the corrosion rate from 570 to 499 mm/year.

Influence of copper-coated graphene films on mechanical and damping properties of bionic laminar CuAlMn matrix composites

Inspired by the structure of nacre, bionic laminar composites composed of 85.6 wt% Cu, 11.9 wt% Al, and 2.5 wt% Mn were prepared using highly flexible Cu-coated graphene films as fillers. The effects of surface modification and graphene films content on the properties were investigated. Results indicated that the loss factor of composites with 0.1 wt% Cu-coated graphene films is improved by approximately 28% and reaches 0.044 compared to uncoated samples. The density and tensile strength are increased by up to 98% and 362 MPa, respectively. This enhancement is attributed to the improved bonding at the graphene films/matrix interface due to the Cu coating, which allows for efficient load transfer. Concurrently, the activation of interlayer sliding in the graphene films dissipates substantial energy. However, an excessive addition of graphene films leads to decreased density and increased internal defects in the composites, resulting in deteriorated properties. This study provides a reference for the preparation of CuAlMn matrix composites with enhanced mechanical and damping properties.

Comparative analysis of spinning techniques on the performance of full-strength-grade engineered cementitious composites: Mechanical characteristics, pore structure, fiber distribution, micromorphology

The spinning techniques used for ultra-high molecular weight polyethylene (UHMWPE) fibers are crucial for enhancing the performance of ECC. However, the specific effects of different spinning techniques for UHMWPE fibers on ECC's performance are not well understood. To address this gap, this study investigates the influence of dry-spun and wet-spun spinning techniques on both the macroscopic mechanical properties and microscopic characteristics of full-strength-grade ECC. Comprehensive tests were conducted, including assessments of tensile, compressive, and flexural strength. Additionally, detailed CT-based 3D reconstruction and SEM analysis were performed to examine the pore structure, fiber orientation, and micromorphology. The findings reveal that the surface irregularities and roughness of dry-spun fibers lead to stress concentration, whereas the more uniform surface of wet-spun fibers enhances their bridging performance. Compared to dry-spun fibers, wet-spun fibers significantly improve ECC's tensile and flexural properties, enhancing ultimate tensile strength by up to 22.7 % and ultimate flexural deflection by up to 50.2 %. Additionally, wet-spun fibers result in a more uniform pore structure and better fiber alignment, creating a denser and more compact matrix. These microstructural improvements contribute to superior load transfer and energy absorption characteristics, enhancing ECC's overall performance and durability. These results underscore the critical role of fiber spinning techniques in optimizing ECC performance, contributing to more durable and sustainable structures in high-performance construction applications.

The influence of steep faults at various avoidance distances on the stability of hard rock caverns: Physical model experiments and DEM simulations

The influence of avoidance distances from steep faults on the stability of hard rock caverns is pivotal in deep engineering, yet research in this area remains scant. This study constructed 10 physical models of granite caverns, incorporating artificial cement-filled faults at various avoidance distances ranging from 0 to 2.4 cavern diameters. Biaxial compression experiments were conducted, utilizing acoustic emission and digital image correlation techniques for monitoring. Coupled with discrete element method simulations, the analysis explored the influence mechanisms of fault-cavern distance on the failure modes of hard rock caverns. The results reveal a positive correlation between the peak strength of specimens and fault-cavern distance. As the distance approaches 0.6 cavern diameters, the fault significantly influences the displacement field, crack number, distribution, and crack initiation location within the specimens. Furthermore, even at 1.2 cavern diameters, the fault still exhibits a notable influence on the stress field, external load transfer paths, cavern failure modes, and the size distribution of spalling debris. These findings can guide the selection of sites for deep hard rock caverns, ensuring a minimum fault-cavern distance of 1.2 cavern diameters to mitigate the risks posed by steep faults to such caverns.

A sandwich-type Winkler-Pasternak double elastic foundation beam model for analysis of nut column load transfer systems of shiplifts

The rack and pinion shiflifts feature its capability of fortification against extreme accidents of unbalance of ship chamber. This requires the load transfer systems of nut columns to be able to transfer the huge and centralized loads from the safety mechanisms to the tower columns in a distributive bearing way. Aiming at exploring a design-oriented computation method for the nut column load transfer systems (NCLTSs), a sandwich-type semi-infinite coupling Winkler-Pasternak double elastic foundation beam model (DEFBM) has been established, with a distributive assumption of the axial constrain force on the interfaces between the nut columns, mortar beds, adjusting beams and the second stage concrete based on the physical model test, has been proposed. A set of formulars for describing the distribution of deflections, internal forces and stress of nut columns and adjusting beams have been derived. A case study of the Three-Gorges shiplift has been conducted to demonstrate the approach of calculation of internal forces and stress by applying the formulas based on sandwich-type Winkler-Pasternak DEFBM, showing the convenience and rationality of the method to parametric layout design of the nut columns and adjusting beams in NCLTSs. Not only to NCLTSs and rack load transfer systems of shiplifts, the sandwich-type Winkler-Pasternak DEFBM also supplies the reference to the modeling and analysis of the rail-embedment structural systems broadly applied in hydraulic engineering.