Identical Loading Research Articles

Numerical investigation of the effect of harrow tine's geometry on fatigue life

Abstract Harrow tines experience large deflections due to varying soil conditions, leading to fatigue failure through cyclic loads. Selecting the appropriate coil diameter, pitch, and number of coils is crucial for designing harrow tines that can withstand these deflections. The aim of this research is to develop new harrow tine designs that offer improved sustainability compared to conventional harrow tines used in the Canadian prairies. Nine double helical torsion spring harrow tine designs were developed, differing in coil diameters, pitch, and number of turns, while keeping the wire diameter constant. A comparative analysis was conducted, considering fatigue life, failure criteria, and stress distribution patterns assessed through Finite Element Modeling (FEM). Additively manufactured 38% scaled harrow tine prototypes underwent load-bearing tests using identical load sets of 20, 50, 100, and 200 grams. The 2T3D2P, 1T4D2.5P, and 2T4D2.5P models emerged as reliable harrow tine designs with higher fatigue life of 14,115, 14,438, and 27,618 cycles compared to the frequently used conventional harrow tine’s 7533.87 cycles. Coil diameter has a preferential influence on achieving higher fatigue life, overshadowing the effects of pitch and the number of coils. Furthermore, models with larger coil diameters displayed greater flexibility against the defined weight loads, as observed in the load-bearing tests.

Quantifying the effects of the microphysical hygroscopic restructuring of soot on ensemble optical properties and satellite aerosol optical depth retrievals

Black carbon, or soot, significantly contributes to atmospheric light absorption due to its low single scattering albedo (SSA). This study investigates the impact of soot's hygroscopic restructuring on satellite remote sensing, focusing on radiative forcing, top-of-atmosphere (TOA) reflectance, and aerosol optical depth (AOD) retrievals. We characterized soot aging using relative humidity (RH) growth factor functions and modeled fresh and aging soot aggregates using a cluster-cluster aggregation algorithm. Bulk optical properties for each RH level were simulated using core-mantle generalized multi-sphere Mie-solution, weighted by the probability density function of soot monomer numbers. We incorporated soot aging models into the 6S radiative transfer model by adjusting the geometric mean radius of the soot component to match bulk SSA values at each aging degree. Extensive radiative transfer simulations were conducted, complemented by an analysis of 16 actual soot-containing cases in China from 2016 to 2019. Results showed that identical soot loads correspond to lower reflectance in dry environments and higher reflectance in humid environments. MODIS AOD retrieval errors approached zero when RH was close to 70 %, likely due to the similarity between the 6S default soot and the aging model at this humidity. Neglecting RH led to overestimations in AOD for cases with RH < 65 % and underestimations in high humidity cases (RH > 75 %). The average MODIS AOD retrieval errors for RH < 65 %, RH between 65 % and 75 %, and RH > 75 % were −33.15 %, −1.80 %, and +42.42 %, respectively. This study underscores the necessity of incorporating RH into satellite AOD retrieval algorithms to enhance accuracy and reduce uncertainties.

Investigation of Ultra-Low Loading of Metallic Oxide Supported Iridium-Based Catalysts in the Proton Exchange Membrane Water Electrolyzers

Iridium (Ir)-based catalysts have been considered as the most promising oxygen evolution reaction (OER) in the proton exchange membrane water electrolyzer (PEMWE). The scarce supply of Ir potentially restricts the development of the PEMWE technology. Reducing the use of Ir catalysts has become one of the most critical tasks. The activity and durability of PEMWE depend heavily on the catalyst loading.[1] Poor in-plane electric conductivity due to catalyst layer not being continuous at ultra-low loadings (~0.1-0.2 mgIr/cm2) catalyst, results in loss of electronic connection of some portions of catalyst layer. Several studies have proposed various strategies to lower the loading of Ir catalysts,such as altering catalyst morphology,[2] introducing a microporous layer (MPL) between the catalyst layer and PTL to improve electron transport in disconnected catalyst layers,[3] or doping Ir-based catalysts with support materials. [4-5] These approaches enhance both in-plane and through-plane electric conductivity, thereby increasing catalyst utilization.In this work, heteroatoms were used as supports or dopants to enhance Ir catalyst utilization and enhance the structural and interfacial stability of the catalyst layer. The microstructure of the metallic oxide support allows IrO2 particles to disperse uniformly, thus enhancing the in-plane conductivity of the catalysts layer. Both commercial metallic oxides supported IrO2 catalysts [6] and laboratory-synthesized catalysts were employed in PEMWE. Different catalyst loadings were investigated, including the ultra-low loading (0.11-0.13 mgIr/cm2) catalysts in this study. We conducted several electrochemical characterization experiments to confirm the improvement of the durability and activity for the IrO2/TiOx and IrO2/NbOx, comparing to the unsupported IrOx catalysts with the identical low Ir loading. A 2V-hold for 100-hour of the accelerated stress testing (AST) indicates the more moderate decay in the current density for supported IrO2 catalysts. Cyclic voltammetry (CV) allows us to monitor the changes of surface oxidation state and the morphology of the Ir-based catalysts during the different operating conditions. Finally, the cell performance of various catalysts on the anode in PEMWE were also evaluated and compared. This study is expected to provide a comprehensive understanding of ultra-low Ir loading in PEMWE.

Fatigue cracking propagation behavior of 10CrNi3MoV steel mismatched welded joints at sub-temperature

This paper investigates fatigue crack propagation behavior of high-strength steel 10CrNi3MoV and its mismatched weldments under low-ambient temperature conditions. The BM and its weldments under four temperatures (T = 20 °C, −20 °C, −40 °C, −60 °C) were tested to quantify Fatigue Crack Growth Rate (FCGR) by specific fatigue tests using two stress ratios (R = 0.1, 0.6) conditions. The findings indicate that an increased stress ratio leads to a higher mean stress, potentially accelerating the FCGR under identical loading conditions. The reduced temperature may elicit advantageous impacts on FCGR behavior for the examined materials. Moreover, the undermatched weldments generally exhibited a lower FCG resistance for 10CrNi3MoV steel under low temperature conditions. The critical temperature point of Fatigue Ductile-to-Brittle Transition (TFDBT) is deduced from the quantitative competitive relationship between the fatigue resistance and embrittlement. FCGR for these materials would be reaccelerated when temperature is lower than TFDBT. Finally, the fitted constants C and m in Paris law were determined to reveal that the TFDBT of studied materials reaches around −40 °C.

Robustness analysis of dynamic progressive collapse of precast concrete beam–column assemblies using dry connections under uniformly distributed load

A series of dynamic progressive collapse tests using the uniformly distributed load (UDL) was conducted, to analyze the robustness of three precast concrete (PC) beam–column assemblies using dry connections of top-and-seat angles (TSA-D), strengthened top-and-seat angles (STSA-D), and high-ductility reinforcement (DSTSA-D), under a middle column removal scenario. Finite element (FE) models were also developed to accurately simulate the collapse process. Based on the tests and FE models, comparative studies were conducted on dynamic and static collapse responses of the PC assemblies with identical configuration, loading regime, and boundary conditions. The results showed that: the horizontal reaction force developments were similar under dynamic and static collapse scenarios; under dynamic collapse scenarios, the initial stiffness of the PC assemblies increased due to the strain rate effect, while the peak vertical reaction forces under the compressive arch action (CAA) were smaller than those under static collapse scenarios, attributed to dynamic damage; under both dynamic and static collapse scenarios under UDL, the beam deformed in a downward convex curved shape, with local material deformation becoming more concentrated under dynamic collapse scenarios. An energy-based method for calculating dynamic collapse resistance was evaluated and revised: 1) the traditional method, which converts static responses from static analysis into dynamic responses was found to underestimate the resistance under small deformations due to neglecting the strain rate effect, and to overestimate ultimate resistance by ignoring dynamic damage; 2) by using dynamic vertical reaction forces instead, a more accurate prediction of the dynamic collapse resistance was achieved with a single dynamic collapse analysis. Additionally, dynamic amplification factors for the PC assemblies were calculated based on FE models and static test results providing basic knowledge in whole PC structural level research.

A Study on the Structural Impact of FLNG Topside Piperack Module Enlargement

&lt;i&gt;To minimize the production time of floating liquefied natural gas (FLNG) units, which are eco-friendly offshore structures, builders are exploring methods to extend the length of piperacks. This approach aims to reduce the number of installations and equipment required. In this study, a static stability analysis (in-place analysis) was conducted using the structural analysis computer system (SACS), a program for analyzing topside structures, to assess the effects of piperack enlargement. Two models were analyzed: the original piperack and a version with double the length. Both models were based on data from an existing FLNG unit, with identical environmental loads applied. The results showed that while relative displacement increased linearly with length, the stress did not follow the same linear pattern. However, stress levels in some braces at the base of the structure increased, indicating the need for larger structural members. From the perspective of in-place analysis, piperack enlargement appears feasible. However, further investigation, including fatigue analysis and assessments of operational and maintenance challenges, is recommended to confirm its long-term viability.&lt;/i&gt;

Elastoplastic plate shakes down under repeated impulsive loadings

When subjected to repeated dynamic impacts at identical load level, a metallic monolithic beam/plate may reach a stable state wherein measurable deformation ceases (i.e., shakedown in elastic state) after undergoing a sequence of elastoplastic deformations, which has been termed as “pseudo-shakedown” (P-S) (Jones, 1973; Shen and Jones, 1992). While the response of a single beam/plate under repeated low-velocity impacts has been thoroughly studied, its dynamic behavior under high-velocity impacts, such as explosive or alternating impulsive loads, is difficult to measure experimentally, due mainly to high costs and setup challenges. In the current study, the method of metallic foam projectile impact was employed to produce repeated impulsive loadings on a fully-clamped elastoplastic monolithic plate made of L907A (a Chinese standard shipbuilding steel). Its dynamic responses, including mid-point deflection versus time histories, final deflections, and deformation modes after each impact, were systematically measured. The phenomenon of dynamic shakedown was observed. To further explore this phenomenon, the method of finite elements (FE) was employed to simulate the repeated impulsive impact test, and its prediction accuracy was validated against experimental results. Unlike an elastoplastic (e.g., steel) monolithic plate subjected to repeated low-velocity impacts, which exhibits zero plastic energy dissipation in the P-S (pseudo-shakedown) state, the same plate under repeated high-velocity impacts shows a small level of plastic energy dissipation in the P-S state, mainly due to more extreme loading conditions. The initial impact momentum, yield strength, and tangent modulus of the material the plate is made of significantly affect both the stable deflection in the P-S state and the number of impacts needed to reach it, while the elastic modulus has limited influence. A modified dimensionless impulse loading number, accounting for the strain-hardening effect, is proposed. An approximately linear relationship between stable deflection in the P-S state and impulsive loading is found in dimensionless form.

Topology optimization and experimental validation of mass-reduced aircraft wing designs

Development and evaluation of a novel design of mass reduced aircraft wing ribs through topology optimization is reported herein. For comparison, the same examination is performed on ribs with normal internal geometry. The wing rib design is based on the Gulfstream G650 transonic jet. The rib is divided into three segments for analysis based around the positions of the two spars. Only the center section of the rib is mass optimized, while the leading and trailing edges of the ribs are kept solid. Methodology in this study includes the k-Ω shear stress transport turbulence model computational fluid dynamic simulation as well as static and transient finite element simulations. The optimized wing rib is found to be between 8% and 15% lighter than traditional wing ribs depending on configuration. Simulation of the wing showed a tip deflection of 13.8 cm upward at an angle of 1.1°. An experimental scaled model of the optimized wing subjected to near identical bending loads as identified in the FEA simulation is applied to validate stress concentrations and performance. It is found that in the simulations, average stress never exceeded the factor of safety prescribed by the FAA. While the average factor of safety on the full computational model was 2.649, the average factor of safety on the experimental model was 9.185. Four strain gauges attached to the experimental model are used to compare the strains at similar locations on the computational model. The experimental results validate the CFD simulation results with acceptable tolerances.

Molecular dynamics simulation of friction in DLC films with different Cr doping levels

This study systematically investigates the impact of varying Cr doping levels on the friction properties of DLC films using molecular dynamics simulations. The results demonstrate that under identical friction velocities and load conditions, the friction force of DLC films significantly decreases when the Cr doping content reaches 16.5 %. High Cr doping levels lead to the formation of Cr atomic clusters at the interface, hindering contact and reducing the number of interface bonds. These clusters act as lubricants, filling the interface gaps and thereby reducing the friction force. Internal stress calculations indicate that Cr doping effectively reduces the average internal stress of DLC films. For DLC films with lower Cr doping levels, the friction force exhibits similar trends under different friction velocities, while films with higher Cr doping levels show a more pronounced response, with friction force increasing at higher velocities. Increasing the load significantly raises the friction force, especially for DLC films with higher Cr doping levels. Furthermore, high Cr doping levels under high loads lead to significant structural damage and adhesive wear. This study provides theoretical and technical references for optimizing the friction performance of DLC films.

Mechanical response analysis of asphalt microstructure under tensile and compressive loading based on finite element methods

This study investigates the micro-mechanical response of asphalt microstructure under tensile and compressive loads using atomic force microscopy (AFM) and digital image processing (DIP). AFM captured images of asphalt surface morphology, and DIP extracted geometric information on microstructures such as bee structures, peri phase, and interstitial structures. Five finite element models were created in ABAQUS to simulate their load-bearing capacities and stress-strain distributions under 1 % and 5 % tensile and compressive strains. The results showed minimal differences in load-bearing capacities among the five models under identical strain loads. However, compressive load-bearing capacity was significantly higher than tensile load, with the asymmetry becoming more pronounced as the load increased. Under 1 % compressive strain, the external load was about 3 % higher than under tensile strain, increasing to 36 % higher under 5 % strain. The bee structure exhibited the smallest stress distribution, while the interstitial structure showed the largest. The average maximum stress in the interstitial structure was 1.2 times that of the bee structure, with stress concentration observed at the interface between the peri phase and interstitial structure. The interstitial structure experienced the smallest strain distribution, while the bee structure endured the highest tensile or compressive strain, with the average maximum strain of the bee structure being approximately 1.25 times that of the interstitial structure. Under compressive loads, the maximum stress and strain on the asphalt surface exceeded those under tensile loads, with the difference averaging around 10 % higher. As the proportion of the peri phase increased, stress and strain distribution became more uniform, alleviating stress concentration phenomena. This study provides a potential method for analyzing the mechanical response of asphalt microstructure. The results deepen our understanding of the complex relationship between asphalt microstructure and its micro-mechanical response. Additionally, they suggest possible directions for improving asphalt performance through microstructure adjustment.

Fatigue damage analysis and mitigation for steel structures using UHM-CFRP prestressed technique

Fatigue stresses in steel bridges can lead to crack propagation, gradually decreasing the structural stability of the bridge. Conventional strengthening techniques for structures have shown limited effectiveness in preventing crack growth. The objective of this research is to enhance the fatigue life of cracked steel beams through the application of ultra-high modulus carbon fiber reinforced polymer (UHM-CFRP) plates. Two sets of tests, including quasi-static testing and fatigue testing, were conducted on both cracked and uncracked steel beams. All beams were tested under identical loading conditions, with a total of five beams examined. Control beams were used to compare fatigue life under different loading ranges. One beam was reinforced with UHM-CFRP plates, another utilized prestressed UHM-CFRP plates, and another employed UHM-CFRP plates with end clamps. The experimental study revealed a significant 8 times increase in fatigue lives for cracked steel beams repaired using the UHM-CFRP compared to the control beam. Additionally, the (10 %) prestressed UHM-CFRP plate not only doubled the fatigue life of identical beams compared to UHM-CFRP plates but also significantly reduced residual deflection during fatigue crack growth, highlighting its efficacy in fatigue resistance.

Investigating the simulation test and acoustic emission characteristics of structural-control type rockbursts in deep underground environments

Deep underground projects are in a complex in-situ stress environment, and rock burst disasters induced by the hard and brittle failure of the rock mass are prone to occur around the tunnel openings. In this study, we aim to investigate the impacts of geological weak surfaces in rock masses on rockbursts and the spatiotemporal evolution of microcracks during the development of rockbursts. To achieve this objective, two sets of cubic specimens containing a circular through-hole were designed. One set of specimens had prefabricated unfilled cracks around the openings. Subsequently, the rockburst development process within the deep tunnel was replicated by subjecting both groups of specimens to identical gradient loading using a true triaxial test system. During the test, a micro camera was used to record the failure of the borehole wall in real-time, and an acoustic emission monitoring system was utilized to capture the stress waves released during structural damage. Finally, a multi-level synergistic analysis of the rockburst damage mechanism was carried out based on the macro-imaging data and micro-acoustic emission data. The results show that failure in high-stress environments within tunnels mainly includes microcrack initiation, particle ejection, crack propagation, local cracking, slabbing spalling, damage penetration, and rockburst damage. The time–frequency domain information of acoustic emission signals is highly perceptive and representative of the structural damage state of the specimens. The mutation characteristics observed in time-domain parameters, such as acoustic emission amplitude, event rate, ringing, and cumulative energy, correspond to drastic alterations in the internal structure of the rock. The distribution characteristics of frequency-domain parameters, such as acoustic emission peak frequency, dominant frequency energy, and frequency centroid, reflect different crack scales and damage modes. The diffusion of frequency centroid indicates that the damage and failure patterns within the rock are evolving towards a more complex direction. The energy magnitude of acoustic emissions represents the damage intensity during the development of rockburst. The root causes of induced structural-control type rockbursts in deep hard brittle rock masses are the combined effects of localized high-stress concentrations and large-scale discontinuous geological structures, such as natural joints, fissures, and structural planes. The naturally occurring large-scale through-type geological weak surfaces within the rock mass reduce the strength of the surrounding rock, alter the location of stress concentration, and change the initial damage characteristics. Moreover, they promote the evolution of rockbursts, thereby increasing their destructive intensity.

Advanced Porous Gold-PANI Micro-Electrodes for High-Performance On-Chip Micro-Supercapacitors.

The downsizing of microscale energy storage devices is crucial for powering modern on-chip technologies by miniaturizing electronic components. Developing high-performance microscale energy devices, such as micro-supercapacitors, is essential through processing smart electrodes for on-chip structures. In this context, we introduce porous gold (Au) interdigitated electrodes (IDEs) as current collectors for micro-supercapacitors, using polyaniline as the active material. These porous Au IDE-based symmetric micro-supercapacitors (P-SMSCs) show a remarkable enhancement in charge storage performance, with a 187% increase in areal capacitance at 2.5 mA compared to conventional flat Au IDE-based devices, despite identical active material loading times. Our P-SMSCs achieve an areal capacitance of 60 mF/cm2, a peak areal energy density of 5.44 μWh/cm2, and an areal power of 2778 μW/cm2, surpassing most reported SMSCs. This study advances high-performance SMSCs by developing highly porous microscale planar current collectors, optimizing microelectrode use, and maximizing capacity within a compact footprint.

Enhanced impact resistance of RC beams using various types of high-performance fiber-reinforced cementitious composites

This study investigates the impact resistance of reinforced concrete (RC) beams using various types of high-performance fiber-reinforced cementitious composites (HPFRCCs). A total of ten large-sized RC beams were fabricated and tested under static and impact loading conditions. Four different types of HPFRCCs with 2% by volume of steel, polyvinyl alcohol (PVA), and polyethylene (PE) fibers were considered. Ultra-high-performance fiber-reinforced concrete (UHPFRC) based on steel fibers demonstrated superior compressive and tensile strengths, while high-performance strain-hardening cementitious composite (HP-SHCC) based on PE fibers exhibited the highest strain and energy absorption capacities. The steel-bar reinforced (R-) UHPFRC and HP-SHCC beams showed superior flexural load capacity compared to reinforced normal strength concrete (R-NSC) beams. The highest ductility of 8.02 was found in the R-HP-SHCC beam, almost 5 times higher than that of the R-NSC beam. By drop hammer impact with a kinetic energy of 30 kJ, the R-UHPFRC beam completely failed due to its higher reaction load and lower structural ductility, while other RC beams made of NSC and HPFRCCs withstood the identical impact load. The R-HP-SHCC beam exhibited the best impact resistance, with a 29.1% lower maximum deflection compared to the R-NSC beam, and the largest residual load capacity after the impact damages. The R-HP-SHCC beam, despite being damaged, showed no reduction in flexural stiffness, yet it demonstrated an impressive 5.4% increase in load capacity compared to the undamaged beam.

Advancements in Dry Coating for Battery Electrodes: Scalable Extrusion Mixing for Control of Electrode Microstructure and Electrochemical Performance

Dry coating of battery electrodes is emerging as a promising alternative technology to the prevailing slurry coating and drying process widely adopted in the lithium-ion battery industry.1,2,3 To date, the most energy-intensive step in cell manufacturing is the drying of slurry-coated electrodes,1 and the adoption of dry coating aims to mitigate both the environmental impact and production costs associated with electrode production. Beyond environmental and economic concerns, producing higher mass-loading electrodes, a crucial aspect for increasing cell energy density, faces inherent challenges with the slurry-coating process: the drying of thick coatings often leads to issues such as electrode cracking and the formation of inhomogeneous electrode microstructures.Bühler and Empa have collaboratively developed and are in the process of scaling up a dry-coating manufacturing method.4 Our process centers around the extrusion mixing of electrode components, followed by calendering of the dry mixture to produce the final electrode and direct lamination onto a current collector. In this presentation, we showcase the adaptability of extrusion mixing in inducing shear fibrillation of polytetrafluoroethylene (PTFE) binder, crucial for achieving the desired electrode microstructures (see Figure 1a and 1b). Furthermore, we demonstrate the capability of our dry-coating technology to produce high-mass loading electrodes with areal capacities of 5 mAh cm-2 or more (see Figure 1c).The presentation encompasses a thorough characterization of dry-coated electrodes, including their microstructure and electrochemical performance in lab-scale batteries. Key aspects, such as rate capability and capacity retention, are evaluated. A comprehensive comparison with slurry-coated electrodes, fabricated using identical active electrode materials, mass fractions, and mass loading, reveals that our dry-coated electrodes exhibit comparable performance to their slurry-coated counterparts.5 The scalability of our dry-coating technology is underscored, highlighting the achievable throughputs necessary for gigafactory-scale production with a single extruder.

A Comparative Blast Mitigation Performance Evaluation of Metallic Sandwich Panels with Honeycomb, Corrugated, Auxetic, and Foam Cores

Due to the high energy absorption capability and excellent bending strength of the sandwich panels, they are mostly preferred as protective structures against explosive blast attacks. The evaluation of their blast-mitigation characteristics through experiments is highly dangerous, costly, time-consuming, and polluting for the environment. Therefore, in this presented work, a series of numerical analyses were performed to evaluate the blast mitigation of the outstanding sandwich panels with honeycomb, corrugated, auxetic, and foam cores. The masses of sandwich panels were kept constant, and their areal densities were maintained constant throughout the study to effectively compare their performance under identical air blast loading conditions. To apply the air blast loads to the designed sandwiches, 1–3[Formula: see text]kg of spherical-shaped trinitrotoluene charges were used for a 100[Formula: see text]mm stand-off distance. The sandwiches are made of high-strength AL-6XN steel and crushable aluminum foam. The rate-dependent Johnson–Cook constitutive model of plasticity and the crushable foam model with volumetric hardening were used for the evaluation of sandwich panels’ plastic deformations. The findings of the work depicted that the honeycomb core is more efficient than the other core structures of the same masses because the sandwich panels with honeycomb core provide smaller back skin deflections, globalized core crushing, and higher core energy absorption than the other sandwich panels for extreme conditions of air blast loading.

Validation of Excess Energy in the H2 Loaded Palladium System

The depletion of conventional energy resources necessitates the exploration of alternative energy sources, such as solar, wind, geothermal, and bio-gas. However, these renewable options have limitations in different climatic conditions and require large land areas for installation, while their output efficiency remains comparatively low. To address this challenge, the study of Low Energy Nuclear Reactions (LENR) presents a promising avenue for green, clean, portable, and sustainable energy. The Centre for Energy Research (CER) at S-VYASA University, Bangalore, India, has actively pursued LENR research for the past 9 years. Research groups have observed that the absorption of hydrogen into metal lattices is a crucial condition for LENR to occur. Various research groups, including CER, have explored metals like nickel, platinum, titanium, and palladium for high levels of hydrogen loading at controlled temperatures and pressures. In this study, two identical reactors were fabricated, one with an active fuel component and the other serving as a control unit. Both reactors underwent identical processes and hydrogen loading protocols. The active reactor consistently exhibited higher skin temperatures compared to the control reactor under the same power input, indicating the generation of excess heat. The experiment ran continuously for three months, showcasing sustained excess temperatures.

Plastic shakedown limit of geosynthetic reinforced coarse-grained soil: Experiments and prediction model

This study aims to explore the accumulated behavior of reinforced coarse-grained soils through cyclic triaxial tests and to develop a prediction model for the plastic shakedown limit. Cyclic triaxial test results illustrate that the reinforced specimens, especially those incorporating geocells, demonstrate the lowest accumulated axial strain and the highest plastic shakedown limit when compared to unreinforced ones under identical cyclic loading. Additionally, the accumulated axial strain at the plastic shakedown limit for reinforced specimens is determined. This strain is then used to determine the additional confining pressure exerted by geogrid or geocell, employing a function proposed by Yang and Han. By integrating the additional confining pressure into the plastic shakedown criterion for unreinforced specimens, a prediction model for the plastic shakedown limit in reinforced specimens is ultimately established. The model's applicability and the accuracy of computed additional confining pressure values are validated using experimental data.

Enhancing the Tribological Characteristics of Epoxy Composites by the Use of Three-Dimensional Carbon Fibers and Cobalt Oxide Nanowires

In this paper, the results of our research were presented into the sliding wear behaviors of reinforced epoxy composites made with 3D networked carbon fibers ornamented with nanowires of cobalt oxides (NWRs@CFs). Composites are made using the cast-in-place method. Under different normal loads and sliding velocities, these composites' wear and friction coefficient performances are assessed. Tests were performed at 400 rpm spindle speed, 10, 20, and 30 N normal load, and a duration of 300 seconds. Pure epoxy exhibits wear rates of 0.449, 0.481, and 0.501 * 10-5 mm3/Nm at 10, 20, and 30N. Conversely, 3D CFs/epoxy composites exhibit lower wear rates (0.334, 0.360, and 0.390 * 10-5 mm3/Nm) at the same pressure. The epoxy composites of NWRs@CFs wear less, measuring 2.1, 3.5, and 0.4 * 10-5 mm3/Nm under applied loads. The effects of speed on the tribological characteristics were also studied, the friction coefficients for 400, 800, and 600 rpm at 10 N. Pure Epoxy has fraction coefficients of 0.449, 0.494, and 0.552µ at 400, 800, and 600 rpm. In comparison, three-dimensional carbon fibers and epoxy composites show reduced wear rates (0.334, 0.376, and 0.304 µ) under identical loads. Epoxy composites of NWRs@CFs have friction coefficients of 0.261, 0.304, and 0.332µ. Pure epoxy has high wear, indicating less friction resistance.

Experiments and investigation of planar high-strength steel joints with Additive Manufacturing

This paper investigates the application of high-strength steel in planar steel joints, specifically X-joints and T-joints, which are crucial connecting components in structural engineering, ensuring structural stability in buildings, bridges, and tower cranes. Conventional steel joints, mainly constructed from low-carbon steel, encounter challenges arising from the low ductility of high-strength steel and its strict welding criteria. The Solid Isotropic Material with Penalization (SIMP) method is employed to perform topology optimization on X-joints with different brace width to chord width ratios and T-joints, enabling the manufacturing of high-strength steel components through the Additive Manufacturing method (AM). The impact of different additive manufacturing orientations on material strength is tested, with results indicating improved mechanical properties when the loading direction is perpendicular to the normal direction of the additive manufacturing layer. Compression tests are conducted using 2D/3D Digital Image Correlation methods (2D/3D-DIC) alongside traditional measurement techniques. The results indicate that the stress distribution of the optimized joint is more rational, and the strength of the optimized joint has improved compared to the tubular joint. The optimized joint exhibits a more distinct load path and apparent failure mode. This optimized joint enables a uniform stress redistribution, enhancing ductility and achieving a strong-joint and weak-component structural mechanism that satisfies the serviceability limit state (SLS). In comparison to non-penetrative tubular joints, no significant cracks are observed under identical loading conditions.