Search Results (567)

In this study, we aimed to address the lack of systematic research on key collision dynamics parameters (elastic restitution coefficient) in the full mechanization of rapeseed operations, which hinders the development of precision agriculture. In this present work, the restitution coefficient of rapeseed was systematically investigated, and a predictive model (R² = 0.959) was also established by using Box–Behnken design response surface methodology (BBD-RSM). The results show that the collision restitution coefficient varies in the range of 0.539–0.649, with the key influencing factors ranked as follows: moisture content (M_c) > material layer thickness (L) > drop height (H). The EDEM simulation methodology was adopted to validate the experimental results, and the results show that there is a minimal relative error (−1% < δ < 1%) between the measured and simulated rebound heights, indicating that the established model shows a reliable prediction performance. Moreover, by comprehensively analyzing stress, strain, and energy during the collision process between rapeseed and Q235 steel, it can be concluded that the process can be divided into five stages—free fall, collision compression, collision recovery, rebound oscillation, and rebound stabilization. The maximum stress (1.19 × 10⁻² MPa) and strain (6.43 × 10⁻⁶ mm) were observed at the beginning of the collision recovery stage, which can provide some theoretical and practical basis for optimizing and designing rapeseed machines, thus achieving the goals of precise control, harvest loss reduction, and increased yields. Full article

Spot-welding joints are widely used in modern industries, and their fatigue life is crucial for the safety and reliability of structures. This paper proposes a method for predicting the fatigue life of spot-welding joints by integrating traditional structural stress methods and machine learning algorithms. Systematic fatigue tests were conducted on Q&P980 steel spot-welding joints to investigate the influence of the galvanized layer on fatigue life. It was found that the galvanized layer significantly reduces the fatigue life of spot-welding joints. Further predictions of fatigue life using machine learning algorithms, including Random Forest, Artificial Neural Networks, and Gaussian Process Regression, demonstrated superior prediction accuracy and generalization ability compared to traditional structural stress methods. The Random Forest algorithm achieved an R² value of 0.93, with lower error than traditional methods. This study provides an effective tool for the fatigue life assessment of spot-welding joints and highlights the potential application of machine learning in this field. Full article

To improve the low-temperature impact toughness of Q235B steel, this paper adopts a heat treatment method combining quenching and spheroidizing annealing to enhance its microstructure and properties and conducts a detailed analysis of the evolution of the microstructure of Q235 steel under the spheroidizing annealing process. The results show that spheroidizing annealing at 700 °C has a significant spheroidizing effect on the pearlite structure: after 6 h of annealing, the room-temperature tensile strength reaches 522 MPa, the elongation is 31.28%, and the impact energy is 323.14 J; as the impact temperature decreases, the impact toughness of Q235B steel decreases, but the impact energy can still remain at 291.62 J under service conditions of −20 °C. This is attributed to the spherical cementite formed by spheroidizing annealing, which has better dispersibility and can reduce stress concentration, thereby improving the low-temperature impact toughness. Full article

To realize accurate ladle pouring, an analytical model of the constant flow rate pouring was established. By integrating a user-defined function (UDF), a CFD simulation model of the constant flow rate pouring was established to investigate the liquid steel pouring behavior under different inner wall inclination angle α, initial liquid volume V_c, and target flow rate q. Finally, the accuracy of the analytical model and the simulation model was verified through experiments. The results show that the experimental results agree well with the theoretical and simulation results, which verify the accuracy of the analytical model and the simulation model. Moreover, the simulation results indicate that increasing both α and V_c leads to an increase in the pouring flow rate. To achieve a stable pouring process and a constant flow rate value, a proper α, V_c and q_t should be selected. In this study α = 7.5° V_c = 70% V_capacity and q in the range of 0.10–0.12 m³/s are proper. To realize constant flow rate pouring, a time-variant ladle angular velocity is obtained and it can be adjusted by the motor speed. Therefore, different constant flow rates could be acquired by adjusting the motor speed, which provide guidance to the casting technology. Full article

Ductile structures have demonstrated the ability to withstand increased seismic intensity levels. Additionally, these structures can be restored to their operational state promptly following the replacement of damaged components post-earthquake. This capability has been a subject of considerable interest and focus in recent years. The study presented in this paper introduces an innovative beam-column connection that incorporates V-shaped steel as the replaceable energy-dissipating component. It delineates the structural configuration and design principles of this joint. Furthermore, the paper conducts a detailed analysis of the joint’s failure mode, stress distribution, and strain patterns using ABAQUS 2022 finite element software, thereby elucidating the failure mechanisms, load transfer pathways, and energy dissipation characteristics of the joint. In addition, the study investigates the impact of critical design parameters, including the strength, thickness, and weakening dimensions of the dog-bone energy-dissipating section, as well as the strength and thickness of the V-shaped plate, on the seismic behavior of the beam-column joint. The outcomes demonstrate that the incorporation of V-shaped steel with a configurable replaceable energy-dissipating component into the traditional dog-bone replaceable joint significantly improves the out-of-plane stability. Concurrently, the V-shaped steel undergoes a process of gradual flattening under load, which allows for a larger degree of deformation. In conclusion, the innovative joint design exhibits superior ductility and load-bearing capacity when contrasted with the conventional replaceable dog-bone energy-dissipating section joint. The joint’s equivalent viscous damping coefficient, ranging between 0.252 and 0.331, demonstrates its robust energy dissipation properties. The parametric analysis results indicate that the LY160 and Q235 steel grades are recommended for the dog-bone connector and V-shaped steel connector, respectively. The optimal thickness ranges are 6–10 mm for the dog-bone connector and 2–4 mm for the V-shaped steel connector, while the weakened dimension should preferably be selected within 15–20 mm. Full article

Resistance spot welding was performed to join a 2 mm thick TA2 titanium plate and Q235 steel plate using nickel foil with thicknesses of 0.02 mm, 0.04 mm, and 0.06 mm as interlayers. The microstructure of the nugget zone and the interface region of the joint were systematically observed and analyzed, and the tensile shear-bearing capacity of the joint was evaluated. As the welding current increased, the tensile shear load of the joint exhibited a trend of initially increasing and subsequently decreasing. When the welding current was 8 kA, the tensile shear load of the joints with an interlayer of 0.04 mm thickness reached a maximum value of 8.02 kN. The results indicate that employing a reduced welding current can effectively prevent the mixing of nuggets on both sides of the titanium and steel interface. This ensures that the intermetallic compounds formed in the interface region are confined to the Ti-Ni series, which is crucial for enhancing the tensile shear load of the joint. Full article

The fire resistance performance of steel beams is of utmost importance to the fire safety of building structures and personnel evacuation. To address the deviation in the assumption of uniform temperature distribution in traditional studies, this study conducted multiple simulation tests. It was found that when the size of the vent was reduced by 50%, the difference in the heating rate in the early stage of the fire was 30% to 50%. Increasing the load ratio from 0.2 to 0.8 can significantly reduce the critical temperature of the steel beam by 15% to 20%, and the corresponding critical temperature is reduced from 670 °C to 565 °C. Based on parametric analysis, a simplified evaluation model of critical temperature for Q460 high-strength steel beams is proposed. The calculation error of the model is less than 5%, which provides a theoretical basis for the whole process of fire protection design. The research achievements break through the limitations of traditional methods and offer innovative approaches to predicting the fire resistance performance of steel beams and their optimized design. Full article

Engineered bamboo has been considered a viable replacement for traditional wood and steel for structural and architectural purposes due to its renewable nature, high strength, and compatibility with different processing techniques. This systematic review analyzed the literature on the mechanical properties and processing techniques of engineered bamboo products, which include bamboo scrimber and laminated bamboo. The literature included in this systematic review was extracted from the Engineering Village platform. The studies retrieved from this platform were filtered to only have been published in top journals (Q1/Q2) related to engineering materials, materials science, and the construction industry. Using this methodology, from the initial 191 identified records, 51 studies that were the most relevant were chosen. The review revealed that bamboo scrimber has better performance for specific mechanical properties, which include its compressive, tensile, and bending strength. Laminated products had higher variability, which was often caused by the type of adhesive, orientation, and quality of adhesion. This study also identified the details of manufacturing processes, such as the adhesive systems, pre-treatment methods, and pressing conditions used. Moreover, the literature exhibited considerable inconsistencies in testing standards, reporting practices, and long-term durability evaluations. This review highlights these challenges and provides recommendations for future research to resolve these issues. Full article

This paper proposes a mathematical description of nitriding atmospheres obtained from a one-component ammonia ingoing atmosphere and a two-component ammonia inlet nitrogen-diluted atmosphere. The Fe-N phase equilibrium diagrams of the nitriding atmosphere in the hydrogen content-temperature (Q-T) system for selected NH₃/N₂ atmosphere compositions are presented. The nitriding atmosphere obtained with different degrees of nitrogen dilution of the ingoing atmosphere was characterized. It has been shown that in processes carried out in nitriding atmospheres obtained from a two-component atmosphere with nitrogen, there is no direct relationship between the value of the nitrogen potential and the degree of dilution of the ingoing atmosphere with nitrogen. It has been shown analytically and confirmed experimentally that with changes in the degree of dilution of ammonia with nitrogen, the hydrogen content of the nitriding atmosphere and, consequently, the nitrogen availability of the nitriding atmosphere change. Using the example of nitriding AISI 52100 steel, it has been experimentally demonstrated that the change in nitrogen availability, caused by a change in the degree of dilution of the ingoing atmosphere with nitrogen, is not accompanied by a change in the value of the nitrogen potential. It has also been shown that the change in the nitrogen availability of the nitriding atmosphere, induced by the change in the composition of the aNH₃/bN₂ ingoing atmosphere, affects the kinetics of nitrogen mass gain in the nitrided layer and the distribution of nitrogen mass between the iron nitride layer and the solution zone. It has also been shown that with the change in nitrogen availability, what changes in addition to the thickness of the iron nitride layer is also the phase composition of the layer. Using gravimetric tests, the mass of nitrogen in the iron nitride layer and the solution zone has been determined. To describe the equilibrium between the NH₃/H₂ atmosphere and nitrogen in the different iron phases, a modified Lehrer diagram in the coordinate system of temperature and hydrogen content in the nitriding atmospheres (T-Q) has been proposed. Full article

This study synthesized two eco-friendly inhibitors—a chitosan–copper metal–organic framework (CS@Cu MOF) and chitosan–Schiff base–Cu complex (Schiff–CS@Cu)—for Q345 steel protection in 3.5% NaCl/1M HCl. Electrochemical and weight loss analyses demonstrated exceptional corrosion inhibition: untreated specimens showed a 25.889 g/(m²·h) corrosion rate, while 100 mg/L of CS@Cu MOF and Schiff–CS@Cu reduced rates to 2.50 g/(m²·h) (90.34% efficiency) and 1.67 g/(m²·h) (93.56%), respectively. Schiff–CS@Cu’s superiority stemmed from its pyridine–Cu²⁺ chelation forming a dense coordination barrier that impeded Cl⁻/H⁺ penetration, whereas CS@Cu MOF relied on physical adsorption and micro-galvanic interactions. Surface characterization revealed that Schiff–CS@Cu suppressed pitting nucleation through chemical coordination, contrasting with CS@Cu MOF’s porous film delaying uniform corrosion. Both inhibitors achieved optimal performance at 100 mg/L concentration. This work establishes a molecular design strategy for green inhibitors, combining metal–organic coordination chemistry with biopolymer modification, offering practical solutions for marine infrastructure and acid-processing equipment protection. Full article

To address the frequent failure of anti-falling devices in inclined shaft tunnel boring machines caused by cyclic loading and fatigue during construction, this study proposes an optimized self-responsive anti-falling device design. Based on the operational conditions of the “Tianyue” tunnel boring machine, a three-dimensional model was constructed using SolidWorks. Finite element static analysis was employed to validate structural integrity, revealing a maximum stress of 461.19 MPa with a safety factor of 1.71. Explicit dynamic simulations further demonstrated the dynamic penetration process of propellant-driven telescopic columns through concrete lining walls, achieving a penetration depth exceeding 500 mm. The results demonstrate that the device can respond to falling signals within 12 ms and activate mechanical locking. The Q690D steel structure exhibits a deformation of 5.543 mm with favorable stress distribution, meeting engineering safety requirements. The energy release characteristics of trinitrotoluene propellant and material compatibility were systematically verified. Compared to conventional hydraulic support systems, this design offers significant improvements in response speed, maintenance cost reduction, and environmental adaptability, providing an innovative solution for fall protection in complex geological environments. Full article

This study investigates a novel pulsed electromagnetic field (PEMF) device for dynamic testing and structural health monitoring. The research utilises a PEMF generator CD-1501 with a maximum energy capacity of 0.5 kJ and a flat multifilament coil (IC-1) with a 100 mm diameter. Experiments were conducted on a model steel stand with two joint configurations, using steel plates of 4 mm and 8 mm thickness. The device’s efficacy was evaluated through oscillation pattern analysis and spectral characteristics. Results demonstrate the device’s ability to differentiate between joint states, with the 4 mm plate configuration showing a 15% reduction in high-frequency components compared to the 8 mm plate. Fundamental resonant frequencies of 3D-printed specimens were observed near 5100 Hz, with Q-factors ranging between 200 and 300. The study also found that a 10% increase in volumetric porosity led to a 7% downward shift in resonant frequencies. The developed PEMF device, operating at 50–230 V and delivering 1–5 pulses per minute, shows promise for rapid, non-destructive monitoring of structural joints. When combined with the coaxial correlation method, the system demonstrates enhanced sensitivity in detecting structural changes, utilising an electrodynamic actuator (10 Hz to 2000 Hz range). This integrated approach offers a 30% improvement in early-stage degradation detection compared to traditional methods. Full article

Reasonable welding methods are of great significance for optimizing the microstructure and ensuring the mechanical properties of welded joints. In this study, ultra-narrow gap welding (UNGW) and submerged arc welding (SAW) were employed to weld Q355E high-strength low-alloy (HSLA) steel thick plates, and the microstructure and mechanical properties of the welded joints were systematically characterized. The UNGW welded joint exhibits superior comprehensive mechanical properties: a room-temperature tensile strength of 664 MPa with 43.1% elongation at fracture, along with higher microhardness and enhanced impact performance at −40 °C, all of which significantly outperform SAW welded joints. This advantage primarily stems from the faster cooling rate during UNGW, which promotes the formation of beneficial acicular ferrite in the joint microstructure. This study provides theoretical support and technical guidance for welding HSLA steel thick plates. Full article

A self-centering prefabricated concrete frame structure has good seismic performance, and its seismic capacity is mainly provided by the recovery force of the unbonded prestressing tendons and the energy-dissipation deformation capacity of embedded steel reinforcement. Relocating embedded reinforcement to external positions enables replaceability of energy dissipation components. And the configuration of external energy dissipation components is the primary factor influencing their energy dissipation capacity. Based on the existing external “Plug & Play” configuration, the internal steel bar size and material properties such as those of steel bar and filling material were varied in this study, and then, cyclic tension-compression experimental studies and numerical simulations were conducted to investigate the energy dissipation performance index and key influencing factors of this type of external composite steel bar. The research results showed that the composite steel bars designed in the experiments exhibited superior overall energy dissipation performance. Specimens utilizing Q345B steel as the core material outperformed those with Grade 30 steel. Moreover, the slenderness ratio of the composite steel bars and the diameter ratio between the end region and weakened segment of the internal steel bars were identified as critical parameters governing energy dissipation performance, and recommendations for optimal parameter ranges were discussed. This study provides a theoretical foundation for implementing external composite steel bars in self-centering structural systems. Full article

Nano-titanium dioxide ceramic coatings exhibit excellent wear resistance, corrosion resistance, and self-cleaning properties, showing great potential as multifunctional protective materials. This study proposes a synergistic reinforcement strategy by encapsulating micron-sized Al₂O₃ particles with nano-TiO₂. A core-shell structured nanocomposite coating composed of 65 wt% nano-TiO₂ encapsulating 30 wt% micron-Al₂O₃ was precisely designed and fabricated via a slurry dip-coating method on Q235 steel substrates. The microstructure and surface morphology of the coatings were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Comprehensive performance evaluations including densification, adhesion strength, wear resistance, and thermal shock resistance were conducted. Optimal coating properties were achieved under the conditions of a binder-to-solvent ratio of 1:15 (g/mL), a heating rate of 2 °C/min, and a sintering temperature of 400 °C. XRD analysis confirmed the formation of multiple crystalline phases during the 400 °C curing process, including titanium pyrophosphate (TiP₂O₇), aluminum phosphate (AlPO₄), copper aluminate (Cu(AlO₂)₂), and a unique titanium phosphate phase (Ti₃(PO₄)₄) exclusive to the 2 °C/min heating rate. Adhesion strength tests revealed that the coating sintered at 2 °C/min exhibited superior interfacial bonding strength and outstanding performance in wear resistance, hardness, and thermal shock resistance. The incorporation of nano-TiO₂ into the 30 wt% Al₂O₃ matrix significantly enhanced the mechanical properties of the composite coating. Mechanistic studies indicated that the bonding between the nanocomposite coating and the metal substrate is primarily achieved through mechanical interlocking, forming a robust physical interface. These findings provide theoretical guidance for optimizing the fabrication process of metal-based ceramic coatings and expanding their engineering applications in various industries. Full article