International Journal of Mechanical and Electrical Engineering

Abstract: Coiled tubing fishing operation is a major technical challenge in petroleum engineering. Especially for high-strength materials such as N80, conventional direct pulling is often limited by the bearing capacity limit of the tubing. In this study, an innovative fishing process combining perforation weakening and axial fracture is proposed. Based on the finite element method of ANSYS software, the influence of tool geometry on perforation load and residual strength of tubing string is systematically investigated. The explicit dynamics method is adopted to simulate the dynamic process of the punch piercing the pipe wall and fracturing the tubing. Meanwhile, the Johnson-Cook damage model is introduced to characterize the failure behavior of N80 material under complex stress triaxiality. The results show that compared with the circular cutter head, the optimized diamond cutter head reduces the piercing load by approximately 45.3% and the fracture load by about 23%, and induces obvious stress concentration zones on the pipe wall. This research provides a theoretical basis for the design of downhole perforation fishing tools. Read More

Abstract: The paper explores the use of a combined approach of computational fluid dynamics and genetic algorithm in improving the performance of airfoils in subsonic sub-flows to achieve high lift and low-drag ratios. Airfoil shapes are modeled with the use of PARSEC geometric parameterization with eleven design variables, which allows exploring the design space systematically and with physical realizations. Simulations of Reynolds-Averaged Navier-Stokes with Spalart-Allmaras turbulence models offer aerodynamic performance analysis at Reynolds number at Re = 3×10⁶ over angles of attack between -4° to 16°. The genetic algorithm optimization model, which uses tournament selection, simulated binary crossover, and polynomial mutation operators, used populations of 50 individuals which evolved over 100 generations to maximize the lift-to-drag ratio at cruise conditions (α = 4°). The findings show that peak L/D = 98.5, which is equivalent to an increase of 26.5% over NACA 2412 base level and 38.7% over NACA 0012. The streamlined design has lift coefficient Cₗ = 0.52 and drag coefficient Cⴅ = 0.00528 by optimized pressure distribution with increased suction peak and better aft pressure recovery. The results of the computational predictions are in great agreement with the experimental validation data with mean absolute error of 2.8% and 4.2% mean error of lift coefficient and drag coefficient respectively, as well as correlation coefficients higher than R² = 0.99. The study lays down systematic optimization procedures that can be used in the design of unmanned aerial vehicles, general aviation purposes, and wind turbine blades to give the aerospace engineers a solid computational foundation of aerodynamic performance improvements Read More

Abstract: To reveal the differences in local thermal instability at rough braking interfaces under different load and rotational-speed conditions, a three-dimensional transient thermo-mechanically coupled finite element model was established. A 5×5×1 mm³ single-sided rough surface region containing 496 asperities was used as the computational domain. Temperature, stress, affected depth, energy dissipation, and frequency-domain fluctuations were compared under three operating conditions. The results show that, when the load increases from 12 kN to 16 kN, the maximum temperature rises from 957.03 °C to 993.10 °C, and the plastic-dissipation depth increases from 0.204 mm to 0.300 mm. Under a 16 kN load, reducing the rotational speed from 48 rad/s to 42 rad/s lowers the maximum temperature to 709.20 °C, but increases the root-mean-square stress amplitude to 265.79 MPa. Lowering the rotational speed can alleviate thermal concentration, but it cannot eliminate contact reconstruction and stress fluctuation induced by high load. Braking risk should therefore be evaluated jointly using the dual indicators of temperature concentration and stress fluctuation. Read More

Abstract: To investigate the local flash temperature, stress oscillations, and elastoplastic energy dissipation induced by asperity interactions on both sides of a high-speed train disc brake, a three-dimensional transient thermo-mechanically coupled finite element model of a dual-roughness disc-pad interface was established. A fixed Weierstrass-Mandelbrot fractal morphology was used to evaluate temperature, von Mises stress, thermal penetration depth, thermoelastic power, plastic dissipation, and frequency-domain responses. The peak temperatures of the brake disc and brake pad reached 1409.5 °C and 1571.9 °C, respectively, and the corresponding peak von Mises stresses were 1079.4 MPa and 1024.6 MPa. The dominant stress frequency was 3395.6 Hz, with a relative oscillation amplitude of 312.10%. Plastic power accounted for approximately 32% and 37% of the theoretical input power in the disc and pad, respectively. Misaligned asperity contact and repeated jumps in contact stiffness jointly caused near-surface heat accumulation, high-frequency instability, and synergistic plastic dissipation. Read More

Abstract: High penetration of distributed energy resources (DERs)—photovoltaics, wind, storage, and flexible demand—is reshaping distribution networks. Bidirectional power flows, tighter voltage limits, and higher uncertainty make traditional passive operation inadequate. Flexible distribution systems (FDSs) address this by coordinating flexibility across source–grid–load–storage. This review synthesizes core FDS work through a three-layer lens: (i) structural flexibility (reconfiguration and controllable interconnection) that expands feasibility; (ii) real-time control (local, distributed/hierarchical, and predictive) that enforces constraints; and (iii) multi-timescale scheduling that allocates resources under forecasts and uncertainty. We emphasize cross-layer alignment—structure shapes controllability, and schedules must preserve regulation margins—and summarize open challenges in uncertainty propagation, scalability, and deployable hybrid (model + data) methods. Read More

Abstract: Thermal management of lithium-ion batteries is critical to ensuring their safe and efficient operation. Phase change materials (PCM) and heat transfer enhancement with fins are mainstream technical solutions at present. In this paper, a topology-optimized fin-PCM composite thermal management model is constructed for 2×3 array 18650 lithium-ion batteries. The thermal performance of three PCMs is compared via numerical simulation, and the influences of phase change temperature, latent heat and thermal conductivity on the maximum battery temperature, maximum temperature difference and liquid fraction are analyzed. The results show that PCM 2 achieves the optimal balance among latent heat capacity, phase change temperature and thermal conductivity under 3C and 4C discharge conditions. At the end of discharge, the maximum temperature of PCM 2 is reduced by 2.49% and 6.17% (3C), 8.54% and 6.12% (4C) compared with PCM 1 and PCM 3, respectively. Meanwhile, PCM 2 presents a stable liquid fraction variation and the best thermal buffering effect. This study can provide a reference for material selection and structural design of passive thermal management systems for high-rate lithium-ion batteries. Read More

Abstract: This paper addresses the issue of lateral vibration of high - speed train car bodies caused by random track irregularity excitation and random wind excitation. It proposes an active control method based on the SABO - LQR algorithm and the secondary suspension system to enhance the running stability and safety of high - speed trains by suppressing the lateral vibration of the car body. First, a dynamic model of the cross - wind - vehicle - track system is established, taking into account both random track irregularity excitation and random wind excitation. Second, considering the difficulty in selecting the weight matrices Q and R during the design of the LQR controller, the SABO algorithm is used for iterative optimization to obtain the optimal weight matrices and the controller. Finally, the effectiveness of the proposed method is further verified through simulation. The results show that the proposed active control method based on the SABO - LQR algorithm and the secondary suspension system has the potential to effectively suppress the lateral vibration of the train car body. Compared with the passive suspension method and the LQR control method, this method can reduce the amplitude of the car body's lateral vibration by 67.13% and 50.30% respectively, thus improving the riding comfort and the running stability of high - speed trains. Read More

Abstract: By integrating multiple modes of locomotion, such as aerial, ground, and surface or underwater operations, multi-modal unmanned aerial vehicles (UAVs) overcome the inherent limitations of single-mode robots in terms of endurance, terrain adaptability, and operational range. They have thus become a significant research direction in the field of robotics. This paper systematically reviews the recent research progress in multi-modal UAV technology, presenting a comprehensive overview from four dimensions: system configuration, key technologies, challenges, and future trends. In terms of configuration, amphibious aerial-ground, aerial-aquatic, and tri-modal UAVs are classified according to their structural design characteristics, and the advantages, disadvantages, and applicable scenarios of solutions such as wheeled, legged, and morphing structures are analyzed. Regarding key technologies, this review summarizes existing research achievements and their limitations, focusing on core issues including motion planning and trajectory optimization, control system design, and cross-medium communication and perception. Building on this analysis, the paper explores the main challenges currently facing multi-modal UAVs, such as structural lightweighting, robustness during mode switching, energy management, and autonomous decision-making. Finally, it identifies the deep integration of structure and function, intelligent control and autonomous decision-making, collaborative swarm operations, and the application of novel energy sources and advanced materials as critical directions for future development. Read More

Abstract: Hexapod robots, their exceptional static stability, redundant limb structures, and strong terrain adaptability, demonstrate broad application prospects in fields such as interstellar exploration, disaster rescue, military reconnaissance, and complex environment operations. Based on a systematic review of multiple high-quality academic papers published in recent years, this paper provides an in-depth review of the current state of hexapod robot technology from key dimensions, including mechanical structure design and optimization, kinematics and dynamics modeling, gait planning and motion control, environmental perception and autonomous decision-making, and adaptability under special operating conditions. The analysis indicates that current research is shifting from traditional single-structure, regular gait, and model-dependent control toward lightweight/reconfigurable structures, adaptive gaits for complex terrains, and intelligent control based on deep reinforcement learning. In the future, integrating advanced sensing technologies and achieving higher autonomy and environmental robustness will be key breakthroughs in hexapod robot research. Read More

Abstract: Excavators are important equipment in many construction projects. In the process of intelligentisation, the technological advancements they have undergone are no longer covered solely by hydraulic technology, but are being explored from multiple perspectives towards the integration of mechanical, electrical, and hydraulic systems. In recent years, the industry has made certain progress in three-dimensional environmental perception and remote operation, and some key technologies have initially established a foundation for engineering applications. However, due to the poor robustness of perception systems and the difficulty of establishing accurate models under complex working conditions, a high level of autonomous operation capability cannot yet be achieved. These issues need to be addressed in the future for excavators to enter the era of intelligentisation Read More