Strojniški vestnik - Journal of Mechanical Engineering

Dynamic Performance of C80 Railway Wagon Under the Influence of Wheel Polygons and Typical Mode Shapes of the Car Body

Wed, 10 Dec 2025 00:00:00 +0000

To investigate the influence of typical mode shapes and wheel polygons on the dynamic characteristics of railway freight car body, this study takes railway freight wagon C80 as the research object. Vehicle-level and system-level finite element models of the C80 railway wagon were developed, revealing that the lateral and vertical stiffness of railway freight cars significantly affects system mode. Furthermore, co-simulation using NASTRAN and SIMPACK was used to establish a fully flexible dynamic model of the C80 wagon. The influence of typical modal frequencies on the dynamic performance of the wagon was analyzed considering the wheel polygon and wear parameters. The results show that suppressing the torsional mode shape of the railway wagon reduces its impact on the derailment coefficient, wheel load reduction rate, axle transverse force and overturning coefficient by over 40 %. When the train speed corresponds to the polygon order, the wheel load reduction rate increases with the polygon wear depth under both the 10th order and 18th order conditions, by as much as 14.4 % when wear depth increases from 0.01 mm to the 0.05 mm for the 18th order condition. In addition, under the 6th order, 10th order, 16th order and 18th order polygon conditions, suppressing the torsional mode notably increased the wheel load reduction rate, especially under the 6th order polygon condition. This research provides valuable guidance for optimizing suspension parameters and controlling polygonal wear in railway wagons, offering a guiding basis for enhancing their dynamic performance of railway wagons.

Two-Stage Optimal Design of Metro Underframe Structures: Based on Topology-Size-Shape Co-Optimization Methodology

Delei Du, Yana Li, Jian Song, Zhengping He, Jianxin Xu — Wed, 10 Dec 2025 00:00:00 +0000

The design of the metro body structure must balance both safety and cost indicators. The underframe is not only the main load-bearing component of the metro body but also accounts a significant portion of its overall mass. To reduce operational costs and enhance the safety performance of the metro body, this paper focuses on optimizing the design of the underframe. A two-stage optimization approach was proposed, addressing the limitation of existing methods and the challenges in balancing realistic operating conditions with manufacturability. First, manufacturing constraints were incorporated using the variable density method, and topology optimization of the underframe sub-model was carried out with the objective of minimizing flexibility-weighted strain energy. Next, the rough topology was refined through parametric optimization after determining the approximate shape of the cross section, resulting in a more precise model. The results show that the proposed optimization method reduces underframe mass by about 4.7 % while lowering the maximum deflection of the metro car body under the maximum vertical load case by 0.601 mm. This demonstrates that the proposed framework efficiently combines optimization capabilities with simplicity.

Kinematics-based Tracking Control Method for Operational Robotic Arm Under Multi-Environmental Constraints

Li Zhou, Yan Liu — Wed, 10 Dec 2025 00:00:00 +0000

The environmental hazards associated with coal mining operations are extremely high, making the use of robotic arms to replace manual labor crucial for improving both the safety and cost-effectiveness of the work process. To address the various environmental constraints, such as spatial limitations, obstacles, and internal and external disturbances, this study proposes a kinematic-based tracking and control method for mining robotic arm. The objective of this numerical study is to mitigate the impact of environmental constraints on the stability of robotic arms, ensuring that they can maintain high precision and stability in complex operating conditions. Simulation results showed that the proposed method enabled the robotic arm to achieve operational thrust peaks exceeding 13,968 N and screw torque peaks greater than 0.06 Nm. The system reached steady state in an average of 0.24 s, with an error reduction of 2.3 %. Compared to other methods, the disturbance tracker reduced the average error by 2 %, and the feedback controller decreased the prediction lag by 5 %. Overall, this method significantly enhances the accuracy and stability of robotic arms in coal mining operations, making it a promising approach for real-world applications.

An Optimal Design Method of Hydrostatic Turntable Based on FPSO Algorithm

Yongsheng Zhao, Jiaqing Luo, Ying Li, Tao Zhang, Honglie Ma — Wed, 10 Dec 2025 00:00:00 +0000

The load capacity of hydrostatic turntables is predominantly governed by the design of oil pads. Optimizing oil pad parameters can substantially enhance turntable performance while reducing power consumption. This study introduces a fuzzy particle swarm optimization (FPSO) algorithm that incorporates compression factors into the particle swarm optimization (PSO) framework to optimize the parameters of oil pads. Reduce its power consumption by about 40 %, while the error between experimental and theoretical values is only 8 %. Compared with traditional PSO algorithms, FPSO converges more reliably in multiparametric environments.

Theoretical and Experimental Investigation on Microcosmic Surface Generation in Precision Grinding with Discrete Method

Yizun Chen, Yu Sun — Wed, 10 Dec 2025 00:00:00 +0000

Surface topography of the workpiece created in precision grinding is influenced by not only key process parameters, but also the distribution characteristics of active abrasive grits on the surface of the grinding wheel, including the number of active grits in the contact zone, the morphology of grits, and the cutting depth of a single grit in a normal direction. Under the conditions of small cutting depth (less than 5 µm) with small eccentrical rotation of the abrasive wheel (less than 3 µm), the influences of the original workpiece surface topography characteristics and the dynamic cutting depth of abrasive grits are often neglected in the study of microcosmic surface generation. In this paper, a discrete method (DM) is used to develop a theoretical kinematics model for the prediction of machined workpiece surface topography. Compared with the characteristics value of surface topography (scratch grooves) between experimental measurement and simulation output, the verification results from the improved prediction model of surface topography present well in comprehensively considering the influences of original surface characteristics, eccentrically rotational behavior of the abrasive wheel and the overlapped situation of scratch grooves on complex process conditions with a prediction error of about 10 %. In comparison with two commonly used empirical formulas in many other research studies, the prediction accuracy of the DM model for machined surface topography improves by 20 %. When calculating material removal volume, the prediction accuracy of incremental volume model of material removal increases approximately by 9 % to 19 % in comparison with the prediction results that take the whole cross-section area of an active grit as a key variable.

Dynamics of Aero-Engine Dual-Rotor Systems under Multi-Flight Attitudes and Simultaneous Rub-Impact Faults

Peixun Tang, Zhengminqing Li, Xiaojing Ma; Yiyan Chen, Xi Liu — Wed, 10 Dec 2025 00:00:00 +0000

High-maneuverability combat aircraft exert extreme loads on aero-engines, potentially triggering destructive rotor-stator rub-impacts and thereby pose a severe threat to flight safety. This study establishes a four-degree-of-freedom (4-DOF) rotor-bearing-disk model for a dual-disk system, specifically tailored to simulate the coupling effects of simultaneous rub-impact faults under diverse flight attitudes and maneuver loads. For benchmarking purposes, a corresponding model free of rub-impact is accordingly constructed. The Newmark-β method is employed to derive solutions for both models. To evaluate how maneuver loads influence the dynamic characteristics of the system, a parametric investigation is conducted to assess the effects of dual-disk rub-impact across three key flight attitudes, namely, rolling, pitching, and yawing. This research offers a critical theoretical basis for enhancing vibration control and conducting failure analysis in fighter engine design, ultimately contributing to the development of safer and more reliable rotor systems.