Mechanical responses research of subway stations under explosion impact load

As the subway station space is closed and the passenger flow is large, subway explosion-proof has always been the focus of station safety personnel. Here we built typical two-story and two-span underground stations model by using LS-DYNA. Through ALE algorithm and fluid structure coupling method, propagation law of shock wave in subway station and damage state of station structures were analyzed in the case of 16.3 kg TNT explosion. It is found that the shock wave mainly propagates along the lateral direction of the station after the superposition and attenuation of the surrounding structures. The maximum displacements of supporting columns, subway stairways, hallway flooring and platform flooring are 1.34 mm, 16.83 mm, 5.354 mm and 112.8 mm respectively. And the overall structure of the station is complete, but local areas are damaged and collapsed. In addition, in order to strengthen the antidetonation stability of subway station structure, the joint of column and platform floor, the joint of column and station hall floor and the reinforcement of stairs should be considered. This paper mainly provides a theoretical basis for the explosion-proof design of station structure

Research of heat transfer processes in motor-axial bearings of traction electric motors of diesel locomotives

Original calculation schemes of the motor-axle bearing and the distribution of heat flows in the process of heat removal from the surface layer of lubricant to the axle journal of the wheel pair and to the motor-axle bearing liner are proposed, taking into account its middle layer. In order to substantiate the maximum amount of heat released in the motor-axle bearings of a freight diesel locomotive of the 2TE10 series and caused by the action of friction forces in the zone of contact their with the journals of the axles of the wheel pairs, taking into account the theoretical foundations of heat transfer and the accepted assumptions in the specified calculation schemes, analytical dependencies were obtained to determine the quantities characterizing heat removal from the mentioned motor-axial bearings using three flows. As a result of implementing the proposed analytical dependencies and performing numerical calculations, it was proved that the operation of the studied motor-axial bearings is carried out in the semi-fluid friction mode and at negative temperatures of the external (atmospheric) air, their normal operation is not ensured due to the low proportion of heat removal by the lubricant, which does not exceed 1.5 percent, and therefore, this leads motor-axial bearings to premature wear and failure, and thereby reduces the operational reliability of the wheel-motor unit of diesel locomotives

Analysis of stress-strain in fully bonded basalt fiber plastic anchors

Based on the field pulling test of BFRP anchor, this study studied the stress-strain distribution of BFRP anchor solids of different lengths, analyzed the spatial and temporal distribution of stress-strain, shear stress distribution, axial force characteristics and shear slip displacement characteristics of the interface between BFRP anchor and slurry, and discussed the working mechanism of BFRP anchor solids of different lengths. The effect of bonding length of BFRP bolt on bonding properties between bolt and grout was quantified. The test results show that: The strain of BFRP bolt increases with the increase of load, and decreases with the increase of buried depth; The axial force increases with the increase of cyclic load and decreases with the increase of anchoring depth; The interfacial shear stress decreases exponentially along the anchoring depth, which can be divided into fast decay and slow decay stages; The bonding strength increases with the increase of bonding length, and the strength increases by 2 % to 27 % for every 0.5 m increase in length. This understanding of shear stress distribution helps in accurately assessing the load - transfer mechanism and the potential failure modes of the anchoring system, which is crucial for improving the design and safety of geotechnical anchoring projects

Determination of the resource of wheel pairs of locomotives during operation on the railways of Uzbekistan

The object of the study is the interaction of the electric locomotive wheel pair and the rail. The subject of the research is the wheel resource. The paper proposes a model for calculating the resource mileage of the electric locomotive wheel pair. The basis of the model is the determination of contact stresses in the wheel pair. The proposed calculation model, when changing the input data, can be used to determine the resource of various wheel pairs and traffic safety, and resource savings

Anomaly detection method of traction motor bearing based on multi-scale sub-band fuzzy entropy manifold fusion index

Detecting early faults in traction motor bearings poses significant challenges due to weak signals and difficulties in identifying fault initiation points with sufficient sensitivity. This paper introduces a novel anomaly detection method based on a multi-scale sub-band fuzzy entropy manifold fusion index (MFMI). The proposed method decomposes vibration signals across multiple scales to capture local features of bearing health, calculates sub-band fuzzy entropy to quantify fault characteristics, and uses locality preserving projection to retain nonlinear structural features while reducing dimensionality. Validation experiments using full-cycle acceleration life vibration signals demonstrate the superior performance of the proposed method. For instance, in the traction motor case, the proposed index detected early damage at the 189th time point, outperforming other indicators that detected damage after the 200th time point. The proposed method also shows higher sensitivity to early degradation trends while maintaining stability during normal operation. These results highlight the practical applicability of the method for early anomaly detection in traction motor bearings, offering earlier and more reliable fault detection compared to traditional methods

Analysis of heat treatment parameters of 60Si2CrV steel to enhance the mechanical properties of elastic structural elements

The article analyzes how the temperature of the quenching medium during heat treatment influences the mechanical properties of spring steel grade 60Si2CrV. It presents the correlations between the quenching medium temperature and such parameters as hardness, tensile strength, and elongation. The study identifies the optimal cooling medium temperature range to be 20-30 °C, which ensures enhanced mechanical performance of the steel. The findings can be applied to improve the heat treatment processes of cylindrical springs used in freight wagons, thereby increasing their service life and operational reliabilit

Static progressive damage finite element analysis of a certain type of composite pressure vessel

In addressing the issue of continuous damage evolution and failure prediction in composite pressure vessels, this paper combines the three-dimensional Hashin criterion with the equivalent displacement method to develop a static damage identification and progressive evolution model capable of accurately simulating material stiffness degradation under complex loading conditions. To validate the proposed model, carbon fiber/epoxy composite pressure vessels were used as the research subject. The UMAT subroutine, coupled with the Wound Composite Model (WCM) plugin, was employed to transform the principal material properties into off-axis properties and to establish the static damage identification and progressive evolution model for composite pressure vessels. Simulation results indicate that the vessel enters an initial damage state at an internal pressure of 62 MPa, with damage continuously evolving as the internal pressure increases, ultimately resulting in complete failure at 73.4 MPa. This model effectively simulates the entire process of damage initiation, propagation, and ultimate failure under internal pressure loading

Advanced design strategies and applications for enhanced higher-order multisegment denatured pascal curve gears

The existing Pascal curve gears suffer from limited flexibility in pitch curves and restricted changes in transmission ratios. This has impeded the application in a range of mechanical systems that require more adaptable gear solutions. For this, a design procedure for higher-order multisegment denatured Pascal curve gear is proposed. This innovative design offers greater flexibility in pitch curves and allows for a broader range of transmission ratios. The analysis of the transmission ratio confirms the theoretical predictions and highlights the effectiveness of the proposed gear design in achieving variable transmission ratios. The transmission mechanism of the higher-order multisegment denatured Pascal curve gear is analyzed and the unified mathematical expression of the families of Pascal curve gear is derived. The non-circular gears with free-form pitch curves can be obtained from higher-order multi-segment denatured Pascal curves by adjusting design parameters to unify different types of pitch curves. This approach provides significant flexibility in achieving specific transmission characteristics. Then the transmission characteristics are discussed. To further validate the design, the visual analysis and design software of the higher-order multisegment denatured Pascal curve gear is compiled based on Visual Basic, and is verified with the example. The novelty Pascal curve gears is applied to drive the differential velocity vane pump. The displacement, instantaneous flow rate, and pulsation rate of the differential velocity vane pump are calculated. The novelty drive mechanism could meet the requirements and have good performance. The application shows that the higher-order multisegment denatured Pascal curve gear is feasible in practice

Dynamic modeling of water level in water transfer tunnels on railroad tunnel forces

This study centers on the impact of water level fluctuations in water transfer tunnels regarding the mechanical response characteristics of railroad tunnels. Via a meticulously designed model test, the variation pattern of tunnel lining strain under diverse water level circumstances is thoroughly examined, furnishing a crucial foundation for the design, construction, and safe operation of tunnel engineering. The outcomes denote that water level alterations remarkably influence the tunnel's mechanical response. Each parameter exhibits disparate trends with the ascending water level, and discrepancies exist in the response features of different cross-sectional locations. The test results are as follows: (1) When the water level in the water transfer tunnel is 1 cm, the compressive strain at the outer elevated arch of section I reaches the maximum, and the compressive strain at the inner left arch foot is also the largest. (2) The tensile strain at the outer right arch waist of section II is the greatest, and the compression at the inner right arch waist is severe; the tensile strain at the outer right arch foot of section II exceeds the compressive strain at the arch top, and the compressive strain at the inner right arch foot is the largest. These findings offer a scientific underpinning for exploring the effect of water level loading on the mechanical response of the tunnel structure within the tunnel section beneath the water transfer tunnel, which is highly significant for enhancing project quality and ensuring operational safety

Development of resource-saving composition of sand-clay mixtures for steel castings with improved physical and chemical characteristics

The paper examines the problems of traditional sand-clay mixtures (SСM) used in steel castings and proposes solutions. Standard compositions including quartz sand, water and bentonite often exhibit limited gas permeability and insufficient strength. To address this, starch and soda ash were introduced as environmentally friendly additives. The scientific novelty of this research lies in the use of starch and soda ash to enhance the binding structure of sand-clay mixtures, thereby simultaneously improving strength and gas permeability without increasing production costs. Experimental analysis confirmed improvements in compressive strength and gas permeability, making the proposed mixture promising for industrial applications