This study investigates the spread patterns of tunnel fires and examines issues related to emergency response. It focuses on the temperature characteristics, spread patterns, conditions leading to multi-source fires, and the efficacy of water mist suppression methods in heavy-haul railway tunnel fires. The research employs theoretical derivations and numerical simulations to achieve its objectives. It was discovered that, during a fire in a heavy-haul railway tunnel, the temperature inside the tunnel can exceed 500 °C. Furthermore, depending on the nature of the goods transported by the train and under specific wind speed conditions, the fire source has the potential to spread to other carriages, resulting in a multi-source fire. Using the numerical simulation software Pyrosim 2022, various wind speed conditions were simulated. The results revealed that at lower wind speeds, the smoke demonstrates a reverse flow phenomenon. Concurrently, when the adjacent carriage on the leeward side of the fire is ignited, the high-temperature reverse flow smoke, along with the thermal radiation from the flames, ignites combustible materials in the adjacent carriage on the windward side of the burning carriage. Through theoretical derivation and numerical simulation, the critical wind speed for the working conditions was determined to be 2.14 m/s. It was found that while a higher wind speed can lead to a decrease in temperature, it also increases the flame deflection angle. When the wind speed exceeds 2.4 m/s, although the temperature significantly drops in a short period, the proximity of combustible materials on the leeward side of the carriage becomes a concern. At this wind speed, the flame deflection angle causes heat radiation on the leeward side, specifically between 0.5 m and 3 m, to ignite the combustible materials on the carriage surface, resulting in fire spread and multiple fire incidents. The relationship between wind speed and the angle of deflection from the fire source was determined using relevant physics principles. Additionally, the relationship between wind speed and the trajectory of water mist spraying was established. It was proposed to optimize the position of the water mist based on its deviation, and the results indicated that under critical wind speed conditions, when the water mist spraying is offset approximately 5 m towards the upwind side of the fire source, it can act more directly on the surface of the fire source. Numerical simulation results show a significant reduction in the maximum temperature and effective control of fire spread. Under critical wind speed conditions, the localized average temperature of the fire decreased by approximately 140 °C when spraying was applied, compared to the conditions without spraying, and the peak temperature decreased by about 190 °C. This modification scheme can effectively suppress the threat of fire to personnel evacuation under simulated working conditions, reflecting effective control over fires. Additionally, it provides theoretical support for the study of fire patterns in tunnels and emergency response measures.

This paper establishes a vehicle-track coupled dynamics model using component force elements (CMP) to analyse the rigid-flexible coupling dynamics of heavy haul freight wagon cross braces, focusing on straight-line running quality, curve negotiation stability, and vibration characteristics. Through systematic simulations of empty and loaded wagon conditions with varying anti-warp stiffness configurations, the research evaluates critical performance metrics, including Sperling ride indices, acceleration profiles, and safety indicators across different curve radii. The analysis at two speeds (60 and 120 km/h) characterises vibration displacement/acceleration patterns at key cross braces locations (endpoints and centre of gravity), with particular emphasis on frequency-domain characteristics and potential resonance phenomena. The results indicate that the flexible cross brace configuration yields nonlinear critical speeds and straight-line stability indices comparable to those of its rigid counterpart. Vibration characteristics demonstrate consistent frequency patterns across different operational conditions. Notably, the dominant lateral Y-direction vibration frequencies approach natural modal frequencies, suggesting potential resonance risks requiring monitoring, though no active resonance was observed. Vertical (Z-direction) vibrations exhibit heightened response amplitudes without triggering modal frequency resonance. The distinct vertical oscillations of the flexible cross braces' centre of gravity are attributed to elastic deformation under dynamic loading.

A friction draft gear model was developed to assess the degraded dynamic characteristics of worn draft gears in the vehicle impact condition. It presents an approach to simulate multiple typical wear profiles of wedge shoes and reflect their effects on the draft gear performance. Based on the rated design indexes and existing overhaul regulations of MT-2 type friction draft gears in China, the safety wear limits for wedge shoes with different wear profiles were classified and assessed. The results indicate that wedge shoes with uniform or concave wear can significantly worsen draft gear performance, and the existing maintenance limit of 1 mm only applies to wedge shoes with uniform wear but not to the most common wedge shoes with concave wear. Also, for wedge shoes with concave wear, when the wear area covers 50%, 75%, and 100% of the total main friction surface, the corresponding safety wear limits are 0.5 mm, 0.8 mm, and 1.3 mm, respectively. Therefore, it is proposed to design multiple graded and dynamic maintenance limits to ensure the service safety of MT-2 type friction draft gears.

To study the tread surface hardness difference that caused by wheel diameter difference of wheelsets, an investigation on corresponding factors of wheelset hardness was done. A group of data including wear rate, wheel diameter, wheel rim hardness and tread hardness was collected to serve as the dataset for neural network. Improved extreme learning machine (ELM) based on particle swarm optimization (PSO) algorithm was chosen to be the main method, trained by dataset and used to predict the tread surface hardness difference. The result shows that PSO-ELM is able to describe the changing trend of tread surface hardness difference, and reaches the best correlation level compared to the original ELM and BP network. Finally, the trained network was applied to analyze the relation between tread surface hardness difference, revealing that the rolled steel is a less sensitive material than the casted steel when meeting hardness or diameter difference.

Mixed freight trains have more diversified vehicle characteristics and train combination modes than unified freight trains, so it is more difficult for mixed freight trains to predict the accident caused by longitudinal impulse. At present, train dynamics theories and numerical simulation methods have been increasingly used to reduce longitudinal train impulse and decrease freight wagon instability. According to these research experiences, this paper focuses on the marshalling modes of mixed freight trains and their effects on the longitudinal in-rain forces. For this purpose, an advanced simulation model for mixed freight trains was developed and several typical mixed marshalling modes were designed and simulated. The results indicate that, for the mixed train including empty and loaded wagons, empty wagons should be arranged at the tail of the train and should avoid being marshalled together. For the mixed train including marshalled wagons with various actual live loads or nominal axle loads, heavier wagons should be centrally arranged in the front part of the train, and meanwhile marshalled wagons should avoid being sorted by weight in the concave and ascending distribution mode. For the mixed train including marshalled wagons with various body types, container flat wagons and oil tank wagons should be arranged as much as possible in the front of the other wagons.

目前铁路货车所采用的基础制动装置大多为杠杆式制动装置.相比于单元式制动装置,杠杆式制动装置运动情况复杂,制动效率较低.对于货车车辆基础制动装置的研究,传统分析方法主要为现场试验法和理论计算法.而这两种方法的应用受到试验成本高、研发周期长、测量误差大以及计算复杂的限制.刚柔耦合分析采用ADAMS和ANSYS仿真软件进行多体动力学联合仿真,对货车基础制动装置性能进行分析研究.通过对比仿真分析数据、理论计算数据和现场试验数据,验证了基础制动装置刚柔耦合分析方法的正确性,对研究货车制动性能及解决基础制动装置所存在的问题提供了一种新的手段.

During train operation, influenced by track irregularity or random wind load, the vehicle body is continuously under the impact of random vibration loads, which will cause fatigue damage to the vehicle structure in severe cases. To ensure train operation safety, an analysis of random vibration fatigue of the door on a new 160 km/h large volume box wagon with movable side walls was carried out. Considering the influence of excitation transmission on bogie, car body and other parts, the vehicle body dynamics simulation model was established through a flexible modeling method, and the door's vertical vibration acceleration spectrum was obtained by using the American sixth grade track line. The door's fatigue damage was calculated with two analyzing methods, which were the frequency domain analysis based on the stress response power spectrum density function and the time domain analysis based on the rain flow counting method. The results show that the door's fatigue life under the two analyzing methods both meet the requirements for operating six million kilometers, and the areas with weak fatigue strength are welding parts on the door seat. The fatigue damage calculated by frequency domain analysis method is 0.89, and that calculated by time domain analysis method is 0.51. The former is more conservative. Finally, the reasons for the difference between the two results are analyzed from three angles, namely the data processing methods, evaluation methods and calculation principles.

内轴箱转向架由于轴箱悬挂内置大幅度降低了车体的抗侧滚刚度,影响其运行性能.为提高其抗倾覆性能,内轴箱转向架通常采取安装抗侧滚扭杆和提高一系悬挂垂向刚度的措施.文章提出了一种抗倾覆装置,以提高内轴箱悬挂高速动车组转向架抗倾覆稳定性.该装置由2条互不连通的回路组成,安装在轮对轴箱和构架之间.在分析抗倾覆装置的基本原理、刚度特性和车辆动力学模型之后,利用MATLAB/Simulink软件,联合AMESim和SIMPACK软件进行联合仿真,得到车辆在不同速度条件下通过大半径曲线时的动力学性能和动态包络线.结果表明,采用抗倾覆装置可以在保证车辆运行稳定性的条件下大幅提高车体的抗侧滚能力,在车辆脱轨系数和轮轴横向力等安全性指标方面有着更优异的表现,同时有着较小的动态包络线.

Against the problem of insufficient lateral flexibility due to the design space limitation of secondary springs of the bogie for a suspended monorail train, an equivalent restoring stiffness formula was deduced from the linear theory of small swing angles for the four-linkage suspension mechanism. Based on the formula, the geometric parameters optimization of suspension system was completed, and the lateral stiffness of the suspension system was improved to the level equivalent to the secondary air spring used on metro trains. Combined with the actual design cases of suspended monorail trains, the four-link suspension mechanism was analyzed from the view of kinematics and dynamics using the multi-rigid-body dynamics approach. The applicability scope and limitation of the equivalent restoring stiffness formula were summarized, and a 3D coupling dynamics model for the whole train was established to analyze and verify the effectiveness of the optimized design solution of the suspension system. The results show that the design solution by reasonably matching the geometric parameters of the four-linkage mechanism can significantly improve the lateral riding quality of the train, but when the train passes through a small radius curve, it will cause more dynamic deviation of the train body.

为研究特定编组下长大坡道对货物列车纵向动力学性能的影响,利用SIM PACK动力学分析软件建立列车纵向动力学模型,分析研究了坡道牵引启动工况与紧急制动工况下的列车纵向动力学性能并做了分析对比,经研究认为在牵引启动工况与紧急制动工况下列车的纵向动力学性能均符合要求.

为了解川藏铁路货运车辆在长大下坡道因循环制动导致的车轮热负荷以及车轮的辐板疲劳问题,首先在不同坡度工况下对列车进行循环制动的模拟计算,得出列车在长大下坡道循环制动的速度时间曲线;然后建立有限元模型,对车轮进行温度场分析;最后根据T B/T 3463-2016疲劳强度评定准则,在制动热应力条件下对车轮辐板进行疲劳强度校核.研究结果表明:在-24‰坡道,车轮辐板疲劳强度符合标准要求;在-30‰坡道,车轮辐板疲劳强度不能满足标准要求.

为模拟三轴构架式转向架货车不同位置旁承失效后的运行性能,基于平面多点支撑力学理论,利用SIMPACK软件建立了全旁承承载三轴构架式转向架货车整车动力学模型,研究了不同位置旁承故障模式下货车的动力学响应.结果表明,最前端和最后端旁承失效将严重降低重车的蛇行运动稳定性;一位转向架的前端旁承失效将引起空车脱轨系数和轮重减载率增大;各旁承失效均会引起重车脱轨系数和轮重减载率增加,影响车辆曲线通过安全性.

采用模糊综合评价方法对铁道客车的技术代系进行了研究.在模糊综合评价方法的基础上,将构成客车的车体、转向架、车钩缓冲装置、制动系统及车载电器设备的关键技术作为评价指标,建立了铁道客车分层次模糊评价模型.通过对各技术指标发展及技术性能指标的模糊化处理,构建了模糊评价矩阵,得到了各型车辆的技术评价值.按照各型车辆的技术评价值分布来判定车辆所属的技术代系,分析结果反映出了我国铁道客车的技术发展历程,可为新一代车辆的研发提供一种技术评价方法.

介绍了澳大利亚标准AS 5100.2:2017的铁路桥梁基准活载等级及其他等级活载图式,提出了桥梁在标准活载和评估车辆载荷作用下所受最大静态剪力和弯矩的计算方法,并推导了相关的计算公式;采用Visual Basic语言编写了校核计算程序,并对计算程序的正确性进行了验证.验证计算和运用实例表明,文章所述计算方法正确,程序计算精度满足实际需求,能够有效指导出口澳大利亚铁路货车设计.

介绍了某型可变轨距转向架制动夹钳随动装置的结构组成和变轨原理,并利用ANSYS软件建立了随动装置的有限元模型.基于EN 13749标准,设计了夹钳随动装置在静强度和疲劳强度下的载荷工况组合,并对其进行校核.分析结果表明:可变轨距转向架制动夹钳随动装置的静强度和疲劳强度均满足使用要求.

The passing speed is much lower than the design speed of curved track when rail grinding wagon performs the curve grinding operation, which results in the excess superelevation phenomenon. The rigid-flexible coupled dynamics model of rail grinding wagon was established using the FEM software ANSYS and the multi-body simulation software Simpack considering carbody flexibility. The contact relationship between the grinding wheels and rail was introduced in the model to study car-body elastic deformation on the dynamic performances. The dynamic responses of curve radius and superelevation were compared and analyzed under grinding operation conditions and free running. The results showed that the car-body elastic deformation mainly affected derailment coefficient and wheel unloading rate, but had little influence on the wheel axle lateral force and roll coefficient. After considering the car-body as a flexible body, curving passing performance of the rail grinding wagon had been improved. Within a certain range, increasing the curve radius and decreasing the superelevation could improve curving passing performance of vehicle. Grinding would worsen curving passing performance of vehicle and increase the risk of derailment.

为研究铁路货车顶置式斜楔轴箱悬挂结构中斜楔摩擦角对三轴转向架动力学性能的影响,基于车辆系统动力学和赫兹非线性接触理论,采用动力学性能仿真软件SIMPACK建立六轴平车非线性动力学模型,分析不同摩擦角对三轴转向架动力学的影响及变化规律.结果 表明,斜楔摩擦角的增大会使车辆垂向振动加速度增加,恶化垂向平稳性,影响车辆的轮重减载率和脱轨系数.给出了该六轴平车斜楔摩擦角的建议值.

为预测摩擦缓冲器的实际工作状态,从几何特征和作用原理的角度,建立详细的MT-2型缓冲器理论模型.首先,通过对缓冲器内部各摩擦元件的运动学和静力学分析,推导出缓冲器在准静态下的阻抗特性;其次,引入附加摩擦系数量化各摩擦元件之间动静态摩擦过渡时的黏滞补偿,并模拟出缓冲器在动态下的阻抗特性;最后,利用C80型货车冲击试验数据对该缓冲器的理论模型进行验证.验证结果表明:总体上,数值模拟和现场试验下的缓冲器示功曲线基本吻合,说明模型的正确性;局部上数值模拟中缓冲器从加载Ⅰ阶段过渡至加载Ⅱ阶段的突变现象在冲击试验中表现的并不明显,还有待进一步完善.

利用大型有限元仿真软件ANSYS建立了一种变轨距动车组转向架轴箱的有限元模型,介绍了该型转向架轴箱的结构特点及其转臂定位方式,根据转向架的设计技术参数计算了轴箱承受的相关载荷,依据欧洲标准BSEN13749:2011制定了轴箱的载荷工况,并对轴箱静强度和疲劳强度进行评估并分析预测轴箱可能出现疲劳破损的位置.结果表明:轴箱的静强度和疲劳强度均满足标准要求,轴箱结构安全可靠.