An improved LuGre model for calculating static steering torque of rubber tracked chassis

Tire and rubber track interchangeable chassis combines the advantages of tire and rubber track,which can greatly improve the maneuverability of military construction machinery.However,there is almost no effective calculation model for the real-time static steering torque.When the relative sliding speed is greater than 0.01 m/s,the influence of friction heating can not be ignored.An improved LuGre model is established to calculate the static real-time steering torque of tire and rubber track interchangeable chassis.Firstly,the friction heating model between rubber and ground is established.Combined with the influence of temperature on the dynamic performance of rubber material,the influence of friction heating on the stiffness and friction coefficient of rubber track is analyzed,and the improved LuGre friction model is established.The steering torque of tire and rubber track interchangeable chassis is affected by rubber material properties,steering speed,pavement type,and ambient temperature.Compared with the original Lu Gre model,the improved LuGre model captures the change in friction torque during multiple in-situ turns due to frictional heating.The error with the experimental data is small,which verifies the effectiveness of the improved LuGre model.

A Newly Developed Differential Steering Rubber-tracked Agriculture Tractor

This paper introduces a newly developed ag tractor.The differential steering system and rubber tracks are described in detail.

Investigations of Tracking Phenomena in Silicone Rubber Using Moving Average Current Technique

In the present work, tracking phenomenon in Silicone rubber material has beenstudied under AC and DC voltage, with ammonium chloride as a contaminant. It is observed that thetracking is more severe under the DC voltages. The tracking time is less under negative DC comparedto the positive DC voltage. The tracking mechanism is explained in detail. The leakage currentduring the tracking studies was as measured and the moving average technique was adopted tounderstand the trend in current flow. The leakage current magnitude is high with thermally agedspecimens compared to the virgin specimen, irrespective of the type of applied voltage. It isrealized that the tracking time and the leakage current magnitude shows an inverse relationship.

High-speed tracked vehicle model order reduction for static and dynamic simulations

In this paper, a model order reduction strategy is adopted for the static and dynamic behaviour simulation of a high-speed tracked vehicle. The total number of degree of freedom of the structure is condensed through a selection of interface degrees of freedom and significant global mode shapes, for an approximated description of vehicle dynamic behaviour. The methodology is implemented in a customised open-source software to reduce the computational efforts. The modelled tracked vehicle includes the sprung mass, the unsprung masses, connected by means of torsional bars, and all the track assemblies, composing the track chain. The proposed research activity presents a comprehensive investigation of the influence of the track chain, combined with longitudinal vehicle speed, on statics and vehicle dynamics, focusing on vertical dynamics. The vehicle response has been investigated both in frequency and time domain. In this last case road-wheel displacements are assumed as inputs for the model, under different working conditions, hence considering several road profiles with different amplitudes and characteristic excitation frequencies. Simulation results have proven a high fidelity in model order reduction approach and a significant contribution of the track chain in the global dynamic behaviour of the tracked vehicle.

Investigations on Tracking and Erosion Resistance of Nano Silicone Composite for High Voltage Outdoor Insulation

In recent times, silicone rubber insulating material is used for power transmission line and substation insulation applications. In the present work, tracking and erosion resistance of the micro size filled and nano size filled silicone rubber material has been studied under the AC voltage, with ammonium chloride as a contaminant, as per IEC 60587 test procedures. The characteristic changes in the tracking resistance of the micro size and nano size filled specimens are analyzed through leakage current measurement. Comparative Tracking Index （CTI） is also evaluated in order to understand the relative behavior of solid electrical insulating material with regard to their susceptibility to surface tracking. Trend followed by the fundamental, third harmonic and fifth harmonic components of the leakage current during the tracking study are analyzed using moving average current technique. It is observed that the harmonic components of leakage current show good correlation with the tracking and erosion resistance of the material. It is noticed that 5 % wt ofnano size filler gives similar performance to that of 30 % wt of micro size filler in silicone composites.

城市地铁橡胶弹簧浮置板轨道动力特性研究

为研究城市地铁橡胶弹簧浮置板轨道结构的动力特性,建立橡胶弹簧浮置板轨道结构的三维有限元分析模型,对轨道系统进行了谐响应分析,探究了系统的振动传递情况;进一步结合车轨耦合理论,建立车辆-橡胶弹簧浮置板轨道耦合动力学模型,研究了橡胶弹簧浮置板轨道的动力特性.研究表明:相比于普通道床,橡胶弹簧浮置板道床在减缓振动方面表现出显著的优势,能有效降低由车辆运行所引起的振动,增强地铁轨道的运行稳定性,延长轨道结构的使用寿命,从而为提高城市地铁的整体性能和运营效率提供有力支持.

叠层厚橡胶支座力学性能及其震振双控性能分析

为实现地铁上盖建筑的震振双控效果,可将叠层厚橡胶支座用于该类结构体系转换层。与普通橡胶支座相比,叠层厚橡胶支座的单层橡胶厚度较大,既可用于水平隔震,又可减小上部结构的竖向振动。为准确评估其在地铁上盖建筑中的效果,设计了第一形状系数为6.82的叠层厚橡胶支座,并对足尺支座开展竖向压缩、水平剪切、竖向拉伸和高面压稳定性能试验。探究了竖向压应力、剪应变和加载频率等对支座力学性能的影响规律,得到了设计阶段叠层厚橡胶支座竖向压缩刚度、水平等效刚度、等效阻尼比和拉应力值等性能指标。基于试验力学性能指标,建立了固接模型、普通橡胶支座和叠层厚橡胶支座的地铁上盖结构模型,分别以选取的地震波和实测三向地铁振动为激励,通过时程响应分析,验证了叠层厚橡胶支座的震振双控效果,为地铁上盖建筑的震振双控提供技术方案。

橡胶混凝土道床车致振动能量俘获研究

随着城市轨道交通运营里程的不断增加,为保证运营安全,需对轨道等结构进行健康监测。目前,既有监测传感器的供电方式主要采用外部市电或蓄电池。如何将列车运行产生的振动能量俘获并用于监测传感器供电,已经成为近些年的研究热点。针对橡胶混凝土道床,设计了一种全新的球型俘能器。通过构建列车荷载作用下橡胶混凝土道床的计算模型,对垂向位移、应力、电压、总电能等指标进行分析。主要结论如下:(1)采用阵列形式将球型俘能器埋入橡胶混凝土道床,最优位置在轨枕之下5 mm;(2)在6 m长橡胶混凝土道床范围内布设10个俘能器,一辆8节编组A型列车驶过可产生毫焦级别的电能,若按照5 min发车间隔估算,1 h俘获总电能122.4 mJ;(3)橡胶混凝土道床较普通混凝土道床更有利于能量俘获,当橡胶含量为10%时,道床内部俘能器阵列所俘获的总电能较普通混凝土提高5%,应力等力学性能指标也在安全范围内。

轮轨激励对橡胶垫浮置板轨道减振效果的影响

以某一组临近的普通整体道床和橡胶垫浮置板轨道为研究对象,对比测试振源加速度,同步调研上线运营列车的净运营里程,并开展车轮不圆顺测试,分析不同轮轨不平顺状态下橡胶垫浮置板轨道的减振效果。结果表明:在评价减振轨道的振动控制能力时,除了针对插入损失(或对比损失)开展客观评价外,也需要分析随着轮轨动态激励的增强是否会导致减振轨道段振动响应超过振动限值的问题;测试线路列车车轮呈现明显的7—9阶多边形磨耗特征,且随着轮轨激励的增强,Z振级相对插入损失的评价结果逐渐增大;橡胶垫浮置板轨道分频减振能力的评价结果与不同频段的激振原理直接相关,轨道扣件系统的自振频率(63 Hz)处轮轨动态激励的增加导致普通轨道的隧道壁振动响应增幅更大,该中心频率处的对比损失随着净运营里程的增加而变大。

Cold-Resistant Rubbers Based on Flexible Polymer Chains

Comprehensive Summary,As one of the three types of polymeric materials,rubber has played an irreplaceable role in various fields such as industrial production,aerospace,military,and national defense.Improving the cold resistance of rubbers and extending their service temperature range have always been one of the main focuses in rubber research.However,there have been few detailed public reports or literatures on the progress or summary of cold-resistant rubbers,creating an invisible barrier for new researchers wishing to enter this field of research.Therefore,starting from the basis of polymer physics,this review introduces the research difficulties in this field and systematically summarizes the research progress in constructing cold-resistant rubbers based on three different types of flexible polymer chains in recent years.In addition,several important properties of cold-resistant rubbers including mechanical performance,oil resistance,and self-healing ability are also discussed along with the summary of recent progresses.Finally,the future challenges and prospects of cold-resistant rubbers are discussed.

机车车辆橡胶元件动态建模及其应用

橡胶的动态特性依赖于外界激扰的幅值和频率。为充分体现铁道车辆橡胶部件的真实物理特性,兼顾动力学仿真计算的精度和时间,基于弹塑性理论建立橡胶元件动态模型。分别用摩擦力和黏滞力表征橡胶的振幅相关性和频率相关性;计算分析简谐激励下橡胶元件的等效刚度和阻尼;将橡胶元件模型结合车辆-轨道耦合动力学模型,分析车辆通过曲线时一系定位节点力的动态特性。研究结果表明:摩擦力提供的等效刚度随激扰幅值的增大而减小,阻尼随激扰幅值的增大而增大;黏滞力提供的等效刚度和阻尼都随激扰频率的增大而增大;橡胶元件在车辆曲线通过的不同阶段可反映不同的动态特性。

填料种类及粒径对轨道减振橡胶垫板动静刚度比的影响

以不同粒径的炭黑、白炭黑、陶土及碳酸钙为填料加到乙丙橡胶中制备轨道减振橡胶垫板,研究了不同填料及粒径对垫板动静刚度比的影响。结果表明,使用炭黑时动静刚度比随粒径增大而减小,使用白炭黑时动静刚度比随粒径增大而增大,而使用陶土和碳酸钙时动静刚度比随粒径变化无规律且变化较小。同时,使用补强型填料炭黑和白炭黑时,垫板动静刚度比比使用填充型填料时的动静刚度比较高。

聚氨酯塑胶跑道老化后耐压缩疲劳性能的研究

研究非渗水型和渗水型两款聚氨酯塑胶跑道在烘箱老化和氙灯老化后的耐压缩疲劳性能。结果表明:随着老化时间的延长,恒定振幅压缩疲劳对塑胶跑道的冲击吸收和垂直变形的影响增大,且在疲劳6万次时塑胶跑道的冲击吸收和垂直变形性能下降速率均增大;相对于非渗水型塑胶跑道,渗水型塑胶跑道在老化和疲劳后的抗滑值明显减小,耐摩擦性能变差。

400 km/h高速铁路小半径曲线地段橡胶浮置板轨道参数优化研究

为了研究400 km/h高速铁路列车经过小半径曲线地段时的动力响应特性,建立小半径曲线地段CRH380B车辆-轨道动力学模型,结合列车实测数据验证模型的准确性,随后模拟列车以400 km/h速度通过7000 m半径曲线路段的动力响应。结果表明:(1)相较于非减振轨道地段,当橡胶浮置板轨道的减振垫铺设刚度为0.019 N/mm^(3)、0.033 N/mm^(3)、0.042 N/mm^(3)、0.1 N/mm^(3)时,轨道减振效果分别为13.4 dB、13.4 dB、12.5 dB、8.6 dB;(2)道床板厚度、减振垫刚度的建议取值分别为300 mm、0.03 N/mm^(3)。研究成果可为400 km/h高速铁路橡胶浮置板轨道结构设计提供理论依据。

四橡胶履带轮式车辆转向力学性能分析与试验

橡胶履带轮是一种能够与轮胎整体快速互换,降低接地比压、提升越野机动能力的特殊行走装置。该文以某型四橡胶履带轮式车辆转向系统为研究对象,首先通过建立断开式转向梯形机构数学模型,得到内轮、外轮转角与油缸位移关系,以及转角特性曲线;通过转向油压测试,得到两轮和四轮转向时转向油缸输出最大转向驱动力及其随左前轮转向角变化曲线。然后对履带轮在混凝土地面上转向受力分析,建立最大平均转向阻力矩数学模型,得到单轮最大平均转向阻力矩。最后提出了基于转向杆件应力应变测试分析转向阻力矩的方法,得到履带轮在混凝土地面2轮和4轮原地转向时转向阻力矩随转角变化的规律,对比分析最大总转向驱动力矩与总转向阻力矩,验证了数学模型和该分析方法的正确性。该文的研究也可对四履带轮式车辆转向系统的结构参数设计和履带轮的接地尺寸、接地比压、轮系布置研究提供参考。

微型农用履带式行走装置的设计方法

针对履带式行走装置行驶路面特性复杂多变的特点,结合农业机械实际工作情况,查阅相关文献,总结农业履带行走装置的设计思路;以农业机械的实际工作环境为背景,对履带式行走装置以及关键机构的设计、参数的确定等问题进行了分析研究;就履带式行走装置在水平面内的接地长度、履带宽度和轨距,驱动轮、导向轮及支重轮设计参数进行分析;同时,又要考虑履带宽度和接地长度的取值不会影响转向性能和整机尺寸。由此为农业用履带行走装置的设计提供了设计思路和方法。

果园运输机单轨道橡胶辊驱动装置驱动性能研究

通过搭建的游动正压力夹紧和双自由度相向扭矩施加方式的试验台进行了单轨道橡胶辊驱动装置驱动性能的试验研究,得出了压缩量、摩擦力与正压力的关系曲线。为了进一步分析橡胶辊变形对摩擦力的影响,利用非线性有限元方法中Mooney-Rivlin模型和增广拉格朗日接触算法进行数值计算,得到了附着面积和压缩量与正压力的关系及接触应力分布、摩擦应力分布和接触状态分布;通过对比,发现仿真正压力与压缩量的关系和实验结果吻合,从而进一步证明了正压力与摩擦力的驱动性能关系的正确性。结果表明,当正压力为2 750 N时,单边最大静摩擦力1 167 N,宏观摩擦因数0.85,附着面积1 909 mm2,压缩量4.6 mm,达到了果园运输作业的静态技术要求,为单轨道新型非线性橡胶辊的设计提供了理论基础。

特高压直流用高导热纳米复合绝缘子耐电痕特性研究

随着特高压复合绝缘子的大规模应用,复合绝缘子的耐电痕能力成为亟待研究的问题。为此,通过基于IEC 60587标准的耐电痕实验以及实验过程中的热放电图谱,研究了高导热纳米复合硅橡胶在高压直流下的耐电痕特性。所用纳米复合硅橡胶材料为室温硫化硅橡胶基体添加纳米氮化硼(BN)。实验结果表明,随着纳米氮化硼颗粒质量分数的提高,硅橡胶复合材料试样表面放电区域的最高温度得到抑制,试样表面温度超过60°C的区域面积增大,停止放电后试样表面温度下降速度升高。实验结果还表明,纳米复合硅橡胶的电蚀损失质量和电蚀深度比未添加纳米颗粒的硅橡胶有明显的下降。因此含有纳米氮化硼颗粒的硅橡胶有较好的抑制热量积累能力,且耐电弧侵蚀增强,能够有效提高硅橡胶的绝缘能力。

桥上无砟轨道橡胶减振垫减振性能试验研究

以成都—都江堰高速铁路工程为背景,通过现场测试试验,研究桥上无砟轨道铺设橡胶减振垫的减振效果。结果表明:铺设橡胶减振垫后,减振垫上钢轨和轨道板的振动略有放大,但影响甚微,而减振垫下底座板、桥梁及地面的振动显著降低,其中底座板的最大振动加速度降低了85%左右;时域内,在距线路中心线0,15和30m处地面的最大竖向加速度振级均降低了9.5dB左右;频域内,在0～6.3Hz频段内,橡胶减振垫的减振效果不明显;在8～20Hz频段内,由于与轨道—桥梁—大地系统本身的自振频率重合,反而放大了地面的振动;在25～100Hz频段内,减振作用明显,且距线路中心线越远,减振效果越显著,但距线路中心线不同距离处对应最大减振作用的频段和插入损失值不同,0m处最大减振作用出现在31.5Hz频段,插入损失值为7.8dB,15和30m处最大减振作用均出现在40Hz频段,插入损失值分别为13.6和16.4dB。可见,橡胶减振垫能够对25Hz以上频段的振动起减振作用。

高压直流复合绝缘子5000h人工加速老化试验

选取不同配方、不同工艺、不同伞形的多种复合绝缘子,在国内首次参照标准IEC61109的老化程序进行了直流5000h人工加速老化试验。直流5000h人工加速老化试验包含直流电应力、日照、高温、高湿度、重污秽等诸多因素对复合绝缘子老化性能的影响。结果表明直流5000h人工加速老化试验可以再现硅橡胶表面憎水性不断丧失与恢复的情况、不同伞型绝缘子的积污特点和表面放电路径的差异;提出了表面放电是复合绝缘子积污和憎水性丧失的主要因素,温度和光照对硅橡胶的憎水性迁移和恢复特性有较大影响。硅橡胶复合绝缘子表面的憎水性在整个5000 h综合老化试验中呈动态变化,在不同的老化因素作用下呈现出不同的憎水性。