Evaluation of the coupled dynamical response of a pantograph—catenary system: contact force and stresses

In this article, the static stresses in a catenary and its vibration modes are calculated by establishing the FEM model of the catenary with Euler-Bernoulli beam elements. The mode shapes of the catenary obtained are considered as the generalized variables which are used in the establishment of the motion equations of the catenary system. The physical model of the pantograph is simplified as a multi-body system with mass, stiffness, damping, and friction. On the basis of having derived the coupled motion equations of the pantograph-catenary system, its dynamic behavior is analyzed in detail and the contact force is calculated. Using the contact force as the external moving load of the FEM model of the catenary, the dynamic stress in the catenary is simulated. Through the detailed analysis and calculation, we not only obtain the dynamic stress response at any element of the catenary, but also its frequency responses. As the dynamic stress in the assistant wire is quite large, the influence of its structure on dynamic stress is analyzed and the way to reduce the dynamic stress is suggested. At last, the calculation method of dynamic stress is validated by a test.     

浮蹄式制动器摩擦片的磨损规律分析

计算分析了制动器中的各摩擦片在制动时的磨损情况，总结出其磨损规律，为摩擦片的设计提供了依据。     

浅谈沥青路面机械化施工与管理

路面材料及其加工工艺,路面施工、施工技术及机械化作业是公路路面工程中的2大要素,共同构成一个有机的整体。从沥青面层材料配合比设计和机械化施工工艺2个方面着手研究,分析了沥青路面施工过程中各施工工艺环节对路面面层平整度的影响,并提出了相应的控制和防治措施。     

Selection of appropriate numerical models for modelling the stresses in mooring chains

Mooring chains are key components for floating platforms. The failure of these components can be catastrophic in terms of the economic and environmental impacts, especially when dealing with the potential failure of FPSOs. However, mooring failures have been regularly occurring much earlier in their service lives than expected, with almost 50% of the reported failures happening in the first 3 years of 20-year design lives. Although the operating stresses play a major role in determining the failure mechanisms of mooring chains, the methods of predicting the operating stresses in mooring chains vary in the openly available literature, and the accuracy of these different numerical methods for predicting types of mooring failures is unknown. There is currently little evidence provided for when one model is appropriate for a particular scenario. Therefore, this paper benchmarks the different available methods for modelling mooring chains under tension, including FE models found in the literature. These models are calibrated and verified against previous studies and compared with experiments and a developed FE explicit model. There is a significant difference in the way that the numerical models behave, which are discussed in terms of their applicability and limitations in modelling mooring chains. The results of this study show that the explicit modelling approach should be utilised for accurate assessment of mooring lines, as it provides the most realistic response, with a substantial reduction in the computational cost and without any convergence problems.     

盾构盘形滚刀损坏机理的力学分析与应用

文章对盾构盘形滚刀损坏的力学机理进行了研究,应用CSM模型对滚刀破岩荷载进行求解,得到了滚刀损坏的临界最大贯入度和滚刀不能转动(偏磨)的临界最小贯入度计算公式,并对影响滚刀破岩荷载和影响临界贯入度的各种因素进行了分析。为便于现场应用,绘制了便于查阅的曲线图,并给出了应用示例。研究结果表明:掘进过程应根据岩石强度和刀具磨损情况的变化调整贯入度范围,其值应控制在临界最小和最大贯入度之间。研究结果对盾构机的现场施工具有指导作用。     

磨耗状态下城际动车组轮轨曲线磨耗特性

以CRH6A城际动车组为研究对象,基于实测磨耗后轮轨型面,利用多体动力学软件Universal Mechanism建立了车辆动力学模型,计算了通过曲线时的轮轨力与轮对位置参数;在非线性有限元软件ABAQUS中,基于任意拉格朗日欧拉方法建立了轮轨三维滚动接触模型,计算了轮轨接触应力特性和滑移特性;基于Archard磨损模型,提出一种车轮表面接触区域磨损速率快速计算方法,研究了新轮、磨耗初期车轮和磨耗到限车轮与新轨、磨耗后钢轨相互作用下,车轮通过曲线时接触区域磨损特性。研究结果表明：新轮和磨耗后钢轨、磨耗初期车轮和新轨、磨耗到限车轮与新轨相互作用下最大法向接触应力分别达到了2 017、1 803和1 668 MPa,比新轮和新轨、磨耗初期车轮和磨耗后钢轨、磨耗到限车轮和磨耗后钢轨3种作用下最大接触应力高出20%以上;新轮和磨耗后钢轨、磨耗初期车轮与新轨、磨耗初期车轮和磨耗后钢轨相互作用下,轮轨间出现两点接触、三点接触,甚至四点接触;在多点接触下,轮缘处接触点表现出应力集中且磨损速率较高的特点,最大磨损速率分别达到2.60×10^-5、3.82×10^-5、3.52×10^-5 mm·s^-1,远高于新轮和新轨、磨耗到限车轮和新轨、磨耗到限车轮和旧轨3种作用下的磨损速率;磨耗到限车轮和新轨与磨耗钢轨相互作用下的磨损速率均相对较小,说明在磨耗后期的车轮磨耗相对较小;轨角磨耗会严重加剧新轮的轮缘磨耗,且磨耗初期车轮具有较高的轮缘磨损速率,应将车轮镟修周期和钢轨打磨周期相协调,并通过涂油等方式降低磨耗初期的轮缘磨损。     

新型离合助力器在离合操纵系统中的应用

介绍了在某轻型卡车离合操纵系统中一种新型离合助力器的结构、原理、优势及应用     

风沙环境下不同强度等级砂浆冲蚀磨损试验研究

针对戈壁风沙流环境特点,采用气流挟沙喷射法,对不同强度等级砂浆进行冲蚀磨损实验,研究冲蚀参数和砂浆强度对冲蚀磨损的影响.实验结果表明,砂浆试样的冲蚀率随冲蚀速度的增大而增大;在低速冲蚀时,强度对冲蚀率影响较小,而在高速冲蚀时,影响较大;各试样速度指数在2.1~2.8之间,与脆性材料的冲蚀磨损预测值相一致.砂浆靶材在45°攻角冲蚀时冲蚀率最低,而在90°攻角冲蚀时冲蚀率最高,符合脆性材料的冲蚀规律.砂浆试样的冲蚀量随冲蚀时间近似呈线性关系增大,不存在冲蚀孕育期.砂浆试样的冲蚀磨损机制为选择性冲蚀磨损.     

小波包分解与共振解调分析在发动机配气机构磨损故障特征提取中的应用

以常见的机械磨损故障——气门间隙过大故障为例进行了试验研究,提取缸盖振动加速度信号进行分析,发现故障状态的时域信号有明显低频周期性冲击,但在频谱的低频区间未现冲击频率;同时,在故障状态频谱中,3 000~4 500Hz范围的高频段振动能量有显著增加。通过小波包分解方法对信号分解至该故障特征频段,再进行希尔伯特解调分析,解调谱现显著的对应低频冲击的频率成分,可作为故障识别特征。分析结果表明,气门间隙过大故障造成的冲击引起缸盖或其部件共振调制现象,综合运用上述时域、频谱和共振解调分析,可对配气机构磨损故障进行故障特征提取,从而为准确诊断故障提供依据。     

WC/Ni60A覆层抗泥沙磨损性能研究

叙述了WC/Ni60A覆层的粉末制备材料和喷焊工艺方法,测试覆层的硬度及沿厚度方向的硬度分布,对35%WC/Ni60A喷焊覆层进行泥沙磨损实验、XRD测试、金相分析和覆层样品磨损形貌观察。在实验基础上讨论该喷焊覆层的抗泥沙磨损性能,分析覆层中硬质相和基体相的成分构成、结合机理,结合泥沙磨损实验结果及其磨损形貌,探讨该覆层材料在泥沙磨损条件下的磨损机理及覆层中硬质相和基体相的作用。