动荷载作用下钢结构涂装的累积损伤机理与量化模型

为研究动荷载作用下公路钢桥涂装层与基体间的协同变形和破坏机制,开发了钢结构涂装层试件的动荷载试验系统,研究了疲劳荷载作用下涂层的破坏模式、附着力、弹性厚度、应变等随循环加载次数的发展规律。结合涂层破坏模式和发展规律,构建了涂层疲劳累积损伤度的计算模型,提出了基于损伤度的涂层破坏分级方法,并结合试验结果进行了验证。结果表明:疲劳荷载将引起涂层的附着力下降、弹性厚度降低和应变松弛,进而导致涂层出现附着破坏、内聚破坏及其组合。涂层附着损伤度是涂层损伤的主要因素,且随加载次数持续增大,当加载次数较大时内聚损伤贡献突出。试验涂装体系在22万次应力循环后附着损伤度最大为0.34,内聚损伤度最大为0.27,总损伤度达0.61,属于严重损伤。提出的损伤度模型及破坏分级方法与试验规律吻合良好,可应用于公路钢桥涂装层受动荷载作用下的寿命预测。     

填石路堤强夯加固施工参数及路基动应力响应规律研究

贵州西部山区的高速公路常采用高填石路堤,强夯法是控制高填石路堤填筑质量的有效方法之一。为确定填石路堤的强夯加固施工技术参数、探讨强夯冲击能量作用下填石路堤内部动应力响应规律,通过现场试验和FLAC3D数值模拟进行研究。采用动土压力盒、位移观测元件,测试强夯冲击能量作用下的动应力以及夯坑沉降量、夯锤周边地表变形等数据,并将现场测试结果与数值模拟结果进行对比分析。研究结果表明:在夯击能量3 000 kN·m下,强夯加固单点夯击次数为12击、夯点间距为4.5 m;强夯作用下填石路堤内部动应力峰值随深度呈指数形式衰减,并且根据动应力峰值的随深度衰减曲线,获得了夯击能量3 000 kN·m下填石路堤强夯有效加固深度为5.0 m。研究结果可为类似工程确定强夯加固施工参数及有效加固深度提供指导。     

船舶齿轮箱用磁流变弹性体动力吸振器的仿真研究

船舶齿轮箱是船舶动力装置的重要传动装置,同时齿轮箱振动又是船舶振动的主要振源之一。因此,对其安装有效的吸振装置很有必要。本文设计了一款用于齿轮箱吸振的磁流变弹性体动力吸振器模型,通过ANSYS软件对其进行不同激励电流下的模态分析和热力学分析。结果表明,该吸振器拥有较宽的移频特性,能够有效控制齿轮箱的振动,同时该模型在强制对流工况下工作性能较好。     

考虑表面粗糙度与轴瓦变形的水润滑轴承动力特性系数计算

本文在传统轴承动力学分析模型的基础上考虑了水润滑轴承轴瓦的刚度、阻尼和轴承质量以及可能存在的接触刚度、阻尼,推导了考虑表面粗糙度和轴瓦变形的扰动压力雷诺方程,对比了混合润滑模型与动力润滑模型、弹流润滑模型的轴承动力特性系数并分析其差异,研究了倾角、粗糙度等参数综合作用下水润滑轴承动力特性系数的变化规律。结果表明,最小膜厚比大于某一阈值时粗糙度增加可提高水膜动力特性系数,轴瓦变形会使动力特性系数减小,同时也会扩大使水膜刚度、阻尼获得增幅的粗糙度范围,但削弱了粗糙度对承载方向刚度、阻尼的增幅效果。此外,在承受载荷一定的条件下,粗糙轴承的动力特性系数在倾角较大时明显小于光滑轴承的对应值。     

考虑临时和预约需求的共享泊位动态分配方法

为解决多居住区共享停车场同时存在临时共享停车需求和提前预约共享停车需求的动态泊位分配问题，本文提出将未来几个时段的共享停车供需同时考虑到当前时段泊位分配中的单时段泊位分配方法，并将本时段泊位匹配结果延伸到后续时段，从而提出共享泊位动态分配流程。对临时停车需求，以用户成本最小为目标确立优先泊位匹配的原则；对预约停车需求，以系统收益最大为目标确立在当前时段结束时统一分配泊位的原则。定义4个指标评价模型效果。 选择来源于成都市某共享停车APP的3个居住小区一天的数据，对模型进行实证研究以及灵敏度分析。研究结果表明：临时共享停车需求和提前预约共享停车需求所占比例在0.4~0.6时，泊位分配后总目标表现最好；将未来几个时段的供需同时考虑到当前时段中，泊位分配效果更好，且考虑的未来时段越多，泊位分配后总目标越好；在泊位分配时，为了较好地保证临时停车需求能够优先分配到泊位，往往会造成总目标变差。     

Experimental research on dynamic responses characteristics and influence laws of gear transmission-propulsion system under gear excitation北大核心CSCD

［Objective］In order to study the dynamic response characteristics and influence laws of a marine gear transmission-propulsion system, a series of bench tests is carried out.［Methods］First, a biaxial gear transmission-propulsion system test bench including a cross connection gear is built. Experiments to test the acceleration response of the gearbox body and propulsion shaft system are then carried out, and the influence of speed, driving mode, axial static thrust, axial dynamic excitation force from the propeller and other factors on the dynamic response characteristics of the system are compared and analyzed. ［Results］The experimental results show that the transmission law of the vibration acceleration response of the gear transmission-propulsion system is mainly at the meshing frequency and its multipliers, as well as peaks in the low frequency band of 30–80 Hz under certain working conditions. ［Conclusion］This study can provide technical support for the vibration and noise reduction design of gear transmission-propulsion systems. © 2022 Journal of Clinical Hepatology. All rights reserved.     

智能车经济性起步车速规划研究

智能车的车速决策影响燃油经济性。以起步阶段加速工况的燃油经济性为优化目标,建立了瞬态燃油消耗模型,并提出了基于该模型的经济性换挡规律制定方法;根据车辆纵向动力学方程,建立了基于前向欧拉离散方法的车速状态转移方程,以及确定相应的初末约束条件、边界条件;基于动态规划最优性原理,提出了智能车起步过程的经济性车速规划方法,建立了基于速度状态搜索策略;根据Matlab/Simulink和CarSim联合仿真,对比了典型驾驶员速度跟随模式的燃油消耗水平,结果表明,基于动态规划优化后的经济性车速及相应的挡位序列具有良好的节油特性,可为智能车经济驾驶的车速规划及挡位规划提供指导。     

Estimating the ride quality characteristics of vehicles with random decrement analysis of on-the-road vibration response data

This paper describes the application of a practical analytical technique based on the random decrement method to estimate the rigid sprung mass dynamic characteristics (frequency response function) of road vehicles using only vibration response data during constant-speed operation. A brief history and development of the random decrement technique is presented, along with a summary of work undertaken on optimal parameter selection to establish the random decrement signature. Two approaches to estimate the dynamic characteristics from the random decrement signature are described and evaluated. A custom, single-wheeled vehicle (physical quarter car) was commissioned to undertake a series of on-the-road experiments at various nominally constant operating speeds. The vehicle, also instrumented as an inertial profilometer, simultaneously measured the longitudinal pavement profile to establish the vehicle's actual dynamic characteristics during operation. The main outcome of the paper is that the random decrement technique can be used to provide accurate estimates of the sprung mass mode of the vehicle's dynamic characteristics for both linear and nonlinear suspension systems of an idealised vehicle.     

某大跨径双塔单索面矮塔斜拉桥动载试验研究

以某大跨径双塔单索面矮塔斜拉桥为依托工程开展数值仿真分析、动载试验和相关比较分析。分析结果表明:实测主梁前四阶竖向弯曲自振频率均比理论计算值大,结构有一定的刚度储备;实测主梁前四阶振型与计算振型基本吻合,未见明显变异区段;该桥梁的动力特性符合设计要求。在无障碍行车工况下,该桥测试部位的冲击系数均大于计算冲击系数,基本随车速的提高而提高;在制动试验和有障碍行车工况下,该桥测试部位的冲击系数相对较大,表明当桥面不平整时,桥面行车对桥梁结构的冲击效应将明显增大。对于结构基频较小的大跨径矮塔斜拉桥,按《公路桥涵设计通用规范》(JTG D60-2015)对桥梁冲击系数取值偏不安全或安全储备偏小,有待进一步研究和探讨。     

Exploiting floating car data for time-dependent Origin–Destination matrices estimation

The study evaluates the added value generated by estimating dynamic demand matrices by information gathered from Floating Car Data (FCD).

Firstly, adopting a large dataset of FCD collected in Rome, Italy, during May 2010, all the monitored trips on a specific district of the city (Eur district) have been collected and analysed in terms of (i) spatial and temporal distribution; (ii) actual route choices and travel times. The data analysis showed that demand data from FCD are usually not suitable to retrieve directly demand matrices, due to a strong dependence of this information from the penetration rate of the monitoring device. Instead, origin–destination travel times and route choice probabilities from FCD are a much more reliable and powerful information with respect to FCD origin–destination flows, since they represent the traffic conditions and behaviors that vehicles experiment along the path.

Thus, several synthetic experiments have been conducted adopting both travel times and route choice probabilities as additional information, with respect to standard link measurements, in the dynamic demand estimation problem. Results demonstrated the strength and robustness associated to these network based data, while link measurements alone are not able to define the real traffic pattern. Adopting both the information of origin–destination travel times and route choice probabilities during the demand estimation process, the spatial and temporal reliability of the estimated demand matrices consistently increases.