负摩擦力对某高桩码头桩基沉降的影响

介绍某高桩码头斜桩下沉桩帽竖向开裂现象,认为主要原因是斜桩未进入良好持力层、斜桩受负摩擦力作用。提出锤击沉桩对软黏土的触变效应、码头岸坡淤积也会对桩产生负摩擦力,并对淤泥层、砂土层的负摩擦力系数取值作了比较。     

沉降柱试验边界摩擦特性及其对试验结果影响分析

沉降柱试验是进行吹填工程室内试验的一种重要方法,目前沉降柱一般用有机玻璃制成,沉降柱的尺寸也从10cm发展到30cm。但是已有沉降柱试验中对沉降柱试验的边界摩擦问题没有深入的研究。进行了吹填淤泥(纯泥和泥砂混合物两种)与有机玻璃之间边界摩擦试验,分析了边界摩擦对沉降柱试验的影响,并探讨了沉降柱尺寸的确定问题。     

重型越野车泄气可行驶系统设计研究

重型越野车行驶环境恶劣,颠簸的路面和尖锐物体很容易对车轮轮胎造成致命损坏,如果发生爆胎和泄气现象将给行车安全带来隐患。为了解决上述问题,文章对重型越野车泄气可行驶的方法进行了研究,设计了一种适用于重型越野车的泄气可行驶系统,通过对轮胎内支撑体的材料选型和结构设计,合理设计与轮辋配合的结构,使得使用该系统的充气轮胎泄气后,不仅能够保证车辆继续行驶一段距离,而且不影响车辆的行驶性能。通过对该系统进行的相关试验验证,表明该系统性能可靠,可满足泄气可行驶的要求。     

铝合金表面状态对搅拌摩擦焊接头组织和性能的影响

研究了铝合金表面状态对搅拌摩擦焊焊接接头组织和性能的影响。试验结果表明:试板表面油污的存在使得焊接接头强度下降为母材的60%左右,同时显著降低接头的塑性;试板表面的氧化膜和油污还会造成焊核区及焊缝前进侧的残余间混结合线缺陷。对焊接接头拉伸断口进行扫描电镜观察发现:拉伸试样的断口中存在油污和A l2O3的聚集物,这些聚集物会成为拉伸时的裂纹源。断口和力学性能综合分析表明:铝合金表面的油污和氧化膜都会降低搅拌摩擦焊接头的强度和塑性。     

长江阶地粉质黏土相似材料配比试验研究

为确定长江阶地粉质黏土相似材料配比方案,本文研究原材料间配比关系。基于三因素三水平正交试验设计方法,以滑石粉、膨润土、石英砂和水为原料,配置基坑模型试验粉质黏土相似材料,通过剪切试验获取九组配比方案的黏聚力和内摩擦角两个物理力学指标,采用极差法和方差法分析各因素的敏感性与显著性,研究滑石粉、膨润土、石英砂以及水含量对黏聚力和内摩擦角的影响规律。结果表明:极差法与方差法分析结果具有一致性,两种方法能合理判断各因素对考察指标的敏感性与显著性;膨润土掺量虽少,但对粉质黏土的黏聚力有很大程度的影响,其次为滑石粉含量,当滑石粉含量增多时,相似材料黏聚力逐渐增大;滑石粉含量为相似材料内摩擦角的主要控制因素。试验方法和结果可为其他模型试验中土质相似材料的配比提供参考。     

Assessing the impact of cornering losses on the energy consumption of electric city buses

In view of the increasing electrification of public city transport, an accurate energy consumption prediction for Battery Electric Buses (BEBs) is essential. Conventional prediction algorithms do not consider energy losses that occur during turning of the vehicle. This is especially relevant for electric city buses, which have a limited battery capacity and often drive curvy routes.In this paper, the additional energy consumption during steering of a BEB is modeled, measured, and assessed. A nonlinear steady-state cornering model is developed to establish the additional energy losses during cornering. The model includes large steer angles, load transfer, and a Magic Formula tire model. Model results show that both cornering resistance and tire scrub of the rear tires cause additional energy losses during cornering, depending on the corner radius and vehicle velocity.The energy consumption model is validated with full scale vehicle tests and shows an average deviation of 0.8 kW compared to the measurements. Analysis of recorded real-world bus routes reveals that on average these effects constitute 3.1% of the total powertrain energy. The effect is even more significant for routes crossing city centers, reaching values up to 5.8%. In these cases, cornering losses can be significant and should not be neglected in an accurate energy consumption prediction.     

冰雪路面摩擦特性与运营风险管控研究综述

冰雪路面的交通安全问题一直是中国交通行业面对的难题，对冰雪路面运营风险进行智能管控是保障交通安全的有效途径。为了推动冰雪路面智能管控技术的应用，明确研究中的关键问题和未来发展方向，综述了国内外冰雪路面智能管控的相关研究进展。首先，阐述了冰雪对交通带来的影响，揭示了人、车、路三者与交通事故的关系，明确了冰雪路面交通事故的根本诱因是由冰雪导致的路面摩擦特性下降；然后，讨论了冰雪路面的胎-冰-路摩擦机理、影响因素、预估模型及其评价方法；进而，对比分析了路表冰雪状态感知技术的多种原理及其适用性，提出了可以用于智能管控的冰雪感知技术要求；最后，总结归纳了常见的冰雪路面运营的静态、动态风险管控方式，其中静态管控方式包括气象法、历史事故数据法和力学特性法，动态方式包括动力学特性法、交通流特性法和综合风险分析法，综合风险分析法可以表征道路运营风险的多因素动态变化，是未来冰雪路面智能管控的主要方式。     

Ship resistance in random ice field of small ice floes made of the substitute material北大核心CSCD

［Objectives］This study focuses on the feasibility of a ship resistance model test in an ice field of small ice floes made of substitute material in order to reveal the resistance components and thereby provide technical support for the design of ice-going ships. ［Methods ］ Ship resistance test in ice floes made of polypropylene (PP) instead of natural refrigerated ice is conducted. By adjusting the sizes, shapes, numbers of ice floes, the random ice field with a given concentration is generated. The geometric phase transition theory predicts that there exists a critical concentration which divides the random ice field into discrete phase (concentration is less than critical value) and connected phase (concentration is greater than critical value). ［Results］The main components of ice resistance in the discrete phase are open water resistance and ship-ice collision resistance, while ice resistance in the connected phase includes ice friction resistance, open water friction resistance and collision resistance. If the fractal dimension of the random ice field is used to redefine the ice resistance coefficient, it is nearly constant in the trial range (speed 0.3–0.9 m/s) when the concentration is smaller than the critical value. When the concentration is greater than the critical value, the ice friction resistance is inversely proportional to speed. ［Conclusions］Polypropylene can replace frozen ice in the prediction of ice resistance. The pure ice resistance of an ice field is divided into two components: ice resistance arising from collision and ice friction resistance arising from accumulation. © 2022 Journal of Clinical Hepatology. All rights reserved.     

A real-time approach to robust identification of tyre–road friction characteristics on mixed-μ roads

ABSTRACT

The interaction between the tyre and the road is crucial for understanding the dynamic behaviour of a vehicle. The road–tyre friction characteristics play a key role in the design of braking, traction and stability control systems. Thus, in order to have a good performance of vehicle dynamic stability control, real-time estimation of the tyre–road friction coefficient is required. This paper presents a new development of an on-line tyre–road friction parameters estimation methodology and its implementation using both LuGre and Burckhardt tyre–road friction models. The proposed method provides the capability to observe the tyre–road friction coefficient directly using measurable signals in real-time. In the first step of our approach, the recursive least squares is employed to identify the linear parameterisation form of the Burckhardt model. The identified parameters provide, through a T–S fuzzy system, the initial values for the LuGre model. Then, a new LuGre model-based nonlinear least squares parameter estimation algorithm using the proposed static form of the LuGre to obtain the parameters of LuGre model based on recursive nonlinear optimisation of the curve fitting errors is presented. The effectiveness and performance of the algorithm are demonstrated through the real-time model simulations with different longitudinal speeds and different kinds of tyres on various road surface conditions in both Matlab/Carsim environments as well as collected data from real experiments on a commercial trailer.     

轮胎稳态模型的分析综述

轮胎稳态模型描述了轮胎稳态运动过程的纵滑、侧偏特性,可以分为理论模型、经验模型和半经验模型.常用的理论模型包括线性模型、UA模型、Dugoff模型、刷子模型和LuGre模型;常用的经验模型包括多项式模型、Burckhardt模型、K-D模型和LC模型;常用的半经验模型包括魔术公式模型和UniTire模型.通过仿真分析,对各种模型描述轮胎运动状态的能力、复杂性、准确性和适用范围进行了比较和研究,对各种模型存在的局限性进行了分析,可为轮胎稳态特性分析和汽车控制系统设计选择轮胎模型提供依据.