山区双车道公路驾驶员疲劳特性研究

山区双车道公路由于地形条件限制线形复杂多变,山体及路侧植被遮挡视线的现象时有发生,增加了驾驶操作的难度和强度.导致驾驶操作频繁、精神紧张.长时间高强度、大负荷的驾驶操作极易产生驾驶疲劳,进而发生交通事故.因此,研究山区双车道公路驾驶员的驾驶疲劳特性,可为山区公路的交通安全设计和管理提供参考,预防交通事故,保证人车安全.     

基于客观测度与主观估算的出行疲劳研究

出行舒适度是影响交通方式选择的要素之一,但由于缺少合理的量化方法,其评价长期停滞于定性描述,难以科学反映不同交通方式的服务水平差异。就典型出行环节进行疲劳测定实验,采集不同情况下出行者在单位时间内的客观体能消耗及其对出行疲劳的主观感受;采用自由模量幅度估计估算出行疲劳的主观感受,并与客观体能消耗进行对比。结果显示,车辆行进方式、乘车姿势、乘客负重、车内拥挤程度等均对体能消耗有显著影响,且客观体能消耗与主观感受之间存在显著差异。最后,利用实验结果以北京市和中山市为例进行案例分析,结果表明,在交通方式选择过程中,体能消耗对出行者产生的影响不亚于出行时耗。     

大型C型独立液货罐Y型接头疲劳强度评估

随着C型独立液货罐的新技术发展,目前在工业界推出了采用双体罐和三体罐构造形式的新颖大型C型独立液货罐。由于双体罐和三体罐构造的要求,在相邻罐体连接处设有Y型接头。该Y型接头位置处由于结构件交汇,构造复杂、应力集中,在船舶运动、蒸汽压力变化,以及温度变化的动载作用下有可能发生疲劳损伤。本文对新颖大型C型独立液货罐Y型接头疲劳强度评估方法的规范技术要求及制定开展了深入详尽的研究,包括对C型独立液货罐疲劳损伤计算工况择取,液货内部动压力计算公式推导,蒸气压力、温度变化等低周疲劳载荷模式确定等,创新提出一整套基于热点应力的C型独立液货罐Y型接头的疲劳损伤评估方法的规范实施要求。进一步地,还推导了基于一般实际情况假设下的C型独立液货罐Y型接头疲劳评估筛分准则,并应用本文上述研究成果和结论,进行了双体和三体罐Y型接头疲劳评估和筛分准则的应用与验证。     

宽浅河道低水头水电枢纽口门区通航水流条件研究

根据重力相似准则,采用比尺为1∶100的整体模型,进行某宽浅河道低水头水电枢纽口门区的通航安全性研究。采用ADV三维流速测量系统进行流速测量;采用标准矩形量水堰控制模型流量;采用差动式尾门调节模型水位。由于河道地形及枢纽布置的原因,上游口门区流速过大,下游口门区形成大范围回流。通过扩大河道过流面积,移除下游河道中心连续小岛,增加闸孔等措施,减小下泄水流流速,改善河道整体水流状态;通过加长导航墙,改变导航墙透水面积,优化口门区域地形等措施极大地改善了船闸上下游引航道及口门区通航水流条件,确保过闸船舶的安全。     

CFRP加固损伤钢板的拉伸及疲劳性能研究

文章基于Dugdale模型理论提出CFRP加固含裂纹钢板加固量的计算方法。通过虚拟裂纹闭合法建立模型来模拟塑性钢板的破坏过程,并完成相关试验,验证了CFRP加固含裂纹钢板有效粘贴长度、有效粘贴宽度取值的有效性。同时利用Paris公式预估疲劳寿命,并结合相关试验数据,探究了CFRP加固对含裂纹钢板疲劳寿命的提高作用。研究表明,有效粘贴长度、有效粘贴宽度的理论取值有效;通过CFRP双侧加固竖裂纹、斜裂纹钢板构件可分别使其疲劳寿命得到显著提高。     

钛合金疲劳小裂纹扩展行为预报方法研究

针对小裂纹扩展阶段裂纹尖端塑性区域尺寸相对于小裂纹长度是不可忽略的问题,在考虑小裂纹效应裂纹扩展速率修正模型基础上,对该模型中裂纹尺寸进行修正,即裂纹长度等于真实裂纹长度加上平面应变状态下裂纹尖端塑性区域一半;并利用修正后的模型对钛合金材料不同情况下疲劳小裂纹扩展速率和寿命进行预报,同时将预报结果与试验值比较.结果表明:修正后的预报模型对小裂纹扩展速率和寿命均有很好的预报效果.     

海上风机支撑结构的时域和频域疲劳对比研究

对海上风机支撑结构进行动力响应分析,求出结构危险节点的载荷谱和功率谱密度函数,结合疲劳损伤模型和Dirlik概率模型,分别在时域和频域内对支撑结构进行疲劳寿命分析.由于时域法计算疲劳寿命需进行应力循环计数,这一过程需处理的数据庞大,耗时长.频域法省去应力循环计数,代之以概率密度函数,可相对准确、快速地计算结构的疲劳寿命.分析结果表明,采用Dirlik概率模型的频域分析法能较准确地反映海上风机支撑结构在随机载荷作用下的疲劳损伤情况,计算结果误差在可接受范围内.     

Environmental impacts of public transport systems using real-time control method

Public Transport (PT) systems rely more and more on online information extracted from both operator’s intelligent equipment and user’s smartphone applications. This allows for a better fit between supply and demand of the multimodal PT system, especially through the use of PT real-time control actions/tactics. In doing so there is also an opportunity to consider environmental-related issues to approach energy saving and reduced pollution. This study investigates and analyses the benefits of using real-time PT operational tactics in reducing the undesirable environmental impacts. A tactic-based control (TBC) optimization model is used to minimize total passenger travel time and maximize direct transfers (without waiting). The model consists of a control policy built upon a combination of three tactics: holding, skip-stops, and boarding limit. The environmental-related measure is the global warming potential (GWP) using the life cycle assessment technique. The methodology developed is applied to a real life case study in Auckland, New Zealand. Results show that TBC could reduce the GWP by means of reduction of total passenger travel times and vehicle travel cycle time. That is, the TBC model results in a 5.6% reduction in total GWP per day compared with an existing no-tactic scenario. This study supports the use of real-time control actions to maintain a reliable PT service, reducing greenhouse gas emissions and subsequently moving towards greener PT systems.     

Electric vehicles for greenhouse gas reduction in China: A cost-effectiveness analysis

There have been ongoing debates over whether battery electric vehicles contribute to reducing greenhouse gas emissions in China’s context, and if yes, whether the greenhouse gas emissions reduction compensates the cost increment. This study informs such debate by examining the life-cycle cost and greenhouse gas emissions of conventional vehicles, hybrid electric vehicles and battery electric vehicles, and comparing their cost-effectiveness for reducing greenhouse gas emissions. The results indicate that under a wide range of vehicle and driving configurations (range capacity, vehicle use intensity, etc.), battery electric vehicles contribute to reducing greenhouse gas emissions compared with conventional vehicles, although their current cost-effectiveness is not comparable with hybrid electric vehicles. Driven by grid mix optimization, power generation efficiency improvement, and battery cost reduction, the cost-effectiveness of battery electric vehicles is expected to improve significantly over the coming decade and surpass hybrid electric vehicles. However, considerable uncertainty exists due to the potential impacts from factors such as gasoline price. Based on the analysis, it is recommended that the deployment of battery electric vehicles should be prioritized in intensively-used fleets such as taxis to realize high cost-effectiveness. Technology improvements both in terms of power generation and vehicle electrification are essential in improving the cost-effectiveness of battery electric vehicles.     

考虑残余应力效应的深潜器耐压壳体疲劳研究

本文考虑焊接残余应力的影响,给出包含裂纹萌生和裂纹扩展全过程的载人深潜器耐压球壳疲劳寿命预报方法,分别基于局部应力-应变法和能计及负应力比效应的裂纹扩展单一曲线模型预报了耐压球壳的工艺疲劳寿命和使用疲劳寿命,研究焊接残余应力大小对球壳疲劳寿命的影响。结果表明,忽略拉伸残余应力的影响将导致疲劳寿命预测结果偏于危险;耐压球壳整体受压时,拉伸残余应力使得球壳局部区域承受拉-压循环载荷,计算使用疲劳寿命过程中须考虑其影响;降低拉伸残余应力可有效提高耐压球壳的疲劳寿命。