共查询到19条相似文献,搜索用时 171 毫秒
1.
2.
3.
为了研究腐蚀缺陷影响下燃气管道运行的应力集中现象,防止管道应力过大而失效,采用有限元方法分析了不同腐蚀深度和腐蚀直径下,管道的应力分布状况.结果表明:在腐蚀深度一定时,腐蚀直径增大应力集中现象逐渐减弱,呈反比趋势;当腐蚀直径一定时,腐蚀深度对管道应力影响较大,是导致管道失效的主要因素.管道防护可通过在缺陷周围焊上补强圈... 相似文献
4.
《现代隧道技术》2020,(4)
为了研究盾构隧道管片接缝密封垫设计参数,文章通过统计数据分析了盾构隧道管片接缝密封垫材质、断面形式、孔洞排布方式等设计现状。基于统计样本以密封垫底边长度为控制变量,对密封垫外轮廓参数进行了线性回归分析。采用数值模拟方法从密封垫闭合孔排数、闭合孔孔型、不同部位开孔率变化等方面分析了几何参数对密封垫防水设计的影响。参考我国相关规范推荐的橡胶硬度范围,分析了橡胶硬度参数对密封垫防水设计的影响。结果表明:盾构隧道管片接缝密封垫闭合孔采用双排孔形式防水效果最好;对孔布置形式能提供更好的防水效果;完全闭合压缩力、垫间平均接触压力均与开孔率呈负相关;橡胶邵尔硬度在60~70度范围内时,垫间平均接触压力与垫砼间平均接触压力均与橡胶硬度呈现线性正相关。 相似文献
5.
由于承受管道载荷的压力容器切向接管结构无法按照常规的设计方法进行开孔补强计算,文中以1台带切向接管的压力容器为例,对筒体与切向接管连接区域进行三维有限元分析,得到了筒体与接管连接区域详细的应力分布。应力分布云图表明:在连接区域产生明显的应力集中,应力强度最大值发生在筒体与接管连接处的外侧,是该结构失效的危险区域。根据JB4732-1995《钢制压力容器—分析设计标准》(2005年确认版)的规定,对该连接区域进行了强度评定,评定结果表明该设备的结构尺寸完全满足强度要求,为进行详细工程设计提供了理论依据。 相似文献
6.
(接上期) 4.1开孔 在对施工作业的管段两端分别开出一个孔是为封堵头塞入管道内进行截堵介质和介质通过这个孔从设置的临时旁路上流通之用. 安装开孔机,开孔机的连接盘与支架上的连接器连接并密封,开启支架上扇形阀,操纵开孔机将开孔刀上的中心钻伸抵管顶就可开始开孔.开孔时,顺时针转动操纵手柄,驱动钻杆旋转,钻杆上装有一对差动内外齿轮,外齿轮的内孔上车有T型螺牙,螺牙又与固定在钻杆上的螺套啮合.带T牙的外齿轮置放在机壳内只作旋转运动,钻杆旋转时通过差动齿轮驱动固定在钻杆上的螺套,从而使钻杆在旋转的同时又作轴向差动移动,开孔刀实现切削开孔.钻杆旋转一周刀具切削进给Xmm,当更换差动齿轮的齿数比时可实现不同的差动进给量. 相似文献
7.
8.
《现代隧道技术》2017,(4)
开孔隔墙隧道是一种新型的高速铁路隧道结构型式,与传统结构隧道比较,列车通过时空气动力学性能有较大不同。文章基于一维可压缩非定常不等熵流动模型及广义黎曼变量特征线法,建立了隧道内列车运行空气阻力分析方法,模拟了不同长度的有开孔隔墙隧道和无隔墙隧道空气阻力最大值和空气阻力平均值的变化规律,得出隔墙隧道可较大幅度地降低空气阻力,速度一定时隧道长度对内置开孔隔墙空气阻力幅值没有影响的结论。文章研究了2 000 m长度内置隔墙隧道的开孔间距、开孔大小和列车运行速度对空气阻力的影响特性,初步探讨了高速列车通过内置开孔隔墙隧道产生空气阻力与压缩波和膨胀波的关系及空气阻力最大值和车速的关系,为今后进一步研究内置开孔隔墙隧道列车空气阻力和该类结构隧道的工程应用提供了一定的基础。 相似文献
9.
10.
软弱围岩的流变效应容易导致隧道二次衬砌开裂,影响结构的安全性和耐久性.因此,文章以广甘高速杜家山隧道为例,建立考虑Weibull损伤分布的混凝土数值计算模型,对流变荷载作用下二次衬砌的损伤演化行为进行了研究.结果表明:(1)若二次衬砌与围岩接触良好,衬砌损伤区域在侧压力系数λ为0.5,1,2时,分别分布在拱腰、拱脚以及... 相似文献
11.
12.
13.
14.
15.
Non-exhaust particle (NEP) emissions from road traffic contribute significantly to Particulate Matter (PM) pollution in urban areas. The primary objective herein is to develop the knowledge required to move toward more sustainable mobility. NEP emissions are studied by means of complementary experiments on chassis dynamometers, on test tracks and at the roadside. Laboratory tests demonstrate that brake wear particles (BWP) emissions can change with braking force and frequency. A brake pad temperature threshold exists, above which the rate of ultrafine particle emissions is quite high. Below this threshold, the BWP emissions are dominant in the accumulation and coarse modes. Test track measurements have demonstrated that tire-road contact particle (TRCP) emissions considerably modify the atmospheric PM background especially for the supermicron fraction. Their number size distribution highlighted an ultrafine and accumulation modes centered at about 40 nm and 200 nm, respectively. The TRCP level increases with vehicle speed and during the acceleration and deceleration phases. Roadside measurements in the urban environment confirm the presence of NEP in significant proportions, in both the accumulation and coarse modes. The chemical composition of NEP differs depending on the size mode: BWP mainly stem from the degradation of brake pad lining materials, while TRCP are a mixture of tire tread wear and re-suspended dust. The presence of Fe-rich particles nevertheless serves as a good indicator of the NEP contribution to PM at the roadside. Lastly, in considering the parameters influencing NEP emissions, a series of recommendations are offered in order to achieve a more sustainable mobility. 相似文献
16.
17.
隔离式道床垫作为一种新型的轨道减振产品,近年来,在国铁和城市轨道交通建设中得到了广泛的应用。本文通过建立隔离式减振垫的有限元模型,研究其固有频率和动力学响应,分析隔离式道床垫的减振性能,为实现减振轨道结构的合理选用提供参考。 相似文献
18.
本文对深圳地铁2号线轨道减振降噪技术的应用情况进行了详细的介绍。其中,对国内地铁无碴轨道上首次试铺应用的隔离式减振垫轨道技术的减振原理、设计方案、施工方法及减振效果实测等进行了分析和探讨。通过实测,隔离式减振垫轨道结构的减振效果满足设计理论分析的要求。 相似文献
19.
Antoine Frémont 《运输评论》2013,33(4):537-554
Abstract It has been acknowledged that logistics is a driving force that shapes the integration of the transport chain. This paper argues that while the liner shipping industry exhibits increased horizontal integration, its vertical integration remains limited. A clear distinction is drawn between freight logistics, container logistics and vessel logistics. Freight logistics is defined as part of the supply chain process, the focus of which is the goods being transported. The purpose of container logistics is to optimize the movements of the containers themselves, an operation that is directly related to vessel logistics which is concerned with maximizing vessel utilization. The paper demonstrates that shipping lines have to find the correct balance between these three types of logistics. Their interest in vertical integration is primarily because the management of container logistics provides direct support to vessel logistics. Their involvement in freight logistics remains unclear and uncertain. 相似文献