双级套管螺纹连接有限元分析

应用ANSYS对双级套管螺纹连接进行性能仿真，建立双级套管螺纹有限元模型，利用接触分析模块，分析螺纹各扣牙受力情况，最后总结了双级套管螺纹连接受力分布规律，并与普通套管螺纹接头作了比较，结果显示双级套管螺纹接头各扣牙受力分布要比普通套管螺纹均匀。研究结果提高了对双级套管接头应力水平的认识，对改进套管连接螺纹设计，提高套管接头的连接质量，促进特殊套管螺纹接头的发展具有一定的参考价值。     

P110长圆螺纹套管粘扣原因分析

某厂生产的规格为Φ139.70 mm×9.17 mm LC P110套管在进行上/卸扣试验过程中发生严重粘扣现象。根据套管螺纹粘扣形貌、螺纹参数、表面处理工艺等,对其粘扣原因进行分析。分析可知,该批套管外螺纹锥度偏大、内螺纹锥度偏小、内外螺纹的紧密距均偏小、螺纹参数配合不当是发生粘扣现象的原因之一;经过上卸扣后,套管内螺纹磷化层大部分脱落,这说明套管磷化层厚度不够,表面处理工艺差。     

膨胀式燃气管道封堵装置研究

文中研制了一种新型的膨胀式燃气管道封堵装置，利用机械传动驱动偏心轮对封堵橡胶盘轴向施压，使其发生径向膨胀并与管壁紧密接触，从而实现可靠的管道封堵。在DN200管道的封堵仿真和现场实验表明，封堵装置操作方便，操作扭矩小于13 Nm,封堵装置与管壁接触压力超过0.4 MPa的封堵带达到7道，实现了对0.4 MPa燃气管道的可靠封堵。     

环向集中力作用管道的变分法受力分析

轴向压入式管道连接是基于材料在过盈配合作用下产生弹塑性变形的基本原理实现相互连接或密封的技术。文中根据设计的管接头,建立其结构的力学模型。利用变分法原理计算管接头在受到环向集中力作用时管道的径向位移,并与弹性力学中薄壁圆筒受环向集中力时简化计算公式的计算数据进行比较。数据对比表明：利用Rayleigh－Ritz变分法计算圆筒模型的管道变形时,其数据经过校正后满足密封性能要求,具有工程实用性。     

高温大直径管道的应力影响分析

高温大直径薄壁管道由于受到径向膨胀的影响,管道易发生塑性变形、泄漏等管道破坏情况。小直径管道的常规应力计算,则对径向膨胀忽略不计。为了解决径向膨胀引起高温大直径管道塑性变形等问题,通过对催化烟气管道的应力模拟与分析,探讨在节点和补偿器建模因素影响下,高温大直径管道应力的变化。结果表明:对于高温大直径薄壁管道,当采用管壁节点时径向膨胀对管道应力的影响较大;当采用复杂补偿器模型时管道节点的位移和约束力改变较大。最后通过数据分析得出采用管壁节点约束可模拟管道径向膨胀和复杂补偿器模型可优化管道应力分析,为高温大直径管道的应力模拟提供参考。     

800kV组合电器用万向力平衡补偿器

高压输变电设备是电力工业的技术基础,而研制结构和性能优异的800kV组合电器用补偿器又是实现高压输变电设备国产化的关键.文中主要针对800kV封闭式组合电器用补偿器进行探讨,设计了万向力平衡式波纹补偿器.它是一种新型的压力平衡型补偿器,它不仅能同时进行轴向和径向补偿,而且能很好地降低补偿器的轴向推力.尤其是当既有轴向又...     

大型沉管隧道管节接头刚度特性研究

沉管隧道管节接头具有调节沉管隧道受力性能以及适应隧道不均匀变形的功能,在隧道运营中起着非常重要的作用。文章以港珠澳沉管隧道管节接头为研究对象,建立了管节接头刚度的三维非线性有限元计算模型,对管节接头的受力变形特征进行了分析,分别得到了管节接头轴向压缩刚度、弯曲刚度与轴向压缩荷载、压缩弯矩之间的变化规律。结果表明:轴向压缩刚度随轴向压缩荷载增大而增大;轴向弯曲刚度随轴向荷载增大而增大,但在相同轴压下,弯曲刚度随弯矩增大而减小。此外,结合管节接头模型试验进一步研究了管节接头轴向压缩刚度和弯曲刚度的变化规律及影响因素,并对比分析了有限元计算结果与模型试验结果,模型试验得出的接头刚度变化规律与有限元模拟结果一致。研究得到的管节刚度对沉管隧道整体计算研究具有重要参考意义。     

异形孔水包爆破数值模拟及现场试验北大核心CSCD

为了提高隧道光面爆破效果,提出异形孔水包爆破技术。以径向不耦合装药和间隔装药的岩石损伤、径向和轴向的爆破效率、径向孔壁压力和现场周边孔炮痕率、岩石破碎情况、隧道超欠挖情况为依据,分析其爆破效果。结果表明:(1)径向不耦合系数的改变对轴、径向爆破效果有影响,间隔装药系数的改变仅对轴向和孔间爆破效果有影响;(2)当K_(d)=1.25时,岩石破坏区集中发生在炸药孔间内,岩石轴向破坏区较小,当K_(d)=1.75时,过量水包出现耗能现象,岩石破坏区较小;(3)异形孔水包爆破技术能产生光滑的隧道开挖轮廓线,渣石更破碎,K_(r)=1.5和K_(d)=1.5为其最优装药系数。     

膨胀岩土地层盾构隧道结构力学行为研究

文章在提出膨胀接触压力概念的基础上,采用接触单元对膨胀接触压力和膨胀力的关系进行了研究,得出了膨胀接触压力与膨胀岩土分布、厚度、结构及地层刚度等的关系;同时对膨胀岩土地层中盾构隧道"荷载-结构"模式外荷载及"梁-弹簧"模型的特点进行了分析;并将其分析结果直接应用到成都地铁2号线膨胀岩土地层盾构隧道的结构分析中,得出了盾构隧道在不同膨胀岩土层、膨胀力、埋深和拼装方式条件下的结构内力值,对隧道结构设计起到了指导作用。     

埋地热油管道正向预热过程的计算与分析

埋地热油管道预热过程是一个不稳定传热过程,埋地热油管道启输过程的土壤温度场是一个沿管道横断面（径向和切向）与轴向的三维非稳态传热问题。通过分析埋地热油管道的几何特性,考虑了沿轴向预热介质温降对土壤温度变化的影响,对埋地热油管线正常运行和正向预热过程时的数学模型进行了适当的简化和处理,并且对正向预热时土壤蓄热量进行了计算,还利用数值计算的方法进行了求解,得到了油温在轴向和径向上的变化规律,在求解数学模型时,对某一断面处的土壤部分的温度场应用有限差分法求解。     

圆锥螺纹测量成像方法

对圆锥螺纹的透射成像方法进行了实验研究和理论分析。透射成像法是将螺纹放在平行光场中以得到清晰的螺纹牙形图像，并用CCD摄像机采集到计算机内部，可用于进一步的尺寸测量。在透射成像时，螺旋线对投影螺纹牙会造成一定的遮挡。可以通过旋转螺纹轴线，使螺旋线的切线与光轴平行的方法消除，但是引入了螺纹牙的投影误差。经过分析，由此产生的投影误差可以忽略。     

剥肋滚压直螺纹套筒钢筋机械现场质量控制方法

文章介绍剥肋滚压直螺纹套筒钢筋机械连接技术,通过实验发现引起钢筋机械接头不合规范的四种因素,并提出通过检验每个套筒尺寸、控制每个钢筋丝头尺寸、检验拧紧力矩、成品检验的四因素检验控制方法来保障该技术现场施工质量。     

Market mechanism design for profitable on-demand transport services

On-demand transport services in the form of dial-a-ride and taxis are crucial parts of the transport infrastructure in all major cities. However, not all on-demand transport services are equal: not-for-profit dial-a-ride services with coordinated drivers significantly differ from profit-motivated taxi services with uncoordinated drivers. In fact, there are two key threads of work on efficient scheduling, routing, and pricing for passengers: dial-a-ride services; and taxi services. Unfortunately, there has been only limited development of algorithms for joint optimization of scheduling, routing, and pricing; largely due to the widespread assumption of fixed pricing. In this paper, we introduce another thread: profit-motivated on-demand transport services with coordinated drivers. To maximize provider profits and the efficiency of the service, we propose a new market mechanism for this new thread of on-demand transport services, where passengers negotiate with the service provider. In contrast to previous work, our mechanism jointly optimizes scheduling, routing, and pricing. Ultimately, we demonstrate that our approach can lead to higher profits and reduced passenger prices, compared with standard fixed price approaches, while also improving efficiency.     

基于法兰联接系统松弛特性的多锥面法兰研究

文中针对现有普通法兰联接系统的应力松弛特性问题,设计了一种新型多锥面法兰,通过对法兰联接系统结构上的改进,去掉了原有法兰连接系统的垫片,明显减少了法兰连接系统的应力松弛,并通过法兰多锥面配合联接和法兰螺纹联接,增强了法兰联接的联接刚度,进一步减小了法兰连接系统的蠕变松弛,改进了法兰联接性能。实验测定和实际应用证明：该新型多锥面法兰可以有效减小法兰联接系统的应力松弛,防止法兰联接失效。     

Evaluating sustainability of supply chains by two-stage range directional measure in the presence of negative data

Assessing sustainability of supply chains is a critical and increasingly complex problem. In recent years sustainability has received more attention in supply chain management (SCM) literature with triple bottom lines including social, environmental, and economic factors. Conventional data envelopment analysis (DEA) models consider decision making units (DMUs) as black boxes that consume a set of inputs to produce a set of outputs and do not take into consideration internal interactions of DMUs. Two-stage DEA models deal with such DMUs. However, existing two-stage DEA models are applicable only in technologies characterized by positive inputs/outputs. This paper aims to build and present a new two-stage DEA model considering negative input-intermediate-output data. Some numerical examples along with some theorems and properties are given to show capability of proposed method. The proposed ideas are used in a case study where 29 Iranian supply chains producing equipment of expendable medical devices are evaluated in terms of sustainability.     

油管螺纹图像处理方法研究

油管螺纹图像主要用于对螺纹形貌的观察和测量。对螺纹图像采用了低通滤波、对比度变换、高通滤波等处理方法,有效地改善了图像的质量。用于尺寸测量的螺纹牙型图像根据其直方图的特征,首先采用灰度阈值分割法分离牙型轮廓,生成二值图像,然后利用跨度最小的Roberts算子提取二值图中螺纹轮廓线,得到的轮廓边缘细致、准确,可以用于尺寸测量。     

A new strategy for minimum usage of external yaw moment in vehicle dynamic control system

Due to the loss of vehicle directional stability in emergency maneuvers, a new complete desired model for vehicle handling based on the linear two-degrees-of-freedom (2DOF) model and tire/road conditions is presented to be tracked by the direct yaw moment control (DYC) system. In order to maintain the vehicle actual motions, yaw rate and side-slip angle, close to the proposed desired responses without excessively large external yaw moment, a complete linear quadratic (LQ) optimal problem is formulated and its analytical solution is obtained. Here, the derived control law is evaluated and its different versions are discussed. It is shown that the side-slip tracking by DYC is more effective than the yaw rate control to stabilize vehicle motions in nonlinear regimes. Also, optimal property of the control law provides the possibility of reducing the external yaw moment as low as possible, at the cost of some admissible tracking errors. Simulation studies of vehicle handling, with and without control, have been conducted using a full nonlinear vehicle dynamic model. The results, obtained during various maneuvers, indicate that when the proposed optimal controller is engaged with the model, improvements in the handling performance through a reduced external yaw moment can be acquired.     

Large-scale dynamic transportation network simulation: A space-time-event parallel computing approach

This paper describes a computationally efficient parallel-computing framework for mesoscopic transportation simulation on large-scale networks. By introducing an overall data structure for mesoscopic dynamic transportation simulation, we discuss a set of implementation issues for enabling flexible parallel computing on a multi-core shared memory architecture. First, we embed an event-based simulation logic to implement a simplified kinematic wave model and reduce simulation overhead. Second, we present a space-time-event computing framework to decompose simulation steps to reduce communication overhead in parallel execution and an OpenMP-based space-time-processor implementation method that is used to automate task partition tasks. According to the spatial and temporal attributes, various types of simulation events are mapped to independent logical processes that can concurrently execute their procedures while maintaining good load balance. We propose a synchronous space-parallel simulation strategy to dynamically assign the logical processes to different threads. The proposed method is then applied to simulate large-scale, real-world networks to examine the computational efficiency under different numbers of CPU threads. Numerical experiments demonstrate that the implemented parallel computing algorithm can significantly improve the computational efficiency and it can reach up to a speedup of 10 on a workstation with 32 computing threads.     

The key principles of optimal train control—Part 1: Formulation of the model,strategies of optimal type,evolutionary lines,location of optimal switching points

We discuss the problem of finding an energy-efficient driving strategy for a train journey on an undulating track with steep grades subject to a maximum prescribed journey time. We review the state-of-the-art and establish the key principles of optimal train control for a general model with continuous control. The model with discrete control is not considered. We assume only that the tractive and braking control forces are bounded by non-increasing speed-dependent magnitude constraints and that the rate of energy dissipation from frictional resistance is given by a non-negative strictly convex function of speed. Partial cost recovery from regenerative braking is allowed. The cost of the strategy is the mechanical energy required to drive the train. Minimising the mechanical energy is an effective way of reducing the fuel or electrical energy used by the traction system. The paper is presented in two parts. In Part 1 we discuss formulation of the model, determine the characteristic optimal control modes, study allowable control transitions, establish the existence of optimal switching points and consider optimal strategies with speed limits. We find algebraic formulae for the adjoint variables in terms of speed on track with piecewise-constant gradient and draw phase plots of the associated optimal evolutionary lines for the state and adjoint variables. In Part 2 we will establish important integral forms of the necessary conditions for optimal switching, find general bounds on the positions of the optimal switching points, justify the local energy minimization principle and show how these ideas are used to calculate optimal switching points. We will prove that an optimal strategy always exists and use a perturbation analysis to show the strategy is unique. Finally we will discuss computational techniques in realistic examples with steep gradients and describe typical optimal strategies for a complete journey.