Analysis of mechanical strengths of extreme line casing joint considering geometric, material, and contact nonlinearities

To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.

基于TLE数据的大气密度反演与校正

用于航天器轨道预报的热层密度模型普遍存在30%左右的误差,影响LEO卫星的精密轨道确定和载荷控制。基于低轨航天器平运动变化与大气密度的关系,使用GRACE(gravity recovery and climate experiment)卫星TLE数据反演2003、2007年沿轨大气密度,通过比较反演值、模型值和实测值的关系分析误差产生原因,使用对数正态分布拟合密度比值。通过分析太阳辐射、地磁指数对大气密度变化的影响,提出一种基于空间环境指数的热层大气密度模型校正与预报方式。使用该方法对2003、2004、2007、2008年的MSIS86模型计算密度进行修正,将模型平均相对误差从33.33%~59.62%降低到11.55%~15.13%,太阳活动低年改进量是高年的1.5~2倍。对2009年经验模型结果进行预报校正,将预报误差降低36.49%,提高了模型精度。

Simulation and Experimental Study of Staple Line Reinforcement Surgery

The aim of this study was to evaluate the effectiveness of BM (basement membrane) and SIS (small intestine submucosa) composite extracellular matrix staple line reinforcement in surgical procedures through finite element modelling simulations and leak-proof performance experiments. The mechanical analyses of soft tissues with and without staple line reinforcement were performed by establishing finite element models of three tissues, namely, stomach, intestine and lungs, under the use scenarios of different anastomosis staple models;and the leak-proof performance of the staple line reinforcement was evaluated by simulating leak-proof experiments of gastric incision margins, intestinal sections, and lung incision margins in vitro. The results showed that the equivalent average stresses of the staple line reinforcement were increased by 20 kPa-68 kPa in gastric and intestinal tissues, and 8 kPa-22 kPa in lung tissues. and that the BM and SIS composite extracellular matrix staple line reinforcement could strengthen the anastomotic structure, and at the same time disperse the high stresses of the anastomosed tissues, which could effectively reduce the postoperative complications such as anastomotic bleeding and anastomotic leakage, and provide a safer and more effective optimized design for surgical mechanical anastomosis. It can effectively reduce postoperative complications such as anastomotic bleeding and anastomotic leakage, and provide a safer and more effective optimized design for surgical mechanical anastomosis.

基于TLE双行根数的航天器机动检测方法

由于不同功能的航天器承担的任务不尽相同、轨道亦不相同等原因,航天器不时需要变轨机动以确保完成任务.对于非合作航天器,其可能的变轨信息预先未知且难以预测,故需要准确快速判断航天器的变轨事件,以及时调整轨道探测策略.由于美国公布的双行根数具有来源稳定、更新频率快和容易获取等特点,本文结合航天器轨道动力学及变轨控制的特点,提出了基于TLE双行根数的航天器变轨机动检测方法,通过检测半长轴的变化量和相对距离最小值实现了在轨航天器轨道面内机动的检测.以METOP-A1和IRNSS 1G两个航天器在2019年6-9月的TLE根数为例,说明使用该方法开展机动检测的操作流程和步骤.同时大量仿真计算结果表明,该方法能够有效解决航天器在轨运行过程中面内机动时间和半长轴改变量的检测以及多次变轨识别的问题,检测精度与TLE根数自身精度及机动量大小相关.

Reduction of electric field strength by two species of trees under power transmission lines

Electrical pollution is a worldwide concern,because it is potentially harmful to human health.Trees not only play a significant role in moderating the climate,but also can be used as shields against electrical pollution.Shielding effects on the electric field strength under transmission lines by two tree species,Populus alba and Larix gmelinii,were examined in this study.The electrical resistivity at different heights of trees was measured using a PiCUS sonic tomograph,which can image the electrical impedance for trees.The electric field strength around the trees was measured with an elf field strength measurement system,HI-3604,and combined with tree resistivity to develop a model for calculating the electric field intensity around trees using the finite element method.In addition,the feasibility of the finite element method was confirmed by comparing the calculated results and experimental data.The results showed that the trees did reduce the electric field strength.The electric field intensity was reduced by 95.6%,and P.alba was better than L.gmelinii at shielding.

Multi-transmission Lines Loaded by Linear and Nonlinear Lumped Elements： FDTD Approach

In this paper, we are interested on studying the Multi-transmission Lines, the analysis is ensured by the FDTD （finite difference temporal domain） method combined with the ABC （absorbing boundary conditions） to predict the current and voltage behavior resulting from the electromagnetic fields all along lines. Simulated results will be compared to commercial software to validate the proposed algorithm.

Effect of rock joints on lined rock caverns subjected to high internal gaspressure

The storage of hydrogen gas in lined rock caverns(LRCs)may enable the implementation of the firstlarge-scale fossil-free steelmaking process in Sweden,but filling such storage causes joints in the rockmass to open,concentrating strains in the lining.The structural interaction between the LRC componentsmust be able to reduce the strain concentration in the sealing steel lining;however,this interaction iscomplex and difficult to predict with analytical methods.In this paper,the strain concentration in LRCsfrom the opening of rock joints is studied using finite element(FE)analyses,where the large-and small-scale deformation behaviors of the LRC are coupled.The model also includes concrete crack initiation anddevelopment with increasing gas pressure and rock joint width.The interaction between the jointed rockmass and the reinforced concrete,the sliding layer,and the steel lining is demonstrated.The results showthat the rock mass quality and the spacing of the rock joints have the greatest influence on the straindistributions in the steel lining.The largest effect of rock joints on the maximum strains in the steellining was observed for geological conditions of“good”quality rock masses.

课程思政视角下校企合作课程“施工组织与管理”教学改革实践

为落实全国高校思想政治工作会议精神,响应“思政教育落实到每一节课”的号召,全面推进大思政课建设的工作;在课程思政视角下,以高职院校工程类专业群中“顶层互选”的校企合作课程“施工组织与管理”为例,从课程思政元素挖掘方法、课程思政元素渗入模式、解析思政元素融入专业课程案例等方面入手,对思政元素有效融入课程教学过程进行研究和实践,实现全员全程全方位育人,保证学生的专业知识学习与思政教育同步同向同行。

基于振动台试验的鱼线固定梅瓶文物响应规律性研究

为了探索鱼线固定梅瓶文物在实际博物馆的地震响应以及抗震效果,首先选取了典型梅瓶文物,并在三层钢筋混凝土框架结构中开展了24种地震工况的振动台试验,然后建立了上述试验所用梅瓶文物的有限元模型,验证了有限元模型的准确性,最后采用增量动力分析法分析了该文物在两种常见直径鱼线保护措施下的运动响应。结果表明:鱼线固定梅瓶文物在地震作用下会产生滑移、摇摆、倾覆以及鱼线断裂等现象;不同楼层下的文物响应差别较大,尤其在大震作用下,高楼层的鱼线固定梅瓶文物易发生倾覆和鱼线断裂破坏,要重视高楼层文物的震前保护措施;在较强的地震作用下,仅依靠增大鱼线直径有时对控制文物的倾覆情况起不到关键性决定作用,需要进一步采取其它措施对文物进行保护。

基于格宾石笼的隧道支护构件静力加载模型试验设计

尽管格宾石笼在边坡、护岸工程、路基加固等工程中已有了一定的应用,但鲜有研究提及格宾石笼在隧道支护中的应用。由于格宾石笼具有一定的承载力和良好的变形适应能力,在应对隧道围岩大变形和高地应力等方面具有一定应用前景,因此,对基于格宾石笼的隧道支护构件静力加载模型进行试验设计具有一定的实际意义。为了方便学生更好地了解格宾石笼作为隧道支护结构的力学作用机理,设计了一种简化的格宾石笼构件成形方法和与之配套的试验加载装置,并提出了基于离散元计算的格宾石笼隧道局部构件数值建模方法,进而对比和揭示了组成格宾石笼构件的两大主要参数(格宾网抗拉强度和填石有效模量)对格宾石笼建构的隧道支护构件静力力学特性差异的影响规律。通过该试验,为学生演示了基于格宾石笼建构的隧道支护局部构件的设计、拼装、试验加载以及数据采集的全过程,旨在为学生深入学习和掌握格宾石笼建构的隧道支护局部构件的试验静力力学行为及其建模方法提供一种新思路。

基于离散元的重载铁路有砟轨道阻力特性研究

研究目的:有砟轨道在重载铁路中广泛采用,随着服役时间的增加,在列车荷载反复作用下,道床性能会随之变化,线路阻力呈现动态发展的时变特性。作为求解梁轨相互作用的关键,准确合理地选取线路纵向阻力是保证梁轨相互作用计算准确的前提,关系梁轨系统的正常使用与安全运营。研究结论:(1)颗粒级配由粗到细,纵向线阻力逐渐减小;摩擦系数由小到大,纵向线阻力稍微增加;(2)结合不同级配建立的道床模型模拟出的纵向线阻力-位移曲线,获得纵向线阻力动态演化模型,可知线路纵向阻力由新建线路的阻力29.7 kN/(m·线)演化到破碎充分时的23.6 kN/(m·线),退化幅度约为20.5%;(3)本研究成果可为开展全服役期内重载铁路的梁轨相互作用等相关研究提供关键参数。

颗粒阻尼器对输电塔线系统减震性能研究

对输电塔线系统进行缩尺模型振动台实验,从时域和频域的角度,对比了调谐质量阻尼器和颗粒阻尼器对输电塔的减震效果。利用ABAQUS建立了颗粒阻尼器控制输电塔线系统的离散元-有限元高精度耦合数值模型,对比了实验和模拟结果,并对塔线系统的耗能情况及颗粒阻尼器内部颗粒运动碰撞情况进行分析。研究结果表明:在地震激励下,颗粒阻尼器的减震效果较调谐质量阻尼器有更好的鲁棒性;该文所建立的颗粒阻尼器控制输电塔线系统模型能够良好地反映试件的动力特性和地震响应;在颗粒阻尼器的控制下,塔线系统总能量降低24.12%。当颗粒之间的碰撞次数和颗粒与容器的碰撞次数满足一定比例关系时,颗粒阻尼器能实现更优的控制效果。

基于BIM技术的浅埋隧道无限元法数值研究

近年来,BIM技术在交通运输基础工程领域的应用日益广泛,如地铁、高铁、公路、隧道等项目全生命周期的管理都有BIM技术的参与。本研究通过BIM软件–Revit建立浅埋隧道的信息模型,基于BIM信息模型,导入ABAQUS有限元分析软件,对越秀公园站浅埋暗挖多孔隧道进行有限元与无限元耦合模拟,验证了无限元在隧道数值模拟中的可行性。其次通过设置不同的工况,验证了无限元与有限元耦合模拟的准确性,并且研究了隧道的开挖对不同工况下,地表沉降和衬砌内力的影响,得出最优的开挖工序,为后续浅埋隧道的力学行为的研究提供借鉴。

基于不同围岩特性的隧洞衬砌厚度优化分析

基于不同围岩特性的隧洞衬砌厚度优化既能实现安全要求又可以降低工程投资。结合某电站引水隧洞,采用有限元分析法对隧洞在不同围岩特性下的受力情况进行数值模拟,计算分析在不同衬砌厚度下的应力、配筋及裂缝宽度情况,综合考虑安全性和经济性对结果进行分析比较,提出了针对不同围岩特性的隧洞衬砌厚度优化方案。研究结果表明,隧洞衬砌在运行期的应力情况是影响衬砌配筋的关键因素,不同围岩特性下衬砌厚度的选择应充分考虑隧洞衬砌应力、所需配筋及裂缝宽度因素影响,当衬砌达到一定厚度后,所需配筋及裂缝宽度趋于稳定。

后调性对位的表象与本质

“后调性音乐”泛指一切非功能调性的音乐。其对位的表现与本质主要体现在横向时间维度与纵向空间维度两个层面,特别是线条、织体、音乐元素、音色音响、逻辑程序等方面。梳理和总结后调性对位的相关形态与技法,并通过对比和关联分析,深入探讨后调性对位与传统对位在表象与本质上的区别与趋同。

抽油管的在线漏磁检测技术

由于复杂的工况,抽油管的内、外壁极易发生损伤。目前,抽油管的检测方式主要是将抽油管抽离油井后送至后线检测场地进行检测,造成了时间、人力、物力的浪费。采用漏磁检测方法,开展了抽油管在起管或下管过程中的在线检测;设计了瓦片式磁化结构,建立抽油管漏磁检测的三维仿真模型;针对抽油管的腐蚀缺陷,改变缺陷尺寸参数,研究了缺陷漏磁场的分布特性;研发了抽油管在线漏磁检测系统,在实验室和油田作业现场对抽油管进行在线检测试验。试验结果表明,该系统能够快速高效地完成抽油管的在线检测,为抽油管的损伤监测提供了一些参考。

与矿山三维地质模型自动关联的剖面图更新方法

露天煤矿开采过程中矿山三维地质模型不断变化,需要随之更新地质剖面图以真实反映当前矿山的地质构造与地层性质。针对目前剖面图更新方法存在剖面图内部图元属性信息与空间信息交互不畅导致剖面图更新不够准确的问题,提出了一种与矿山三维地质模型自动关联的剖面图更新方法。通过设计矿山三维地质模型与剖面图元关联关系的概念模型与逻辑模型,实现模型图元与剖面图元对象名称的关联;通过在剖面图上设置水平和高程位置的定位坐标,将剖切所得对象关联至相应的剖面图位置,实现模型图元与剖面图元空间位置坐标的关联,以达到矿山三维地质模型与剖面图属性信息、空间信息等图元数据关联的目的;根据矿山三维地质模型中发生改变的图元确定需要更新的区域,提取区域内各剖面线并根据关联关系得到相应的剖面图,进一步通过遍历判断图元属性更新标志位和几何更新标志位的状态,自动更新各剖面图中属性或几何形状发生变化的剖面图元。应用结果表明,该方法实现了剖面图与矿山三维地质模型的关联,以及剖面图的自动更新;利用该方法自动更新后的剖面图中定位坐标数据与更新前一致,验证了剖面图更新方法的准确性。

基于ISM模型的邮轮航线要素分析及优化研究

在全球经济增长乏力的情况下,我国邮轮产业方兴未艾,围绕着南海开发,中国—东盟合作前景一片广阔。本文以粤港澳大湾区为邮轮母港出发地,以邮轮航线优化要素为影响因子,建立要素解释结构模型,分析邮轮航线要素对优化方案的重要性程度,以及各个要素之间的影响关系。

利用TLE数据分析LEO卫星轨道异常的新方法——综合判据法

及时准确地发现在轨卫星的轨道异常意义重大.通过有效的异常算法、能够找出发生轨道异常的碎片或航天器,为空间碎片碰撞预警系统分析和验证碰撞事件提供数据支持.通过对利用TLE(Two Line Elements)数据分析LEO在轨卫星轨道异常的方法研究,提出了一个利用单个卫星相邻根数时间差控制加综合判据的判别方法分析表明,相对于取单一因素阈值的判别方法,综合判据法能够最大限度地减少漏判,并且保持相对较高的判断准确率.

基于TLE的空间目标碰撞预警计算

地球轨道上数量日益增长的空间飞行物体对在轨航天器及人类航天活动构成了严重威胁。分析了空间目标两行轨道根数(TLE)的格式及构成;阐述了相应的SGP4/SDP4轨道近似解析解模型算法;提供了轨道坐标系和惯性坐标系之间的转换关系;利用TLE数据和SGP4/SDP4模型进行了空间目标碰撞预警计算。该方法对于航天器初步威胁评估具有重要意义。