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.

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.

Mechanical analysis of transmission lines based on linear sliding cable element

In order to study the sliding characteristics when the cable structures are connected with other rods, a string of sliding cable dements （SCE） consisting of one active threenode SCE passing through the sliding point and multiple inactive two-node SCEs is put forward. Based on the updated Lagrangian formulation, the geometric nonlinear stiffness matrix of the three-node straight sliding cable dement is deduced. The examples about two-span and three-span continuous cable structures are studied to verify the effectiveness of the derived SCE. Comparing the cable tension of SCE with the existing research results, the calculating results show that the error is less than 1%. The sliding characteristics should be considered in practical engineering because of the obvious difference between the cable tension of the SCE and that of the cable element without considering sliding characteristics.

Static and Dynamic Analysis of Mooring Lines by Nonlinear Finite Element Method

This study has focused on developing numerical procedures for the static and dynamic nonlinear analysis of mooring lines. A geometrically nonlinear finite element method using isoparametric cable element with two nodes is briefly presented on the basis of the total Lagrangian formulation. The static and dynamic equilibrium equations of mooring lines are established. An incremental-iterative method is used to determine the initial static equilibrium state of cable systems under the action of self weights, buoyancy and current. Also the Newmark method is used for dynamic nonlinear analysis of ocean cables. Numerical examples are presented to validate the present numerical method, and examine the effect of various parameters.

Mechanical response of transmission lines based on sliding cable element

In order to study the sliding characteristics when the cable is connected with the other rods in the transmission line structures,a linear sliding cable element based on updated Lagrangian formulation and a sliding catenary element considering the out-of-plane stiffness coefficient are put forward.A two-span and a three-span cable structures are taken as examples to verify the sliding cable elements.By comparing the tensions of the two proposed cable elements with the existing research results,the error is less than 1%,which proves the correctness of the proposed elements.The sliding characteristics should be considered in the practical engineering because of the significant difference between the tensions of sliding cable elements and those of cable element without considering sliding.The out-of-plane stiffness coefficient and friction characteristics do not obviously affect the cable tensions.

STUDY ON THREE-DIMENSIONAL FINITE BODIES CONTAINING CRACKS USING THE FINITE ELEMENT METHOD OF LINES

The three-dimensional finite element method of lines is presented, and the basic processing description of 3D FEMOL in cracking questions is given in detail. Applications to 3D bodies with cracks indicate that good accuracy can be obtained with relatively coarse girds. In particular, application to the tension specimen shows very good agreement with the evaluation of stress intensity factors, which is better than the results of other methods. This implies a considerable potential for using this method in the 3D analysis of finite geometry solids and suggests a possible extension of this technique to nonlinear material behavior.

Higher-Order Line Element Analysis of Potential Field with Slender Heterogeneities

Potential field due to line sources residing on slender heterogeneities is involved in various areas,such as heat conduction,potential flow,and electrostatics.Often dipolar line sources are either prescribed or induced due to close interaction with other objects.Its calculation requires a higher-order scheme to take into account the dipolar effect as well as net source effect.In the present work,we apply such a higher-order line element method to analyze the potential field with cylindrical slender heterogeneities.In a benchmark example of two parallel rods,we compare the line element solution with the boundary element solution to show the accuracy as a function in terms of rods distance.Furthermore,we use more complicated examples to demonstrate the capability of the line element technique.

Cracking analysis of fracture mechanics by the finite element method of lines(FEMOL)

The Finite Element Method of Lines （FEMOL） is a semi-analytic approach and takes a position between FEM and analytic methods. First, FEMOL in Fracture Mechanics is presented in detail. Then, the method is applied to a set of examples such as edge-crack plate, the central-crack plate, the plate with cracks emanating from a hole under tensile or under combination loads of tensile and bending. Their dimensionless stress distribution, the stress intensify factor （SIF） and crack opening displacement （COD） are obtained, and comparison with known solutions by other methods are reported. It is found that a good accuracy is achieved by FEMOL. The method is successfully modified to remarkably increase the accuracy and reduce convergence difficulties. So it is a very useful and new tool in studying fracture mechanics problems.

Three-axis magnetic flux leakage in-line inspection simulation based on finite-element analysis

With the increase of pipelines, corrosion leakage accidents happen frequently. Therefore, nondestructive testing technology is important for ensuring the safe operation of the pipelines and energy mining. In this paper, the structure and principle of magnetic flux leakage （MFL） in-line inspection system is introduced first. Besides, a mathematic model of the system according to the ampere circuit rule, flux continuity theorem, and column coordinate transform is built, and the magnetic flux density in every point of space is calculated based on the theory of finite element analysis. Then we analyze and design the disposition of measurement section probes and sensors combining both three-axis MFL in-line inspection and multi-sensor fusion technology. Its advantage is that the three-axis changes of magnetic flux leakage field are measured by the multi-probes at the same time, so we can determine various defects accurately. Finally, the theory of finite element analysis is used to build a finite element simulation model, and the relationship between defects and MFL inspection signals is studied. Simulation and experiment results verify that the method not only enhances the detection ability to different types of defects but also improves the precision and reliability of the inspection system.

Line-element based nonlinear adaptive piecewise compensating correction for LVDT sensors

In order to solve the linear variable differential transformer （LVDT） displacement sensor nonlinearity of overall range and extend its working range, a novel line-element based adaptively seg- menting method for piecewise compensating correction was proposed. According to the mechanical structure of LVDT, the output equation was calculated, and then the theoretic nonlinear source of output was analyzed. By the proposed line-element adaptive segmentation method, the nonlinear output of LVDT was divided into linear and nonlinear regions with a given threshold. Then the com- pensating correction function was designed for nonlinear parts employing polynomial regression tech- nique. The simulation of LVDT validates the feasibility of proposed scheme, and the results of cali- bration and testing experiments fully prove that the proposed method has higher accuracy than the state-of-art correction algorithms.

COMPUTATION OF STRESS INTENSITY FACTORS BY THE SUB-REGION MIXED FINITE ELEMENT METHOD OF LINES

Based on the sub-region generalized variationM principle, a sub-region mixed version of the newly-developed semi-analytical ＇finite element method of lines＇ （FEMOL） is proposed in this paper for accurate and efficient computation of stress intensity factors （SIFs） of two-dimensional notches/cracks. The circular regions surrounding notch/crack tips are taken as the complementary energy region in which a number of leading terms of singular solutions for stresses are used, with the sought SIFs being among the unknown coefficients. The rest of the arbitrary domain is taken as the potential energy region in which FEMOL is applied to obtain approximate displacements. A mixed system of ordinary differential equations （ODEs） and algebraic equations is derived via the sub-region generalized variational principle. A singularity removal technique that eliminates the stress parameters from the mixed equation system eventually yields a standard FEMOL ODE system, the solution of which is no longer singular and is simply and efficiently obtained using a standard general-purpose ODE solver. A number of numerical examples, including bi-material notches/cracks in anti-plane and plane elasticity, are given to show the generally excellent performance of the proposed method.

Long interspersed elements in three species of Gracilaria (Gracilariaceae, Rhodophyta)

In order to find out whether long interspersed elements （LINEs） existed in macro-algae gehomes or not, we tested the LINE homologues in representative families （species）： Gracilaria （G. eucheumoides Harv., G. tenuistipitata Chang et Xia, and G. textorii （Sur） De-Toni）, Laminaria （L. longissima Miyabe and L. japonica Aresch.）, and Ulva （U. lactuca L. and U. pertusa Kjellm.） during 2004 to 2005. Polymerase Chain Reaction （PCR） was carried out with degenerate oligonucleotide primers designed from LINEs of rice homologues and Cin4 of maize. Cloning and nucleotide sequencing of the PCR products revealed that 4 clones that derived from 3 species of Gracilaria have LINE homologues. The nucleotide sequences of the 4 LINE homologues diverged greatly, but the amino acid sequences deduced from them were relatively conserved. The endonuclease regions of the LINE homologues greatly diverged from that of other plants, but they had closer phylogenetic relationship to Zepp elements in Chlorella sp., which indicated that sequence divergence by vertical transmission has been a major influence on the evolution of algal LINEs.

Breakthrough in the China's Separation Technology for Extraction of Rare Earth Elements

Separation technology of rare earth elements （REEs）, as the critical step in the separation process, had long been fraught with technical difficulty. A research project conducted by Baotou Shibo Rare Earth Extraction ＆ Equipment Co. Ltd., Baotou REE Research Institute, and Baotou Steel ＆ REE Group Hi-Tech Co. Ltd （Inner Mongolia）, has successfully solved the problem using a centrifugal extractor and advanced techniques to achieve a key breakthrough.

A FINITE ELEMENT METHOD FOR STRESS ANALYSIS OR ELASTOPLASTIC BODY WITH POLYGONAL LINE STRAIN——HARDENING

In this paper, the stress-strain curve of material is fitted by polygonal line composed of three lines. According to the theory of proportional loading in elastoplasticity, we simplify the complete stress-strain relations, which are given by the increment theory of elastoplasticity. Thus, the finite element equation with the solution of displacement is derived. The assemblage elastoplastic stiffness matrix can be obtained by adding something to the elastic matrix, hence it will shorten the computing time. The determination of every loading increment follows the von Mises yield criteria. The iterative method is used in computation. It omits the redecomposition of the assemblage stiffness matrix and it will step further to shorten the computing time. Illustrations are given to the high-order element application departure from proportional loading, the computation of unloading fitting to the curve and the problem of load estimation.

STUDY ON THE EXCITATION BEHAVIOUR OF RARE EARTH ELEMENTS IN DC ARC BY AXIAL-INTRODUCTION OF AEROSOL

In order to eliminate influence of the carriers on the evaporation of rare earth elements in DC arc,a de- vice which introduces axially the sample aerosol has been designed to study the effects of controlled-atmos- phere,discharge current,electrode polarity and introduction direction of aerosol on the emission of rare earth elements in DC arc discharge.The influence of various matrices and carriers on the line density and excitation condition of rare earth elements have also been studied,then the related excitation mechnism is proposed.

Finite Element Analysis of the Dynamic Behaviour of Transmission Line Conductors Using MATLAB

The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature such as wind loading. This imposes a periodic force on the conductors which is highly undesirable. It is therefore important for engineers to account for the possible effect of the wind loading when designing the power line. Investigations have shown that modeling the exact dynamic behaviour of a conductor is very difficult. Based on this fact, getting the exact analytical solution to conductor vibration is difficult, which is almost impossible, hence the numerical approximation becomes an option. This paper presents the developed finite element method used to analyse the dynamic behaviour of transmission line conductors. The developed FEM （finite element method） is implemented on MATLAB. The numerical analysis using MATLAB that is presented in this paper is used to simulate the response of the conductor when subjected to external loading in the time domain. The simulation is used to analyse the transverse vibration of the conductor. The formulation of the stiffness matrix and load vector is done and the results obtained are used to evaluate the conductor＇s internal energy dissipation. This finite element solution is compared with the results documented in literature. This numerical simulation is also used to investigate the effects of varying the axial tension on energy dissipation within the strands. Hence, this evolved in physically appropriate energy characterization process that can be used to evaluate the conductor self-damping with respect to line contact.

Einstein’s Non-Euclidean Line Element Theory and Quantum Mechanics Interpretation

In “The third speech on the wave mechanics” (1926), E. Schodinger pointed that the Hamilton-Maupertuis principle as a classical starting point of wave mechanics in the definition of generalized coordinate space line element, introduced the generalized non-Euclidean geometry, and finally obtained the wave equation including Laplace operator in the generalized non Euclidean geometry line element. At the 1927 meeting of the Prussian Academy of Sciences in Berlin, Albert Einstein read a paper entitled “Does Schodinger’s wave mechanics determines the dynamics of a system’s movement completely or only sence in statistics?”. In this paper, Einstein used the Schodinger equation to obtain a representation of the kinetic energy, and used the non-Euclidean line element of the Configuration space to define the velocity component of a single particle, and return to determinism. But Bothe pointed out that when people considered a system composed of two subsystems, the wave function of the whole system can be decomposed into two simple products of the wave function of the two subsystems, but the hidden variables are dependent on each other. Einstein be-lieved that this was not acceptable, gave up the publication of the paper on the non-European line hidden variables theory. In the long-term controversy with the Copenhagen school, Einstein was convinced that the probability interpretation of the wave function was indispensable because of the incompleteness of quantum mechanics, but not the wave function probability led to the incompleteness of quantum mechanics. Any attempt to seek a complete explanation of quantum mechanics is inevitable to change the current formal system of quantum mechanics.