Two-Layer Contact Nonlinear Mechanical Analysis of Flexible Drilling Tool in the Wellbore

The lack of research on flexible drilling tool leads to limited application of ultra-short radius horizontal wells.The flexible drilling tool is different from the conventional drilling tool.The flexible drilling pipe involves a mutual transition between the structure and the mechanism during the deformation process.At the same time,the flexible drilling pipe and the eccentric guide tube,the guide tube and the wellbore generate random contact.In this paper,3-D beam elements,universal joint elements,rigid beam elements and the beam-beam contact elements are combined to establish a two-layer contact nonlinear finite element model of the flexible drilling tool in the wellbore.The dynamic relaxation method is introduced for numerical solution.The feasibility of the model and the algorithm is verified by an example.The mechanical analysis of flexible drilling tool under the four hole inclinations in the oblique section is carried out.It is found that the flexible drilling pipe has a“folded line”deformation.The contact force between the flexible drilling pipe and the guide tube is randomly distributed.The contact force between the guide tube and the wellbore in the oblique section is greater than that in the vertical section.As the hole inclinations increase,the torque and axial force transmitted to the drill bit gradually decrease.

Numerical Exploration of Asymmetrical Impact Dynamics: Unveiling Nonlinearities in Collision Problems and Resilience of Reinforced Concrete Structures

This study provides a comprehensive analysis of collision and impact problems’ numerical solutions, focusing ongeometric, contact, and material nonlinearities, all essential in solving large deformation problems during a collision.The initial discussion revolves around the stress and strain of large deformation during a collision, followedby explanations of the fundamental finite element solution method for addressing such issues. The hourglassmode’s control methods, such as single-point reduced integration and contact-collision algorithms are detailedand implemented within the finite element framework. The paper further investigates the dynamic responseand failure modes of Reinforced Concrete (RC) members under asymmetrical impact using a 3D discrete modelin ABAQUS that treats steel bars and concrete connections as bond slips. The model’s validity was confirmedthrough comparisons with the node-sharing algorithm and system energy relations. Experimental parameterswere varied, including the rigid hammer’s mass and initial velocity, concrete strength, and longitudinal and stirrupreinforcement ratios. Findings indicated that increased hammer mass and velocity escalated RC member damage,while increased reinforcement ratios improved impact resistance. Contrarily, increased concrete strength did notsignificantly reduce lateral displacement when considering strain rate effects. The study also explores materialnonlinearity, examining different materials’ responses to collision-induced forces and stresses, demonstratedthrough an elastic rod impact case study. The paper proposes a damage criterion based on the residual axialload-bearing capacity for assessing damage under the asymmetrical impact, showing a correlation betweendamage degree hammer mass and initial velocity. The results, validated through comparison with theoreticaland analytical solutions, verify the ABAQUS program’s accuracy and reliability in analyzing impact problems,offering valuable insights into collision and impact problems’ nonlinearities and practical strategies for enhancingRC structures’ resilience under dynamic stress.

Passive inter-modulation scattering analysis of reflector considering contact nonlinearity

Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communication system with broad-band channel and high-sensitivity receiver. Therefore, it is necessary to construct a model to simulate this process in order to predict the level of PIM. This paper is aimed at constructing some plate models with one-dimensional and two-dimensional contact nonlinearity sections illuminated by two-tone waves, and calculating the scattered field at a fixed-point in space using time-domain physical optics method. By taking fast Fourier transform （FFT）, we get the spectrum of the scattered field and then analyze the generated PIM products. At the end of this paper, some numerical examples are presented to show the influence rules of the relative factors on PIM. The results indicate the variation of the level of PIM with the number of the nonlinear regions, the nonlinear spacing, and the incident power levels.

Experimental and numerical study on microcrack detection using contact nonlinear acoustics

This paper introduces a non-classical nonlinear acoustic theory for microcrack detection in materials,comparing contact nonlinearity with material nonlinearity.The paper's main work concentrates on the experimental and numerical verification of the effectivity of contact nonlinear acoustic detection by using the contact nonlinear parameter fl',which can be represented by the ratio of the second-harmonic amplitude to the square of the firstharmonic amplitude.Both experiments and numerical tests are performed.The results show that fl'is sensitive to the initiation of microcracks and varies with the development of the microcracks.The numerical test illustrates the decline offl'when microcracks penetrate each other.

Nonlinear Contact Between Inner Walls of Deep Sea Pipelines in Buckling Process

In order to study buckling propagation mechanism in deep sea pipelines, the contact between pipeline's inner walls in buckling process was studied. A two-dimensional ring model was used to represent the pipeline and a nonlinear spring model was adopted to simulate the contact between inner walls. Based on the elastoplastic constitutive relationship and the principle of virtual work theory, the coupling effect of pipeline's nonlinear large deformation and wall contact was included in the theoretical analysis with the aid of MATLAB, and the application scope of the theoretical model was also discussed. The calculated results show that during the loading process, the change in external pressure is closely related to the distribution of section stress, and once the walls are contacting each other, the external pressure increases and then remains stable after it reaches a specific value. Without fracture, the pipeline section will stop showing deformation. The results of theoretical calculations agree well with those of numerical simulations. Finally, in order to ensure reliability and accuracy of the theoretical results, the collapse pressure and propagation pressure were both verified by numerical simulations and experiments. Therefore, the theoretical model can be used to analyze pipeline's buckling deformation and contact between pipeline's inner walls, which forms the basis for further research on three-dimensional buckling propagation.

Nonlinear Contact Between Pipeline's Outer Wall and Slip-on Buckle Arrestor's Inner Wall During Buckling Process

In order to theoretically study the buckle propagation of subsea pipelines with slip-on buckle arrestors, a two-dimensional ring model was set up to represent the pipeline and a nonlinear spring model was adopted to simulate the contact between pipeline's inner walls and between pipeline's outer wall and slip-on buckle arrestor's inner wall during buckle propagation. In addition, some reverse springs are added to prevent the wall of left and right sides separating from the inner wall of slip-on buckle arrestors. Considering large deformation kinematics relations and the elastic-plastic constitutive relation of material, balance equations were established with the principle of virtual work. The variation of external pressure with respect to the cross-sectional area of pipelines was analyzed, and the lower bound of the crossover pressure of slip-on buckle arrestors was calculated based on Maxwell's energy balance method. By comparing the theoretical results with experiment and finite element numerical simulation, the theoretical method is proved to be correct and reliable.

基于UEL的水电机组导轴承支架非线性连接模态特性分析

模态分析是水电机组故障诊断的重要方法,但其传统方法缺少对接触部分非线性接触的模拟手段,直接影响模态分析的准确性,也无法对链接部位的失效过程及趋势进行分析。该文基于用户自定义单元子程序接口(user-defined element subroutine interface,UEL),建立了结合部三维非线性专用分析单元模型。推导所提模型有限元格式的基本方程,获得表征材料非线性特性的本构关系;给出螺栓连接的固定结合部的静态分析,以及立式水轮发电机导轴承支架的模态分析算例;给出导轴承支架的支臂末端螺栓连接变刚度计算的工程应用实例。实验与仿真对比结果表明了建立的UEL三维非线性接触分析专用单元模型的正确性;连接失效分析表明了随着导轴承支架接触刚度的下降,会在整机模态频率计算中引入新的频率段这一结果的重要性。

竖向地震引起的城市高架桥的车‒桥耦合作用

建立了典型城市高架桥的车‒桥耦合作用简化模型,利用非线性接触单元模拟桥面和车辆之间的耦合,并选取不同频谱特性的竖向地震动作为激励,研究汽车质量、频率、地震动频谱特性和峰值加速度等多个参数对车‒桥耦合系统动力响应的影响。结果表明,车辆质量和车辆振动频率以及地震动频谱特性均对车桥耦合系统有较大的影响,在共计1866个工况中有221个工况出现了车桥分离的现象;车桥分离对桥梁竖向位移响应多表现为不利,同时还大幅增加了车辆对桥面的碰撞力;在统计意义上,车桥分离的峰值加速度的平均值随着汽车质量的增加而增加,随着汽车频率的增加而减小,随着地震动平均周期的增大而减小。

扣件刚度非线性对波磨区轮轨瞬态滚动接触行为的影响

WJ-8型扣件橡胶垫板刚度在长期服役过程中表现出非线性特征,静刚度随荷载增加而降低,为提高三维瞬态滚动接触有限元模型计算精确性,本文以LMA踏面车轮及CHN60型钢轨为基础,基于显式积分算法,将以往研究中线弹性扣件转化为非线性扣件,建立考虑扣件刚度非线性特征的三维轮轨瞬态滚动接触有限元模型,研究刚度非线性对车轮与钢轨波磨间高频动态响应及瞬态接触行为的影响,并重点分析了波磨工况下时频域内轮轨接触力、轴箱加速度的变化信息.结果表明:扣件非线性对轮轨接触力变化影响明显,主要表现为车轮行驶至扣件前端时强振动导致橡胶垫板表现为柔软特性使轮轨接触力减小,车轮行驶至扣件上方时在轴重作用下振动减弱表现为刚硬特性使轮轨接触力增大,轮轨力变化差异最大达到13.1%.

一类具有非线性出生率和饱和恢复率的随机SEIR传染病模型的动力学行为

研究了一类具有非线性出生率和非线性接触率的随机SEIR传染病模型的绝灭性、持久性与平稳分布问题。同时利用计算机数值模拟验证了所得结论。本文所得结果改进了相关文献的结论。

基于非线性弹簧的圆锥滚子轴承建模与分析

为解决风机主轴承滚动体数目多、尺寸大,进行有限元分析计算量大、收敛困难的难题,提出一种基于非线性弹簧的圆锥滚子轴承有限元等效模型,滚动体沿轴线方向分片,各分片与滚道接触以及球基面与挡边接触的“载荷-变形”关系采用弹簧单元等效模拟,等效弹簧的刚度通过赫兹接触理论确定。以某兆瓦级风机主轴承为例分析了该模型滚动体载荷分布及套圈整体变形,并与实体滚动体接触分析计算结果进行了对比。结果表明:基于非线性弹簧的等效模型能准确反映轴承内部载荷分布及整体变形情况,大大缩减计算量,为风机圆锥滚子主轴承的设计与分析提供了理论依据和指导。

盘式制动器温度场的分析研究

针对制动器温度场的研究分析,建立额定起重量32 T的钳盘式制动器三维模型,同时在Workbench中添加制动器材料的各个参数,设置摩擦副间的接触关系,施加制动盘和制动衬片载荷、约束,对制动器制动过程产生的温度场进行仿真。使用LM算法建立包括时间、摩擦因数、制动压力、初始转速的多元非线性数学模型,通过Matlab进行回归分析。最终拟合结果和有限元仿真结果吻合,验证了起重机制动器温度模型的正确性。

参变量变分原理的提出、发展与应用

参变量变分原理及其参数二次规划算法是由钟万勰院士1985年针对弹性接触边界非线性问题首次提出来的,经过将近40年的不断发展,目前参变量变分原理已经成功应用于各个领域,其中包括弹塑性分析、接触问题、润滑力学、岩土力学、变刚度杆系结构、先进材料性能分析、材料的蠕变与损伤、柔性结构力学和LQ最优控制等各个工程领域.本文首先回顾了参变量变分原理的起源,介绍了参变量变分原理的基本概念,然后以弹塑性分析问题为例,阐明建立参变量变分原理的理论模型以及实现数值参数二次规划求解原理,最后详细回顾了参变量变分原理的基本理论与相应数值算法在各个领域的发展及其工程应用,展示了参变量变分原理在求解各类非线性问题的特色与优势.

基于交叉迭代法的车辆-轨道非线性空间耦合振动模型及算法改进

针对车辆-轨道非线性空间耦合系统动力学分析计算量大、计算耗时长及计算精度难以保证的问题,对车辆-轨道非线性空间耦合振动模型和交叉迭代法进行改进。运用有限元法分别建立车辆和轨道空间子系统动力学模型,在基于“迹线法”构建轮轨接触几何关系的基础上,提出“投影对点作差法”搜索轮轨空间接触点位置,并引入轮轨准弹性接触对其进行修正,精细化轮轨接触关系;结合车辆-轨道非线性空间耦合系统特点,改进基于Newmark数值积分的交叉迭代求解系统动力学方程的算法,并给出完整的数值计算步骤。通过与相关文献进行对比,验证改进模型和算法的有效性。结果表明:改进模型的分析精度更高,搜索轮轨空间接触点位置的速度更快;改进算法的计算过程更完善,步骤更清晰;改进的模型和算法在提高计算精度的同时,仍然具有较快的计算效率,且使数值编程更易实现,方便工程应用。

多叶式径向动压气体箔片轴承预紧力仿真

为获取多叶式径向动压气体箔片轴承大预紧装配过程中各部件状态,基于显式动力学方法建立了该类轴承的非线性接触模型,并讨论了预紧量、静态偏心率对转轴表面应力分布的影响,研究结果表明:多叶式箔片结构在平箔片搭接区域及与转轴接触区域应力较大;当无静态偏心时,转轴表面应力分布呈周期对称状态,有静态偏心时,则呈余弦形式,且应力波峰波谷数量与箔片数量一致;同时,预紧量越大,转轴表面应力越大,而静态偏心率越大,转轴表面主要受压区峰谷间应力差越大。

基于接触非线性的升降机构刚度影响分析

本文以大型重载升降机构为研究对象,首先通过三种方法分析了风载荷对其刚度的影响:一是将其近似为等直杆弯曲问题,并利用解析法进行了弯曲挠度计算;二是通过有限元方法,开展了升降机构线性静力学仿真分析;三是开展了升降机构刚度试验。然后将试验结果和以上两种结果进行了对比,分析结果间存在较大差异的原因,并基于接触非线性理论,对仿真方法进行了改进。改进后的仿真计算结果与试验结果吻合较好,证明了该方法的正确性。该方法可提高设计阶段升降机构仿真分析的准确性,具有较高的工程应用和推广价值。

五强溪水电厂底孔密封性能仿真模拟研究

针对水电站闸门水封存在密封性能在运行过程中裂化、密封性能预测困难、水封更换时螺栓预紧量的确定缺乏理论依据等问题,提出基于多元线性回归的螺栓预紧量补偿模型。结合工程实例,通过Ogden公式建立方头P型水封橡胶超弹性本构模型,建立复杂工况下水封密封结构非线性有限元计算模型。基于Ansys计算了4种影响因素下的水封接触应力,分析了多种影响因素与水封密封性能之间的独立影响和综合影响规律,在有限元分析的基础上,基于多元线性回归建立了接触应力计算公式,构建了螺栓预紧量补偿模型,实现了水封密封性能反演和螺栓预紧量补偿计算。结果表明,基于螺栓预紧量补偿模型得到的接触应力与预期值的平均相对误差为7.6%,最大相对误差为16.9%,模型能够实现在水封安装工况改变时对螺栓预紧量进行修正,从而得到预期水封密封性能,为实际工程中水封结构的设计、安装提供了可靠依据。

混凝土中灌浆套筒的本构模型研究

提出了通过改变灌浆套筒位置处钢筋弹性模量模拟套筒连接混凝土构件的有限元建模方法,套筒和钢筋本构模型采用双折线本构模型,通过汇总60个灌浆套筒钢筋拉拔试验结果并对数据进行拟合,给出了套筒本构曲线与钢筋本构曲线之间的关系式。使用推导出的关系式计算套筒本构曲线,通过ABAQUS有限元软件,利用非线性弹簧模拟钢筋粘结滑移、粘性接触模拟钢筋粘结滑移和界面裂缝,对3个灌浆套筒连接预制构件进行滞回分析。通过对比滞回曲线、钢筋应变、钢筋滑移量和界面裂缝,发现模拟结果与试验值吻合程度较高。

分支井完井双管转向筒工具

分支井钻完井技术具有高效利用井口槽、提高采收率等特点,为解决分支井完井双管转向筒送入拔出过程摩阻难以准确控制的问题,研制了分支井完井双管转向筒工具,实现主井眼和分支井眼生产管柱同时回插密封。通过构建三阶段有限元仿真模型,分析了双管转向筒工具在回接筒中的送入与拔出过程,研究了摩擦因数、主分支井筒分离角及转向筒偏离方位角等因素对送入阻力、拔出阻力及等效应力的影响,摩擦因数对最大等效应力影响不明显,对行进阻力影响较大;分支井与主井筒之间的分离角对最大等效应力和行进阻力响应较大;偏离方位角对最大等效应力影响不明显,但对行进阻力影响显著,作业时应维持较小的偏离方位角,建议控制在45°以内。通过地面试验和实验井试验进行了验证,结果表明,建立的数值模型及分析方法能有效模拟双管转向筒送入拔出过程,相对采用传统简化方法计算的阻力误差由55%降至13%,实验井的产量较邻井提高了50%,验证了该工具的有效性,为分支井工具设计与作业提供了技术支持。

压气储能地下洞室密封钢衬的非线性力学响应特征

依托某压气储能电站实际工程,基于ABAQUS平台,研究密封钢衬应力的非线性影响因素,分别探究了围岩与混凝土材料非线性、密封钢衬-混凝土接触非线性的影响机理。结果表明,浅埋地下储气洞室围岩初始地应力水平不高,巨大气压导致围岩局部塑性屈服,混凝土严重开裂,密封钢衬高应力区-混凝土严重开裂区-围岩塑性区三者存在对应关系;考虑密封钢衬-混凝土之间的接触关系,使得密封钢衬应力分布更加均匀;检修期在重力影响下密封钢衬顶部与混凝土脱开,检修后再加压密封钢衬应力分布出现调整现象,顶部应力峰值和应力不均匀度有所增大;密封钢衬应力峰值随摩擦系数与缝隙值的增大而增大,当摩擦系数大于0.5时其影响不明显,随缝隙的变化梯度大致为30~40 MPa/mm;地下储气洞室密封钢衬受力分析时需同时考虑材料非线性与接触非线性,以保证密封钢衬具有足够的安全储备。