Tunnelling performance prediction of cantilever boring machine in sedimentary hard-rock tunnel using deep belief network

Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.

Four-Beam Model for Vibration Analysis of a Cantilever Beam with an Embedded Horizontal Crack

As one of the main failure modes, embedded cracks occur in beam structures due to periodic loads. Hence it is useful to investigate the dynamic characteristics of a beam structure with an embedded crack for early crack detection and diagnosis. A new four-beam model with local flexibilities at crack tips is developed to investigate the transverse vibration of a cantilever beam with an embedded horizontal crack; two separate beam segments are used to model the crack region to allow opening of crack surfaces. Each beam segment is considered as an Euler-Bernoulli beam. The governing equations and the matching and boundary conditions of the four-beam model are derived using Hamilton＇s principle. The natural frequencies and mode shapes of the four-beam model are calculated using the transfer matrix method. The effects of the crack length, depth, and location on the first three natural frequencies and mode shapes of the cracked cantilever beam are investigated. A continuous wavelet transform method is used to analyze the mode shapes of the cracked cantilever beam. It is shown that sudden changes in spatial variations of the wavelet coefficients of the mode shapes can be used to identify the length and location of an embedded horizontal crack. The first three natural frequencies and mode shapes of a cantilever beam with an embedded crack from the finite element method and an experimental investigation are used to validate the proposed model. Local deformations in the vicinity of the crack tips can be described by the proposed four-beam model, which cannot be captured by previous methods.

NONLINEAR DYNAMIC MODELING AND PERIODIC VIBRATION OF A CANTILEVER BEAM SUBJECTED TO AXIAL MOVEMENT OF BASEMENT

Dynamic modeling of a cantilever beam under an axial movement ofits basement is present- ed. The dynamic equation of motion for thecantilever beam is established by using Kane's equation first andthen simplified through the Rayleigh-Ritz method. Compared with oldermodeling method, which lineari- zes the generalized inertia forcesand the generalized active forces, the present modeling takes thecoupled cubic nonlinearities of geometrical and inertial types intoconsideration.

Artificial Neural Networks Based Integrated Predictive Modelling of Quality Characteristics in CNC Turning of Cantilever Bars

The objective of this study is to develop an effective approach for product quality prediction in Computer Numerical Control turning of cantilever bars. A systematic predictive modelling procedure based on experimental investigations, neural network modelling and various statistical analysis tools is designed to produce the most accurate, practical and cost-effective prediction model. The modeling procedure begins by exploring the relationships between cutting parameters known to have an influence on quality characteristics of machined parts, such as dimensional errors, form errors and surface roughness, as well as their sensitivity to the process conditions. Based on these explorations and using numerous statistical tools, the most relevant variables to include in the prediction model are identified and fused using several artificial neural network architectures. An application on CNC turning of cantilever bars demonstrates that the proposed modeling procedure can be effectively and advantageously applied to quality characteristics prediction due to its simplicity, accuracy and efficiency. The experimental validation reveals that the resulting prediction model can correctly predict the quality characteristics of machined parts under variable machining conditions.

Nonplanar flow-induced vibrations of a cantilevered PIP structure system concurrently subjected to internal and cross flows

Pipe-in-pipe(PIP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PIP structure system usually consists of two concentric pipes and one softer layer for thermal insulation consideration.The total response of the system is related to the dynamics of both pipes and the interactions between these two concentric pipes.In the current work,a theoretical model for flow-induced vibrations of a PIP structure system is proposed and analyzed in the presence of an internal axial flow and an external cross flow.The interactions between the two pipes are modeled by a linear distributed damper,a linear distributed spring and a nonlinear distributed spring along the pipe length.The unsteady hydrodynamic forces due to cross flow are modeled by two distributed van der Pol wake oscillators.The nonlinear partial differential equations for the two pipes and the wake are further discretized by the aid of Galerkin’s technique,resulting in a set of ordinary differential equations.These ordinary differential equations are further numeri cally solved by using a fourth-order Runge-Kutta integration algorithm.Phase portraits,bifurcation diagrams,an Argand diagram and oscillation shape diagrams are plotted,showing the existence of a lock-in phenomenon and figure-of-eight trajectory.The PIP system subjected to cross flow displays some interesting dynamical behaviors different from that of a single-pipe structure.

Simulation of perforated rectangular cantilever immunosensor for estimation of bacterial pathogens

Micro fabricated and multilayered perforated cantilever beam immunosensor was modeled using CoventorWare for the estimation of bacterial antigens of Bacillus Anthrax, Pseudomonas aeruginosa, Coryne Bacterium Diptheria and Treponema pallidum. A rectangular cantilever beam with perforations was simulated with dimensions as length-200 μm, width-10 μm and thickness-0.5 μm. Each perforation is rectangular with length-10 μm, width-5 μm and thickness-0.5 μm. The theoretical and FEM simulations were carried out with five immunoglobulin antibodies, IgA, IgD, IgE, IgG and IgM for the estimation of bacterial antigens. The effect of perforation in cantilever beam and molecular size of antibody and antigen on the performance of the sensor has been studied. The cantilever beam without perforation showed a deflection of 1.8 e + 02 μm whereas the cantilever beam with perforation showed an increase deflection of 1.9 e + 02 μm. With IgG, the difference between analytical and simulation values is positive and low especially with low molecular weight antigens Pseudomonas aeruginosa and Treponema pallidum. The low molecular weight IgG influences the antigen-antibody interaction more fvourably. The simulated perforated rectangular cantilever beam with IgG antibody is a more promising model for the fabrication of a sensor for the estimation of highly motile Pseudomonas aeruginosa and Treponema pallidum.

大跨长挑臂钢箱组合梁桥抗风性能试验研究

为了解大跨长挑臂钢箱组合梁桥抗风性能及选取合适的声屏障形式,以挑臂长7.5 m的钢箱组合梁桥——临猗黄河大桥为背景,基于有限元计算的施工及成桥阶段桥梁动力特性指标,制作1个缩尺比1∶50的最大悬臂施工状态钢箱梁、2个缩尺比1∶60的成桥状态不同声屏障设置形式(直线形、折线形,高度均为2.5 m)钢箱组合梁节段模型进行风洞试验,分析施工和成桥状态主梁断面的涡振、颤振和驰振性能。结果表明:施工状态的钢箱梁抗风稳定性良好,涡振、颤振和驰振性能均满足设计要求;常遇风攻角为0°、±3°时,成桥状态下,设置2.5 m高折线形声屏障可有效抑制主梁涡振响应,且颤振与驰振稳定性均满足规范要求;设置2.5 m高直线形声屏障的主梁发生明显的竖向涡振现象。该桥主梁最终采用2.5 m高折线形声屏障。

歪闪古建木构架整体纠偏方法与数值模拟

由于环境与人为等因素的长期影响,木结构古建筑普遍存在倾斜歪闪等损伤问题,严重影响了古木建筑的安全,亟需纠偏修复。研究尝试提出一种整体纠偏方法,构建木构架结构纠偏理论计算模型,通过数值模拟方法分析了纠偏过程的可行性,并以某多层木结构建筑的纠偏复位过程为例加以验证。结果表明:纠偏后结构楼层偏移明显减小,纠偏过程中主要结构构件仍然处于弹性范围内,纠偏效果良好,可为同类古建木构架纠偏理论研究提供借鉴。

基于Ansys Workbench的悬臂结构直接优化设计

本文对悬臂梁结构进行了模型数据参数化,利用Ansys Workbench对悬臂梁结构进行直接优化设计,建立以质量最小为最优目标的非线性多约束数学模型。通过计算和分析输入参数对优化目标的敏感性和响应(总变形和等效应力),确定最佳的优化方案。经过直接优化,该悬臂结构质量比原来减轻了47.8%,优化效果良好,达到了最初进行优化的目的,实现利用材料更经济的结果,为类似结构的轻量化设计提供了思路。本方法具有较好的可行性,可优化得到结构性能较好的悬臂结构几何布局方案,可为此类悬臂结构的轻量化优化设计提供技术支撑。

新型钢结构泊位的设计与实施

以中国香港地区某项目为工程背景,基于施工现场特点,设计一种新型悬臂式钢结构靠船设施,更好地适应项目临时性建设的需要,实现材料循环利用和成本节约。对比分析新型悬臂钢结构泊位与传统码头泊位的区别与优势;结合当地水文条件,利用有限元模型对其进行内力计算及稳定性分析。结果表明,新型钢结构泊位的抗剪、抗弯、抗拉、抗压、屈曲稳定以及变形等均可满足安全要求,且具有安装工期短、投资小、可环保回收的优势。研究结果可为同类工程项目的设计与实施提供借鉴。

平转施工桥梁转体角速度及角加速度合理取值分析

关于水平转体施工桥梁的转体角速度限值问题存在较大的争议,现有标准提出的0.01~0.02 rad/min的平转角速度限值偏于保守,造成部分转体桥无法在正常的铁路天窗时间内完成转体,而一些工程实际采用的转速大幅超过现有标准,但并未对结构安全造成任何影响。本文对转体角速度和角加速度与结构效应的对应关系进行理论分析,对国内相关研究成果进行归纳总结,并结合襄北编组站大桥的模型试验数据,按照转体悬臂长度提出转体角速度和角加速度合理取值范围。推荐取值为:悬臂长度不大于40 m时,角速度宜控制在0.05 rad/min以下;悬臂长度大于80 m时,角速度宜控制在0.025 rad/min以下;悬臂长度在40~80 m时,转体角速度的上限值可内插取值;转体角加速度宜控制在2.2×10^(-5)~4.2×10^(-5)rad/s^(2)。

悬臂结构地震响应分析的广义单自由度模型研究

针对有限元方法存在计算时间过长的缺点,不适用于需要多次响应分析的结构抗震性能评估问题。进行了悬臂结构线性地震响应分析的广义单自由度模型研究,提出了多项式形函数和基于多项式形函数的单自由度模型,并通过与有限元分析结果的对比分析,调查了基于多项式形函数的单自由度模型对典型地震波激励下结构响应分析的有效性。结果表明:提出的基于多项式形函数的广义单自由度模型平均误差为7.20%,为提高建模准确性,建议采用水平集中荷载施加方法进行多项式形函数参数估计。

Experiment and performance analysis of serpentine-shaped cantilever beam for pipeline vibration-based piezoelectric energy harvester prototype development

Pipelines produce vibrations during fluid or gas transportation.These vibrations are less likely to cause structural failure as they exist with a small magnitude and can be harvested into useful energy.This paper presents a study on the piezoelectric energy-harvesting method converting mechanical energy from pipeline vibration into electrical energy.The performance of the serpentine-shaped piezoelectric cantilever beam was observed to check whether the design can produce the highest output voltage within the allowable vibration region of the pipeline from 10 to 300 Hz through finite element analysis using COMSOL Multiphysics software(Supplementary Material).In addition,this study investigates the energy-harvesting potential of the proposed design under real pipeline vibration conditions through a lab vibration test.The harvested energy output is evaluated based on various vibration frequencies and amplitudes,which gives an idea of the device and its performance under different operating conditions.The experiment result shows that the energy harvester produced an open-circuit voltage of 10.28-15.45 V with 1 g of vibration acceleration.The results of this research will contribute to the development of efficient piezoelectric energy harvesters adapted for pipeline environments.

基于力法的格构梁节点荷载分配方法及悬臂段长度优化设计

格构梁节点荷载简化分配方法的不足在于无法考虑2个方向的梁上其他节点荷载的影响且对文克尔(Winkler)地基上梁的类型进行了主观假定。为克服格构梁节点荷载简化分配方法的上述缺点,提出了一种基于力法的格构梁节点荷载分配方法。根据节点静力平衡条件及变形协调条件,新的格构梁节点荷载分配方法通过构建并求解线性方程组,能够合理地将作用在节点的集中力分别分配给2个方向的纵梁和横梁。进一步地,引入一个格构梁边坡锚固案例并等比例地增加纵梁和横梁的悬臂长度。不同基床系数条件下,基于新的节点荷载分配方法将格构梁节点荷载分配给纵梁和横梁,然后对各梁单独进行弯矩计算。以悬臂最大正弯矩与跨中最大负弯矩比值的绝对值接近1为评价指标,对格构梁最优悬臂长度进行了评价。节点荷载分配结果表明,随着悬臂长度的增加,分配给纵梁和横梁的荷载逐渐趋于稳定。弯矩计算结果表明,随着基床系数的增大,悬臂长度对格构梁弯矩的影响逐渐减弱。不同边坡基床系数条件下,当悬跨比在0.2~0.4之间时,悬臂各梁最大正弯矩与跨中最大负弯矩趋于均衡。因此,基于力法理论的节点荷载分配方法的提出为格构梁内力的精确分析及悬臂长度优化设计提供了可靠的理论依据。

大悬臂宽幅混凝土箱梁横隔梁计算方法分析

为研究大悬臂宽幅混凝土箱梁横隔梁的计算分析方法,参照现有混凝土宽箱梁横隔梁计算模式,研究横隔梁杆系单元模型的简化建模方法,重点针对横隔梁两侧的加腋和顶底桥面板的计算长度进行分析,分别取0~10倍顶底板厚度的计算长度,并结合midas Civil分析横隔梁顶部主拉应力和最大负弯矩,探求该类型箱梁断面的最佳顶底桥面板计算长度取值。同时采用Abaqus三维软件建立实体模型,对比杆系单元模型的计算结果,验证建模方式的合理性。结果表明,采用大悬臂宽幅混凝土箱梁横隔梁计算时,断面纵向两侧取4倍顶底板厚度的计算长度最为合理,相对于常规混凝土宽箱梁横隔梁计算方法支座处横隔梁顶部主拉应力减小了7.8%,结果更加安全;根据对比可知,采用该计算方法建立的大悬臂宽幅混凝土箱梁杆系单元横隔梁模型结果与实体模型计算结果基本接近,横隔梁横向主应力和主拉应力仅分别增加了7.7%和2.7%。

花篮螺栓紧固式斜拉杆受力型悬挑脚手架力学模型分析

花篮螺栓紧固式斜拉杆受力型悬挑脚手架是近些年各地常用的一种资源节约型高效的新型悬挑脚手架,其最大优势在于通过在结构侧面利用螺栓固定悬挑型钢,斜拉杆通过花篮螺栓收紧后充分参与受力。各地纷纷出台了该类型悬挑脚手架的安全技术标准,但大部分标准中均将悬挑架受力模型简化为:悬挑钢梁承受全挑高荷载,斜拉杆参与受力,钢梁锚固端为铰接。在悬挑结构不设置下部临时支撑的工况下,悬挑型钢未设置前,悬挑型钢处于悬挑受力状态,通过半刚性嵌固端承受悬挑弯矩且弯矩值较大,而目前大部分地方标准中均忽略了这一不利计算工况。该文深入分析了各种工况下悬挑钢梁的力学状态,给出了下部不设置临时支撑状态下按两阶段计算,并将荷载效应叠加的计算方法,深入推导了嵌固端的节点转动刚度和转角计算公式,为精确计算悬挑结构的内力和变形提供了依据。

基于有限元仿真的某脱落电连接器拉脱力研究

本文介绍了一种基于有限元仿真的某脱落电连接器拉脱力研究方法,传统的力学研究以试验为主,成本高,试验周期长,因而大大增加了电连接器的研制周期。本文以力学理论为基础,利用有限元分析仿真技术,建立力学仿真影响参数,从而快速完成电连接器的优化分析,并通过试验验证了该方法的有效性,旨在提供一种电连接器有限元仿真的思路和方法。

压电梁式获能器获能机理的研究

基于压电理论和欧拉伯努利梁模型建立了悬臂梁式压电获能器的理论模型。应用哈密顿变分原理推导了控制方程和边界条件,并在建模时考虑容抗的影响。采用伽辽金法求解控制方程的一般解的形式,分析了获能器在基底处于谐波振动下的输出功率和输出电压。研究结果表明,容抗明显降低了获能器的输出功率。由于容抗的影响,最佳输出功率和输出电压的外接电阻是不同的,最大输出功率对应的外接电阻为500 kΩ,最大电压对应的外接电阻为3 MΩ。在设计时要保证基座振动频率尽可能地接近获能器的固有频率,当基座振动频率与固有频率相等时输出功率和输出电压达到最大值。该研究结果为压电获能器的优化设计提供了理论基础,具有重要的研究意义和工程实用价值。

3D Nonlinear XFEM Simulation of Delamination in Unidirectional Composite Laminates: A Sensitivity Analysis of Modeling Parameters

This article presents a three-dimensional extended finite element (XFEM) approach for numerical simulation of delamination in unidirectional composites under fracture mode I. A cohesive zone model in front of the crack tip is used to include interface material nonlinearities. To avoid instability during simulations, a critical cohesive zone length is defined such that user-defined XFEM elements are only activated along the crack tip inside this zone. To demonstrate the accuracy of the new approach, XFEM results are compared to a set of benchmark experimental data from the literature as well as conventional FEM, mesh free, and interface element approaches. To evaluate the effect of modeling parameters, a set of sensitivity analyses have also been performed on the penalty stiffness factor, critical cohesive zone length, and mesh size. It has been discussed how the same model can be used for other fracture modes when both opening and contact mechanisms are active.

Study of Longitudinal Oscillations of a Building on the Basis of Continuum Plate Model

Continuum plate model in the form of a cantilever anisotropic plate developed in the framework of the bimoment theory of plates describing seismic oscillations of buildings is proposed in this paper as a dynamic model of a building. Formulas for the reduced moduli of elasticity, shear and density of the plate model of a building are given. Longitudinal oscillations of a building are studied using the continuum plate and box-like models of the building with Finite Element Model. Numerical results are obtained in the form of graphs, followed by their analysis.