Optimization of Fixture Number in Large Thin-Walled Parts Assembly Based on IPSO

There are lots of researches on fixture layout optimization for large thin-walled parts.Current researches focus on the positioning problem,i.e.,optimizing the positions of a constant number of fixtures.However,how to determine the number of fixtures is ignored.In most cases,the number of fixtures located on large thin-walled parts is determined based on engineering experience,which leads to huge fixture number and extra waste.Therefore,this paper constructs an optimization model to minimize the number of fixtures.The constraints are set in the optimization model to ensure that the part deformation is within the surface profile tolerance.In addition,the assembly gap between two parts is also controlled.To conduct the optimization,this paper develops an improved particle swarm optimization(IPSO)algorithm by integrating the shrinkage factor and adaptive inertia weight.In the algorithm,particles are encoded according to the fixture position.Each dimension of the particle is assigned to a sub-region by constraining the optional position range of each fixture to improve the optimization efficiency.Finally,a case study on ship curved panel assembly is provided to prove that our method can optimize the number of fixtures while meeting the assembly quality requirements.This research proposes a method to optimize the number of fixtures,which can reduce the number of fixtures and achieve deformation control at the same time.

Warm bending mechanism of extrados and intrados of large diameter thin-walled CP-Ti tubes

In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was researched. By EBSD analysis and Vickers hardness test, the changes of microstructure and strength of the tubes at different bending temperatures of 293, 423 and 573 K, were analyzed. The results show： 1） The extrados of the bent tube deforms mainly by slip, along with few twinning, and the preferred orientation is similar to that of the initial tube; the intrados of the bent tube experiences compression deformation mainly by {1 012} tensile twinning, and the twinning makes the preferred orientation of wall materials change sharply. 2） The Vickers hardness values of both the extrados and intrados of the samples after bending increase greatly; the Vickers hardness values of the intrados are much higher than those of the extrados, and Vickers hardness values of the RD-TD planes are always higher than those of the RD-LD planes, which are related to the different deformation mechanisms.

Eliminating shrinkage defects and improving mechanical performance of large thin-walled ZL205A alloy castings by coupling travelling magnetic fields with sequential solidification

ZL205 A alloys with large thin-walled shape were continuously processed by coupling travelling magnetic fields(TMF)with sequential solidification,to eliminate the shrinkage defects and optimize the mechanical performance.Through experiments and simulations,the parameter optimization of TMF and the influence on feeding behavior,microstructure and properties were systematically studied.The results indicate that the magnetic force maximizes at the excitation current of 20 A and frequency of 200 Hz under the experimental conditions of this study,and increases from center to side-walls,which is more convenient to process thin-walled castings.TMF can break secondary dendritic arm and dendrites overlaps,widen feeding channels,prolong the feeding time,optimize the feeding paths,eliminate shrinkage defects and improve properties.Specifically,for as-cast state,TMF with excitation current of 20 A increases ultimate tensile strength,elongation and micro-hardness from 186 MPa,7.3%and 82.1 kg/mm^(2) to 221 MPa,11.7%and 100.5 kg/mm^(2),decreases porosity from 1.71%to 0.22%,and alters brittle fracture to ductile fracture.

A finite element analysis of a large thrust elastic metal-plastics bearing bush for a hydraulic turbine

Presents the study on the pressure and friction fields of the lubricant film on the surface of a large thrust elastic metal plastic bearing bush in a hydraulic turbine using the method of finite element analysis and the stress and displacement fields in the vertical direction of the bush surface obtained to provide a theoretical basis for the design of contour lines and investigation into the causes for destruction of bushes, and concludes with test results that 1) the stress on the surface of the bush is not uniform; 2) a tension stress tends to occur near the oil ingress and egress edges but it is minor; 3) the biggest displacement in the vertical direction appears where x=84 and Y=1 153 and has a value of 0.022 mm; 4) the deformation of the bearing bush is harmful to the maintenance of lubricant film.

One-Step-Installation of Offshore Wind Turbine on Large-Scale Bucket-Top-Bearing Bucket Foundation

In 2010,the first offshore wind turbine with integrated installation was established in Qidong sea area of Jiangsu Province,China,which led to the implementation phase of one-step-installation technique based on the design and construction of large-scale bucket-top-bearing (LSBTB) bucket foundation.The critical technique of LSBTB bucket foundation included self-floating towing,penetration with adjustment of horizontal levelness,removability and one-step-installation.The process of one-step-installation included the prefabrication of LSBTB bucket foundation in onshore construction base,installation and debugging of wind power,overall water transportation of foundation and wind power system,and installation of foundation and offshore wind turbine on the appointed sea area.The cost of one-step-installation technique was about 5 000 Yuan/kW,which was 30%-50% lower than that of the existing technique.The prefabrication of LSBTB bucket foundation took about two months.During the one-step-installation process,the installation and debugging of wind power and overall water transportation need about one to two days in sea area within 35 m depth.After the proposed technique is industrialized,the cost will be further reduced,and the installation capacity is expected to be up to 500 wind turbines per year.

Two-Dimensional Large Deformation Finite Element Analysisfor the Pulling-up of Plate Anchor

Based on mesh regeneration and stress interpolation from an old mesh to a new one, a large deformation finite element model is developed for the study of the behaviour of circular plate anchors subjected to uplift loading. For the deterruination of the distributions of stress components across a clay foundation, the Recovery by Equilibrium in Patches is extended to plastic analyses. ABAQUS, a commercial finite element package, is customized and linked into our program so as to keep automatic and efficient running of large deformation calculation. The quality of stress interpolation is testified by evaluations of Tresca stress and nodal reaction forces. The complete pulling-up processes of plate anchors buried in homogeneous clay arc simulated, and typical pulling force-displacement responses of a deep anchor and a shallow anchor are compared. Different from the results of previous studies, large deformation analysis is of the capability of estimating the breakaway between the anchor bottom and soils. For deep anchors, the variation of mobilized uplift resistance with anchor settlement is composed of three stages, and the initial buried depths of anchors affect the separation embedment slightly. The uplift bearing capacity of deep anchors is usually higher than that of shallow anchors.

新疆巴楚小海子岩体铁钛成矿特征及资源利用前景

新疆巴楚小海子是近年来在塔里木大火成岩省探获的一个低品位-大吨位岩浆型钒钛磁铁矿床,其成岩成矿机制以及资源利用前景尚不清楚。文章针对小海子岩体2种含矿岩相橄榄辉长岩和橄榄辉石岩开展了地质地球化学研究。橄榄辉长岩相和橄榄辉石岩相虽然在空间上关系不明,但岩相学观察表明它们矿物组成的差异与矿物堆晶作用有关,且二者具有相似的稀土元素球粒陨石标准化和微量元素原始地幔标准化配分曲线,说明是同源岩浆演化的产物,橄榄石较低的Fo值(67.9~72.5)指示幔源母岩浆在深部岩浆房中发生了分异。小海子岩体和与相距约45 km的瓦吉里塔格相比,岩石组成和地球化学组成相似,表明为同源岩浆成因,但后者矿物组成变化范围更大,指示瓦吉里塔格岩体在形成过程中经历了更高程度的分离结晶作用,这可能是造成瓦吉里塔格岩体比小海子岩体的w(TiO_(2))更高的原因。小海子岩体虽然w(TiO_(2))较低(3%~4%),但铁钛氧化物固溶体分离结构不发育,且矿物颗粒粗大,使得铁和钛选矿解离比中国其他地区的钒钛磁铁矿更为容易,因此钛资源利用前景巨大,笔者建议出台地方性的勘查技术规范,为这类铁钛资源的开发利用提供技术标准。

三星堆古蜀文化遗址博物馆大型螺旋坡道结构设计与分析

三星堆古蜀文化遗址博物馆中庭的螺旋坡道采用钢箱梁结构体系,最大半径28.7m,水平投影长度118.5m。介绍了大型螺旋坡道结构体系选型和边界条件的对比过程,采用通用计算软件MIDAS Gen建立多尺度整体模型考虑螺旋坡道和主体结构的相互作用,通过静力分析和反应谱分析考察螺旋坡道在不同荷载作用下的承载能力和变形,并采用有限元软件ANSYS建立分析模型进行连续倒塌分析。结果表明,螺旋坡道采用钢箱梁结构具有较好的整体刚度,静力荷载和地震作用下坡道的应力和变形均满足规范要求,并具有较好的抗连续倒塌能力。

大型轴承套圈超声相控阵曲面自适应聚焦与多通道自动化检测方法

大型轴承套圈作为风电、轨道交通、工程机械领域装备的关键部件,其制造过程中产生的裂纹、夹渣、孔洞等缺陷会严重影响装备整机的服役性能与质量安全。针对大型轴承套圈尺寸大和结构复杂等特点,研究了液固耦合曲面结构中阵列声场分布规律和超声相控阵曲面自适应聚焦法则,给出了大型轴承套圈超声相控阵分区检测方法,开发了大型轴承套圈超声相控阵自动化检测系统,对直径2958 mm的某型风电轴承套圈进行自动化检测应用验证,可有效检出套圈曲面试块的横通孔缺陷和套圈的平底孔缺陷。

一种新型大直径多盘土锚承载力数值模拟分析

新型大直径多盘土锚是采用专业扩孔成盘装置进行多次扩孔,形成多个空腔,在钻孔中放入带有对中支架的钢绞线,灌注水泥砂浆,固化后得到的。为研究该土锚抗拔特性,将等直径土锚作为对照组,运用FLAC3D软件对其在不同荷载作用下的极限抗拔承载力、竖向位移、轴力、锚盘承担荷载和侧摩阻力等方面进行数值模拟分析。结果表明:相同条件下,新型大直径多盘土锚的极限抗拔承载力相较于等直径土锚提高了50%;达到各自极限抗拔承载力时,新型大直径多盘土锚的竖向位移相较于等直径土锚减少了24.22%;新型大直径多盘土锚的侧摩阻力较小且增速较慢,达到极限抗拔承载力时,锚盘分担荷载占施加总荷载的32.094%。

某大型集装箱船中间轴承故障分析与处理

某大型集装箱船为系列船,其中有2条船发生了同样的中间轴承轴瓦烧毁故障,因此开展该型船故障原因分析尤为重要。通过对推进系统的设计、安装调试和运营记录等多方面进行问题排查,并进行失效分析,还原故障的发生过程,分析故障的发生机理,从而提出了改进措施。通过故障案例分析,可为推进系统类似故障分析及处理提供经验和参考。

大高宽比矩形钢管混凝土柱压弯性能研究

为了研究大高宽比矩形钢管混凝土柱的压弯性能,对大高宽比钢管混凝土短柱进行偏压试验并结合有限元模拟补充了4组试件进行对比,包括不同偏心率、高宽比、钢管壁厚度、截面尺寸情况下柱性能的对比分析。最后参考常用的4本国内外规范进行柱承载力计算,对比并判断现有规范是否适用。结果表明:试件破坏模式均为长边鼓曲,当荷载小于极限承载力的80%时,横截面高度上的应变分布服从平截面假定;随着偏心率增大,柱延性提升,在偏心率超过0.205后,柱延性开始下降;随着壁厚增加,柱延性提升,在壁厚达到8 mm后,柱延性开始下降;随着高宽比提升,柱延性降低;随着截面尺寸增大,在壁厚不变的情况下,柱延性降低,在壁厚等比例增大时,柱延性变化不大;随着高宽比、截面尺寸、钢管壁厚度的增大,柱承载力提升;随着偏心率升高,柱承载力降低;参考规范JGJ 138—2016对大高宽比钢管混凝土柱偏压承载力的计算更为准确。

中国盾构隧道工程关键技术的新进展综述

从研究背景与思路、机制/原理、材料/装备、技术论证、试验研究、工程应用等方面介绍中国大直径盾构掘进主轴承事故分析及国产主轴承的自主研发、盾构隧道工程安全高效掘进渣土适配性改良技术及配套材料、盾尾安全保障核心材料研发、盾构隧道新型管片连接技术、城市隧道三模掘进机关键技术等5个方面关键技术的最新进展情况。认为:1)自主研制的超大型盾构机用直径8.01 m主轴承大型套圈纯净度、大型滚子纯净度、大型套圈疲劳性能、大型滚子硬度均匀性、套圈材料淬透性和淬硬层深度、保持架焊缝疲劳寿命和拉断力均优于进口水平;构建了真实对数曲线大型滚子设计方法,突破了高精度大型滚子加工技术,处于国际先进水平,高精度加工和装配保证了零件尺寸精度及形位公差均满足设计要求;通过产品验收、装机应用论证和工程应用,表明应用该大直径主轴承不会产生接触疲劳强度不足和微动引起的疲劳磨损,可用于超大直径盾构隧道工程建设。2)针对黏性、富水砂性和硬岩等复杂地层,以改善岩土环境为核心,研发出了高配向密度的聚合型泡沫剂、高分子抗黏剂、喷涌防止剂和耐磨抑尘剂等环保型系列渣土改良剂,形成了盾构泥饼、喷涌和磨损原位改良主动防控技术,建立了通用地层适配性盾构渣土动态改良技术体系,保障了盾构安全高效掘进。3)针对盾构掘进过程中的盾尾密封失效难题,研发了“黏-稠-流”有机统一的新型盾尾密封油脂,温度敏感性低(黏温系数0.4)、抗水压能力强(最高抗水压3.5 MPa),整体性能提高1.3倍,为盾尾安全提供了有力保障;针对盾构同步注浆浆液泌水、离析和地层沉降难题,研发出了同步注浆充填剂,优化了惰性充填浆液配比,30 min零泌水,实现了壁后惰性充填,保障了管片壁后注浆质量和地层沉降精细化控制。4)新型管片连接技术采用环缝插入+纵缝滑入的连接形式,可以高标准地控制隧道接缝张开量和错台量,管片制作及拼装精度高,可降低接缝防水难度,提升成型隧道的质量,无需设置手孔,无需人工紧固作业,自动化程度高,施工效率高,可节约施工成本及改善洞内拼装作业环境。5)研制出的土压+泥水+TBM三模掘进机能够满足复杂多变、软硬不均复合地层等几乎所有地层的掘进施工,且可在不停机、不拆装设备的前提下实现掘进模式的快速转换,在TBM掘进模式下螺旋输送机+泥浆管道可协同排渣,解决了富水硬岩地层掘进排渣难的问题,机械化和智能化程度高,安全可靠,施工效率高,可改善工人作业环境,节省工期和成本。中国盾构隧道建设取得的巨大成就,推动了中国乃至世界盾构隧道技术的发展和进步,但仍时有安全事故发生,需从装备、材料、技术、管理等方面进一步研究和突破。在今后较长的时间内,中国盾构隧道(尤其是大直径盾构隧道)仍将处于高速建设发展期,面临的建设条件将越来越复杂,技术难度和挑战也将越来越大。要实现盾构隧道建设的快速、安全、健康,需处理好盾构隧道技术领域的关键问题,实现盾构隧道关键核心技术的突破。上述关键技术仍需不断完善并加强推广和应用,以促进中国盾构隧道建设向高适应性、高智能、高可靠性、高效益、高质量、高安全性和低能耗方向发展,形成适合于中国“土壤”的盾构隧道新技术。

孪生数据驱动的大型矿井提升机主轴承随机振动系统的设计可靠性分析

设计阶段的大型矿井提升机主轴承随机振动系统的设计可靠性分析因试验样本不足,无法获取振动加速度响应的完备概率信息。提出了概率信息不完备下大型矿井提升机主轴承设计可靠性分析的技术路线:滚动轴承多尺度耦合系统动力学模型-振动加速度概率密度演化-概率密度演化路径随机过程建模-振动功率谱密度的概率分布-基于条件概率的设计可靠度计算。运用已采集的工况数据驱动建立滚动轴承多尺度耦合系统动力学模型,开展了振动加速度概率密度演化研究;基于概率密度演化和Karhunen-Loève展开,提出了滚动轴承振动加速度的非平稳随机过程建模方法,获得了滚动轴承振动加速度随机序列的孪生数据;研究了大型矿井提升机主轴承振动加速度功率谱密度的概率分布,并计算了大型矿井提升机主轴承在服役时间上的设计可靠度指标。

一种钻孔用回转支撑装置

超大型轴承因为尺寸大、质量大,导致在钻孔过程中轴承容易调整不灵活,定位也不准确,针对上述情况设计了一种钻孔用的可旋转支撑装置。此装置针对超大型轴承套圈的特性,提供一个可完成旋转、支撑的工作台,有效地解决了大兆瓦轴承套圈安装孔的倒角和攻丝的加工问题,提高了工作效率。

基于GADF-MDSC的特大型轴承深度迁移故障诊断方法

针对工程应用中特大型轴承运行工况复杂以及故障数据匮乏,导致其故障特征提取不全面的问题,提出了一种基于格拉姆角差场-多尺度深度可分离卷积(Gramian angular difference field-multi-scale depthwise separable convolutions,GADF-MDSC)的特大型轴承深度迁移智能诊断方法。首先,构建GADF-MDSC故障诊断网络,该网络分为三大模块:图像转换、特征提取、输出部分。图像转换模块采用GADF编码方式将振动信号转换为二维图像;特征提取模块通过MDSC提取综合故障特征信息,并利用双向门控循环单元筛选融合特征;输出部分由Softmax函数预测轴承故障类型的概率分布。然后,利用源域数据预训练模型,将预训练模型权重参数作为目标域训练模型初始化参数,冻结除底层外的所有参数,使用目标域数据微调模型,实现深度迁移故障诊断任务。最后,通过两种特大型轴承试验对深度迁移模型进行验证。试验结果表明,所提方法在目标域样本仅有5.00%的条件下,仍能保证较高的跨工况精度,达到86.04%,且迁移效果优于其他方法。

浅埋超大跨隧道出口偏压段双层初期支护承载特征研究

为研究双层初期支护在开挖跨度达26.3 m、拱顶覆土约10.6 m的下北山2号浅埋超大跨4线隧道出口偏压段的工程应用效果,采用数值模拟方法比较单层初期支护和双层初期支护方案的承载特征差异,采用现场实测方法研究出口偏压段双层初期支护的受力特征。研究结果表明:1)浅埋超大跨隧道在偏压侧的右拱脚~右拱肩范围内支护结构受力偏大,存在局部应力集中,采用双层初期支护技术时的结构承载安全性和对围岩拱顶沉降的控制效果均优于单层初期支护技术;2)出口偏压段的实测水平收敛最大值为18.5 mm,荷载偏压侧的围岩沉降值达49.5 mm,二次支护施作后在拆撑施工阶段能有效稳定围岩变形;3)由双层初期支护受力的实测结果可知,传递到二次支护上的接触压力与对应位置围岩/一次支护接触压力之比为16%~33%,荷载偏压侧的右拱脚及右拱肩位置的二次支护轴力约为一次支护轴力的15%,通过二次支护的施作补强了一次支护对偏压侧的承载作用,采用双层初期支护技术提高了浅埋超大跨隧道出口偏压段支护结构的安全储备。

稀土Ce含量对GCr15SiMn轴承钢冲击性能的影响

制备了不同Ce加入量的GCr15SiMn轴承钢,并对其冲击性能的变化及影响因素进行分析。结果表明:钢中MnS和Al2O3夹杂物在适量Ce的作用下变为球形或椭球形且尺寸较小的稀土夹杂物;稀土夹杂物的种类和数量随Ce含量的增加而增加,Ce加入过量后,夹杂物出现聚合长大导致其尺寸变大且形貌不规则;随着Ce含量的增加,试样的冲击性能先升高后降低,当Ce含量为0.016%时,直径3μm以下小尺寸夹杂物占比最多,夹杂物分布最弥散,且试验钢冲击性能最佳,比不加Ce时提高了173.7%,Ce含量过高时反而降低冲击性能。

水泥土大直径单桩水平承载性能试验研究

为研究水泥土中大直径单桩的水平承载性能,开展了水泥土中大直径单桩水平承载性能离心机试验,分析了加固前后桩基水平承载力、弯矩和水平土抗力-水平位移(p-y)曲线的变化规律.基于黏土典型p-y曲线,考虑土体径向非均质性和桩径效应,修正初始地基反力模量和极限土抗力,提出了一种适用于水泥土加固桩水平承载力的计算模型.结果表明,相比未加固桩,加固桩的水平承载力明显提升,单桩初始刚度和极限承载力分别增加2.61倍和6.29倍.加固桩和未加固桩的桩身弯矩随荷载和深度变化趋势大致相同,但加固桩的最大弯矩位于泥面附近.水泥土加固可以提高桩身p-y曲线的初始刚度和极限土抗力,进而提高桩基水平承载力.计算值与实测值吻合较好,从而验证了所提计算模型的合理性.

基于荷载试验的预应力混凝土刚构桥承载能力评估

为了检测高墩大跨宽体箱梁刚构桥的桥梁承载能力及其动力特性,了解桥梁的健康状况,分析是否能满足设计及使用的要求。以凤凰特大桥为工程背景,建立有限元分析模型,通过静载试验和动载试验的结果与计算模型理论值进行对比和分析。在静载试验下,该桥的挠度校验系数为0.710~0.884,应变测点校验系数为0.603~0.800,相对残余应变和相对残余变位均小于20%。动载试验下桥梁左右两幅自振振动频率最小值为4.103 Hz,实测桥跨最大冲击系数为0.039。凤凰特大桥主桥左幅、右幅静载试验结论表明桥跨在正常使用状态下的承载能力能够满足公路-Ⅰ级汽车荷载的使用要求,动载试验结果表明,受检桥跨的实测自振特性及动力响应满足设计要求。