Revisiting the elastic solution for an inner-pressured functionally graded thick-walled tube within a uniform magnetic field

In this paper, the mechanical responses of a thick-walled functionally graded hollow cylinder subject to a uniform magnetic field and inner-pressurized loads are studied. Rather than directly assume the material constants as some specific function forms displayed in pre-studies, we firstly give the volume fractions of different constituents of the functionally graded material(FGM) cylinder and then determine the expressions of the material constants. With the use of the Voigt method, the corresponding analytical solutions of displacements in the radial direction, the strain and stress components, and the perturbation magnetic field vector are derived. In the numerical part, the effects of the volume fraction on the displacement, strain and stress components, and the magnetic perturbation field vector are investigated. Moreover, by some appropriate choices of the material constants, we find that the obtained results in this paper can reduce to some special cases given in the previous studies.

Modeling and Investigation of the Wall Thickness Changes and Process Time in Thermo-Mechanical Tube Spinning Process Using Design of Experiments

Tube spinning technology is one of the effective methods of manufacturing large diameter thin-walled shapes. In this research, effects of major parameters of thermo mechanical tube spinning process such as preform's thickness, percentage of thickness reduction, mandrel rotational speed, feed rate, solution treatment time and aging treatment time on the wall thickness changes and process time in thermo-mechanical tube spinning process for fabrication of 2024 aluminum spun tubes using design of experiments (DOE), are studied. The statistical results are verified through some experiments. Results of experimental evaluation are analyzed by variance analysis and mathematic models are obtained. Finally using these models, input parameters for optimum production are achieved.

An approach for optimization of the wall thickness (weight) of a thick-walled cylinder under axially non-uniform internal service pressure distribution

Today, improving the weight/load carrying capacity ratio of a part is the matter of studies in most of the scientific and industrial areas.Autofrettage dimensions, the amount of material removed from outer and inner radius while manufacturing and the service pressure applied affect the residual stress distribution throughout the wall thickness and hence the load-bearing capacity of a thick-walled cylinder. Calculation of residual stresses after autofrettage process and optimization of autofrettage outline dimensions by using the amount of service pressures applied are common issues in literature.In this study, mandrel-cylinder tube interference dimensions were renovated by using traditional methods for swage autofrettage process of a gun barrel. Also, the residual stresses in the cylinder after autofrettage process, inside and outside material removal process and the variable service pressure throughout the cylinder applied were taken into consideration and incorporated into the design. By using the constrained optimization method, wall thickness(thus the weight) was optimized(minimized)to achieve the specified safety factor along the length of the cylinder. For the same cylinder, the results of the suggested analytical/with residual stress calculation approach were compared to analytical/without residual stress calculation results and numerical topology optimization method calculation results. Since the experimental measurement results are not yet available, it was not possible to compare them with the calculation results.The suggested approach enabled 22.9% extra weight reduction in proportion to numerical topology optimization and enabled 4.2% extra weight reduction in proportion to analytical/without residual stress optimization.Using this approach, the gain from residual stresses after autofrettage operation, the loss of residual stresses after material removal, and the effects of service pressures can be taken into account for each stage of design.

Numerical evaluation of an autofrettaged thick-walled cylinder under dynamically applied axially non-uniform internal service pressure distribution

A dynamical moving pressure structural numerical calculation model using the internal ballistics calculation pressure-time results was constituted and the vicinity of the internal ballistics and quasiinternal ballistics structural model was checked. The Von Mises stresses obtained by the dynamical structural numerical model calculations and the Von Mises stresses calculated from the shot test strain measurements were compared. The difference for the worse case was 20% and for the best case was 0.1%.Furthermore, the model gave better agreement for the higher charge masses. The numerical structural quasi-internal ballistics computation model created was verified for the top charge mass which represents the highest stress condition and used in a gun barrel design.

NON-LOCAL MODELING ON MACROSCOPIC DOMAIN PATTERNS IN PHASE TRANSFORMATION OF NiTi TUBES

Recent experiments revealed many new phenomena of the macroscopic domain patterns in the stress-induced phase transformation of a superelastic polycrystalline NiTi tube during tensile loading. The new phenomena include deformation instability with the formation of a helical domain, domain topology transition from helix to cylinder, domain-front branching and loading-path dependence of domain patterns. In this paper, we model the polycrystal as an elastic continuum with nonconvex strain energy and adopt the non-local strain gradient energy to account for the energy of the diffusive domain front. We simulate the equilibrium domain patterns and their evolution in the tubes under tensile loading by a non-local Finite Element Method （FEM）. It is revealed that the observed loading-path dependence and topology transition of do- main patterns are due to the thermodynamic metastability of the tube system. The computation also shows that the tube-wall thickness has a significant effect on the domain patterns： with fixed material properties and interfacial energy density, a large tube-wall thickness leads to a long and slim helical domain and a severe branching of the cylindrical-domain front.

仪表配管工程用TUBE管简析

石化、化工自控仪表配管工程设计中经常用到Tube管。本文依据国内外标准和规范,对比分析了Tube管和Pipe管的区别,阐述了Tube管自身的特点和优势,说明了Tube管表面光洁度、材料、硬度和壁厚等因素对仪表管路连接的影响。通过比较各类标准规范以及结合工程设计经验,对仪表安装用Tube管的常用尺寸规格、壁厚的选择、温度及材料的影响做了说明。介绍了Tube管连接用卡套接头的原理、特点及应用,适当地选择Tube管及卡套接头将会给仪表配管工程带来便利。

新型切口厚壁钢管耗能支撑抗震性能研究及参数分析

为了解决现有金属耗能装置连接复杂或容易发生非预期破坏等问题,提出了一种新型切口厚壁钢管耗能支撑(energy-dissipation brace with notched thick-walled steel tube,EDB-NTWST)。该支撑主要依靠首次提出的切口厚壁钢管(notched thick-walled steel tube,NTWST)耗能,震后仅需更换NTWST即可完成修复,因而可提高结构震后修复速度。针对切口厚壁钢管的不同布置方式,给出了两种支撑的构造形式,并推导了NTWST简化力学分析方法。通过试验研究,验证了理论计算及数值模拟的准确性。采用参数化分析方法,设计了16个NTWST试件,在单调加载和循环荷载下分别对其进行了有限元分析。结果表明:EDB-NTWST的滞回曲线饱满,变形能力强,延性高,可将损伤集中于NTWST上,能够实现可重复使用的目标;简化力学分析方法与试验结果吻合较好,可用于EDB-NTWST的初步设计;NTWST的力学性能能够通过调整其设计参数进行改变,承载力的提高可通过加大耗能环厚度来实现,增加耗能环的数量可以显著提高其变形能力,增加耗能环的宽度并减小中径,是提高NTWST延性的有效方法。

聚合物三腔微管挤出口模结构对胀大变形的影响

聚合物熔体的模内流动状态与模外胀大变形直接影响微挤出制品的成型质量。文中基于Carreau模型,采用数值模拟方法,研究了聚合物三腔微管挤出过程中口模壁厚差与空心度结构特征对胀大变形行为的影响。结果表明,影响挤出胀大变形程度的关键因素是口模出口附近的轴向速度分布;内外壁厚差会导致较大壁厚位置处对应的型坯厚度增大,而较小壁厚位置处的型坯厚度减小,壁厚差变化对薄壁区域壁厚变形影响较大,达到91.4%;空心度减小能提升口模出口附近轴向速度分布均匀性,减小了70.1%的变形程度;基于胀大变形规律逆向补偿设计了口模形状与尺寸,明显改善了制品成型质量。研究结果对聚合物多腔微管的口模结构优化设计具有理论意义与工程应用价值。

Analysis and experiment of cross-section flattening incoreless tube bending

In order to predict the flattening rate of the cross-section accurately during the tube ben- ding, the generation principle, the solution and the influence factor of the cross-section flattening were studied. On the basis of the plane-stress and the assumption that the plastic volume is con- stant, three-dimensionai strain formulas were established in consider of the cross-section flattening. Considering the wail-thickness change, the approximate calculation formulas of short axis flattening rate were deduced, with the outer diameter and the inner diameter as parameters. Because different materials have different cross-section flattening rates, a material correction factor was introduced to modify the formula based on experiments. Finally, the validity of the theoretical formulas was proved according to the calculation and the experiment results, which can provide a reference for the forming quality prediction in tube bending.

散粒体填充FRP缠绕管桥梁防撞装置冲击吸能特性及构造参数研究

针对传统被动防撞装置可能存在的体积大、造价高、维护困难以及对撞击力的削减效果有限等缺陷,提出一种新型防撞装置,该装置在纤维增强复合材料(FRP)缠绕管内部密填低密度耗能散粒体,并将多个防撞节段拼接成整体,环绕桥墩以抵御船舶撞击。为了解该新型防撞装置的防撞性能并选取合适的构造参数,分别对纤维缠绕角度±45°、±75°的新型防撞装置局部试件进行冲击试验及有限元模拟,并对缠绕角度与缠绕管壁厚进行防撞性能构造参数分析。结果表明:有限元模型与试验结果吻合良好,缠绕角度为±75°的新型防撞装置相比于缠绕角度±45°的新型防撞装置在冲击作用下更易发生剪切破坏,比选得到壁厚为4 mm、缠绕角度为±45°的新型防撞装置在6.0 m冲击高度下的冲击力峰值削减率达到55.82%,防撞效果最优。

脉冲涡流检测在核电厂管道的应用

[目的]为了提高换热效率,核电厂的凝结水管线、主给水管线、疏水管线及部分抽气管线管道外侧均加装了包覆层,目前对于铁磁性管道的检测手段主要为常规超声技术及超声导波技术。上述检测技术受限于检测环境及前提条件,检测难度较大。文章旨在提高带保温层管道的检测效率,丰富技术手段,缩短检修工期,提高核电厂经济效益。[方法]通过研究核电站低频电磁干扰下脉冲涡流检测方法的可行性和可靠性,利用感应电压测量值与计算值建立最优化参数反演问题,并结合参数之间的耦合关系式,根据管道脉冲涡流场时域解析解的基础上,建立感应电压测量值与计算值特定关系式,建立最优化参数反演问题,并结合参数之间的耦合关系式,提出1种针对核电厂带保温管道在役运维的脉冲涡流检测技术。[结果]利用文章提出的铁磁管道相对壁厚脉冲涡流检测方法对核电厂在役样管进行检测,并将检测结果与常规超声检测结果进行对比,得出二者检测结果误差在5%左右。[结论]脉冲涡流检测结果可靠,适用于核电厂铁磁管道壁厚腐蚀减薄的无损检测与评估。

基于Mori-Tanaka方法的功能梯度厚壁圆筒近似热弹性理论解

【目的】功能梯度厚壁圆筒的热弹性问题存在不考虑组分材料微观结构影响,已有文献只给出了基于Mori-Tanaka方法功能梯度厚壁圆筒受力学和热学荷载的数值解,并且只考虑了球形夹杂这一单一夹杂形状的情形。【方法】基于Mori-Tanaka方法对功能梯度厚壁圆筒的热弹性问题进行分析,给出了一种近似热弹性理论解,该理论解不仅与数值解契合度高,而且可以考虑夹杂形状对物理量的影响,最后分析了不同边界条件下夹杂形状对径向位移和各向应力的影响。【结果】结果显示,在两种边界下,夹杂形状对径向位移都有较大的影响;但在温度边界下,夹杂形状对径向应力有较大影响,对轴向应力和周向应力影响较小;在应力边界下,夹杂形状对轴向应力影响较大,对周向应力和径向应力影响较小。

V形截面管充液压制圆角充填行为研究

基于力学分析,利用有限元模拟和充液压制成形实验研究了V形截面管圆角成形所需内压。在不同内压下对成形管材壁厚的变化进行了充液压制实验研究。并通过理论计算选择合适的实验参数,成形出符合要求的扭力梁结构件。结果表明:圆角半径越小,成形所需内压越大;V形截面管内圆角半径随着内压的增加而减小,外圆角半径随着内压的增加而增大;V形截面管壁厚增厚主要发生在上侧圆角区,减薄主要发生下圆角区,并且最大减薄发生在下圆角中心区。

浅谈开孔补强设计在常规压力容器中的应用

分析说明了常规压力容器上开孔补强的设计规定和设计过程,论述了几种常用的开孔补强的结构型式,并阐述了不同补强结构的适用范围和补强效果,最后举例说明了如何针对实际工程案例进行开孔补强设计。

有限壁厚圆管的声辐射

为研究有限壁厚圆管的声辐射特性,使用二维(2D)轴对称时域计算流体动力学(computational fluid dynamics,CFD)方法计算了管口反射系数和端部修正。无限薄圆形管道计算结果与理论值吻合良好,从而证明了计算方法的正确性。研究了壁厚对管口声辐射的影响,计算结果表明,随着壁厚的增加,反射系数的幅值逐渐减小,端部修正系数则明显增大。通过对计算结果的多项式拟合,给出了反射系数和端部修正的拟合公式。最后应用该拟合公式计算管口的辐射声阻抗,结合有限元方法计算了有限壁厚膨胀腔消声器的减噪量(noise reduction,NR),通过与使用自动匹配层计算得到的结果对比,验证了拟合公式的准确性和实用性。

超高层核心筒异形超厚钢板剪力墙施工技术分析

文中以某超高层建筑项目为例,探析了超高层核心筒异形超厚钢板剪力墙施工技术,采用BIM技术模拟深化,以优化安装顺序、焊接工艺流程,并对焊缝变形提出有效的控制措施。结果表明,除外观质量外,其余检查项目合格率均超过95%,符合国家规范要求,表明该技术方案能够取得良好的应用效果。

支气管内置管泵药治疗厚壁空洞型肺结核的临床效果

目的探究支气管内置管泵药治疗厚壁空洞型肺结核的临床效果。方法选取赣州市第五人民医院2019年10月至2020年12月收治的60例厚壁空洞型肺结核患者作为研究对象,按照抽签法分为观察组和对照组,每组各30例。对照组采用常规抗结核化疗治疗,观察组在常规抗结核基础上加用支气管内置管泵药治疗。比较两组的痰结核菌转阴率、空洞闭合率、复发率、不良反应。结果两组治疗1个月后的痰结核菌转阴率比较,差异无统计学意义(P>0.05);观察组治疗2个月后的痰结核菌转阴率高于对照组,差异有统计学意义(P<0.05);而治疗6个月后,两组患者的痰结核菌均转阴,差异无统计学意义(P>0.05);治疗1个月后,两组的空洞闭合率比较,差异无统计学意义(P>0.05),而治疗2、6个月后,观察组空洞闭合率为90.00%、93.33%,均高于对照组的43.33%、56.67%,差异有统计学意义(P<0.05);随访1年,两组的厚壁空洞型肺结核复发率比较,差异无统计学意义(P>0.05);两组不良反应总发生率比较,差异无统计学意义(P>0.05)。结论支气管内置管泵药治疗厚壁空洞型肺结核疗效显著,可促进痰找结核菌转阴,提高空洞闭合率,复发率低,无明显不良反应。

小弯曲半径管材绕弯成形壁厚增厚行为预测

为了有效预测和控制0Cr21Ni6Mn9N高强不锈钢管小弯曲半径绕弯成形壁厚增厚行为,实现精确绕弯成形,基于所建立的可靠的有限元模型,并结合正交试验,研究了工艺参数对高强不锈钢管小弯曲半径绕弯成形壁厚增厚影响的显著性及规律。结果表明:影响壁厚增厚的显著性工艺参数依次为:管材与防皱块间隙C_(w)、管材与压块间隙C_(p)、管材与防皱块摩擦因数f_(w)、管材与芯棒间隙C_(m)和芯棒伸出量e;壁厚增厚率随着C_(w)、C_(p)和e的增加而减小,随着f_(w)和C_(m)的增加先减小后增大;建立了最大壁厚增厚率与显著性工艺参数之间的多元线性回归预测模型,其预测结果与正交试验结果之间的最大相对误差为4.20%,可用于快速准确地预测高强不锈钢管小弯曲半径绕弯成形壁厚增厚行为。

径向锻造加工率对TC4钛合金管材组织与性能的影响

对TC4钛合金斜轧管坯分别进行23.4%、43.8%和52.8%三种加工率的无芯轴径向锻造,研究不同加工率对管材内壁质量、尺寸、显微组织和力学性能的影响。结果表明:随着径向锻造加工率的增加,内壁起皱量和壁厚增量随之增大,同时壁厚均匀性变差;部分片状α发生球化,片状α和少量等轴α并存;抗拉强度和屈服强度随着加工率的增大而增加,塑性无明显变化。

600MW机组省煤器爆管原因

某600 MW机组省煤器发生爆管事故,采用宏观观察及壁厚测量、磁粉检测、化学成分分析、力学性能测试、金相检验、扫描电镜及能谱分析等方法分析爆管原因。结果表明:弯管外表面磨损严重及腐蚀造成壁厚减薄量过大,并且爆裂弯管处圆度超标,在内压膜应力的作用下,弯管外弯复圆过程会产生较大的弯曲应力和拉应力,故弯管外弯部位表面承受的应力进一步增大,使剩余壁厚无法承受内部介质的压力,从而造成爆管事故。