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.

Velocity Field and Variation of Wall Thickness During Tube Dieless Upsetting

Theoretical analyses show that the variation of wall thickness is in direct proportion to outer-diameter, inter-diameter, and (√1 + Rs) (Rs is sectional increase ratio of tube), the theoretical calculated results of wall thickness during tube dieless upsetting are very approximate to the experimental one. As the width of deformation field increases, both the variation of wall thickness and the derivative of wall thickness variation to width of deformation field (tf/to) reduce.

Effects of process parameters on numerical control bending process for large diameter thin-walled aluminum alloy tubes

Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.

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.

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.

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.

Thin-Walled Tube Extension by Rigid Curved Punch

Computer model is developed for non-steady and steady-state process of thin-walled tube extension by the rigid punch with curved profile. Rigid-plastic membrane shell theory with quadratic yield criterion is used. Tube material normal anisotropy, work hardening, wall thickness variation and friction effects are considered. FORTRAN programs of the model predict distributions of the thickness, meridian stress, yield stress and pressure along curved generator of deformed tube and the tube extension force versus punch displacement relation. Model predictions are correlated with experimental data.

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。

圆形截面钢管混凝土受弯构件塑性发展系数的双因素计算模型研究

为了综合考虑截面几何和材料特性对圆形截面钢管混凝土(CFST)受弯构件抗弯强度的影响,选择截面厚径比和材料强度比作为自变量,研究建立了圆CFST受弯构件截面塑性发展系数的二元函数计算表达,并建立了截面抗弯强度计算模型。首先在确定厚径比和强度比取值范围的基础上,设计1 656个圆CFST受弯构件的数值模型,利用纤维模型法计算确定每个构件的截面抗弯强度和塑性发展系数。然后选择截面钢管壁厚与外径之比、钢管强度与核心混凝土强度之比作为自变量,通过回归分析建立圆CFST构件的截面塑性发展系数的二元函数表达式,据此提出了圆CFST构件截面抗弯强度的计算模型。最后通过与试验数据、现行设计规范和研究文献中不同计算模型进行对比分析,验证了建立的圆形截面钢管混凝土受弯构件的截面塑性发展系数和抗弯强度计算模型具有更高的精度和适用性。

用于风电钢塔筒的加劲钢管压弯性能试验研究

薄壁圆钢管广泛应用于风电机组锥筒型钢塔筒中,其在径厚比较大时易出现局部失稳,进而导致塔筒承载能力下降。该文提出了一种可用于风电钢塔筒的纵向加劲钢圆钢管结构形式,并进行了6个试件的压弯加载试验,以研究加劲肋形式及径厚比大小对加劲圆钢管压弯性能的影响。试验结果表明:在相同用钢量下,加劲肋有效改善了钢管的局部屈曲,改变了结构的破坏形态,增大了钢管的塑性发展程度,从而提升了钢管的承载力及延性,其中T型加劲肋的增强效果更为明显。并将试验模型与有限元建模进行对照,互相验证了准确性。最后使用现有设计标准对试验结果进行了初步评估,无加劲肋试件与各设计标准吻合良好,但现有计算方法低估了加劲试件的承载力。

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。

爆炸动载下金属柱壳破片速度场分布研究

针对格尼(Gurney)公式无法描述破片速度场沿圆柱壳体轴向变化的问题,该文通过AUTODYN软件建立仿真模型,分析了长径比和壳体壁厚对破片速度场分布的影响。考虑爆炸加载下壳体断裂过程,修正了Gurney公式。基于上述研究,将壳体长径比和相对壁厚引入指数形式的修正因子中,建立了破片速度场轴向分布模型。通过实验验证了该模型的合理性。研究结果表明:对于圆柱形战斗部,相对壁厚为常数,长径比越大,战斗部形成破片速度越接近v 0;长径比为常数,壳体相对壁厚越小,战斗部形成破片速度越接近v 0。将该文理论结果与Gurney理论结果以及实验结果进行对比,该文理论结果误差均在7%以内,大部分误差小于3%,与实验结果更加吻合,验证了该文建立的破片速度场轴向分布模型的合理性。该文理论模型可为杀伤战斗部破片参数精准设计提供参考。

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。

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。

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。

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。

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。

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。

LNG真空绝缘双壁管应力的影响因素研究

管路的应力受多种因素影响,包括管道的基本参数(压力、温度、管径等)和外界因素。文中选取管径和壁厚进行研究,以LNG真空绝缘双壁管为例,分别对双壁管的内管和外管在不同管径和壁厚情况下的应力进行计算分析,研究这2个因素对管道应力的影响规律,以此得出4组内外管径和壁厚的组合方案,再次通过应力分析比较,初步确定双壁管内外管径和壁厚的最优组合方案,为后续的管路设计和布置优化提供参考。