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.

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.

Experimental and Numerical Research on Deformation Behavior of Thin-Walled and Large Expansion Ratio Guide Vane Liner in Hydroforming Process

Some tube hydroforming process tests and further research work were conducted to manufacture hollow guide vane liners( made of super alloy GH3030).The relative thickness( t0/ OD) of the tubular blank is approximately 0. 01,and the maximum expansion ratio( Dmax/ OD) of the needed part is more than 40%,and the length to diameter ratio of the expansion regionis more than 3. 0. It is very hard to manufacture this kind of ultra-thin-wall,curved axis and large expansion ratio tubular part without fracture and wrinkles. The success of the process is highly dependent on useful wrinkles with appropriate internal pressure and axial feeding. A simplified finite element model and a theoretical model are used for detecting the deformation behavior and forming laws. Further study results demonstrate that the useful wrinkles do not appear at the same time and middle-wrinkles need bigger axial force than tube-end-wrinkles and feeding-wrinkles. The wrinkles can transfer bigger axial force after its wave peak has come into contact with the die inner surface. The thickness thinning rate of the element at the peak is bigger than that at the trough. With the increase of the axial and hoop stress ratio,the critical buckling stress also increases. Microstructure examination results show that the grain size in the maximum thinning zone has been stretched and refined after the large deformation and annealing treatment.The process is feasible and the finished part is qualified.

Soil Plug Effect Prediction and Pile Driveability Analysis for Large-Diameter Steel Piles in Ocean Engineering

Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.

An Approach to Stability Analysis of Embedded Large-Diameter Cylinder Quay

The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and offshore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, embedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of significant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.

Forming Characteristics of Al-alloy Large-diameter Thin-walled Tubes in NC-bending Under Axial Compressive Loads

Tube thinning control without wrinkling occurring is a key problem urgently to be solved for improving the forming qualities in numerical control （NC） bending processes of large-diameter Al-alloy thin-walled tubes （AATTs）. It may be a way solving this problem to exert axial compression loads （ACL） on the tube end in the bending. Thus, this article establishes a three-dimensional （3D） elastic-plastic explicit finite element （FE） model for the bending under ACL and has its reliability verified. Through a multi-index orthogonal experiment design, a combination of process parameters, each expressed by a proper range, for this FE model is derived to overcome the compression instability on tube ends. By combining the FE model with a wrinkling energy prediction model, an in-depth study is conducted on the forming characteristics of large-diameter AATTs with small bending radii and it can be concluded that （1） The larger the tube diameters and the smaller the bending radii, the larger the induced tangent tension stress zones on tube intrados, by which the tube maximum tangent compression stress zones will be partitioned in the bending processes; thus, the smaller the ACL roles in decreasing thinning degrees and the larger the compression instability possibilities on tube ends. （2） The tube wrinkling possibilities under ACL are larger than without ACL acting in the earlier forming periods, and smaller in the later ones. （3） For the tubes with a size factor less than 80, the ACL roles in decreasing thinning degrees are stronger than in increasing wrinkling possibilities.

Forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters

With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.

斜轧轧管与皮尔格轧管对大口径薄壁无缝钢管性能影响

通过对斜轧轧管机组生产的φ813 mm×28 mm规格和皮尔格轧管机组生产的φ711 mm×24 mm规格的15CrMoG无缝钢管的化学成分、常温拉伸、高温拉伸、硬度、冲击和金相组织等试验分析,研究了斜轧轧管与皮尔格轧管两种不同无缝钢管轧制方式对大口径薄壁无缝钢管性能的影响。结果表明:在相近轧制比的前提下,两种轧制方式对常温拉伸、高温拉伸及硬度等性能指标无影响,斜轧轧管方式生产的15CrMoG无缝钢管,其横纵向性能差异较小,冲击韧性更优。

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。

市域线大直径隧道预制中隔墙拼装姿态分析

为控制大直径隧道预制中隔墙拼装质量,基于上海市机场联络线,对其内部预制中隔墙的拼装姿态进行研究和分析。在规定中隔墙坐标系后,分别对中隔墙在有、无初始拼装误差下的拼装姿态进行研究,得到中隔墙在上述工况下的姿态信息及其底面平面方程解析表达。分析结果表明:1)当中隔墙无初始拼装误差或其仅有平动或转动初始拼装误差时,不同控制点位的选取和调节系统千斤顶的顶进顺序不会对中隔墙的拼装控制产生影响,可根据所得中隔墙姿态表达式对其拼装姿态进行控制;2)当中隔墙仅存在平动或转动外的初始拼装误差时,应依据调节系统不同顶进顺序对中隔墙姿态进行单独计算,再依据所得表达式对中隔墙拼装进行控制,提高中隔墙拼装精度。将解析公式应用于中隔墙施工,取得了良好的工程应用效果。

大直径盾构隧道预制中隔墙顶部节点整体受力分析研究

市域线大直径盾构隧道中隔墙主要承受由列车行驶产生的水平风压载荷,基本不承受竖向外载荷,使得其顶部节点是重要结构,需要对其力学性能进行研究。本文依托上海市机场联络线,介绍了其中隔墙顶部节点构造信息及数值模型等背景资料,随后阐述了不同构造下顶部节点计算分析与结果,最后对可能出现的顶部节点失效情况进行了受力分析。结果表明:今后中隔墙设计可按照连接件与中隔墙间无间隙的情况进行计算;当前连接件的焊缝、黏结强度均有一定安全储备;在可能出现顶部连接件掉落的情况下中隔墙会产生最大42.17 mm的侧向变形。

长距离超大直径薄壁煤气管道施工技术研究

长距离超大直径薄壁煤气管道施工技术是一项新型技术,对于支撑煤炭产业发展及煤气资源供应发挥了重要作用。为了有效地应用管道施工技术,文章从煤炭工程的视角出发,结合实际工程案例,分析和研究该技术的施工难点、关键技术措施,旨在寻求高效、安全、经济的煤气管道施工技术方案,为煤炭工程的可持续发展提供支持。

连续管技术与装备在深层页岩气开发中的浅析

为了促进深层页岩气连续管技术进步,提高连续管装备在深层页岩气井的作业能力和安全水平,总结深层页岩气连续管作业技术与装备发展现状,调研深层页岩气连续管作业技术与装备面临的挑战;分析深层页岩气连续管作业技术与装备的发展需求,总结深层页岩气连续管作业技术与装备研究难点。基于此,提出了深层页岩气连续管作业技术与装备发展方向和研究建议,即配备大管径、超长下深能力连续管作业装备,推进延长下深技术发展,持续提升作业安全性,加强数字化连油建设及发挥辅助配套的作用等。同时提出了大管径、超长下深能力连续管作业装备的结构形式和现场作业流程,大管径、大容量滚筒的结构和作业模式,延长下深新作法、提升连续管作业安全性的具体措施和辅助配套的用法和配套要求,对深层页岩气连续管作业具有很强的指导意义。未来连续管应用需适应深层超深层、超长水平段、套管变形井等复杂井作业需求,是深层页岩气连续管作业技术与装备发展及现场应用的主要方向。

弯曲参数对304不锈钢管材大曲率无芯弯曲成形性的影响

针对管材无芯弯曲多缺陷耦合的成形问题,以管材壁厚变化率及截面短轴变化率作为成形指标,在不同弯曲参数下进行304不锈钢管材大曲率无芯弯曲试验,结合硬度测试及微观组织表征,研究了弯曲参数对弯曲成形及微观组织演变的影响规律。结果表明:随着弯曲速度、弯曲角度及相对管径的增大,壁厚变化率呈增加趋势,且壁厚增厚率始终大于壁厚减薄率,同时,弯管截面畸变程度加剧。在各弯曲参数下,管材弯曲内外侧均发生奥氏体向马氏体转变,马氏体组织含量及硬度与壁厚变化率呈正相关关系,中性层几乎不存在马氏体。通过选择合适的工艺,最终弯制出相对弯曲半径为1.4的合格弯管。

大直径盾构隧道中隔墙施工流程及精度控制

以上海机场联络线3标为工程背景,对大直径盾构隧道中隔墙的作业过程及误差控制进行研究。首先,根据设计方案和施工情况,对中隔墙的整体施工流程进行梳理。其次,确定了中隔墙的安装方法,同时针对中隔墙安装精度提出相应的控制措施,既提高了中隔墙的施工效率,又具有安全稳定、成本低且易推广等特点。最后,选取部分中线拼装偏差测量数据,对中隔墙安装时的精度控制效果进行A类不确定度分析。结果表明:中隔墙的旋转中心距离中隔墙底部为4034 mm,中隔墙的抬升高度为1838 mm。对第995、1000、1005环的中线偏差数据采用A类不确定度予以评判,测量结果分别为1.05、2.05、3.06 mm,检测的次数各为20次,自由度为19,置信概率95%,测量精度很高。

加筋大直径搅拌桩重力式挡土墙技术在深基坑工程中的应用

为提升软土地区深基坑工程的工程质量,文中以某高层建筑项目为例,设计加筋大直径搅拌桩重力式挡土墙支护方案及对该方案的施工技术进行分析,并对工后的施工效果进行评价。结果表明,施工后的桩底标高为150mm,桩位偏差为15mm,桩的垂直度偏差为0.5%;桩身完整均匀,桩身混凝土强度达到1.2MPa;基坑围护结构最大变形位移值为20mm。所有的检测值未超过预警值,满足设计方案的要求。加筋大直径搅拌桩重力式挡土墙技术的工程总造价为8210.4万元,比钻孔灌注桩高了3.6%;施工周期为60d,比钻孔灌注桩的施工周期缩短了50%。加筋大直径搅拌桩重力式挡土墙技术具有优良的社会经济效益。

水网地区大口径及大壁厚管道项目管理创新实践

在复杂的水网地区,大口径及大壁厚管道施工是一项极具挑战的工程。由于地基承载力差、焊接层(道)数多、沉管下沟难度大等特点,传统的施工方法往往难以应对。以中俄东线天然气管道工程(永清—上海)南通—甪直段工程的项目实例,通过作业带清理及运布管施工、全自动焊施工、严控坡口加工钝边厚度、控制管口组对间隙、优化焊接参数、层(道)焊接完成后检查焊接头、增加防潮措施、顶管穿越段冲砂沉管及漂管回拖、沉管下沟等一系列关键工序施工技术的创新实践,形成了一套适用于水网地区大口径及大壁厚管道的施工技术措施,促进了水网地区大口径及大壁厚管道项目建设的顺利开展,也为今后类似的管道施工建设提供了项目管理经验借鉴。

广西苗儿山大厚度水敏性地层冲洗液技术研究及应用

广西苗儿山地区铀矿找矿潜力巨大,但局部地区地层复杂,存在大厚度水敏性地层及破碎地层,钻探施工中频繁遇到孔壁坍塌及钻孔超径等难题,导致孔内事故频发,严重影响施工进度。因此,对该地区水敏性岩心进行了矿物成分和微观特征分析,分析结果表明水敏性地层含有大量蒙脱石、高岭石、水云母等粘土矿物,且微裂隙发育,水化膨胀严重。针对以上问题,通过室内实验评价,优选了新型成膜护壁材料,进一步研制了护壁性良好的成膜护壁冲洗液体系,其最优配方为:5%成膜A剂+3%成膜B剂+1.5%改性沥青+1%随钻堵漏剂+1%封堵剂+0.6%增粘剂+0.2%包被剂。该冲洗液API滤失量为5~8 mL,相对膨胀降低率达到87%以上,可有效抑制水敏性岩心水化膨胀,护壁效果明显。该技术在苗儿山地区3个试验钻孔成功应用,顺利钻穿水敏性地层,未发生岩心分散、孔壁坍塌等问题,取得了良好的应用效果,初步形成了针对该地区水敏性地层的成膜护壁冲洗液技术。

深埋大直径管线原位保护工况下地下连续墙施工技术

针对城市核心区域地下工程施工过程中管线迁改制约施工难题,创新出一种深埋大直径管线原位保护工况下地下连续墙施工技术,并在南京惠民大道综合改造工程中成功应用。文章以应用案例为依托,重点对导墙工艺改进、成槽机改造、成槽工艺创新及钢筋笼吊装措施进行介绍,为类似工程提供参考。

薄壁大口径PE管材弯曲有限元分析

对加入钢丝网的薄壁大口径PE管,运用有限元法分析其在弯曲过程中出现的内侧失稳起皱、横截面畸变等问题。采用理论分析、数值模拟和实验研究相结合的方法,对薄壁大口径PE管材弯曲进行有限元分析,在分析PE管材弯曲机理和失效形式的基础上,通过实例得出有钢丝网PE管材的弯曲所受应力主要由钢丝网承载,结合弯曲测试,发现加入钢丝网可有效增强管材的刚度、抑制管材弯曲时内侧失稳起皱和横截面畸变等现象的发生,有限元数值模拟结果与实验结果较为一致,说明有限元数值模拟分析的可靠性。