CT20钛合金薄壁管材数控冷弯成形行为研究

薄壁管材的小弯曲半径数控弯曲成形十分困难,外侧壁厚减薄是弯管成形中的加工缺陷之一,对于钛合金薄壁管尤为严重。采用模拟与实验相结合的方法,对规格为58 mm×1.5 mm的CT20钛合金管材数控弯曲成形过程中弯曲段的壁厚减薄进行了研究,得到相对弯曲半径对壁厚减薄的影响规律。结果表明,CT20钛合金管材冷弯成形时的极限相对弯曲半径(R/D)为2。     

介绍高炉冷却壁水管弯制的一种方法

我矿新建的300m~3高炉冷却壁水管用φ45×6无缝钢管制成,比100m~3高炉的冷却壁水管管径大、管壁厚,而且技术要求高。开始我们用灌砂热煨弯管法进行弯制,质量难以保证。后想改成用钢管冷煨弯管法弯制,但没有电动煨管机,一时又买不到。为此,我们设计制作一套胎模。胎模根据冷却壁水管的管径和弯曲半径来设计,胎模凹槽深度要大于管子半径5mm左右,槽太浅弯管会变扁、槽太深管子不易脱模。再根据水管的弯头尺寸,设计出“井”字托滚式胎架。胎模固定在压力机的压杆头上,“井”字托滚式胎架放在压力机工作台上,结构如图所示。压力机的压力约40t,压杆头下降的速度75mm/min。我们用这套胎模压制了新建的300m~3高炉第九层、第十层冷却壁中的水管236根,弯头表面圆滑、无伤痕、无裂纹,质     

小弯头管缺陷分析及弯曲成形工艺优化

当今空调铜管的发展趋势表现为小口径、薄壁,小弯头管在弯制过程中易出现管口扁平、外侧管壁开裂和内侧起皱等缺陷。采用DEFORM有限元软件分析了铜管弯制过程中缺陷产生原因,并对芯杆位置和尺寸进行了优化。研究结果表明:当弯曲角度为180°时,铜管易产生外侧裂纹,并由外侧向内侧扩展;在弯曲角度为0~90°范围内铜管内侧易出现起皱现象;Φ7×0.41mm铜管弯曲时较优的芯杆直径为5.80mm,提前量为2mm。根据以上参数,对铜管进行了弯曲试验,并没有出现外裂、内皱和扁平等缺陷,获得了优良的小弯头管。     

薄壁钛焊管卷管孔型研究

薄壁钛焊管是目前最佳抗蚀冷凝管,是滨海电站制造凝汽器不可缺少的材料。本文主要介绍生产薄壁钛焊管的关键孔型,并对研制的U、V、W形双半径孔型加以比较。指出,V形和W形孔型可以控制卷管过程中钛带的“跑偏”,其中W形孔型为生产薄壁钛管的最佳孔型。     

基于ABAQUS模拟的高强钢弯曲半径对弯曲性能的影响研究

双相钢是新型实用的先进高强钢,由于其成形性能好、应用前景广阔,逐渐成为汽车用钢的重要构成部分,而其弯曲性能则是评判材料成形性的重要标准之一。应用ABAQUS模拟软件对DP980钢板90°角弯曲试验过程进行了仿真模拟,并通过3点弯曲试验对仿真结果进行验证,研究了不同厚度下安全弯曲时的最小弯曲半径。研究结果表明,一定厚度条件下,弯曲半径越小,钢板越不容易成形。对于厚度为1. 75 mm的DP980钢板,弯曲半径为4 mm时,弯角处无裂纹产生;而当弯曲半径减小为1. 25mm时,弯角处出现裂纹,则可知该厚度下其安全成形的最小弯曲半径在1. 25～4 mm之间。     

新型近β型钛合金TLM细径薄壁小曲率弯管的技术研究

TLM是一种新型近β型钛合金,具有较低弹性模量、中高强度、高疲劳强度、高塑韧性、良好耐磨性以及耐腐蚀性,可以生产各种规格的细径薄壁管材,在交换器、阀门、高压气管、油管等领域有着广阔的应用前景。将其制成弯管,其应用领域还会扩大。而通常的弯管生产方法主要用于相对弯曲半径Rx≥1.5的弯管,对于相对弯曲半径Rx1.5的弯管(即小曲率弯管),存在着拉应变和压应变变化大,壁厚变化率大,加工过程不容易控制等因素,严重影响着细径薄壁管材的应用。通过对管材弯曲过程受力变形进行分析,控制回弹,设计模具和改进加工工艺,对相对弯曲半径Rx≈1.1的TLM钛合金细径薄壁管材进行90°和180°弯曲,对其外形和其各种参数进行测量。试验结果表明,自行设计的模具可顺利地完成新型近β型钛合金细径薄壁管材的小曲率弯管,为生产提供了一定的参考价值。     

航天科工集团公司钛合金管热弯模具试模成功

<正>中国航天科工集团公司第二研究院699厂自主研发设计的钛合金管热弯模具于2014年5月试模成功,这标志着该厂大口径、薄壁型钛合金管热弯模具研制获得突破。此项研究填补了国内高精度热弯模具研制的空白。据介绍,此次由西工大提出设计需求的大口径薄壁钛合金管热弯模具,属于集加热、循环水冷、     

铝合金管材6061自由弯曲成形工艺仿真及优化

金属管材是工业领域中结构承重、输送气体和液体的重要部件。自由弯管成形技术有助于实现管件生产的高精度、高性能、高效率和数字化，其精度控制理论和成形技术的研究具有重要的工业应用价值。本文选择直径 30 mm 壁厚 2.0 mm 的铝合金管材6061为仿真优化对象，通过相关基础实验获得材料的基本力学数据，用于仿真模型参数的表征。同时，结合管材压弯实验验证本构模型成形预测的有效性。在完成仿真模型表征和验证的基础上，对铝合金管材的自由弯曲成形过程进行仿真模拟，分析对比了影响自由弯曲成形的各工艺参数，确定了该工况下最优的移动模与管材间隙大小、摩擦系数和进给速度等。该研究有助于优化管材空间自由弯曲成形工艺，具有一定的工业应用价值。      

弯管零件注塑模的计算机辅助设计

采用组合式型腔和斜导柱抽芯机构成形弯管零件,自动化程度较高,提高了生产效率。用Moldflow模流软件对注塑过程进行有限元模拟,并对模具工作过程进行仿真。结果表明,该模具结构合理,可以生产出符合技术要求的弯管零件。     

双半径中部反向弯曲孔型设计的理论探讨

本文在双半径法和边缘弯曲法的基础上,介绍了一种冷弯圆管的中部反向弯曲孔型设计理论。通过分析证明:用反向弯曲孔型成形薄壁圆管,可以明显减小带坯边缘部分和中心部分的延伸不均匀性,避免边缘波浪和折皱;减少变形区纵向的应力不均匀分布,防止产品弯曲;减少产品壁厚的不均匀性;提高产品质量。在理论分析的基础上提出了中部反向弯曲的孔型设计方法。     

大滚弯模量铝型材滚弯机的研制

文章介绍了滚弯机结构原理,生产工艺流程,滚弯功率计算,数控工艺算法,反弹补偿等关键技术,开发出大滚弯模量滚弯机,经厂家一年多的使用,成功实现了高铁边梁等大滚弯模量铝合金型材的弯弧加工,其成品精度高,重复性好,使用效果达到了进口设备的同等水平。     

Bending Fatigue of Cable Stays

Large amplitude stay-cable vibrations have been observed numerous times in the past few years in two long-span cable-stayed bridges in Texas: the Veterans Memorial Bridge near Port Arthur and the Fred Hartman Bridge near Baytown. In most cases, these vibrations have occurred in combination with light rain and relatively low winds. The rainwater forms rivulets on the cable that change the aerodynamic cross section of the smooth cable stays. This paper describes the field measurements, analytical models of vibration, fatigue tests carried out in Japan, and the development of planned laboratory fatigue tests that will be carried out at Ferguson Laboratory during 2001. The full-size cable fatigue tests will assess the relationship between the amplitude of cable vibration and fatigue damage. A future paper will relate these experimental results to the stays of the Veterans Memorial and Fred Hartman bridges in order to provide an estimate of the fatigue damage that may develop in their stays.     

Bending Behavior of Helically Wrapped Cables

A mesoscale mechanical model of the bending behavior of helically wrapped cables under tension is developed. The model accounts for the nonlinear dissipative behavior of the cable arising from the slippage of wires under friction forces. It is shown that the bending stiffness rapidly diminishes with increasing cable curvature, over a range that can be as large as 2 orders of magnitude. The model can be used to assess the static and dynamic response of helically wrapped cables in such applications as conductors in substations and transmission lines subjected to earthquake effects, where significant changes in the cable curvature may occur.     

Bending behavior of carbon nanotube-reinforced composites

The multi-scale modeling method was utilized to study the bending characteristics of a carbon nanotube (CNT) and CNT-reinforced composites.Through combining molecular dynamics and continuum mechanics,the tensional and flexural modulus of a CNT were calculated by a finite element model constructed by reticulate beams with solid cylinder shape and energy equal to C-C bonds.Then,another beam element with hollow cylinder shape and equivalent stiffness was utilized in place of a CNT in a matrix,thus,a multi-scale representative volume element (RVE) model of CNT-reinforced composite was established.Using this RVE model,the bending behavior of CNT-based composites Was analyzed.The influence of diameter D,length L,aspect ratio L/D,volume fraction,chiral of CNTs and shape of RVE as well as the arrangement of CNTs in matrix on the rein-forcement effect of flexural modulus of resultant nanocomposites were further discussed.The obtained data provide useful information for the design of CNT-reinforced composites.     

Bending deformation of rotating metallic tubes

The bending deformation of rotating metallic tubes is considered. This deformation is often used for the straightening of tubes produced by rolling or drawing to increase their quality. The elastoplastic bending deformation of rotating metallic tubes is shown to differ substantially from the conventional deformation of fixed tubes.     

带钢弯裂原因分析

针对泰钢生产的一批热轧带钢在加工使用过程中出现弯裂的现象,采用金相显微镜、XL30扫描电镜、气体含量分析等方法,对弯裂带钢取样进行组织状态、夹杂物、晶粒度、断口形貌、氧含量等检验。结果表明:弯裂带钢的断口呈木纹状,发纹处存在大量氧化铁,其基体主要由铁素体和珠光体组成,有少量索氏体及屈氏体,晶粒度以9～10级为主,有较为明显的带状组织,夹杂物为硅酸盐、硫化物及少量氧化物。钢中氧含量高(97×10-6～250×10-6)及夹杂物多是引起带钢弯裂的主要原因。     

Bending Stiffness of Fiber-Reinforced Circular Seismic Isolators

The reinforcing elements of multilayer elastomeric isolation bearings, which are normally steel plates, are replaced by a fiber reinforcement. In contrast to the steel reinforcement which is assumed to be rigid, the fiber reinforcement is flexible in extension. This paper presents the theoretical approach to analyze the bending stiffness of the fiber-reinforced circular isolators. The elastomer is assumed to be incompressible and pressure dominant. The stiffness formula is derived. The influence of fiber flexibility on the mechanical properties of fiber-reinforced circular isolators under bending moment, such as the pressure in the elastomer, the stress in the reinforcement, and the bonding shear stress between the elstomer and the reinforcement, are presented.     

Air Bending Process for Load Optimised Profiles

In this paper the air bending of Tailor Rolled Blanks (TRB) to load optimised profiles is investigated. A new flexible modular tool system has been developed in order to locally adapt the die height to the spring back which is more pronounced in thinner areas in comparison to thicker areas of the TRB. With the new tool system the dies can be modulated according to the thickness distribution of the Tailor Rolled Blank, whereas the amount of die lifting depends on the thickness difference and the corresponding variance of mechanical properties. In bending tests with several specimens having a constant thickness a linear relation between the increasing part angle and a stepwise increased die lifting was observed. With this linear dependency the amount of die lifting can be calculated and thus applied on bending of TRB. Special consideration is required for the die adjustment in the area of the linear thickness transition, therefore three different die arrangements have been investigated. The results of different bending tests are compared and evaluated in order to apply the new technique to form a new car body floor structure in profile intensive construction. By using load optimised profiles in combination with a steel 22MnB5 which has been heat‐treated at defined sections the survival space of a car passenger in a side pole impact has been enormously increased by more than 40 %.     

浅析螺纹钢成品波浪弯缺陷的工艺优化

本文介绍轧制热轧带肋钢筋时,在对定尺剪剪切后的定尺成品观察后,成品外观呈周期性的波浪形状,经过测量严重部位的单米弯曲度在0.4%~0.10%,不满足《GB 1499.2-2007钢筋混凝土用钢》国标要求,同时影响着产品外观质量;工艺改进之后,无论产品总长度弯曲度还是单米弯曲度,均控制在国标4%的范围内,进一步提高了产品外观质量,提高了酒钢热轧带肋钢筋的品牌形象。