不同模具组合对0Cr21Ni6Mn9N不锈钢管数控弯曲成形质量的影响

采用有限元法研究了不同模具组合下0Cr21Ni6Mn9N不锈钢管数控弯曲应力应变分布、壁厚变化和截面畸变规律。研究结果表明：在弯曲模、夹块和压块组成的基本模块的基础上,添加防皱块会导致等效应力、切向拉应力和切向拉应变增加,而切向压应力、等效应变和切向压应变减小;添加芯棒会导致切向应力和等效应变减小,而等效应力和切向应变增大;同时添加防皱块和芯棒则会导致等效应力、切向应力和切向应变增大,而等效应变减小。添加防皱块会导致弯管截面畸变率增大,但对壁厚变化率影响不大;添加芯棒能够有效抑制弯管截面畸变,且壁厚减薄率仅为9.0%~9.15%,远小于15%的航空标准。综合考虑0Cr21Ni6Mn9N不锈钢管数控弯曲成形质量和生产成本,可确定出最优的模具组合为弯曲模+压块+夹块+芯棒。     

绕弯成形工艺参数对薄壁管回弹的影响分析

为探究绕弯工艺参数对薄壁管弯曲回弹的影响,通过正交试验设计,应用有限元软件DYNAFORM建立了不同工艺参数下薄壁管绕弯三维模型,模拟了弯曲成形及卸除载荷后的回弹过程,对回弹角度进行了极差分析和方差分析。分析表明:防皱模间隙、镶块间隙、弯模间隙、芯棒前伸量对回弹影响相对较大,各模具与管件的摩擦对回弹影响较小;回弹随防皱模间隙、镶块间隙、芯棒前伸量的增大而减小,随弯模与管件间隙的增大而增大;所有工艺参数对回弹的影响不具有显著性。减小弯模与管件间隙,增大防皱模、镶块、压模与管件间隙及芯棒前伸量将有助于减小薄壁管回弹。     

薄壁管绕弯工艺参数对壁厚影响分析

为探究薄壁管绕弯加工中各工艺参数对管件壁厚的影响。结合正交试验设计,利用有限元软件DYNAFORM进行了管件绕弯过程仿真,对管件弯曲段外侧和内侧壁厚数据进行了极差分析和方差分析。芯棒伸出量和压模摩擦因素对管件弯曲段外侧减薄率有较大影响,其中芯棒伸出量对减薄率的影响具有显著性;防皱模与管件间隙、压模摩擦因素、压模与管件间隙、芯棒与管件间隙对弯曲段内侧增厚率影响较大,但所有工艺参数对内侧增厚率的影响均不具有显著性。优化参数后的试验表明:减小防皱模、压模、芯棒与管件的间隙及芯棒伸出量,适当增大压模及芯棒与管件的摩擦有助于薄壁管获得更高的壁厚质量。     

工艺参数对21-6-9高强不锈钢管数控弯曲壁厚减薄影响的显著性分析

为实现21-6-9高强不锈钢管数控弯曲精确成形,提高其成形质量与成形极限,需要对弯曲过程中壁厚减薄进行有效控制。基于ABAQUS/Explicit有限元软件平台,建立了21-6-9高强不锈钢管数控弯曲三维弹塑性有限元模型,并对其可靠性进行了验证。通过有限元模拟和正交试验,研究了工艺参数对21-6-9高强不锈钢管数控弯曲壁厚减薄影响的显著性及规律。结果表明,影响壁厚减薄的显著性工艺参数依次为芯棒伸出量、管材与芯棒间隙、管材与防皱块摩擦因数、管材与芯棒摩擦因数、管材与压块摩擦因数和弯曲速度,其影响规律为：壁厚减薄率随着芯棒伸出量、管材与防皱块摩擦因数、管材与芯棒摩擦因数、管材与压块摩擦因数、弯曲速度的增大或管材与芯棒间隙的减小而增大。采用多元线性回归方法建立了最大壁厚减薄率与显著性工艺参数之间的回归预测模型,经对比验证,回归预测模型结果与正交试验结果之间的相对误差不超过5%。     

间隙对薄壁矩形管绕弯成形截面畸变影响的研究

基于ABAQUS/Explicit,建立了铝合金薄壁矩形管绕弯成形过程三维有限元模型,并对其可靠性进行了验证.模拟分析了芯棒与管坯间隙、压块与管坯间隙、防皱块与管坯间隙及弯曲模与管坯间隙对管坯截面畸变的影响规律.研究结果表明:减小芯棒与管坯间的间隙及弯曲模与管坯间的间隙都可减小管坯截面畸变的程度;而压块与管坯间隙及防皱块与管坯间隙的改变对管坯截面畸变率影响不大.     

间隙对铝合金帽型材绕弯回弹规律影响研究

回弹是型材弯曲成形中不可避免的现象,模具与型材间间隙是影响回弹量的重要因素之一。为研究间隙对型材回弹半径和回弹角的影响,基于数值模拟软件ABAQUS建立了5052铝合金帽型材数控弯曲及卸载回弹的有限元模型,并实验验证了所建有限元模型的可靠性,分析了压块、防皱块、弯曲模及夹块与型材间间隙对回弹的影响。研究发现:减小弯曲模、夹块与型材间间隙回弹减小,减小压块与型材间间隙回弹增大,而防皱块与型材间间隙对回弹影响不明显。     

有芯弯管模具设计

1.有芯弯管原理 有芯弯管是在弯管机上利用芯棒使管材沿弯曲模绕弯的工艺方法（见图1）。弯管胎膜固定在机床主轴上并随主轴一起旋转。管子在镶块1与夹紧块2的作用下压紧于弯曲模胎上。为了保证弯管质量,避免折皱和断面畸变,弯曲模胎、芯棒及防皱板都必须具有与管坯外表面吻合的型槽,以利于将管坯外壁卡紧,同时芯棒从管坯内部支撑管壁。     

船用大直径厚壁管数控弯曲工艺参数对壁厚影响的显著性分析

为实现船舶管件数控弯曲精确成型,更好地研究船用大直径厚壁管壁厚变化率,提高其成型质量,需对其弯曲过程中壁厚减薄进行有效控制。基于有限元分析软件Dynaform建立船用20#管绕弯成型过程有限元模型,对其进行可靠性验证,再通过有限元分析和虚拟正交试验对弯曲段外侧最小壁厚数据进行极差分析和方差分析,研究工艺参数对于壁厚减薄影响的显著性及规律。结果表明:管件数控弯曲成形过程中工艺参数对最大壁厚减薄率影响的显著性顺序依次为:芯棒与管材摩擦系数、芯棒前伸量、芯棒与管材间隙、夹模与管材间隙;壁厚减薄率随着芯棒与管材摩擦系数、芯棒前伸量以及夹模与管件间隙的增大而增大,随着芯棒与管件间隙增大而减小。同时利用多元线性回归方法建立显著性工艺参数与最大壁厚减薄率之间的回归方程,经对比验证,对于规格为Φ140mm×4.5mm(t)×420mm(R)船用20#大直径厚壁管,此回归预测模型结果与正交试验之间的相对误差不超过5%。     

不同模具组合对航空导管数控弯曲的影响

金属导管作为飞机的主要部附件之一,在飞机的内部起着压力传递、燃油传输、气体输送、电缆保护等作用,其数控弯曲成形的质量将直接影响飞机的飞行安全。为满足飞机内部各部位的设计需求,对其弯曲成型的质量要求不断加深,应用有限元分析的方法进行数值模拟,研究不同模具组合对导管数控弯曲成形质量的影响,对航空导管的制造有着重要的指导意义。基于有限元模拟软件建立了1Cr18Ni10Ti不锈钢管的有限元模型,分析其弯曲变形过程,研究出便于导管制造的模具组合方式。     

浅谈模具质量的提高

冲压模具的形式很多,种类包括冲孔模、落料模、弯曲模、拉深模等,近年来冷冲模的应用越来越广泛。模具的使用寿命直接影响产品质量、加工效率和成本的重要因素。本文从模具的合理设计、模具材料的合理选用及正确的热处理技术等方面探讨了提高冷冲模具质量的途径。     

数控弯管工艺知识库研究

通过分析弯管各个加工参数及模具对弯管成形的影响,设计了数控弯管工艺知识库.通过该知识库,用户可以查询以往加工记录、模具、弯管机等信息,方便了数控弯管的工艺参数选取与资源的管理.在数控弯管工艺知识库的基础上,通过运用CBR方法,得到了弯管回弹角,减少了试弯次数,提高了数控弯管效率.     

薄壁管数控弯曲成形过程有限元模拟系统的研究

建立了合理有限元分析模型,研究了有限元系统中单元的选取,边界和摩擦条件的处理,迭代收敛因子的确定以及起皱预测准则的建立等关键技术的处理。在此基础上自主开发了可预测起皱的薄壁管数控弯曲成形过程三维刚塑性有限元模拟系统。同时对该有限元系统的起皱预测结果进行了验证,并给出了一些模拟结果。     

数控弯管的空间转角数据转换算法

应用矢量弯管原理,推导和比较了数控弯管的空间转角数据转换的三种算法;并基于空间三角形算法,采用可视化编程软件VC＋＋6．0开发了三维弯管数控系统软件,实现自动弯管。     

Optimization of processing parameters for double-ridged rectangular tube rotary draw bending based on grey relational analysis

The rotary draw bending of double-ridged rectangular tube is a complex nonlinear physical process with multifactors coupling effects. Processing parameters, especially clearances and friction coefficients between tube and various dies, have a significant effect on the forming quality of the double-ridged rectangular tube in rotary draw bending. If the values of these processing parameters are inappropriate, some defects including cross-sectional deformation, wall thinning, and wall thickening easily occur in the bending process of double-ridged rectangular tube. So optimization of these processing parameters is of great importance to control these defects. Based on the grey relational analysis method combined with the orthogonal experimental design and finite element simulation, a grey relational analysis model was established for the rotary draw bending process of double-ridged rectangular H96 brass tube. With the model, optimization of clearances and friction coefficients between tube and various dies was implemented with consideration of interactive effects of the above defects. The results show that (1) the main factors influencing cross-sectional deformation, wall thickening, and wall thinning are tube–mandrel clearance Δc _m, tube-bending die clearance Δc _b, and tube–mandrel clearance Δc _m, respectively. (2) The optimal values of clearances Δc _m, Δc _p, Δc _w, and Δc _b and friction coefficients μ_m, μ_p, μ_w, and μ_b of tube–mandrel, tube–pressure die, tube–wiper die, and tube-bending die are 0.15, 0.2, 0.2, 0.2, 0.02, 0.3, 0.06 and 0.17 mm, respectively. Furthermore, the verification for the optimal values of these processing parameters was carried out, and the double-ridged rectangular H96 bent tube obtained by using the optimal values of these processing parameters has the minimum values of cross-sectional deformation, wall thinning, and wall thickening and can satisfy the national aviation industry standards.     

Effect of clearance on wrinkling of thin-walled rectangular tube in rotary draw bending process

The clearances between tube and various dies have a significant and complicated influence on the onset of wrinkling during the rotary draw bending process. To study the effect of clearance on wrinkling, a 3D finite element (FE) model of the process for thin-walled rectangular aluminum alloy tube has been built using the explicit code ABAQUS/Explicit and validated by comparing the experiment. Then, simulation and analysis of the process have been carried out based on the model. The influence laws of clearances between tube and various dies on wrinkling have been studied and the reasonable combination of clearances obtained using the combination method of 3D FE simulation and orthogonal experimental design. The results show that with the increase of tube mandrel clearance, Δc _m, and tube bending die clearance, Δc _b, the wrinkling wave number decreases rapidly, whereas the wrinkling wave height increases sharply. The effects of tube wiper die clearance, Δc _w, and tube pressure die clearance, Δc _p, on wrinkling are not significant. The reasonable combination of clearances is Δc _m?=?0.15 mm, Δc _b?=?0 mm, Δc _w?=?0 mm, and Δc _p?=?0 mm. These achievements are helpful to the design and optimization of the process.     

数控弯管工艺数据管理系统的研究

数控弯管工艺过程复杂,对数控弯管工艺数据进行有效管理,是实现数控弯管精确成形数字化和工艺规划自动化的重要基础。本文对数控弯管工艺数据管理系统进行了研究,通过总结数控弯管工艺的理论研究、模拟研究和实验研究结果,提炼出了影响数控弯管成形的重要参数,建立了数控弯管工艺数据库的数据模型,在SQL Server2000中建立了数控弯管工艺数据库,基于该数据库运用面向对象的C#语言,以V isual Stud io.NET作为前台开发环境开发了数控弯管工艺数据管理系统。该系统可以通过访问数控弯管工艺数据库实现对数控弯管工艺过程各参数数据的可视化管理,同时可以初步实现知识推理得到缺陷产生的原因及采取对策,以及通过对数据库的搜索实现工艺参数的优化。     

Towards an integrated robust and loop tooling design for tube bending

Bent tubular parts have attracted extensive applications in various industries due to high strength and light weight. However, tube bending (TB) is a strong knowledge-based tri-nonlinear physical process with multi-tool constrains, and minor inappropriate tooling design may induce several failures such as wrinkling, over thinning (even fracture), section distortion, and springback. In response to the urgent requirements of the tubular products with mass quantities and diverse specifications, we proposed an integrated methodology for robust and loop tooling design for TB by combining several technologies such as knowledge-based engineering, parametric CAD modeling, and parametric finite element modeling. Via the spreadsheet formatted rules extracted from different sources of knowledge, several sequences are automatically conducted to preliminarily avoid the wrinkling and section distortion, including the selection of tooling sets (bend die, clamp die, pressure die, wiper die, or mandrel die with flexible balls), the determination of die dimensions, 3D modeling of both external and internal tools, die assemble, and the selection of material type for each die. Then, by importing the feature parameters of tools into 3D-finite elements models, the bendability of tube under previously designed multi-tool constraints is quantitatively evaluated in terms of multi-defect, and the springback can be calculated to redesign the bending die by radius reduction. The design variables are only tube diameter, wall thickness, bending radius, bending angle, and material types. The tool design system is then implemented, and the reliability and efficiency of the system are experimentally verified in the aviation industries regarding several practical bending cases with different specifications and tubular materials.