一种考虑包辛格效应的等效拉深筋模型

基于Voce各向同性硬化模型和Armstrong-Frederic随动硬化模型,建立了一个考虑包辛格效应影响的混合硬化模型,并通过CR4钢板的拉压循环实验验证了该混合硬化模型的准确性。将该混合硬化模型引入Stoughton等效拉深筋阻力模型,替换原有的各向同性硬化模型,考虑包辛格效应的影响对该等效拉深筋阻力模型进行了改进。利用专门设计的拉深筋阻力测定装置,针对矩形拉深筋和半圆形拉深筋,分别获取了不同几何结构参数下的拉深筋阻力,经实验验证,改进后的等效拉深筋模型能够有效地提高拉深筋阻力的计算精度。     

Equivalent drawbead models for sheet forming simulation

Equivalent drawbead models associated with drawbead types, with which the geometrical modeling of drawbeads can be replaced in a numerical simulation of the stamping process, are introduced. The accuracy of the equivalent drawbead models rapidly computing the drawbead restraining and opening forces, based on the hybrid membrane/bending method accommodating Barlat’s anisotropic yield function for the plane stress state and the modified Chaboche model considering the Bauschinger effect and transient behavior under the plane strain condition, is verified by comparing the equivalent drawbead forces with those obtained from the finite element simulation. Moreover, the drawbead forces computed by equivalent drawbead models are employed in a finite element simulation of the automotive fender stamping process, from which the effectiveness and applicability of equivalent drawbead models are observed by comparing strains and draw-ins with those measured in the tryout panel.     

板料冲压成形数值模拟中等效拉延筋模型的建立与实现

设置拉延筋是板料拉深成形过程中控制材料流动的有效方法。在板料成形数值模拟中,为节省计算时间,常采用等效拉延筋模型。本文在参考国内外有关资料的基础上,建立了一种等效拉延筋模型。模型中考虑了拉延筋约束力、塑性厚向应变以及垂直于压料面的约束保持力的影响,并在程序中予以实现。文中给出了一个计算实例。     

An analysis of drawbead restraining force in the stamping process

A theoretical model based on the virtual work principle was proposed to calculate the restraining force produced by the drawbead located on a stamping die surface. In the theoretical model the deformation of the sheet metal drawn over the groove shoulder or bead is assumed to be subjected to bending, sliding and unbending processes, and only the sliding process is responsible for the frictional force. The governing equations derived from the theoretical model were solved by a numerical procedure. In order to validate the proposed model, the finite element simulations were also performed to calculate the drawbead restraining forces for various steels. The simulated results together with the experimental data obtained from the published literature were compared with the predicted values calculated by using the numerical procedure. The good agreement between the simulated results, experimental data and the calculated values justifies the proposed theoretical model.     

梯形拉深筋等效约束阻力模型研究

对拉深成形过程中板料经过梯形拉深筋时的变形情况进行了分析,运用能量法建立了一种简单实用的梯形拉深筋等效约束阻力计算模型,利用Dynaform软件对梯形拉深筋的等效约束阻力进行了模拟,将计算结果与模拟结果进行了比较。分析结果表明:在拉深成形过程中,如拉深筋设置在圆弧部位,板料经过拉深筋后最终等效约束阻力是随拉深过程的进行而变化的;板料通过设在直线段的筋产生的等效约束阻力,在一定的压边力下,其值为恒定的值;理论计算与模拟值基本吻合,在数值模拟时,该模型可以作为等效拉深筋使用。     

基于数值模拟的拉延筋约束阻力计算方法研究

在汽车覆盖件拉深成形中,拉延筋可以在较大范围内调节和控制板料的变形程度和变形分布,抑制多种成形质量问题的产生.其中,拉延筋几何参数起着重要的作用.本文以矩形拉延筋为例,建立了拉延筋约束阻力计算有限元模型,对拉延筋几何参数与约束阻力之间的关系进行分析研究.结果表明:拉延筋约束阻力与凹槽圆角半径和凸筋圆角半径成反比,与筋高成正比.结合某轿车B柱加强板实例,通过优化其拉延筋结构参数,得到当1号等效拉延筋高8mm、凸筋和凹槽圆弧半径3mm;2号等效拉延筋高4 mm、凸筋和凹槽圆弧半径6mm时,该制件成形质量达到最佳.     

A LOOP DRAWBEAD RESTRAINING FORCE MODEL IN SHEETMETAL DEEP DRAWING PROCESS

1. IntroductionIn the sheet metaJ fOrming process9 deep drawing is used frequently in the automotiveor packaging industry to manufacture products with comPlicated shapes and ctirvatures.In the deep drawing process, a sheet metal, the blank, is clamped between a die and a blankholder. The specific shape of the punch and the die is transferred to the blank during thedefor.atio.[1--4].In the deep drawing process, the material flow is restrained by both the friction con-dition and the blankholde…     

Computational characterization of drawbeads: A basic modeling method for data generation

The purpose of this investigation is to better understand the behaviour and effects in modeling of drawbeads in sheet metal forming simulation. A finite element model is developed to examine how various modeling aspects, such as element size, number of integration points, material hardening, influence the results. Furthermore, some process parameters such as friction and tool geometry are also discussed.In the modeling of drawbeads in large-scale sheet metal forming analysis using finite element methods it is common to use an equivalent drawbead model. This is due to the need for very dense finite element meshes resulting in demands for extreme computer resources. Generation of input data for an equivalent drawbead model has to be reliable and simple. Herein one method is presented on how to use a plane strain model using actual bead geometry to derive data for the equivalent drawbead model as it is implemented in LS-DYNA^TM.     

板料拉延成形中压梗约束力的计算机预测

在汽车覆盖件的成形中, 通常在压料面设置压梗, 以消除起皱, 提高成形质量。压梗约束力是一个很重要的参量,拉延材料的力学性能、压梗的几何尺寸以及摩擦系数等均对它有影响。本文基于人工神经网络基本理论, 建立了压梗约束力的网络模型, 并用该模型对压梗约束力进行了计算机预测, 预测结果与试验结果比较接近。本文的模型和结果对于有限元模拟系统的建立以及压力机吨位的合理选用和确定, 具有重要的参考价值。     

A simulation-based prediction model of the restraining and normal force of draw-beads with a normalization method

This paper proposes a simulation-based prediction model to predict the restraining and normal force of drawbeads for the sheet metal forming process. A reliable prediction model is constructed for the equivalent drawbead by a modified DOE (Design of Experiment) method, which consists of the Box-Behnken design and a simplified full factorial design. To construct prediction models of draw-bead forces, draw-bead forces are first calculated by finite element analysis and confirmed by experiments followed by an approximation with second order regression equations in various design cases. To increase the accuracy of prediction models, normalization of draw-bead forces is conducted based on the effectiveness ratio of design variables in a regression analysis. The normalized draw-bead forces are then approximated by second order regression equations again. The accuracy of the prediction models constructed is verified by comparing the prediction results with the simulation results in the entire design space.     

拉延筋约束阻力的数值模拟研究

在覆盖件的数值模拟中,为提高等效拉延筋的模拟精度,需要建立合理有效的拉延筋约束阻力求解模型。文章根据平面应变假设,建立了合理的数值模拟研究模型。模拟结果表明,弯曲过程中存在鲍辛格效应和加工硬化等现象。将该模型提取的拉延筋阻力曲线用于模拟软件,模拟结果与真实拉延筋模拟结果及物理实验进行比较,验证了该模型的合理性与有效性。该模型为研究拉延筋约束阻力提供了一种有效可行方案。     

汽车覆盖件成形中拉延筋约束力的模拟计算

通过拉延筋基本单元模拟试验，对板料在筋内变形机理、压边力和筋的几何参数对拉延筋约束力的影响规律，拉延筋约束力随模具包角变化的规律及板料拉过筋时的变形情况进行了研究，建立了拉延筋约束力计算模型。     

2D elasto-plastic FE simulation of the drawbead drawing process

The drawing process including the locking and pulling phase under a drawbead of circular and rectangular section shape is simulated by means of a static-implicit FE code developed by the authors for 2D elasto-plastic simulation of sheet metal forming. The influence of the main bead geometrical parameters on the binder hold down force (BHDF) and drawbead restraining force (DBRF) is analyzed. The deformation law and loading characteristics of the sheet around the drawbead are studied during the two sequential phases. The calculated results show a good agreement with the experimental data. The investigation lays a foundation for setting up an applied drawbead model in the future 3D simulation of drawbeads.     

拉深筋成形二维弹塑性有限元数值模拟

利用开发的拉深筋二维弹塑性有限元数值模拟软件 ,对圆形筋和矩形筋就压筋和成形的连续过程进行了数值模拟 ;分析了拉深筋主要几何参数对压筋力和拉深筋阻力的影响 ,研究了压筋和成形两个阶段板料在拉深筋作用下的变形规律与受力特点。模拟结果与实验结果吻合良好 ,为建立一种实用的等效拉深筋模型及进一步的三维拉深筋成形模拟奠定了基础。     

Drawbeads in sheet metal forming

Drawbeads are used to control the flow of sheet metal into the die cavity during stretch-draw forming of large panels. They prevent wrinkling in formed panels, reduce the blankholder force, and minimize the blank size needed to make a part. Drawbead restraining forces (pulling forces) and failure locations in the formed sheets are usually evaluated by using drawbead simulation tooling. In this article, a drawbead simulation apparatus is used to assess the influence of variation in material, bead penetration, and fric-tion conditions on the drawbead restraining force. Results from the test can be used as input for sheet metal forming simulation programs.     

遗传算法结合神经网络实现拉延筋优化设计

传统的冲压模具设计中,拉延筋设计和布置主要依靠经验,这使得模具设计和制造周期延长.以某汽车侧壁外板的拉深工序为例,讨论了神经网络技术与遗传算法在拉延筋优化设计中的综合应用问题.建立了反映板料成形参数与拉延筋阻力之间非线性映射关系的BP网络模型.利用该训练好的神经网络可以实现拉延筋的优化设计.由于相对于进行工艺试验来说数值仿真比较省时省力,因此,利用Dynaform模拟汽车侧壁外板的拉深成形过程,建立训练样本.在网络的训练方法上利用遗传算法进行了优化,有效地提高了神经网络的模拟精度.     

基于迭代学习控制模型的覆盖件模具拉深筋优化算法

提出了基于迭代学习控制模型的覆盖件模具拉深筋优化算法,极大地提高了优化效率。利用成形状态函数,成形质量函数和学习律函数构建工艺参数优化的迭代控制模型。将该模型应用到拉深筋阻力值优化中,利用有限元模拟代替很难显示表达的状态函数,预测给定工艺参数方案下板料成形后的应力应变状态。根据单元的应变状态,定义拉深筋线段的局部缺陷程度为成形质量函数,评价拉深筋周围的成形质量好坏。学习律函数不仅参考拉深筋段周围的成形质量偏差确定拉深筋阻力值的改变量,同时还能智能更新学习增益修正拉深筋阻力值的改变幅度,加快了优化收敛速度。通过门内板的算例,证明了该拉深筋优化算法的快速性和实用性。     

半圆形拉深筋尺寸参数对其阻力的影响

通过数值模拟和实验相结合的方法 ,研究了半圆形拉深筋的高度、圆角半径等参数对拉深筋阻力的影响 ,分析了不同尺寸参数下拉深筋阻力的构成特点。研究表明 ,拉深筋高度和拉深筋圆角半径对阻力均有显著的影响。其中拉深筋高度与阻力之间存在较好的线性关系 ,是控制拉深筋阻力的首选参数。拉深筋的高度变化主要影响拉深筋的摩擦阻力 ,而圆角半径主要影响局部圆角的变形阻力。最后在实验和分析的基础上 ,给出了半圆形拉深筋的设计调整原则     

拉延筋约束阻力的一种解析计算方法

根据虚功原理和对板料在拉延筋处变形的分析,得到平均外力的计算公式,然后参考Levy方法提出了一种计算拉延筋约束阻力的参数拟合公式,并根据试验得到参数值。公式中考虑了材料的各向异性和应变速率敏感性。通过将计算结果与Nine的试验结果进行对比,证明了该计算方法对各种材料的有效性。     

Drawbead design and performance

Experiments on drawbead restraining in sheet metal forming with several bead configurations were carried out. With the binder hold-down force as an independent variable, the magnitude of the restraining force, the amount of metal flow through the bead, and the sensitivity of these quantities with respect to lubrication were determined. Performance of these beads as viewed from shop floor practices was discussed.