铝合金板材电磁脉冲拉深实验与有限元模拟

在金属板材的电磁脉冲拉深成形中,采用一种使成形件凸缘部分的材料可以径向流动的方法。形成了一种拉深—胀形特点相结合的成形工艺,可以提高材料的拉深极限。在此基础上通过改变电压和板料直径等工艺参数,可获得更大拉深高度。     

半球形凸模拉深过程的动力显式有限元分析

本文基于连续介质力学及有限变形理论 ,建立了用于三维板料成形过程分析的有限元模型 ,开发了动力显式算法的板料成形过程模拟的有限元分析程序DESSFORM3D。采取集中质量矩阵 ,用动力显式积分的方法 ,使位移计算显式化 ,避免了由材料、几何、边界条件等高度非线性因素引起的计算收敛问题。对半球形凸模拉深过程进行模拟计算 ,并把模拟结果与实验结果进行对比 ,验证了软件的计算结果     

新型液压—机械拉深模与工艺过程数值模拟

介绍一种新型液压—机械拉深模装置,液压力能在拉深过程中形成径向推力、摩擦保持及流体润滑效应,建立与新型液压—机械拉深模相应的数值模拟模型,通过添加节点力和单元力来实现径向推力和凹模腔压力建模。用建立的模型,设置与实际试验相一致的工艺参数,对08Al拉深钢板进行数值模拟计算,将模拟计算结果与实际实验结果进行对比,说明径向推力和凹模腔液压力建模的正确性,为进一步进行液压—机械拉深工艺研究奠定基础。     

Numerical simulation of cup hydrodynamic deep drawing

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矩形盒深拉深成形有限元模拟

针对矩形盒成形过程中各种形式的起皱和拉裂问题，采用MSC．Marc有限元分析软件对矩形盒深拉延成形过程进行模拟。建立了包括板料、凸模、凹模及压边圈在内的整体分析模型，通过对成形过程中拉深件的等效应力进行比较，分析了不同的凸模圆角半径、凹模圆角半径及凸模角半径对矩形盒拉深成形的影响。此外，还对模拟结果做了进一步的分析，得出了凸凹模圆角半径之间的相应关系，以便合理的确定矩形盒深拉延成形时二者的取值范围。考察了模拟方法的可行性和可靠性。     

拉深试验机在润滑剂评定中的应用

阐述了拉深试验机3个综合评定项目－最大拉深力P、摩擦系数μ和极限拉深比LDR在润滑剂评定中的意义,给出了试验机在拉深用润滑剂研制和筛选中的应用实例,并对结果进行了分析讨论。     

飞行平台罩爆炸拉深实验研究及数值模拟

在简单介绍爆炸拉深基本原理的基础上应用ANSYS软件中的LS-DYNA模块,对具有复杂曲面的航天飞行平台罩建立了显性动力学弹塑性力学模型,并做了相应简化后,成功地进行了爆炸拉深成形过程的有限元数值模拟,获得了爆炸变形过程中不同时刻的应力、应变分布规律,以及变形过程中的危险截面等重要结果.该模拟结果与实验结果基本一致,对制定工艺参数、改进模具结构和坯料尺寸提供了重要依据.     

Numerical simulation of various cross sectional workpieces using conventional deep drawing and hydroforming technologies

This study focuses on the determination of optimum sheet metal forming process and process parameters for various cross sectional workpieces by comparing the numerical results of high-pressure sheet metal forming, hydro-mechanical deep drawing (DD) and conventional DD simulations. Within the range of each cross section, depth, characteristic dimensions ratio and fillet radius have been altered systematically. Steel of types St14 and DC04 have been used as the specimen material in the numerical analyses and the experimental verification throughout the study. All numerical simulations have been carried out by using a dynamic–explicit commercial finite element code and an elasto-plastic material model. During the analyses each workpiece was simulated by the three competing processes. The results of analyses, such as sheet thickness distribution, necking, forming of radii etc., are used for assessing the success of each forming process alternative. The analyses revealed that depending on the workpiece geometry and dimensional properties certain processes are preferable for obtaining more satisfactory products. Working windows for each process have been established based on the analyzed parameters of the circular, elliptic, rectangular and square cross sectional product geometries. This data is expected to be useful for selecting the appropriate production process for a given workpiece geometry and understand the limits of each sheet metal forming processes.     

Explicit incremental-update algorithm for modeling crystal elasto-viscoplastic response in finite element simulation

Computational stability and efficiency are the key problems for numerical modeling of crystal plasticity, which will limit its development and application in finite element （FE） simulation evidently. Since implicit iterative algorithms are inefficient and have difficulty to determine initial values, an explicit incremental-update algorithm for the elasto-viscoplastic constitutive relation was developed in the intermediate flame by using the second Piola-Kirchoff（P-K） stress and Green stain. The increment of stress and slip resistance were solved by a calculation loop of linear equations sets. The reorientation of the crystal as well as the elastic strain can be obtained from a polar decomposition of the elastic deformation gradient. User material subroutine VUMAT was developed to combine crystal elasto-viscoplastic constitutive model with ABAQUS/Explicit. Numerical studies were performed on a cubic upset model with OFHC material （FCC crystal）. The comparison of the numerical results with those obtained by implicit iterative algorithm and those from experiments demonstrates that the explicit algorithm is reliable. Furthermore, the effect rules of material anisotropy, rate sensitivity coefficient （RSC） and loading speeds on the deformation were studied. The numerical studies indicate that the explicit algorithm is suitable and efficient for large deformation analyses where anisotropy due to texture is important.     

板料拉延中的润滑

论述了板料拉延成形时的摩擦、磨损特征和润滑机理 ,探讨了拉延时润滑油的使用问题 ,为生产实际中润滑油的选择提供了理论根据和实用参考。     

Finite element modeling and experimental results of brass elliptic cups using a new deep drawing process through conical dies

This paper introduces a new technique for deep drawing of elliptic cups through a conical die without blank holder or draw beads. In this technique an elliptic-cup is produced by pushing a circular blank using a flat-headed elliptic punch through a conical die with an elliptic aperture in a single stroke. A 3D parametric finite element (FE) model was built using the commercial FE-package ANSYS/APDL. Effects of die and punch geometry including, half-cone angle, die fillet radius, die aperture length and punch fillet radius on limiting drawing ratio (LDR), drawing load and thickness strain of the cup have been investigated numerically for optimal process design. A die with half cone angle of 18° has shown the best drawability for the new technique. An experimental set-up has been designed, manufactured, and used for experimental production of elliptical shaped sheet-metal cups. A total of seven punches having aspect ratios ranging from 2 to 2.25 and a die with an aspect ratio of 2 have been manufactured and used. Tensile tests were carried out to obtain the stress–strain behavior for the formed sheet metal. Experiments were conducted on blanks of brass (CuZn33) with initial thicknesses of 1.5, 1.9, 2.4 and 3 mm at different clearance ratios (c/t). Effects of blank thickness and clearance ratio on limiting drawing ratio, drawing load and thickness strain were numerically and experimentally investigated. Finite element model results showed good agreement with experimental results. An elliptic cup with a limiting drawing ratio (LDR) of 2.28 has been successfully achieved using the proposed technique and set-up.     

Simulation of ultrasonic-vibration drawing using the finite element method (FEM)

In ultrasonic-vibration drawing, wires are drawn while ultrasonic vibration is applied to a drawing die. Prior studies provide experimental proof that ultrasonic-vibration drawing reduces drawing resistance, improves lubrication and prevents wire breakage. In the future, ultrasonic-vibration drawing is expected to contribute to the drawing of difficult-to-draw materials and operations, such as shaped wires, ultrafine wires, and the wire drawing operation in semidry or dry condition. However, a detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because the ultrasonic-vibration processing phenomenon occurs at high speed. Therefore, we attempted to understand the processing mechanism of ultrasonic-vibration drawing using the finite element method (FEM). ABAQUS was used for the FEM. Drawing force and stress–strain distributions in drawn wires were analyzed. From these studies, we quantitatively clarified the mechanism of improved drawing characteristics, such as decreased drawing force.     

Hydromechanical deep drawing of cups with stepped geometries

This paper deals with the hydromechanical deep drawing of metal cups with complex stepped geometries. Two materials, a low-carbon steel (DC04) and stainless steel (DIN 1.4301), have been researched. A die set with a maximum possible deep drawing ratio β_0,max = 3.0 for a punch diameter 100 mm has been designed and constructed. The die set is designed to withstand fluid counter pressures up to 200 MPa. Pressure control is achieved using a micro-metering pressure control valve. The process is initially simulated using the FEM solver LS-DYNA. Experiments have been conducted with two punch geometries. The punch geometries consist of cylindrical and conical wall segments. Complex positive and negative features are manufactured in the punch bottom face. The ability of transferring complex features from the punch onto the blank surface with high deep drawing ratios is investigated. Extended limiting deep drawing ratios of β_0,max = 3.0 for DC04 and β_0,max = 2.875 for DIN 1.4301 have been achieved.     

Adhesive wear in deep drawing of aluminum sheets

This paper focuses on the experimental validation of the common model for adhesive wear initiation by Czichos et al. for conventional aluminum deep drawing operations. A strip drawing test with a 90° bending process is used for the studies. The local contact conditions at the drawing edge are examined by analytical examination and numerical simulation on different degrees of refinement. Contact normal stresses and temperature profiles are investigated and correlated with the experimental observation of adhesive wear.     

Numerical simulation and analysis on the deep drawing of LPG bottles

Deep drawing is one of the most used sheet metal forming processes in the production of automotive components, LPG bottles and household goods, among others. The formability of a blank depends on the process parameters such as blank holder force, lubrication, punch and die radii, die-punch clearance, in addition to material properties and thickness of the sheet metal. This paper presents a numerical study made on the deep drawing of LPG bottles. In particular, the application of both variable blank holder forces and contact friction conditions at specific location during deep drawing are considered. The numerical simulations were carried out with DD3IMP FE code. A variable blank holder force strategy was applied and the numerical results were compared with results from other blank holder force schemes. It is evident that the proposed variable blank holder force scheme reduces the blank thinning when compared to other schemes; the friction coefficient also has a significant influence on the stress–strain distribution.     

一种基于AutoCAD的三维有限元模拟可视化方法

介绍一种基于ＡｕｔｏＣＡＤ的三维有限元模拟可视化方法。在ＡｕｔｏＣＡＤ平台上, 开发接口程序, 生成图形交换文件（ＤＸＦ）,能够准确而高效地实现三维实体网格和三维曲面网格的可视化。该方法只需对ＤＸＦ文件生成的图形, 用ＡｕｔｏＣＡＤ中ＨＩＤＥ命令进行消隐, 不再需要编制复杂的消隐程序。此外,还可用该方法实现三维有限元模拟的速度场以及应力和应变等场变量等值线图的可视化。该方法把有限元数值模拟与ＡｕｔｏＣＡＤ紧密衔接起来,为实现三维有限元模拟的可视化提供了一条简便而高效的途径     

High wear resistant deep drawing tools made of coated polymers

A methodology for the rapid production of drawing tools with high wear resistance to form free-form shaped sheet metal parts is developed. Hard material shells are thermally sprayed on an original mould and supported by a polymer. The bonded shell is removed from the original mould and acts as the surface of the forming tool. Deep drawing experiments show that the wear resistance of these hybrid tools is adequate to form high-strength steels. The tools are a suitable alternative to existing tool systems for the intended use in small up to medium size productions.     

摩托车油箱外壳拉深模具的虚拟制造

基于UGⅡ和Dynaform软件,以摩托车油箱外壳拉深模具为例,简述了虚拟制造技术的应用。     

Finite element simulation on the deep drawing of titanium thin-walled surface part

The deep drawing of titanium thin-walled surface part was simulated based on a self-developed three-dimensional finite element model. After an investigation on forming rules, a virtual orthogonal experimental design was adopted to determine the significance of processing parameters, such as die radius, blank holder force, and friction coefficient, on the forming process. The distributions of thickness and equivalent plastic strain of the drawn part were evaluated. The results show that die radius has a relative major influence on the deep drawing process, followed by friction coefficient and blank holder force.