Numerical simulation of aluminum alloy ladder parts with viscous pressure forming

1　INTRODUCTIONTheeffectofstressstatesonaxisymmetricsheetformabilityhasbeenstudiedundertheconditionofsolidmetalpunchforming [14 ] ,andtheeffectofblankholderpressure (BHP) ,frictioncoefficientandpunchconfigurationonthestressstateshasbeenob tained .Becauseofthedisadvantagesofsolid punchforming ,newformingtechnologyisneededtoim provethestressstatesofthesheetinformingprocessandtomeettherequirementofforminglow plastici ty ,complexshapeparts .Viscouspressureforming(VPF)isarecentlydevelopedfle…     

有限元模拟用于优化镁合金板碟形拉深成形的模具参数

运用有限元的方法,对厚度1.2mm、直径52mm的AZ31B镁合金板常温冲压成直径为29mm的碟形件进行模拟,通过分析模具参数对最大主应力值及拉深性能的影响,优化出适合于该工艺的模具参数,并进行相应的试验。模拟结果表明,凹、凸模圆角半径、凹凸模间隙的优化,能降低最大主应力值并延缓裂缝的产生,从而提高镁合金塑性成形性能;模拟得到较优凹模圆角半径2.6mm、凸模圆角半径1.8mm,适宜的凹凸模单边间隙为1.3mm。试验结果表明,高径比随着模具参数的变化而增加,材料的成形性能大幅提高,验证了有限元模拟结论的可靠性。     

椭球形制件复合成形规律的研究

采用理论分析、数值模拟与实验验证相结合的方法,对椭球形制件的复合成形规律进行了研究。建立了应力分界圆半径的数学表达式,理论分析表明,应力分界圆半径的大小与板料的初始尺寸、厚度、摩擦系数、压边力大小和凹模圆角半径等因素有关。当压边力、坯料尺寸以及摩擦系数加大,而相对圆角半径减小时,应力分界圆半径变大,复合成形中胀形成分加大;反之,应力分界圆半径减小,拉深成分增加,揭示了复合成形的阶段性特征。数值模拟结果表明,应力分界圆半径是动态变化的,椭球形制件复合成形具有明显的阶段性特征,没有直线段的椭球形制件的成形可分为纯胀形、以胀形为主的胀形-拉深复合成形和以拉深为主的拉深-胀形复合成形3个阶段;在成形的第Ⅰ、Ⅱ阶段初期,坯料尺寸和压边力的大小对应力分界圆半径影响不大;在第Ⅱ阶段后期和第Ⅲ阶段,随毛坯尺寸和压边力的增大,应力分界圆增大。在变形过程中存在两个可能发生失稳起皱时刻,即第Ⅱ阶段初期和第Ⅲ阶段初期。试验验证了理论分析和数值模拟所得的结果。     

Influence of variables in deep drawing of AA 6061 sheet

Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance as forming process,also serves as a basic test for the sheet metal formability.The effect of equipment and tooling parameters results in complex deformation mechanism.Existence of thickness variation in the formed part may cause stress concentration and may lead to acceleration of damage.Using TAGUCHI's signal-to-noise ratio,it is determined that the die shoulder radius has major influence followed by blank holder force and punch nose radius on the thickness distribution of the deep drawn cup of AA 6061 sheet.The optimum levels of the above three factors,for the most even wall thickness distribution,are found to be punch nose radius of 3 mm,die shoulder radius of 8 mm and blank holder force of 4 kN.     

Finite element analysis of sheet Hydromechanical forming of circular cup

Sheet hydroforming is a process of converting flat sheet into desired component geometry by using water pressure in a controlled manner. This paper dealt with sheet Hydromechanical forming (SHMF) of circular cup. In this process, blank is first placed on the lower die (a fluid chamber combined with draw ring) and then after sealing the blank between blank holder and draw ring, punch progresses to deform the blank. Pressure of the fluid chamber is also increased simultaneously with the punch progression. The present work endeavours to understand the effect of strain hardening exponent, anisotropy ratio and interfacial friction between blank and tools surfaces for different modes of deformation––stretching to drawing mode on sheet Hydromechanical forming of circular cups.A finite element (FE) model was developed for simulating the SHMF process using dynamic explicit, commercial code, LsDyna. The model after experimental validation used for studying the effect of above parameters on the process. The analysis reveals that higher cup depth with minimum thinning for forming dominated by stretching mode can be achieved with material of higher anisotropy ratio, strain hardening exponent by using a rough punch and effective lubrication at blank-die–blank holder interfaces. On the other hand in case of drawing as mode of deformation, thinning is influenced mainly by interfacial friction condition between blank and tool surfaces as compared to material properties.     

前翼子板成形数值分析

根据正交试验法原理,应用板料成形软件PamStamp 2G,在其他成形条件一定的情况下,对前翼子板在不同压边力、板料与模具间摩擦因数、凸模和凹模间隙、虚拟凸模成形速度下的成形进行数值分析。将模拟结果同实际成形件厚度比较,通过极差分析,得出上述因素对前翼子板成形的不同影响,其中压边力、虚拟凸模速度对成形影响较其他因素大。     

方形盒制件圆角处拉深破裂的数值模拟

金属薄板成形的数值模拟技术在冲压件生产和模具设计中起着重要的作用。文章借助Dynaform软件对某方形盒制件拉深破裂现象进行数值模拟,分析其产生原因和影响因素,并利用正交实验找出防止该制件圆角破裂的拉深条件组合。结果表明,在冲压速度、凸模圆角半径、摩擦系数和板料厚度4个因素中,凸模圆角半径对盒形件拉深破裂的影响最大。为降低因圆角处板料剧烈减薄而产生破裂的几率,盒形件拉深时应采用较大的凸模圆角半径。     

The effect of die materials on the strain distribution in electro-galvanized sheet steel forming

The punch load and strain distribution of two deformed sheet steels, aluminum killed drawing quality steel (AKDQ Bare) and electro-galvanized drawing quality steel (AKDQ E.G.), are examined under the various process conditions including, die materials, punch speed, blank holding force, drawbead height and lubricant. The punch load and strain distribution ot Bare sheet steel forming is higher than that of E.G.sheet steel on the Kirkesite die set and are reversed on the GM 241 die set. The punch load and strain distribution on the Kirkesite die set is lower than those of the GM 241 die set. The changes of punch load and strain distribution ot the deformed cup for two sheet steels are affected by the frictional behavior of each sheet steel. It shows that the changes of frictional behavior having to be considered in the die design.     

Numerical simulation for the multi-point stretch forming process of sheet metal

Multi-point stretch forming (MPSF) is a flexible manufacturing technique to form large sheet panels of mild curvature. The traditional fixed shape-stretching die is replaced by a matrix of punch elements, and the sheet metal are stretch-formed over the multi-point stretching die (MPSD) generated by the punch element matrix. In this paper, extensive numerical simulations of the processes for stretching parabolic cylinder, toroidal saddle and sphere parts were carried out by dynamic explicit finite element analysis. The forming results using multi-point die were compared with those of using traditional die. The use of an elastic cushion to suppress dimpling of the part caused by the discrete punch elements was investigated along with a discussion of its influence on part shape accuracy. The effect of the size of punch element and the shape of MPSD on the shape accuracy of formed parts were analyzed. The results may provide useful guidance on determining MPSF parameters and optimizing MPSF manufacture processes.     

基于载荷下降法的双相钢DP590拉深减薄率研究

采用载荷下降法研究了双相钢DP590在不同压边力下拉深成形的减薄率。采用BCS-50AR通用板材成形性试验机进行有无润滑条件的对比拉深试验,获得成形力-凸模位移关系曲线。试验结果发现,拉深件凸缘部位和凹模圆角处的润滑有利于拉深成形,而无润滑条件下的拉深容易破裂。拉深件凸缘部位增厚,凹模圆角处和筒壁部位均有不同程度的减薄。危险断面处的减薄率最大,破裂情况下的最小减薄率为28.6%,无破裂情况下的最大减薄率为19.3%,达到实际生产要求。     

基于正交试验和能量转换的精密级进模多步拉深成形研究

应用正交试验方法,采用Dynaform对精密级进模多步拉深成形进行有限元数值模拟。结合能量转换原理,研究各步拉深中凹、凸模圆角半径、拉深高度以及压边力等工艺参数对成形件厚度和回弹的影响,并找出各因素影响的主次顺序。以射频(RF)连接器的壳件为例,通过上述方法优化各步成形参数,用以指导模具设计。     

货车侧板成形工艺及模具设计

从变形性质、压边方式、成形次数和成形力4个方面对货车侧板的成形工艺进行了理论分析和计算 ,得出了该零件属于胀形性质的起伏成形的结论。模具省略了压边装置 ,解决了设备能力不足的问题。其导向通过将凸、凹模设计成近仿形结构来实现 ,在简化结构的同时较好保证了凸、凹模的间隙 ,是1副性能价格比高的模具     

板成形数值模拟影响因素的正交试验分析

根据正交试验原理，应用板料成形软件对不同压边力、模具与板料间摩擦系数、凸凹模间隙和板料初始尺寸进行数值模拟，将数值模拟的厚度同实际成形件的厚度进行比较，得出上述因素对前翼子板成形结果的影响，并预测了前翼子板较优的理论成形条件。     

Development of incremental deep drawing process

This paper deals with development of an incremental deep drawing process. On a newly developed incremental deep drawing set-up, the aluminium sheets are formed; the forming is carried out by deep-drawing the blank as in the conventional method but incrementally. Fractures at the punch or die corner in the blank may or may not occur depending on the conditions; the process parameters involved are punch size, punch corner radius, increment in punch displacement, blank holding force or pressure, etc. It is thus shown that different shapes are formed by one set of common tools. It is thereby confirmed that incremental deep drawing is possible without using a particular tool set for a particular shape.     

Effects of pre-bulging on 2024 aluminum alloy complex-shaped components

To improve the poor plasticity of 2024 aluminum alloy sheet, which causes wrinkle and fracture in conventional deep drawing of complexshaped components, hydromechanical deep drawing (HDD) with pre-bulging was investigated. The loading paths of chamber pressure and pre-bulging pressure were designed and optimized by numerical simulations and experiments, and effects of loading paths were obtained and analyzed for thickness, stress and defects. A reasonable loading path was determined. Thickness is more uniform when pre-bulging pressure is 2 MPa and chamber pressure is 15 MPa. The suspending area of a blank wrinkles easily between the punch and the die when pre-bulging pressure is smaller than 1.5 MPa; fracture occurs for the suspending area of blank between the punch and the die when pre-bulging pressure is larger than 8 MPa. The results show that a helpful friction can be generated, the stress state can be improved, and fracture and wrinkle can be avoided by a reasonable pre-bulging in the suspending area of the blank for a complex-shaped component. The uniformity of thickness and forming limit can be enhanced.     

材料和目标形状对多点拉形成形精度的影响分析

多点拉形是将整体拉形模具离散成多点模具,可以在一套多点拉形模具上实现不同形状零件的拉形,省去了模具的设计、制造等大量的生产成本,实现了蒙皮件的柔性成形。多点拉形主要适于成形小曲率、大变形的蒙皮件,材料和目标曲面形状都是影响多点拉形成形结果的重要因素。通过对3种材料成形不同曲率半径球形件的多点拉形过程进行数值分析,研究材料和成形件目标形状对多点拉形的影响。结果表明,在成形件中心区域的形状误差小于边缘区的形状误差,拉伸方向的形状误差大于垂直拉伸方向的误差,成形件的曲率半径越小,成形件的形状误差越大。     

凸模圆角半径对钢板冲压成形的影响

圆角半径的确定一直是冲压件工艺设计的关键技术,本文采用实验与理论模型相结合的手段,研究了凸模圆角半径对钢板冲压成形的影响。结果表明：冲压成形中的开裂位置和凸模圆角大小有关;圆角处的减薄率基本上与相对圆角半径R／t成反比;极限成形高度随凸模圆角半径的增大而增大。     

圆筒形件充液拉深成形精度

本文系统地研究了平底和球面圆筒形件充液拉深成形精度。充液拉深成形中，由于高压液体紧紧将毛坯贴向凸模表面，因而零件具有良好的贴模性并能获得很高的内径精度。同样，由于液压的施加在凸模圆角和压边圈之间产生与凸模运动方向相反的局部胀形，减小了凸模圆角处的弹复，提高了侧壁及球面件底部的形状冻结性。但是，平底零件的底面形状因液压的施加而使形状冻结性不好，平面度降低。     

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.     

拉形动态摩擦系数的正交试验分析

用正交设计法对拉形时的摩擦系数进行了测定,方差分析结果表明,平整量越大摩擦系数越小;润滑剂对摩擦系数的影响最大;摩擦系数随凸模行程的增大而增大,且基本为线性关系。凸模圆角半径处的摩擦系数比凹模圆角半径处的摩擦系数普遍大,这是由凸模圆角半径处的板材变形程度大、板材表面粗糙化大所引起。