AZ31B镁合金板液压-机械拉深试验研究

对AZ31B镁合金板进行液压-机械拉深试验,分析其变形特点和液压力对其成形性能的影响规律,并对液压拉深件的破裂现象进行了分析.试验结果表明,AZ31B镁合金板在液压-机械拉深时的成形性能比普通拉深时的差,主要原因是AZ31B镁合金板本身的塑性变形能力差,液压力未能及时发挥作用.     

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.     

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.     

高强度铝合金板材的温热介质充液成形研究

在温度20℃～300℃的范围内,对厚度1.2mm的7B04-T6高强度铝合金薄板在应变速率分别为0.0006s-1、0.006s-1和0.06s-1的条件下进行了单拉试验,并在此基础上利用MSC.Marc有限元软件进行了筒形件温热介质充液成形的差温热力耦合数值模拟,研究了成形温度、冲压速度和液室压力对于成形性能的影响。结果表明,在冲压速度15mm/min以及液室压力1MPa的情况下,零件的最大成形高度由常温下的20.5mm提高到了300℃时的31.6mm。     

阶梯型内凹筒型件液压拉深成形极限研究

应用ABAQUS／Explicit有限元软件,对不同特征尺寸的阶梯型内凹筒型件液压拉深成形中液压反力的上、下成形极限进行了研究,探讨了相应的液压反力工作区域以及工作区域的变化特征,并对拉深件的破坏模式以及相对优化的加载路径进行了讨论。     

Enhancing formability in hydromechanical deep drawing process adding a shallow drawbead to the blank holder

In this paper, a new method was proposed in order to enhance the limiting drawing ratio (LDR) of AA5754-O in the hydromechanical deep drawing process (HDD). In the proposed method, a shallow drawbead was added to the blank holder to increase LDR so as to provide strain hardening of a large region on the flange of the sheet material in addition to pre-bulging process which affects particularly only the initial stage but not the later ongoing process. So the LDR of the AA5754-O was increased from 2.65 to 2.787 by enlarging the region of strain hardening in the flange and partially reducing wrinkling tendency due to occurred tensile stresses using the convenient pressure and blank holder force profiles. The importance levels and their convenient values for height of drawbead, pre-bulge height and pressure, surface roughness of the punch were determined with analysis of variance (ANOVA) is a statistical method. ANOVA analysis illustrated that adding a shallow drawbead to the blank holder is the most effective factor between the investigated factors for the HDD process. While the effects of the pre-bulging pressure and pre-bulging height were determined as quite small, the surface roughness of the punch was found unimportant compared to the effect of the shallow drawbead. The highest LDR value was obtained with 1 mm drawbead height, 5 mm pre-bulging height, 10 MPa pre-bulging pressure and 2.8 μm surface roughness of the punch.     

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.     

Improvement of deep drawability by radially pressurized fluid

Developments in the automobile and other sheet metal industries demand continuous improvements in the deep drawing processes. The areas of improving deep drawing processes include higher forming limits so that much deeper products can be obtained with less power consumption. In this paper, the idea of applying hydraulic pressure in the radial direction on the periphery of the blank is theoretically analyzed. This radial pressure is generated due to the punch movement within the fluid chamber and is directed through a by-pass to the blank periphery. The problem is solved for a work hardening material using the finite difference method. The stress and strain distributions in the flange of the shell are determined and the limiting drawing ratio is calculated at the instant when the strain in the thickness direction reaches a critical value. This critical value is assumed to be the strain hardening exponent of the drawn material. The results show significant increase in the limiting drawing ratio as the radial pressure increases.     

Numerical simulation of two-stage deep drawing of complex-shaped parts

1　INTRODUCTIONInrecentyears ,withtherapiddevelopmentofcomputersoftwareandhardware ,andtheintersectionandcombinationofcomputertechnology ,graphics ,mechanicsandprocessengineering ,thecomputeraid edengineering(CAE)technologybasedonnumericalsimulationhasbeenwidelyappliedinthesheetmetalformingfield[1,2 ] .Nevertheless ,untilnow ,thenu mericalsimulationisconfinedtosimulatesomebasicmodesofdeformationsuchasbending ,deepdraw ing ,bulgingandflanging .Forthedeformationofcomplexwork pieces ,forexa…     

盒形件增量拉深成形数值模拟及工艺试验

为了探索板料增量拉深成形的特点和规律,设计了增量拉深成形轨迹,用Deform-3D模拟软件,对盒形件增量拉深过程进行了数值模拟,分析了凹模圆角半径和凸模进给速度对成形件质量的影响,获得了成形过程中的等效应力和等效应变;并设计了具有双向调节机构的增量拉深模,在Gleeble1500D热模拟试验机上进行了工艺试验验证.结果...     

盒形件无模充液拉深工艺参数研究

基于Dynaform平台对盒形件无模充液拉深工艺参数进行分析与研究,结果表明,合理地控制液体加载路径、预胀形压力以及成形时的液体压力可有效提高板料成形性能和成形件质量,通过与传统拉深工艺比较,无模充液拉深工艺在摩擦保持效应的作用下,拉深件壁厚更加均匀一致,盒形件一次拉深最大相对高度可达到4。     

轧制差厚板盒形件充液拉深成形的数值模拟

为了解决轧制差厚板在拉深成形过程中的破裂、起皱、过渡区移动等缺陷问题,应用充液拉深方法完成差厚板零件的成形。通过数值模拟技术,对轧制差厚板的充液拉深成形性能进行研究,完成差厚板盒形件充液拉深成形的仿真,对比分析充液拉深成形与普通拉深成形的优势,讨论液体压力对于差厚板成形性能的影响。结果表明,采用充液拉深技术能够改善差厚板的成形性能。随着液体压力的增加,厚度减薄率呈现先减小后增大的趋势,而过渡区移动量则逐渐减小。大尺寸的差厚板对液体压力的变化更为敏感,但无论对于哪种尺寸的板料,采用合适的液体压力均能够获得高质量的差厚板零件。     

Hydromechanical Deep-Drawing of Aluminium-Alloys at Elevated Temperatures

This paper presents a technology that combines the different effects used in hydromechanical and warm deep drawing to reduce the drawing force and to increase the transmittable drawing force in the deep drawing process of aluminium sheets by flange heating and by using a counter pressure. Adequate process parameters and an optimised tool design are discussed in thermo-mechanically coupled Finite Element Simulations. The required system parameters, such as temperature and strain rate dependent flow curves, temperature dependent friction coefficients and heat transfer coefficients, were detected in different model experiments for the numerical simulations. Experimental results are presented to highlight the possibilities and limitations of this forming method.     

筒形件液压拉深的研究现状及进展

在阐述板料液压拉深方法原理和分析国内外板料液压拉深典型装置的基础上,将板料液压拉深方法分为液压软凸模拉深、液压辅助压边拉深、对冲液压拉深、液压—机械拉深和内高压拉深等5种。对这些典型板料液压拉深装置及其工艺原理的发展及现状进行了详细的介绍和分析。最后对板料液压拉深工艺存在的问题作了阐述。     

压边间隙对圆柱杯反向深拉延成形质量的影响

对ＮＵＭＩＳＨＥＥＴ９９圆柱杯深拉延－－反向深拉延标准考题（Ｂｅｎｃｈｍａｒｋ－Ｃ）,进行了有限元数值仿真,将计算结果与Ｋｉｍ Ｈｙｕｎｇ ｊｏｎｇ的实验结果做了比较。在此基础上,分析了第一次拉延过程的工艺参数－－压边间隙对后续工序成形质量的影响,指出第一次成形的压边间隙在１．６￣１．８ｍｍ之间时,第二次成形的变形余裕度最大,即成形质量最好。研究说明,开展多工序成形过程的数值仿真有着重要的意义。     

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.     

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。     

变压边力对矩形件成形性能的影响

起皱和断裂是板料成形过程的主要失效模式 ,合理控制成形过程中压边力 ,可以消除这些缺陷 ,提高成形性能。本文通过对随位置变化的变压边力作用下的矩形盒拉深过程进行数值模拟 ,研究各部位压边力变化对整体成形性能影响、及其影响范围 ,为分块压边圈的压边力的调整提供一定的依据。     

Effects of temperature and blank holding force on biaxial forming behavior of aluminum sheet alloys

Biaxial forming behavior is investigated for three aluminum sheet alloys (Al 5182 containing 1% Mn (5182+Mn), Al 5754, and 6111-T4) using a heated die and punch in the warm forming temperature range of 200–350 °C. It is found that, while all three alloys exhibit significant improvement in their formability compared with that at room temperature, the non-heat-treatable alloys 5182 + Mn and 5754 give higher part depths than that of heat-treatable 6111-T4. The formability generally increases with decreasing BHP (BHP), but increasing the forming temperature and/or BHP minimizes the wrinkling tendency and improves the forming performance. The stretchability of the sheet alloys increase with increasing temperature and increasing BHP. For the alloys and forming conditions involved in the current study, the formability, measured in terms of part depth, comes mainly from the drawing of metal into the die cavity, although stretching effects do influence the overall forming behavior. The optimum formability is achieved by setting the die temperature 50 °C higher than the punch temperature to enhance the drawing component. Setting the die temperature higher than the punch temperature also improves the strain distribution in a part in such a manner that postpones necking and fracture by altering the location of greatest thinning.     

不锈钢材的橢圆杯拉伸成形分析

采用Prandtl-Reuss塑流法则和Hill的屈服判据,结合有限变形理论及updated Lagrangian formulation的概念,将四边形四节点退化壳元素偶合到刚性矩阵中,组成三维有限元素的分析模式来处理板材成形问题。以材料拉伸试验所得的样片断裂面厚度为数值分析的破断准则,探讨椭圆杯拉伸成形过程中冲击荷载与冲程的关系、工件厚度分布、变形过程及成形极限等。由数值分析与实验结果得知,冲击荷载随着冲程的增加而增大,当载荷达到最大值后,样片随着冲程的增加而继续变形,直到拉伸完成为止。工件最小厚度集中在工件与压头长轴接触处,因长轴的曲率半径比短轴的小,故料片在长轴处承受了最大拉伸应力。经由椭圆压头周长与初始样片周长所定义的极限拉伸比得知,此椭圆杯成形的极限拉伸比为2.136。