A study on joining magnesium alloy high pressure die casting components with thread forming fasteners

With tremendous weight saving potential,magnesium alloy high pressure die casting components have been widely used for automotive applications.Magnesium fastening technology is thus becoming increasingly important to design engineers.Joining as-cast holes of magnesium high pressure die casting components with thread forming fasteners provides significant advantages for the assembly process,overall cost benefit and joint integrity.This type of joint is thus preferred for structural applications.Designing the thread forming fasteners with as-cast holes follows the general rules for designing for the machined holes,including carefully designing the variables such as the assembly torque range,the length of thread engagement,the hole diameter and required failure mode.In addition,special attention needs to be paid to the draft angles of the magnesium cast components that are required for the die casting process.In this paper,the effects of above key factors,individually and combined,on the joint performance of thread forming fasteners with as-cast blind holes of AM60B magnesium components are studied.A joint design philosophy was proposed to optimize both joint performance(the prevailing torque,the failure torque and the failure mode)and manufacturing easiness(the hole diameter and corresponding draft angle).The detailed design considerations for as-cast holes of magnesium HPDC are discussed and explained through a hypothetical example.

Dimpling Suppression by Chamfered Rotatable Cubic Punch in Reconfigurable Die Forming

The dimpling defects caused by conventional hemispherical punch in doubly curved sheet metal reconfigurable die forming process were considered.The rotatable cubic punch (RCP) was developed to suppress the dimpling defects more effectively and conveniently.The former punch contacts with the work-piece through a point-surface contact and the latter punch contacts with the work-piece through a surface-surface contact.A series of stamping experiments were carried out using three different punches (hemispherical punch,RCP,chamfered-RCP) with three different loads.Some finite element simulations about the stamping experiments were carried out.The dimple scales were evaluated through the dimple depths.The corresponding data were obtained by 3-D scanning and FE result analysis respectively.A 3-D plate forming machine was developed,in which chamfered-RCP was adopted.Plate forming experiments were carried out on this machine.The stamped samples show a clear basis for the performance of chamfered-RCP.The study provided a means to guide the design of punches for dimpling suppression used in reconfigurable die.

Superplastic forming of Ti6Al4V alloy using ZrO_(2)-TiO_(2) ceramic die with adjustable linear thermal expansion coefficient

Firstly,the relation between the coefficient of thermal expansion(CTE)and the volume fraction of TiO_(2) was investigated, and also the influence of relative density of ceramic on the CTE was studied.The results show that the volume fraction of TiO_(2) and the relative density both make influence on the CTE of ZrO_(2)-TiO_(2) ceramic.According to the results,the ZrO_(2)-TiO_(2)(volume fraction of TiO_(2) is 27%)ceramic die with the similar CTE(8.92×10^(-6) ℃^(-1))to Ti6Al4V was fabricated.Secondly,to evaluate the dimensional accuracy of the workpiece superplastically formed,the Ti6Al4V impression experiment was performed.The result shows that the dimensional inaccuracy of workpiece is 0.003.Thirdly,in order to evaluate the practicability,the experiment of superplastic forming Ti6Al4V using ZrO_(2)-TiO_(2) cylinder ceramic die was carried out.The Ti6Al4V cylinder shows good shape retention and surface quality,and high dimensional accuracy.The ceramic dies seem to be adequate for superplastic forming the high accuracy Ti6Al4V, and the trials have confirmed the potential of the ZrO_(2)-TiO_(2) ceramic die.

FEA technique of hot plate forming process using cell-typed die with cooling device

Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG tank.Cell-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process,and an air-cooling device is separately installed inside the lower die.A finite element analysis (FEA) technique was developed,which included hot forming,air flow,cooling and thermal deformation analysis for the hot plate forming process using the cell-typed die.Further,the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis.A small-scale model test of the process was conducted to verify the FEA technique.The analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.

Study on the Deformation Characteristics of the Sheet Hydroforming with a Movable Die

An improved sheet hydroforming process with a movable die is proposed and investigated by elastoplastic FEM. The effects of varied process parameters on the deformation of the sheet blanks were investigated. The effects of the movable die on the FLD were also analyzed. Using a movable die may increase the forming limit of the blank and improve the forming performance. Moreover, the drawing ratio of the blank may be increased by changing the process conditions such as blank holder force and the counterforce of the movable die on the blank.

Heat shock behavior of permanent die during non-solid near-net forming process

Heat shocks caused by alloy melt and coat spraying are the main reason of die plastic deformation and early fracture. Based on theoretical analysis of heat shock phenomenon, two characteristic parameters of die damage caused by heat shock were proposed, which are heat shock plastic deformation index (HSPI) and heat shock crack index (HSCI). The effect of heat shock on die plastic deformation and fracture behaviors was described quantitatively by these two parameters. HSPI represents approaching of heat shock stress to die yield stress. Plastic deformation will happen on a die if this index reaches 1. HSCI represents approaching of heat shock stress to die tensile strength. Die fracture will happen if this index reaches 1. According to theoretical analysis of heat transfer, theoretical models of HSPI and HSCI were established. It is found that, the smaller the interfacial thermal resistance (ITR) is, the higher the pouring temperature and die temperature are before heat shock, and the greater the HSPI and HSCI are, which can be fitted as exponential curves, linear and cubic curves.

Humanoid Based Intelligence Control Strategy of Plastic Cement Die Press Work-Piece Forming Process for Polymer Plastics

The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control in parameters of forming process, the paper explored the humanoid based intelligence control strategy. In the paper, it made the anatomy in control puzzle resulted in uncertainty such as chemical component of plastic cement etc., summarized up the characteristic of cybernetics in forming process, researched on the humanoid based intelligence control strategy, and constructed the control algorithm of forming process in plastic cement work-piece. Taking the process experiment of temperature and pressure control as an example, it validated the good dynamic and static control quality through simulation of control algorithm constructed in this paper. The experimental results show that the control algorithm explored in this paper is reasonably available.

Effect of Deformation Condition on Axial Compressive Precision Forming Process of Tube with Curling Die

The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp< 1, otherwise △/2rp>1.

基于NX PDW和Dynaform的电瓶箱加强板级进模快速设计

CAD(Computer aided design)和CAE(Computer aided engineering)相结合的先进模具设计技术,能够显著提高冲压模具设计效率和设计质量,是现代模具设计的发展方向。以一款汽车电瓶箱加强板多工位级进模设计为例,在分析零件结构特征确定成形工艺的基础上,应用西门子级进模设计模块(NX PDW),快速实现了加强板级进模结构的详细设计。同时,针对加强板弯曲成形过程中可能出现的回弹、起皱、破裂等缺陷,应用冲压成形Dynaform模拟软件进行分析验证,能够确保所获得模具结构的合理性。经验证,该设计方法可为同类零件的级进模快速设计和验证提供参考。

Effect of process parameters on sheath forming of continuous extrusion sheathing of aluminum

The effect of flow passage length in the die cavity and extrusion wheel velocity on the shape of aluminum sheath during the continuous extrusion sheathing process was analyzed by using finite element methods based on software DEFORM 3D and experimentally validated. The results show that by increasing the flow passage length, the velocity of metal at the cross-section of sheath tends toward uniformity, the values of the bending angles of sheath gradually approach the ideal value of zero and the cross-section exhibits a better shape. The extrusion wheel velocity has negligible effects on the bending shape and cross-section of the sheath product when a long flow passage is used.

Analysis and Optimization on Factors Affecting Forming Quality of Half Axle Gears Warm Precision Forging

Half axle gears is produced by precision forging popularly because of the advantages in minimum machining allowances, lower material consumption and good service properties. But the forming quality of precision forging is difficult to control. Many simulations and analysis of precision forging process were taken by previous researchers. But no concrete method is proposed to evaluate and optimize the forming quality of half axel gears. The primary purpose of this work is improving the forming quality of half axel gears by analyzing and optimizing the affected factors of forming quality. The enclosed-die warm forging process of half axle gears was developed, and a new type of die-set used on double action hydraulic press was brought forward. The main influential factors of precision forming quality were analyzed after the forming process had been simulated by using finite element method（FEM）. These factors include die structure, web thickness and web position. A method used to evaluate the forming quality was established, which investigated the maximal forming load, the metal filling rate and the material damage factor. The FEM simulations of half axle gears precision forging were evaluated by this method. The results show that the best forming quality can be achieved when the punches were added with bosses, the web located at the middle plant of the gear, and the web thickness was 30 percent of the inner hole diameter. Verification experiments taking the above optimized parameters were performed on a 7.8 MN double action hydraulic press. The trial products were formed well. And their geometric precision meets the demand. The verification result shows that the optimization of the influential factors, according to the simulations and the evaluation method, can improve the forming quality. The new structure of precision forging die-set and the new evaluation method guarantee a high forming quality ofhalfaxel gears.

Conformal optimal design and processing of extruding die cavity

Aimed at the optimal analysis and processing technology of die cavity of special-shaped products extrusion, by numerical analysis of trigonometric interpolation and Conformal Mapping theory, on the non-circle cross-section of special-shaped products, the conformal mapping function can be set up to translate the cross-section region into unit dish region, over numerical finite interpolation points between even and odd. Products extrusion forming can be turned into two-dimension problem, and plastic stream function can be deduced, as well as the mathematical model of the die cavity surface is established based on deferent kinds of vertical curve. By applying Upper-bound Principle, the vertical curves and related parameters of die cavity are optimized. Combining with electrical discharge machining (EDM) process and numerical control (NC) milling machine technology, the optimal processing of die cavity can be realized. Taking ellipse-shaped products as an instance, the optimal analysis and processing of die cavity including extruding experiment are carried out.

火锅菜盆复合模设计

根据火锅菜盆的尺寸、结构和材料厚度,对其冲压工艺进行分析,并设计了“落料+第1次成形+拉深”复合模、第2次成形单工序模、侧冲孔单工序模。在复合模中,120°的斜边可视为拉深工序的压边圈,将第1次成形120°夹角的工序排在拉深工序前。在第2次成形70°夹角的单工序模的下模中设计了活动顶板,与上模的成形凸模将120°的斜边压住,防止120°的斜边变形。在“落料+第1次成形+拉深”复合模和第2次成形单工序模中,在下模成形零件的底部设置橡胶垫块,在上模向下运动时橡胶垫块的弹力将材料顶住,同时给上模向下运动腾出空间,防止模具零件卡死。

深轮辐齿坯多工位闭式模锻材料流动规律研究

探索闭式热模锻成形时材料的流动规律是控制充填不满等成形缺陷、获得高精度模锻件的理论基础。针对深轮辐齿坯件热模锻成形时易出现填充不满的问题,以某SCr420H深轮辐齿坯为研究对象,基于齿坯件结构分析,设计了“下料-加热-镦粗-预锻Ⅰ-预锻Ⅱ-终锻”的多工位闭式热模锻工艺方案;基于Deform软件,构建了深轮辐齿坯件多工位闭式热模锻全流程有限元模拟模型;采用试验验证了有限元模型的可靠性,并对多工位闭式热模锻成形过程中材料的流动规律进行了研究。结果表明:镦粗比为3.7时,可获得外形良好的圆饼形预制坯,镦粗时受上下表面摩擦效应的影响,材料径向流动不均匀,在坯件腰部出现鼓形;预锻Ⅰ工位成形出用于定位的底面内凹结构,同时减小了后续工位材料填充难度;预锻Ⅱ和终锻成形时的材料流动规律相似,成形前期材料集中流向轮缘部分、成形中期主要流向轮毂部分、末期流向圆角处;终锻成形时未出现材料填充不满的缺陷,在成形后期,少量金属材料从终锻上下模的导向间隙中流出,形成纵向飞边。通过生产试验,成形出填充良好的深轮辐齿坯件,模拟数值获得温度与实际生产数值最大误差不超过3.15%,纵向飞边高度小于0.5 mm,零件各尺寸偏差均小于0.2 mm,验证了所设计多工位闭式模锻工艺的合理性。

高速钢桶焊缝机电机座支撑脚复合模设计

针对高速钢桶焊缝机电机座支撑脚使用2 mm厚的SECC板料进行中小批量冲压成形的要求,设计了3副模具用于制件的4道工序成形。冲孔落料和修边压印采用倒装式复合模结构、切分模和弯曲模采用正装结构,且切分模和弯曲模集成在1副模具内。弯曲模中设计了凸模驱动的双滑块内收弯曲成形机构,该机构在制件弯曲壁的两侧都使用滑块进行夹紧驱动弯曲,能有效防止弯曲回弹,保证了制件的弯曲成形尺寸。模具结构简单实用,成形工艺设计合理,实现了制件的自动化生产。

Viscous warm pressure bulging process of AZ31B magnesium alloy with different ellipticity dies

Based on the bulging principle of different ellipticity dies, the methyl vinyl silicone rubber with excellent thermal stability and heat transfer performance was chosen as the viscous medium. The finite element analysis and experiments of viscous warm pressure bulging （VWPB） of AZ31B magnesium alloy were conducted to analyze the influence of different ellipticity dies on the formability of AZ31B magnesium alloy. At the same time, based on the grid strain rule, the forming limit diagram （FLD） of VWPB of AZ31B magnesium alloy was obtained through measuring the strain of bulging specimens. The results showed that at the temperature range of viscous medium thermal stability, the viscous medium can fit the geometry variation of sheet and generate non-uniform pressure field, and as the die ellipticity increases, the difference value of non-uniform pressure reduces. Meanwhile, according to the FLD, the relationship between part complexity and ultimate deformation was investigated.

基于Dynaform的汽车覆盖件拉延模具设计

以板料成形非线性有限元分析软件Dynaform为平台,介绍汽车覆盖件拉延模具型面设计过程,对某种汽车引擎盖冲压成形过程进行数值模拟,根据模拟结果进行成形性分析,为优化工艺参数和模具结构提供强有力的工具。

TC4钛合金复杂曲率蒙皮热成形失稳缺陷及消除方法

为解决钛合金复杂曲率板材零件的高精度成形技术性难题,以厚3.0 mm的TC4钛合金薄壁复杂曲率蒙皮作为研究对象,利用PAM-STAMP有限元分析软件对蒙皮零件进行热成形工艺仿真与分析。结果表明:仿真预测结果与试验结果均表现出零件会产生褶皱或死褶缺陷,导致零件无法正常交付使用。基于仿真数据,分析了复杂曲率蒙皮零件成形失稳缺陷的产生原因,采用一种新方法为零件热成形模具设计了压边装置,优化了成形效果。经实际生产验证可知,优化后的模具结构可以有效解决成形过程中产生的成形缺陷,成形后表面质量好、材料厚度分布均匀,且型面精度满足设计和装配的使用要求。

轴承坯料机械手轴盖3D多工位级进模设计

针对轴承坯料机械手轴盖制件一套三件的成套冲压成型生产要求,运用3D设计软件UG设计了一副11工位连续级进模用于轴盖成套制件的生产。模具中所设计的11工位包括冲孔、落料、拉深、翻边、侧切、侧冲孔等工艺成型手段,模具达到的效果是材料利用率达到64.23%,制件生产效率可达45套/min,模具制造成本降低5%。相比于传统多工序多套单冲模成型工艺,生产效率提高10倍以上。模具中,使用1次拉深成型、3次精修,对多级拉深成型件进行加工能有效降低制件加工难度;使用步进电机送料,氮气弹簧压料和顶料,使模具设计难度大为降低;使用了两种楔紧块驱动型侧滑块机构对制件进行工艺面切除加工和精整形,及燕尾槽压块驱动上模侧冲孔滑块机构使制件的侧面加工得到了可靠保证。使用UG设计软件设计了模具的3D结构,较之于2D排位设计方法,更能有效避免设计缺陷,模具设计效率和可靠性更高。

铝合金变直径管材旋弯渐进成形规律有限元模拟研究

研究设计了一种用于旋弯渐进成形的双辊柔性弯曲模,其可对管材施加较强周向约束,且成形中可自适应转动。相比传统圆弧型单辊弯曲模,新型双辊柔性弯曲模能够有效降低旋弯渐进成形弯曲力,提高成形稳定性,并抑制管材截面畸变。在此基础上,建立了铝合金管材旋弯渐进成形-回弹全过程有限元模型,并通过与柔性弯曲成形对比,分析获得了旋弯变形耦合对成形结果的影响规律,发现在旋压基础上引入弯曲工步,会引起一定程度的截面变形和壁厚不均匀现象;在弯曲基础上引入旋压工步,会减小弯曲段截面变形量,增加内外脊线壁厚差异,加剧起皱风险,减小成形后的回弹变形。