A formability index for the deep drawing of stainless steel rectangular cups

The effects of process parameters on the formability of the deep drawing of rectangular cups made of SUS304 stainless steel were investigated by both the finite element analysis method and the experimental approach. A statistical analysis was employed to construct an orthogonal chart which reflects the effects of the process parameters and their interactions on the formability of rectangular cup drawing. The material properties and the forming limit diagram (FLD) of SUS304 stainless steel were obtained from the experiments conducted in the present study and were employed by the finite element simulations. In the finite element analysis, the strain path that led to fracture in the drawing process was examined and the failure modes caused by different process parameters were also identified. With the help of statistical analysis, a formability index for the deep drawing of SUS304 stainless steel rectangular cups was constructed and the critical value of the formability index was determined from the finite element simulation results. The actual drawing processes of rectangular cups were also performed in the present study. The validity of the finite element simulations and the formability index were confirmed by the good agreement between the simulation results and the experimental data. The formability index proposed in the present study provides a convenient design rule for the deep drawing of SUS304 stainless steel rectangular cups.     

Flow characteristics of accelerating pump in hydraulic-type wind power generation system under different wind speeds

Influences of hydraulic pressure on forming features in micro hydro deep drawing are different from those in normal drawing due to the small size of specimens. In this study, micro hydro deep drawing of SUS304 sheets was carried out in order to study the impacts of the hydraulic pressure on the quality of the drawn cup. Experimental results indicate that there is a critical hydraulic pressure range from 3 to 6 % of the blank’s initial yield stress, where wrinkling and earing development trends change twice. The wrinkling and the earing of the drawn cup also reach their local extremes in the critical pressure range. The cup earing value moves in the opposite direction from the wrinkling value. Hydraulic pressure affects the wrinkling and the earing of the drawn cup through changes in the micro-frictional condition, the shape of the blank and its strain-stress state. Micro-finite element (FE) simulation which takes these factors as well as the material size effects into consideration showed similar results to the experimental ones, thus validating the experimental results and the suitability of the micro-simulation model for micro-forming FE simulation. The experimental and simulation results indicate that the critical hydraulic pressure based on the blank’s initial yield stress can restrict the wrinkling and the earing of the drawn cup. Ultra-high pressure has the potential to avoid the cup wrinkling and earing.     

Experimental and mathematical analysis of simulation results for sheet metal parts in deep drawing

In this paper, deep drawing of conical and cylindrical cups without blank holder is investigated using a conical die design. These cups are produced by pushing circular blanks by pushing the flat head punch in a single stroke. ANSYS APDL 14.0 was then used to investigate the effects of die and punch geometry, half-cone angle, die and punch fillet radius, and drawing load. The thickness distribution of the cup was numerically investigated to determine the optimal process design, and mathematical analysis was adopted to determine the thickness distribution and longitudinal stress calculation. An experimental set-up was designed to validate the simulation results for conical and cylindrical shaped sheet-metal cups. Tensile tests were carried out to obtain the flow of the stress-strain curve for the simulation. The drawing characteristics of materials were investigated by performing Erichsen cupping and Vickers hardness tests. Experiments were conducted on blanks of aluminum alloys and stainless steel with initial thicknesses of 1.5 mm. A cylindrical cup of ss304 with LDR of up to 2.2 and conical cup of AA1100 with LDR of up to 2.7 were successfully achieved. Finite element simulation results showed good agreement with the mathematical and experimental results.     

The effect of a multistep deep-drawing process with circular and rectangular shapes on the deformation of AZ31 magnesium sheets

This study has mostly focused on the forming limit, microstructural change, and anisotropy that arise from rectangular and circular deep drawing of magnesium sheets. Moreover, this study predicts the change in the material thickness and the forming depth at the first forming process that produces the rectangular cup by the deep drawing of the rectangular blank. Further, by using the rectangular cup that is formed by the first forming process, when the circular and square cups in the rectangular cup are simultaneously manufactured in the so-called second forming process, the effect of the clearance between the die and punch on the change in the product thickness according to forming depth associated with microstructural analysis is investigated. The forming temperature is optimized to maximize formability. The results obtained in this study are utilized as data for predicting the die clearance and the change in the thickness.     

The design of blank’s initial shape in the near net-shape deep drawing of square cup

Deep drawing process is very useful in industrial field because of its efficiency. The deep drawing is affected by many process variables, such as blank shapes, profile radii of punch and die, formability of materials and so on. Especially, in order to obtain the optimal products in deep drawing process, blank shape is very important formability factor. In this paper, the finite element method is used to investigate the cup height of the square cup drawing process. In order to verify the prediction of FEM simulation of the product’s height and forming load in the square cup drawing process, the experimental data are compared with the results of the current simulation. A finite element analysis is also utilized to acquire the designed profile of the drawn products, a reverse forming method for obtaining the initial blank’s shape according to the forward square cup drawing simulation is proposed. The design of initial blank’s shape is also certified to obtain the designed profile of drawn cups by experiment. The influences of the blank’s shape on the height of product, the forming load, the maximum effective stress and the maximum effective strain are also examined.     

An Analysis of Draw-Wall Wrinkling in a Stamping Die Design

Wrinkling that occurs in the stamping of tapered square cups and stepped rectangular cups is investigated. A common characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsup-ported. In the stamping of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling is examined using finite-element simulations. The simulation results show that the larger the die gap, the more severe is the wrinkling, and such wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping of a stepped rectangular cup, an actual production part that has a similar type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles is determined using finite-element analysis. The good agreement between the simulation results and those observed in the wrinkle-free production part validates the accuracy of the finite-element analysis, and demonstrates the advantage of using finite-element analysis for stamping die design.     

Numerical and experimental investigation of pulsating blankholder effect on drawing of cylindrical part of aluminum alloy in deep drawing process

In this study, the effect of a new pulsating blankholder system has been investigated on improving the formability of aluminum 1050 alloy. By using this system, during each pulsating cycle, first, the metal was easily flowed into the die through removing the blankholder force, and then the blankholder force applied by springs was employed to prevent excessive metal flow and wrinkling. Deep drawing of cylindrical cup was simulated by ABAQUS6.7 software. Cup depth, tearing, and thickness distribution of the experimental and numerical analyses were then compared. The results indicated that by using the pulsating blankholder system coupled with proper frequency and gap, the cup depth can be increased and thickness distribution can be improved. Further, good agreement was observed between simulation and experimental results.     

车用热成形先进高强度钢板样件的热胀形特征及成形性分析

通过高温热胀形特征分析,研究热冲压22MnB5合金在不同温度下的成形性,并利用Dynaform软件仿真验证。比较成形温度在800 ℃和700 ℃时样件的热胀形特征,结果表明,在800 ℃时成形,样件由于平面应变方向主应变过大,拉压应变区次应力为负值,造成拉伸破裂;在700 ℃下冲压成形的试件,各部分应变都处于安全区域,双向拉伸区域和拉伸-压缩复合区域的变形均匀,较前者成形性良好。另外,提出关于热成形先进高强度钢(Advanced high strength steel, AHSS)样件,其最佳成形温度不是现有文献报道的800～850 ℃的范围内,该结论为深入探索最佳成形温度、提高成形性提供了方向;建立成形前的快冷法(冷速不低于27 ℃/s),降温到目标温度700 ℃左右冲压成形。试验证明：通过该方法,样件的成形性明显改善,微观结构更为致密。     

Optimization of the design parameters of modified die in hydro-mechanical deep drawing using LS-DYNA

The use of a modified die enhances the limiting draw ratio compared to that obtainable in a conventional deep drawing operation. Application of these dies, in conventional deep drawing, eliminated the use of blank holder but enhances the tendency of wrinkling in drawn products. In hydro-mechanical deep drawing process, the punch deforms the blank to its final shape by moving against a controlled pressurized fluid. In this paper, a new concept of the application of modified dies in hydro-mechanical deep drawing is presented. The finite element (FE) simulations of a deep-drawing process using modified dies are performed using the 2-D explicit finite element code LS-DYNA, with the aim of optimization of design parameters and the results are compared with the experimental values. The initial design steps in the design of modified die in finite element simulation were taken from the concept of Tractrix die. The use of Tractrix die enhances the draw ratio but simultaneously increases the tendency of wrinkling. In this paper the design parameters of modified Tractrix die for hydro-mechanical deep drawing are optimized for the successful drawing of cups. It is also experimentally verified that by using such modified dies in hydro-mechanical deep drawing, deeper cups are drawn without wrinkling.     

半绝缘砷化镓中本征缺陷的光学显微研究

本文利用光学显微技术系统分析热处理对液封直拉法生长的半绝缘砷化镓(LEC SI-GaAs)中本征缺陷的影响。实验结果表明,晶体生长后的热处理可以影响砷沉淀的密度与分布。500℃热处理对As沉淀的密度无明显影响;真空条件下,在850~930℃范围内热处理AB腐蚀坑变浅,砷沉淀数量增加;真空条件下,高于1100℃热处理后,砷沉淀几乎消失。晶体中砷沉淀的密度会随热处理条件的不同而变化,本文对其机理进行探讨。     

超高压压缩机填料盘过盈配合过盈量设计方法

超高压压缩机是生产低密度聚乙烯的核心装置,其设计和制造还有待研究和完善。填料盘是其关键部件之一,填料盘过盈配合的过盈量是一个重要设计参数,国内还未见成熟的设计方法。为了研究如何确定过盈量,使内盘三向应力始终压缩和填料盘整体等效应力最小,建立填料盘理论模型,对填料盘的过盈量进行优化分析。理论分析可知填料盘内盘最大周向应力在排气压力下为压缩应力时,内盘即获得三向压缩应力状态;随着过盈量的增大,内盘的最大周向应力逐渐变小并由拉伸应力转变为压缩应力,而整体最大等效应力先减小再增大。对填料盘实际结构的有限元分析也得到相同的结论。理论分析推导得到排气压力下最大周向应力为零时的过盈量以及整体最大等效应力最小时的过盈量。分析认为过盈量的设计应当取和中较大的值就能满足内盘三向压缩应力状态以及整体最大等效应力最小的要求,填料盘的设计可以参考该结论。     

Die shape design for T-shape tube hydroforming

In this paper, two design methods for T-shape tube hydroforming dies are proposed, namely, the extrusion-cutting-fillet method (ECFM) and the intersection-fillet method (IFM). Simulations on hydraulic expansion and axial feeding of T-shape tube hydroforming with two dies using the program DEFORM-3D were performed. The influence of the two dies on workpiece formability of T-shape tube hydroforming was examined. Experiments were carried out with SUS304 stainless steel tube at room temperature. A qualified product of T-shape tube, without wrinkling or bursting, was obtained using the die designed by the IFM method.     

Effect of bright annealing on stainless steel 304 formability in tube hydroforming

Effects of bright annealing (BA) on enhancing formability of stainless steel 304 tube in a tube hydroforming (THF) process were studied. The tube material was the metastable austenitic stainless steel 304 with an initial thickness of 0.5 mm and an outer diameter of 31.8 mm. Both FEA and experimental results showed that THF process of the investigated part alone failed to achieve desired tube expansion of the diameter of 50.8 mm without severe fracture. Thus, a heat treatment process, also known as bright annealing (BA), which caused little to none oxide on the surface of annealed tube, was considered. Initially, effects of different annealing parameters such as temperature and holding time on the material formability were investigated using tensile tests. Stress–strain responses of various conditions were compared. As a result, an annealing process consisted of heating at the temperature of 1,050 °C, holding for 30 min, and rapidly cooling by purging N₂ gas was identified. This annealing should be applied intermediately after a pre-forming step. With the aid of the BA process, tube deformation was significantly increased and the required tube expansion could be therefore attained. In addition, strain-induced martensitic transformation occurred during the forming process was examined by X-ray diffraction (XRD) method. The amounts of martensite taking place in tubes (pre-forming, post-forming, and after annealing) were determined and discussed.     

The effect of laser cutting parameters on the formability of complex phase steel

An experimental advanced high-strength steel grade CP700 was cut using a matrix of laser process parameters in order to generate an understanding of the influence that traverse cutting speed, power and assist gas pressure have on cut-edge formation. The formation of laser cut-edges has been assessed and related to the heat-affected zone microstructure, kerf perpendicularity, surface roughness and waviness properties. It is these characteristics that are significant towards influencing the hole expansion capacity formability properties of laser cut-edges, which were determined to show significant improvements in the formability when using optimum laser cut-edges. Understanding the effect of laser cutting process parameters on the factors influencing striation formation and microstructural deformations was critical towards being able to produce an optimum level of formability.     

Development of a hydroforming setup for deep drawing of square cups with variable blank holding force technique

Sheet hydroforming is a process that uses fluid pressure for deformation of a blank into a die cavity of desired shape. This process has high potential to manufacture complex auto body and other sheet metal parts. Successful production of parts using hydroforming mainly depends on design aspects of tooling as well as control of important process parameters such as closing force or blank holding force (BHF) and variation of fluid pressure with time. An experimental setup has been designed and developed for hydroforming of square cups from thin sheet materials. Square cups have been deep drawn using constant and variable BHF techniques. A methodology has been established to determine the variable BHF path for successful hydroforming of the cups with the assistance of programmable logic controller and data acquisition system. Finite element (FE) simulations have also been carried out to predict formability with both of these techniques. It has been found that it is possible to achieve better formability in terms of minimum corner radius and thinning in the case of variable BHF technique than in the case of constant BHF technique (constant force during forming and calibration). The results of FE analysis have been found to be in good agreement with experimental data.     

热处理条件对Mg-PSZ陶瓷四方相马氏体相变温度及线膨胀量的影响

本文研究用工业原料制备的Mg-PSZ材料热处理条件对其马氏体相变温度及线膨胀量的的影响,着重研究两个低共析区1300℃和100℃分解热处理的结构变化与M s及ΔL/L的关系,指出1100℃热处理条件下马氏体相变的曲线特性。     

Calculations from texture of earing in deep drawing for FCC metal sheets

The present study aims to calculate the height at each peripheral position of a cup drawn from polycrystalline sheet using texture data. In the analytical treatment the polycrystalline sheet is simplified to an aggregation of many single crystals with various orientations, and the texture is represented by a three-dimensional crystallite orientation distribution function. The ear is calculated crystallographically using the orientation distribution function as a volume fraction of a certain oriented crystal. In the experiment aluminium, Al-Mg alloy and copper sheets which are treated under various conditions of cold rolling and heat treatment are used. The average textures over the thicknesses of the sheets are measured by the Schulz reflection method. The calculated ears based on the measured textures are compared with the experimental ears for each material. The results show that all the principal features of the ears of drawn cups are predicted satisfactorily by the calculation.     

深海刚柔组合负压吸附装置的力学特性与吸附效果分析

柔性吸盘被广泛用于陆上气动负压系统中,但对于深海高压环境来说,柔性材料抵抗外界压力的能力较差,导致其过度变形,吸盘有效作用面积减少,吸附能力减弱甚至丧失。通过综合考虑柔性吸盘的良好密封特性及刚性吸盘有效作用面积不变的特性,设计了一种由柔性吸盘、刚性吸盘及卡箍组成的吸盘形式,通过有限元仿真分析了吸盘的密封性能和预紧力情况,确定了吸盘的尺寸和选型,并搭建了试验台,对吸盘的预紧力、密封性能和吸附力进行了试验。结果表明:吸盘在预紧力为390 N时完全变形,此时吸盘在外界环境压力11 MPa,吸盘内部压力1 MPa的情况下,15 min内吸盘内部压力没有发生变化,吸盘没有发生泄漏,且可以提供至少15000 N的吸附力。     

Finite element analysis of the long-term fixation strength of cemented ceramic cups

Clinical studies have shown that adequate fixation of ceramic cups using bone cement is difficult to achieve. As the cement-ceramic bond strength is low, a satisfactory fixation strength requires a cup design that allows mechanical interlocking, although such a design will probably promote cement cracking and therefore cup loosening in the long term. An investigation has been carried out to establish whether a cemented ceramic cup can be designed in such a way that both a satisfactory initial fixation strength is obtained and cement cracking is reduced to levels found around PE cups functioning well in vivo. By means of finite element analysis, the fatigue loading of three geometrically different cemented acetabular cups, with ceramic and PE material properties, has been simulated, and the severity of the crack patterns produced in the cement has been analysed. Furthermore, the fixation strength has been analysed by simulating a pull-out test prior to and after fatigue testing. All ceramic cups produced much larger amounts of cement damage during fatigue testing than any PE cup, caused by stress concentrations in the cement that were attributable to the high stiffness of the ceramic. Even a completely smooth ceramic cup produced more damage than a sharp-grooved PE cup. Owing to the excessive cement cracking, the fixation strength of the ceramic cups dropped after fatigue loading. It is concluded that cemented ceramic cups have an increased risk of long-term mechanical failure by comparison with PE cups, and that a ceramic cup design that combines sufficient fixation strength with low cement failure may be difficult to achieve.     

1060纯铝微杯形件微拉深成形研究

微拉深成形以其高效率、低成本、高质量等优点成为一种可行的制造开口、空心、薄壁微型零件的微细加工方法。然而,由于微型化的影响,使得微拉深要比宏观拉深更加困难。研制精密微型落料-拉深复合模,成形出内径仅为1 mm的微杯形件。试验材料采用厚度为50 μm的1060纯铝,在真空氛围下经300 ℃分别退火1 h和8 h。微拉深试验在SANS CMT-5504电子万能试验机上进行,试验速度为0.05 mm/s,润滑剂为聚乙烯薄膜。研究退火工艺和压边力对拉深力、拉深比、制耳和起皱的影响。试验结果表明,顺利成形出质量良好、拉深比为2.1的微杯形件;经退火处理的坯料,拉深力降低,拉深比增大,制耳减弱;随着压边力的增加,起皱减弱,但当压边力超过一定数值后则导致拉裂。