GENERAL COMPUTER MODEL FOR SHEET METAL DEEP-DRAWING PROCESS

A new comprehensive computer model was developed for sheet metal deep-drawing process, based on the theory of plastic anisotropy and under consideration of the effects of bending, blank-holding force, strain-hardening, the variation of thickness and tooling geometry. The model could be used to simulate the deforming stages of deep-drawing process and get the continuous distributions of stress and strain from the radial drawing region of material over a die and the stretch-forming region of material over a punch. It is concluded that the total strain theory can be used as a substitute for the incremental strain theory to analyse the force and deformation in sheet metal deep-drawing process. In addition, the effect of bending was also obtained.

Simulation of annealing process effect on texture evolution of deep-drawing sheet Stl5

A two-dimensional cellular automaton method was used to simulate grain growth during the recrystallization annealing of deep-drawing sheet St 15, taking the simulated result of recrystallization and the experimental result of the annealing texture of deepdrawing sheet St15 as the initial condition and reference. By means of computer simulation, the microstructures and textures of different periods of grain growth were predicted. It is achieved that the grain size, shape and texture become stable after the grain growth at a constant temperature of 700℃ for 10 h, and the advantaged texture components { 111 } 〈 110 〉 and { 111 } 〈 112〉 are dominant.

FLANGE EARING AND ITS CONTROL ON DEEP-DRAWING OF ANISOTROPY CIRCULAR SHEETS

The Hill's quadric anisotropy yield function and the Barlat-Lian anisotropy yield func- tion describing well anisotropy sheet metal with stronger texture are introduced into a quadric-flow cor- ner constitutive theory of elastic-plastic finite deformation suitable for deformation localization analy- sis.And then,the elastic-plastic large deformation finite element formulation based on the virtual power principle and the discrete Kirchhoff shell element model including the yield functions and the constitutive theory are established.The focus of the present research is on the numerical simulation of the flange earing of the deep-drawing of anisotropy circular sheets,based on the investigated results, the.schemes for controlling the flange earing are proposed.

Geometrical, microstructural and mechanical characterization of pulse laser welded thin sheet 5052-H32 aluminium alloy for aerospace applications

Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry.The microstructure and mechanical properties of the weldments were also investigated.Relationships between the parameters and weld bead geometry were found.High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at(I)high pulse energy(25 J)and high average peak power(4.2 kW)and(II)low pulse energy(17.6 J)and low average peak power(2.8 kW).The weld joint formed at lower heat energy input exhibited finer dendritic grain structure.Mg vapourisation and hard phase compound(Al0.5Fe3Si0.5)formation decreased in the weld joint formed at lower heat energy input.Consequently,the tensile strength of the weldment formed at lower heat energy input(168 MPa)is by a factor of 1.15 higher but showed^29%decrease in hardness(111 HV0.1)at the joint when being compared with the weldment formed at higher heat energy input.Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.

LATERAL STABILITY OF ALTERNATIVE HORIZONTAL LEVITATION ELECTROMAGNETIC CONTINUOUS CASTING OF ALUMINIUM SHEET

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Effect of Atmospheric Plasma Paint Removal on the Fatigue Performance of 2024-T3 Aluminium Alloy Sheet

This article documents fatigue testing that was conducted using as-painted (baseline) and Atmospheric Plasma de-painted specimens made of 0.063 inch thick 2024-T3 aluminium alloy sheet. The intent of the test program was to determine whether AP de-painting would alter the fatigue properties of this aluminium substrate. AP de-painting process parameters were selected based on previous work that would remove the topcoat, while leaving most of the primer intact. This process was repeated five times to simulate service experience, where aircraft typically undergo five paint/de-paint cycles in their lifetime. As-painted (baseline) and five times de-painted specimens were fatigue tested under constant amplitude conditions, at two load ratios and several maximum stress levels. Ten samples per condition were used to establish statistical behaviour and repeatability. The test results and statistical analysis demonstrated that the selected AP process parameters did not have a detrimental effect on the fatigue performance of 2024-T3 aluminium alloy sheet.

A computer control system for automatic TIG welding of aluminium alloy sheets

Aimed at the welding ttechnological requirements of foe missile shell,a computer control system for automatic TIG welding of aluminium alloy sheets has been developed in this paper.The hardware of the system is composed of the four sub-systems,i.e.weldingpower source,arc length controller,welding wire feeder and welding head traveller.The software of the system comprises the on-line executing program and the off-line serving program.The operating principle,specifications and control of the system are introduced.The experiments indicate that the system possesses rational hardware structure and practical software function,and has solved the problem of high frequency interference to the computer control system. Therefore,the control system can satisfy the requirements of automatic TIG welding of the missile shell.

Prediction of Earing in Deep Drawing of Roll-cast Aluminium Alloy Sheets

Commercial aluminium alloy sheets are presently sem ic ontinuously, direct chill casting billets that are hot and cold rolled to the fi nal gauge. Interest has been shown in continuous methods which eliminate the ho t rolling step through rapid solidification of the molten metal to the final sla b. Accordingly, sheets are produced by homogenization, cold rolling, intermedia te and final annealing of these roll-cast slabs. The problem of earing is of gr eat concern as it causes frequent interruption of production runs and leads to m aterial wastage. Therefore, it is quite desirable that earing can be predic ted and consequently necessary measures be taken to minimize or eliminate this u nwanted phenomenon. It is accepted generally that, the principal source of earing is the crystallogr aphic anisotropy arising from non-random distribution of crystal orientations i n the material. Accordingly, several attempts have been made to correlate the m echanical and crystallographic properties of the materials to the earing behavio ur for predictive purposes. Some of these are based on continuum concepts which concentrate on the macroscopic rather than the microscopic aspects of the mater ials. To accommodate the microstructural features of the material, some models have been developed. A more recent approach which provides a connection between texture and plastic anisotropy parameters of the material is the Continuum Mech anics of Textured Polycrystals (CMTP) method proposed by Lin et al. A simplifie d version of this method has been suggested by Chan with promising accuracy for aluminium and copper sheets. AA3105 and AA8011 aluminium alloy sheets were used in this investigation. The a s-cast slabs were cold rolled to the final thickness of 1.0 mm. Different anne aling temperatures in the range of 420 ℃ to 540 ℃ produced a range of R-value s. Circular blanks of 60 mm diameter were machined and deep drawn using a cylind rical flat-bottom punch of 33 mm diameter. The heights of the drawn cups were measured at 0, 45 and 90° to the rolling direction, with the aid of a microme ter accurate to 10 -2 mm. The earing percentage was then calculated usin g the following formula: % earing=h p-h v1/2(h p+h v)(1) where h p is the distance between the bottom of the cup and the peak of ear , and h v is the distance between the bottom of the cup and the valley of t he ear. For the measurement of plastic strain ratios (R-values), tensile specimens cut at 0, 45 and 90° to the rolling direction were photogridded with 1mm square s. These specimens were then stretched in the range of uniform deformation and the dimensional changes were measured with the aid of a travelling microscope. The strain ratios, whether R 0, R 45 or R 90 were determined from the following equation: R θ=dε wdε t=dε wdε l+dε w(2) where Θ refers to the specimen orientation and dε w and dεl refer to the transverse and longitudinal strains of the gauge section, respectively. The av erage strain ratio, R, and the parameter ΔR were then calculated from: R=14(R 0+2R 45+R 90)(3) ΔR=12(R 0-2R 45+R 90)(4) where R 0, R 45 and R 90 values are determined using specimen s cut at 0, 45 and 90° to the rolling direction, respectively. Finally, a continuum mechanics approach using different yield criteria is employ ed for the prediction of earing behaviour under different conditions of the mate rials. Instead of using texture data, the yield stress values are obtained by d ifferent anisotropic yield criteria such as; Hosford, Hill, and Zhou. The predicted earing profiles are compared to the experimental data and the suit ability of different yield criteria is discussed.

Study on Theory and Application of the Energy Method used for Analyzing Compressive Instability in Sheet Forming

It is pointed out that there was serious weakness w he n using the energy method for studying compressive plastic instability in sheet forming in the past. Where applying the deduced instability strengths to relativ e engineering analysis, theoretical solutions were away from practices. Its basi c reason is that simplified process in mathematical analysis of elastic bending energy was completely applied to that of plastic bending energy. Where the cambe r expressed by function of displacement normal to a plate was approximated to re alistic deflective camber, the displacement of deflected plate to compressed dir ection was neglected. With the aid of the improved instability strengths, the pr edictions on both critical buckling dimension of blank in cup deep-drawing with out blankholder through cylindrical die or conical die and the minimum blankhold er pressure to prevent buckling under constant load are universally in agreement with both experimental results and experiential data. On the bases of above-mentioned improvement, the approximate expressions for bo th the curvature and the twist used in equation of the energy of elastic bending are also ameliorated. Thus the obtained general equations for both the energy a nd the work done by internal force in plastic bending of a plate are more precis e than before. In the analyses of plastic buckling of shell with bending moment, the effect of bending moment is considered through the work done by simulative bending for ce. The method proposed in this paper can not only simplify analyses but also ge t practical result.

Quantitative Evaluation for Drawability of Sheet Metal

The theoretical evaluating method is given for the drawability of the sheet with normal anisotropy. The general solution on the cracking load of deep-drawing is deduced, which is based on three kinds of hardening curve of materials most in use. The distributions of stress and strain in the deformed region and the drawing force are obtained by the numerical method. The limiting drawing ratio is calculated through computer-aided simulating test. The experiments of deep-drawing to four kinds of sheet metals express that the relative errors between the predictive and the experimental results about the cracking load and the limiting drawing ratio are within 5%. The drawability of common sheet metals can be quantitatively evaluated in precise terms by means of the theory and the method advanced in this paper.

Micro Crack of Aluminum Sheet During Cold Rolling

The micro crack of aluminum sheet during cold rolling lubricated with emulsions is investigated. Experi-ments show that micro cracks occur after cold rolling process and this is attributed to various parameters, for instance, the thin oxide film formed at the sheet surface. The micro crack spacing thus becomes an important parameter which deserves more concerns. The aspect ratio of these micro cracks is then analyzed theoreti-cally, which takes into consideration of the oxide fracture process. The good agreement between the obser-vations and the theoretical predictions validates the analysis. The approach can shed some new lights on the mechanical process of aluminium sheet during cold rolling.

汽车轻量化材料表面处理技术创新研究

基于铝材在车身中占比的不同,对钢铝混合车身材料的表面处理技术进行创新研究。研究表明:当使用传统磷化工艺对钢铝混合车身材料进行表面处理时,冷轧板、镀锌板和铝板表面均形成均匀致密的磷化膜,铝板产渣量低于4 g/m^(2);应用后处理工艺对钢铝混材进行表面处理时,铝板在后处理工艺的磷化槽液中不生成磷化膜,而经过钝化工序处理后表面形成钝化膜,铝材在磷化液中的产渣量低于0.5 g/m^(2);当使用无磷化成工艺对钢铝混材进行表面处理时,钢铝混合车身材料可以同槽形成Zr化膜,且所有板材形成的残渣量低于0.2 g/m^(2)。

基于AutoForm分析的铝板背门内板成形性能研究

为解决铝板材料成型性和延展性差、背门内板产品形状复杂导致铝板背门内板设计及生产困难的问题,基于AutoForm有限元软件在理论上对铝板背门内板成形性进行模拟分析,通过对不同方案的模拟分析,确定最终成形方案并指导现场生产,同时在现场调试中得到验证。

3003-H14电池壳用铝合金板材晶粒粗大问题研究

使用金相显微观察(OM),扫描电子显微观察(SEM),电子背散射衍射分析(EBSD)等手段,研究了3003-H14电池壳用铝合金板材生产过程中成品表面晶粒粗大导致表面质量不佳的问题。研究发现,粗晶现象主要发生在板材表面,粗晶层深度约为150μm,晶粒尺寸超过1 mm。相较于晶粒尺寸正常试样,晶粒粗大试样拥有更低的α-AlFeMnSi化合物占比,更多的亚微米尺度AlMnSi析出相,更大的化合物尺寸以及更不均匀的化合物尺寸分布规律。通过文献调研、调取生产流程的工艺信息以及小炉均匀化热处理试验的复现,分析认为,均匀化强度不足导致亚微米尺度的AlMnSi相析出过多,阻碍了再结晶形核,导致了晶粒的异常粗大。经过对均匀化热处理环节的把控与调整,粗晶问题得到解决。

退火对汽车用5182铝合金板材组织与性能的影响

采用单向拉伸试验、金相显微分析和扫描电镜观察,研究了退火工艺对汽车用5182铝合金板的力学性能、应变硬化指数及显微组织的影响。结果表明,5182铝合金板材随着退火温度的上升,保温时间的延长,抗拉强度略有下降,但伸长率和应变硬化指数却大幅提高,分别达到26.5%和0.34。在380℃退火24 h,材料已完成再结晶,且晶粒细小均匀,拉深性能较优。

6000系铝合金汽车板预时效及组织性能

通过硬度、拉伸和成形性实验及透射电镜、扫描电镜、能谱和金相分析,研究了Mg、Si和Mn含量的变化对6000系汽车板铝合金的显微组织、力学性能及成形性的影响,并探讨适宜的预时效处理工艺.研究结果表明:提高合金中的Mn含量,可增加合金中不可溶结晶相及弥散相粒子的数量,前者对合金的延伸率不利,后者阻碍了合金固溶处理过程中的再结晶.对于Si过剩的合金,提高合金中Mg和Si的质量比和Mn含量会使其强度升高,延伸率、应变硬化指数、塑性应变比和埃利克森值被降低.合金板材固溶处理水淬后立即预时效,较为适宜的预时效(固溶处理后立即在170℃下进行5～10 min的短时预时效)不仅能降低其自然时效的硬度,而且能提高人工时效的硬化效果,有利于车身构件的冲压成形和烤漆硬化能力的提高.

汽车用铝合金板拉深性能评估参数

为了准确地评估汽车用铝合金板的拉深性能,在单向拉伸试验、平面应变拉伸试验和圆筒件拉深试验获得的样本基础上,采用回归分析方法,全面地分析了汽车用铝合金板各种材料性能参数与其拉深性能之间的对应关系。研究表明:在所给出的材料性能参数中,xb值(平面应变抗拉强度与单向抗拉强度之比)对极限凸模行程的相关性最为显著,其次是硬化指数n及宽度颈缩率ψ等参数,而厚向异性系数r与铝合金的拉深性能并不相关。上述结果表明,在评估汽车用铝合金板的拉深性能时,使用xb值为评价指标最为准确。

韩国铝箔毛料和国产铝箔毛料的比较研究

采用光学显微镜、电子显微镜、Ｘ－ 射线衍射仪等手段比较研究了两批韩国铝箔毛料和五批国产铝箔毛料的显微组织。研究表明，进口毛料和国产毛料中化合物相的类型有较大不同。进口料中化合物相以α（ＦｅＳｉＡｌ）和β（ＦｅＳｉＡｌ） 相为主，而国产毛料中化合物相以ＦｅＡｌ３ 和α（ＦｅＳｉＡｌ） 相为主；进口毛料中固溶的硅含量较低，但晶粒尺寸较大。分析了固溶硅含量、Ｆｅ／Ｓｉ 比和晶粒尺寸等对铝箔轧制性能的影响及针孔增多的原因。

铝合金板成形中摩擦与润滑的研究进展

概述了铝合金板成形过程中的摩擦机理、摩擦模型和润滑的发展现状。全面分析了铝合金板成形的影响因素,阐述了润滑剂的作用机理,展望了其发展趋势,提出铝合金成形应走环保型'绿色'润滑之路。

变压边力条件下铝合金板的成形窗口

在由塑性成形理论和能量法分别建立的临界破裂和临界起皱压边力模型基础上,构建了变压边力情况下汽车用铝合金板的成形窗口,并分析了拉深比、材料参数和模具参数对成形窗口的影响规律。对比实验表明:在整个有效压边力范围内,数学模型构建的成形窗口能够与实验相吻合,且铝合金6111-T4和5052-O的成形窗口明显小于钢板st14的。而影响因素分析显示:随着拉深比降低、厚向异性系数(r)增加和凹模圆角半径(Rdp)增大,成形窗口明显扩大;n值增加,成形窗口虽然有所扩大,但是效果并不明显。