Characteristics of deformation joining of aluminum-stainless steel composite sheet

1　INTRODUCTIONAseveryoneknows ,aluminumandstainlesssteelaredifficulttoweldtogether[16 ] .Inthepast,braz ing ,projectionweldingaswellasaluminizingwereused .Nowadays ,anewmethodisputforward ,inwhichthealuminumsheetandstainlesssteelsheetheatedbyinductionheaterareconnectedbypressureofascrew press .Notonlycanthismethodimprovebondingbehaviorofthecompositesheet,butalsocanitraisetheproductivity greatly .Thistechnologyiscalleddeformationjoining ,i.e .pressjoining .InChi na ,ithasbeensuccessfully…     

树脂复合层压金属板塑性应变比r值的研究

采用实验研究为主，理论分析为辅的方法，以SPCC／Polymer／SPCC、SPCC／Polymer／L4为研究对象，研究了树脂复合层压金属板在单向拉伸时的r值的变化规律，并揭示了该变化规律对板料变形的影响。研究结果对进一步研究树脂复合层压金属板有一定参考意义。     

Finite element analysis for delamination of laminated vibration damping steel sheet

The material structure of laminated vibration damping steel sheet（LVDSS） was introduced in detail. An interface cohesive model between the skin sheets was developed by using a contact/interface approach, and the model was applied to simulate ＂T＂-peel and lap-shear processes of LVDSS. The interface contact stress distribution during the ＂T＂-peel and lap-shear processes is obtained, and the finite element analysis（FEA） results agree satisfactorily with the corresponding experimental results. As a result, the model is suitable to simulate the cohesive of LVDSS     

SiC/BN层状陶瓷的阻力曲线行为

利用压痕一强度法测定了SiC／BN层状陶瓷的阻力曲线行为，并与SiC单相陶瓷做对比。结果表明：2种材料均呈现出上升阻力曲线行为，其中，SiC／BN层状陶瓷显示出更为优越的抗裂纹扩展能力，其阻力曲线上升较陡，上升幅度较大；SiC单相陶瓷的阻力曲线上升较缓且上升幅度较小。分析认为，这与其不同的增韧机制有关。原位增韧是SiC单相材料韧性提高的主要原因，而裂纹遇到弱界面时发生偏转、分叉、脱层等是层状陶瓷材料抗裂纹扩展能力提高的主要原因。     

高级薄板钢用连铸保护渣的特性

本文综述了高级冷轧薄板常见缺陷（条片状缺陷和白斑缺陷）的产生机理及采取的相应对策，提出高级薄板用连铸保护渣应具备下列特性；高粘度、高表面张力、低凝固温度、熔渣性能稳定等。     

激光叠焊板超塑性行为研究

采用高温拉伸试验研究了TC4钛合金激光叠焊板的超塑性行为,观察了叠焊接头超塑性变形前后的显微组织。试验结果表明,TC4钛合金激光叠焊试样超塑性变形断裂位置在母材,显微组织观察没有发现微裂纹,证明激光叠焊接头能够承受焊接板的超塑性变形而不破坏,为激光焊/超塑成形组合工艺的实际应用提供理论和试验依据。     

Annealing behavior of rolled AZ31 alloy sheet

The annealed microstructures of the rolled AZ31 alloy sheets were examined by using light optical microscopy. The mechanical properties were measured by tensile testing, with their crystal orientations analyzed by X-ray diffraction （XRD）. After the annealing treatment, the elongated grains were transformed to equiaxed grains with uniform and homogeneous structures. The changes of microstructure decreased the yield strength and enhanced the elongation. The analysis of XRD shows that the AZ31 alloy sheet possesses intense basal-texture, which is weakened during the recrystallization while reinforced during the grain growth. The intense basal-texture induces low ductility, which hence makes the further rolling more difficult. The results indicate that the optimum annealing treatment during AZ31 alloys sheet rolling is at about 300 ℃ for 60-120 min.     

Determination of frictional behavior in sheet metals using orthogonal arrays

Frictional behavior of two sheet materials, aluminum-killed drawing-quality steel (AKDQ) and electro-galvanized (zinc) drawing-quality steel (AKDQ-EG), is examined under conditions of varying die material, die radius, crosshead speed, and lubricant. Tests are conducted using a special apparatus designed to measure front and back tension on uniform tensile strip specimens pulling over a circular die, simulating both frictionless and frictional conditions under certain sheet-metal-forming conditions. Use of a specially designed test apparatus with four contact angles for the same test condition minimizes the error associated with the use of single measurements for the determination of friction coefficient. Lubricant and die material play important roles among different factors examined in determining the coefficient of friction. Die radius has the most pronounced effect on the coefficient of friction. Implication of these results on actual sheet forming processes are discussed.     

Experimental and numerical investigation of laminated steel sheet in V-bending process considering nonlinear visco-elasticity of polymer layer

Laminated steel sheet consists of two steel sheets and a polymer layer which bonds them. During forming process, mechanical properties of polymer layer significantly influence the shape of final product. In this study, a continuum model in which nonlinear visco-elasticity is taken into account has been developed for polymer layer of laminated steel sheet and implemented in a commercial finite element program by material subroutines. Lap-shear test and T-peel test have been conducted to obtain parameters of this continuum model. Two different methods are compared to establish a better method for modeling the polymer layer deformation in lap-shear test simulation. One is cohesive zone element and the other is contact method. In order to assess calculation efficiency, both explicit and implicit procedures are used to simulate lap-shear test, and T-peel test is simulated by implicit procedure to evaluate accuracy. The result indicates that cohesive element is easier to solve convergence problem and implicit procedure may save much simulation time. T-peel test data can be used to describe the normal mechanical behavior of polymer layer in an acceptable range. Finally, V-bending forming process has been studied to investigate the effect of polymer layer on the springback and final deformation shape through experiment and numerical simulation. The result indicates that the comparison between numerical simulation and experiment is in good agreement. The finite element model can accurately predict the final shape after bending and springback.     

加载速度和存放时间对树脂复合减振板弯曲类回弹的影响规律

随着树脂复合减振板的冲压件在汽车及家电等领域的广泛应用,其冲压成形性能研究受到重视。该文从加载速度及成形件的存放时间的关系出发,研究树脂复合减振板的弯曲回弹特性,通过采用90°V形弯曲件回弹模型,针对4种不同的加载速度和工件的存放时间,对树脂复合减振板进行回弹试验。试验结果表明,在加载速度为0.5mm/s~5mm/s时,随着加载速度的增加,树脂复合减振板的回弹角逐渐减小,直到趋于稳定;无论哪种加载速度,树脂复合减振板的回弹角均随存放时间的增加而减小,直到趋于稳定。     

温模条件下镀锌钢板摩擦行为研究

开发了温模条件下钢板摩擦行为的评估装置,在此基础上研究了模具温度变化对镀锌钢板成形表面摩擦行为的影响。结果表明,不同镀层特性的镀锌钢板的摩擦系数随模具温度变化呈现出不同的变化规律。当模具温度升高时,热镀纯锌、电镀纯锌和热镀锌铁合金的摩擦系数均有所升高。由于预磷化膜的存在,预磷化电镀锌钢板的摩擦系数随模具温度变化有所波动,且总体维持在较低的数值。电镀纯锌钢板表面摩擦系数在模具温度较低时变化不大,但在模具温度较高时大幅度上升。     

Pulsed TIG welding-brazing butt joints of aluminum-stainless steel thin plates with different fillers

Aluminum and stainless steel plates with 1.5 mm thickness are joined by pulsed TIG welding-brazing process with ER1100, ER4043 and ER2319 fillers, separately. Good weld formation can be obtained by adjusting appropriate pulse parameters. The effects of the fillers on that the thickness of the intermetallic compound （ IMC ） and tensile strength of the joints are investigated. SEM results indicate layer with ER2319 filler is about 2 ~m, which is thinner than 2. 5 p~m of ER1100 filler and 3.5 txm of ER4043 filler. Moreover, the element distribution in both IMCs and welded seams with three fillers are different because of the different compositions of fillers. The results of mechanical property tests suggest that the joint strength with ER2319 filler is the highest, while the joint impact energy is the lowest. The joint with ERllOO filler exhibits the best comprehensive mechanical pet.formanee.     

镁合金AZ31轧制板材的单向拉伸行为

通过单向拉伸试验研究了AZ31镁合金轧制板在不同温度和应变速率下的力学性能。根据镁合金在50℃~400℃范围内的单向拉伸曲线分析结果,找出AZ31镁合金的抗拉强度、伸长率随变形温度、变形速度的变化规律。结果表明:AZ31镁合金轧制板的塑性随着应变速率的降低有明显提高;温度的升高可明显改善轧制板的塑性;当应变速率为1.5×10-2s-1、温度为400℃时,伸长率达到123.9%。     

退火态Ti2AlNb合金板材的超塑性变形行为

研究退火态Ti2AlNb合金热轧板材在温度为940～980 ℃和初始应变速率为8.33×10-4～1×10-2 s-1时的超塑变形行为.结果表明:该合金具有良好的超塑性;在本实验范围内,其最高伸长率可达400%,最佳超塑条件为960 ℃和1.67×10-3 s-1,可用作超塑性成形工艺制作复杂构件.     

Experimental and numerical investigation of grid sheet bending behavior in four-roll bending

Grid sheet is a sandwich material consisting of two metal face sheets and a core of woven wire mesh that are joined by welding. It has been designed to act as an actively cooled heat shield, e.g. for steam turbine casings. For this purpose, cylindrical parts have to be produced from initially flat grid sheet. This paper focuses on four-roll bending of grid sheet. It is shown that springback and the number of failed spot welds after forming can be reduced by stress relief annealing and appropriate forming conditions. A finite element model of roll bending of grid sheet is presented, which has been set up to predict springback and spot weld failure.     

Deformation behavior of hot dip galvanized coatings in complex sheet metal forming

The hot dipped galvanized coatings of flexible tubes with variable corrosion resistances were examined by x-ray diffraction and scanning electron microscopy (SEM). Accelerated corrosion was related to wide cracks formed during roll forming of coatings with coarse spangle sizes and preferred orientation of Zn basal planes parallel to the coating surface. Coarse spangled coatings with reduced preferred orientation of basal planes parallel to sheet surfaces formed only thin cracks and accommodated forming strain primarily by plastic flow. Coatings with fine spangle sizes and preferred parallel basal plane orientations developed networks of fine cracks during forming. The zinc coatings with fine cracks did not expose sufficient steel to cause accelerated galvanic corrosion.     

Mg-Gd-Y-Zr合金热轧板材的粗晶超塑性行为与微结构

对初始晶粒度为66μm的轧制板材在不同温度和不同变形速率下进行超塑性拉伸实验,研究Mg-Gd-Y-Zr合金粗晶热轧板材的超塑性行为与微结构特征。在温度为435℃、应变速率为5×10-4s-1的变形条件下获得的最大伸长率为380%,应变速率敏感系数为0.56。合金的表观变形激活能高于镁的晶界扩散激活能或晶格扩散激活能;合金的超塑性变形机制为晶格扩散控制的位错协调晶界滑动机制。微结构分析结果表明:第二相钉轧晶界,较软的不规则块状的β相承受了部分塑性变形。     

Effect of EDT surface texturing on tribological behavior of aluminum sheet

Surface texturing, which fabricates micro dimples or micro channels on the surface of parts, is a growing technique for improving tribological characteristics of materials. Currently, electrical discharge texturing (EDT) technique, one surface texturing method suitable for mass production, is being used to texture aluminum sheets for the applications in automotive industry. It has been widely accepted in industry that EDT improves the forming behavior of aluminum sheets due to better friction behavior. However, how the textures on the surface of sheet metal change the friction behavior has not been investigated. In this paper, the influence of EDT on the friction behavior of aluminum automotive sheet at different contact pressures and sliding speeds is investigated based on both experimental studies and numerical simulations. To fully investigate the tribological behaviors, a flat-on-flat friction test device was built and a numerical code based on mixed lubrication theory was developed. It was found that EDT texturing can reduce the friction coefficient of contacting pair at high contact pressure, however, increase friction coefficient at low contact pressure. Numerical simulations confirmed this finding. Furthermore, the model provides valuable information for the prediction of friction behavior of EDT sheets and helps to optimize processing parameters for various forming processes using EDT aluminum sheets.