Microstructure Distribution Characteristics of High-Strength Aluminum Alloy Thin-Walled Tubes during Multi-Passes Hot Power Backward Spinning Process

The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .

Forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters

With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.

Effects of process parameters on numerical control bending process for large diameter thin-walled aluminum alloy tubes

Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.

Significance-based optimization of processing parameters for thin-walled aluminum alloy tube NC bending with small bending radius

Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element （FE） simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm （initial tube outside diameter D0 × initial tube wall thickness t0 × bending radius R）, and qualified tubes are produced.

Sequential multi-objective optimization of thin-walled aluminum alloy tube bending under various uncertainties

Combining the design of experiments(DOE)and three-dimensional finite element(3D-FE)method,a sequential multiobjectiveoptimization of larger diameter thin-walled(LDTW)Al-alloy tube bending under uncertainties was proposed andimplemented based on the deterministic design results.Via the fractional factorial design,the significant noise factors are obtained,viz,variations of tube properties,fluctuations of tube geometries and friction.Using the virtual Taguchi’s DOE of inner and outerarrays,considering three major defects,the robust optimization of LDTW Al-alloy tube bending is achieved and validated.For thebending tools,the robust design of mandrel diameter was conducted under the fluctuations of tube properties,friction and tubegeometry.For the processing parameters,considering the variations of friction,material properties and manufacture deviation ofmandrel,the robust design of mandrel extension length and boosting ratio is realized.

Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and crashworthiness.They can be produced at room temperature by the electrohydraulic forming process.In the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoidal corrugation tube has been assessed.In particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been used.Through the range analysis and variance analysis of the experimental data,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was determined.Multiple regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established accordingly.The following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of 0.001.Better optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with OED.The response surface method in CCD was more suitable for the design and optimization of the considered process parameters.

Combined stress waves with phase transition in thin-walled tubes

The incremental constitutive relation and governing equations with combined stresses for phase transition wave propagation in a thin-walled tube are established based on the phase transition criterion considering both the hydrostatic pressure and the deviatoric stress. It is found that the centers of the initial and subsequent phase transition ellipses are shifted along the sigma-axis in the sigma tau-plane due to the tension-compression asymmetry induced by the hydrostatic pressure. The wave solution offers the 'fast' and 'slow' phase transition waves under combined longitudinal and torsional stresses in the phase transition region. The results show some new stress paths and wave structures in a thin-walled tube with phase transition, differing from those of conventional elastic-plastic materials.

Microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by a horizontal continuous casting with heating-cooling combined mold technology

A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe 10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting （cooling mold casting） were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the pro- duction efficiency of a BFel0 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012}〈 621 〉. Compared with cooling mold casting （6 = 36.5%）, HCCM can improve elongation （3 = 46.3%） by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe 10 cupronickel alloy tube.

Cross-sectional distortion behaviors of thin-walled rectangular tube in rotary-draw bending process

The cross-sectional distortion usually appears during rotary-draw bending process of thin-walled rectangular tube with small bending radius.To study the cross-sectional distortion of the tube,a three-dimensional finite-element model of the process was developed based on ABAQUS/Explicit code and its reliability was validated by experiment.Then,the cross-sectional distortion behaviors of the tube were investigated.The results show that a zone of larger circumferential stress appears on the tube when bending angle reaches 30°.And in the larger circumferential stress zone,the sagging phenomenon is produced obviously.The maximum cross-sectional distortion is located in the larger circumferential stress zone and the angle between the plane of maximum cross-sectional distortion and the bending reference plane is about 50°.The position of the maximum cross-sectional distortion keeps almost unchanged with the variation of the clearances between dies and tube.

Experimental and numerical assessment of energy absorption capacity of thin-walled Al 5083 tube produced by PTCAP process

The energy absorption capacity of the Al5083 thin-walled tube produced by parallel tubular angular pressing(PTCAP) process was evaluated. Also, microstructure, mechanical properties, and anisotropy coefficients were studied in the peripheral and axial directions. Results showed that values of energy absorption decreased with processing pass increasing and the values for the unprocessed, first and second passes were obtained to be 167, 161.4 and 160.7 J, respectively. The differences between the simulation results for the energy absorption values and their experimental values for the unprocessed, the first and the second PTCAP passes samples are about 5%, 10%, and 13%, respectively. The energy absorption capacity was related to the anisotropy coefficient and microstructure. The results demonstrated that grain refinement occurred and ultimate tensile strength(UTS) and microhardness after the first and second PTCAP passes were enhanced, while the increase rate in the first pass was much severer. Also, by applying PTCAP, the deformation modes were altered, such that the deformation mode of the annealed tube was quite symmetrical and circular while for the first and second passes there have been triple and double lobes diamond. The results of the numerical simulation for the deformation mode of the annealed and PTCAPed tubes were consistent with the experimental results. The deformation mode of tubes is dependent on their mechanical properties and variation of the mechanical properties during PTCAP process.

Die Casting Mold Design of the Thin-walled Aluminum Case by Computational Solidification Simulation

Recently, demand for the lightweight alloy in electric/electronic housings has been greatly increased. However, among the lightweight alloys, aluminum alloy thin-walled die casting is problematic because it is quite difficult to achieve sufficient fluidity and feedability to fill the thin cavity as the wall thickness becomes less than 1mm. Therefore, in this study, thin-walled die casting of aluminum （Al-Si-Cu alloy： ALDC 12） in size of notebook computer housing and thickness of 0.8 mm was investigated by solidification simulation （MAGMA soft） and actual casting experiment （Buhler Evolution B 53D）. Three different types of gating design, finger, tangential and split type with 6 vertical runners, were simulated and the results showed that sound thin-walled die casting was possible with tangential and split type gating design because those gates allowed aluminum melt to flow into the thin cavity uniformly and split type gating system was preferable gating design comparing to tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. Also, the solidification simulation agreed well with the actual die-casting and the casting showed no casting defects and distortion.

Simulation of temperature field and metal flow during continuous semisolid extending extrusion process of 6201 alloy tube

A continuous semisolid extending extrusion （CSEP） method was proposed. Temperature field and metal flow during continuous semisolid extending extrusion process of 6201 alloy tube were studied. During the process, the temperature in the roll-shoe cavity decreases gradually, and the isothermal lines of the alloy deviate from the shoe side to the work roll side in the roll–shoe gap. Metal flow velocity decreases gradually from the surface of the work roll to the surface of the shoe. In the extrusion mould, alloy temperature decreases gradually from the entrance to the exit and from the center to the sidewall of the mould. The extending cavity is radially filled with the alloy. The flow lines in the tube corresponding to the centers of the splitflow orifices and the welding gaps are dense, and the corresponding harness values are high; there are 8 transitional bands between them. In order to prepare 6201 alloy tubes with good surface quality, the pouring temperature from 750 ℃ to 780 ℃ was suggested.

Machining Deformation Prediction of Thin-Walled Part Based on Finite Element Analysis

For the problems of machining distortion and the low accepted product during milling process of aluminum alloy thin-walled part,this paper starts from the analysis of initial stress state in material preparation process,the change process of residual stress within aluminum alloy pre-stretching plate is researched,and the distribution law of residual stress is indirectly obtained by delamination measurement methods,so the effect of internal residual stress on machining distortion is considered before finite element simulation. Considering the coupling effects of residual stress,dynamic milling force and clamping force on machining distortion,a threedimensional dynamic finite element simulation model is established,and the whole cutting process is simulated from the blank material to finished product,a novel prediction method is proposed,which can availably predict the machining distortion accurately. The machining distortion state of the thin-walled part is achieved at different processing steps,the machining distortion of the thin-walled part is detected with three coordinate measuring machine tools,show that the simulation results are in good agreement with experimental data.

Residual Stress Relaxation of Thin‑walled Long Stringer Made of Aluminum Alloy 7050‑T7451 under Transportation Vibration

Thin-walled long stringer made of aluminum alloy 7050-T7451 is prone to deformation during transportation,so a research of residual stress relaxation was launched in this paper.The transport resonance stress of long stringer was analyzed based on the power spectral density of road transport acceleration.The residual stress relaxation experiment of aluminum alloy 7050-T7451 under different equivalent stress levels was designed and carried out.According to the amount of residual stress relaxation in the experiment,an analytical model was established with the equivalent stress level coefficient.The deflection range of long stringer was evaluated under different damping ratios.The results show that when the equivalent stress exceeds 0.8σ0.2,the residual stress relaxation of the thin-walled samples occurs.The residual stress relaxation increases linearly with the equivalent stress,which is logarithmically related to the loading cycle.The deformation caused by residual stress relaxation of the long stringer is proportional to the square of the length and the bending moment caused by stress rebalance,and inversely proportional to the moment of inertia of the structure.As the damping ratio decreases from 0.03 to 0.01,the total deflection of the long stringer increases from 0 to above 1.55 mm.

Effect of blank quenching on shear spinning forming precision of 2219 aluminum alloy complex thin-walled components

The quenching-spinning(Q-S)process,i.e.,shear spinning after blank quenching,has been increasingly utilized to form 2219 aluminum alloy complex thin-walled components.However,the changes in material property,shape and stress of the blanks after quenching will affect the spin-ning forming precision.In this study,the rules and mechanisms of these effects are investigated based on a combined finite element(FE)model including blank quenching and component spinning process.The results indicate that the increase of material strength and the existence of distortion of the quenched blank lead to a notable increase in the non-uniformity of the circumferential compres-sive stress in the spinning area and the increase of the flange swing height during spinning.These changes result in an increase in the wall thickness and component-mandrel gap of the components.The quenching residual stress has little effect on wall thickness and roundness but can noticeably reduce the component-mandrel gap.This is because that the existence of quenching residual stress of the blank can lead to the decrease of the maximum circumferential compressive stress of the workpiece in spinning and an obvious drop in the maximum compressive stress after reaching the stress peak.Quenching distortion is the main factor affecting the roundness.Moreover,the opti-mized installation way of the blank for spinning is obtained.

国家标准《铝及铝合金热挤压管第1部分:无缝圆管》述评

介绍了国家标准GB/T 4437.1-2023《铝及铝合金热挤压管第1部分:无缝圆管》的修订原则和主要内容,评价了该标准的水平和创新点,并展望了铝合金标准的未来发展趋势。

热处理对2219铝合金薄壁旋压管组织与性能的影响

本文对2219铝合金薄壁旋压管进行了退火、固溶及时效热处理,研究了热处理工艺对微观组织、拉伸性能和液压胀形性能的影响。结果表明:2219铝合金旋压管在400℃以下退火时以回复为主,温度高于450℃时发生再结晶。随退火温度升高,基体组织逐渐由形变组织向再结晶组织转变。固溶处理时随固溶时间延长,再结晶程度逐渐增加,位错密度降低。经退火和固溶处理后,管材的硬化率和延伸率显著提高,抗拉强度随着退火和固溶温度升高而逐渐增大,固溶处理后抗拉强度达到340 MPa,延伸率提高到25%。时效处理后管材的抗拉强度进一步提高到435.2 MPa。管材液压胀形极限随热处理温度升高而升高,固溶态2219铝合金旋压管具有较好的液压胀形能力,适合进行液压成形。

铝合金三通管铸造工艺设计及优化

文中针对铝合金三通管铸件的结构进行了工艺分析,结合铝合金材质特点确定了该铸件的铸造工艺方案和工艺参数,设计计算了三通管铸件的浇冒口尺寸,通过对设计工艺进行数值模拟分析铸件的充型和凝固过程,通过流场发现采用底注开放式浇注系统可以最大程度地保证充型的平稳性;通过凝固场发现在铸件热节位置设计保温冒口和冷铁可以有效消除缩孔和疏松缺陷,试制铸件满足探伤和无损检测技术要求,获得了优化的工艺方案。

工艺参数对铸态7075铝合金管旋压成形强度的影响

工艺参数对铸态7075铝合金管旋压成形强度的影响至关重要。本文以抗拉强度与屈服强度作为成形质量指标,系统地分析了压下量、预热温度、进给比和摩擦条件等工艺参数对铸筒旋压件强度的影响。结果表明:随着压下量的增加,管的抗拉强度与屈服强度增加;随着预热温度的上升或者进给比的增加,管的抗拉强度与屈服强度先增加后减少;随着摩擦系数的增加,管的抗拉强度与屈服强度先增加后减少,但变化不明显。

多胞铝合金薄壁管耐撞性分析与区间优化设计

铝合金多胞薄壁管轴向压缩在能量吸收方面比普通方形管具有更优的力学性能,在汽车、航空、军事装备以及其他产业应用前景非常广泛。为研究挤压型材6061-T6铝合金材料各向异性特征,在板材上分别沿挤压方向0°、45°、90°取样进行单轴拉伸力学特性试验,获取相应的应力-应变曲线和各向异性特征参数,基于各向异性硬化行为的屈服准则建立材料本构模型。设计口字、日字、目字等构型截面并对管件进行准静态压溃试验,通过对比分析变形-压溃力曲线表明目字型多胞铝合金薄壁结构具有更加优越的耐撞性能。为进一步获得目字型薄壁管最优设计参数,考虑泊松比、弹性模量等材料参数波动对结构耐撞性能产生不确定性影响,建立多胞铝合金薄壁管耐撞性区间不确定性优化模型,采用区间可能度方法将其转化为确定性问题,结合人工神经网络(artificial neural networks,ANNs)模型与交错投影寻踪遗传算法(intergeneration projection genetic algorithm,IP-GA)方法对该问题进行双层嵌套优化,分析不同可能度水平对不确定性优化结果的影响,为不同可靠性优化设计的选择提供指导性意见。