Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending

3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%.

Effect of small tool pin profiles on microstructures and mechanical properties of 6061 aluminum alloy by friction stir welding

The effect of small tool pin profiles on the microstructures and mechanical properties of 6061 aluminum alloy joints using friction stir welding （FSW） technique was investigated. Three different tool pin profiles： threaded tapered cylindrical （T1）, triangular （T2） and square （T3） were used to produce the joints. The results indicate that the weld joints are notably affected by joining with different tool pin profiles. The triangular tool pin profile produces thebest metallurgicaland mechanical weld properties compared with other tool pin profiles. Besides, the lowest tensile strength and microhardness are obtained for the joint friction stir welded with square tool pin profile. It is observed that the smaller tool pin profile and shoulder diameter lead to narrow region of heat affected zone （HAZ） and a desired level of softening. The fracture surface examination shows that the joints are also affected when welding with different types of tool pin profiles. The fracture surface shows that the triangular specimen fails with a ductile fracture mode during the tensile test, while the brittle fracture modes are observed in the joints fabricated with other tool pin profiles （T1 and T3）.

Simulation of temperature and stress in 6061 aluminum alloy during online quenching process

The cooling curves of 6061 aluminum alloy were acquired through water quenching experiment. The heat transfer coefficient was accurately calculated based on the cooling curves and the law of cooling. The online quenching process of complex cross-section profile was dynamically simulated by the ABAQUS software. The results suggest that the heat transfer coefficient changes during online quenching process. Different parts of the profile have different cooling velocity, and it was verified by water quenching experiment. The maximum residual stress of the profile was predicted using FEM simulation based on ABAQUS software The relations between the temperature and stress were presented by analyzing the data of key points.

High-strength aluminum alloys hollow billet prepared by two-phase zone continuous casting

The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope.During the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient.The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed.Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.

Laser-pulsed MIG hybrid welding technology of A6N01S aluminum alloy

Welding research of A6N01S-T5 aluminum alloy profile for high-speed train was done by using laser-MIG hybrid welding and MIG welding individually. And the weld appearance,welding distortion,mechanical properties of the joints and microstructures were analyzed. The test results demonstrated that high-efficient welding for the profile can be achieved by using laser-MIG hybrid welding,the speed of which can be over 3. 0 m/min. The processing had a good gap bridging ability,even if the gap of the butt joint was up to 2. 0 mm,a good weld appearance can also be got. While the hybrid welding speed was greater than 2. 5 m/min,the welding distortion of the laser-tandem MIG hybrid joints was just about 33% of that of the MIG joints,but the welding efficiency was over 3 times of MIG welding. And tensile strength of the hybrid joints was 85% of that of A6N01S-T5 base metal,9% higher than that of the MIG joints. Fatigue properties was tested individually with pulsed tensile fatigue method in the condition of 1 × 10~7 lifetime. The test results demonstrated that the fatigue strength of the joints was a little lower than that of base material,which could be up to 115 MPa. But the fatigue strength of hybrid welding joints was 107. 5 MPa,which was 23% higher than 87 MPa of MIG welding joints.

Optimization of process parameters to maximize ultimate tensile strength of friction stir welded dissimilar aluminum alloys using response surface methodology

Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding （FSW） has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy （AA6351 T6-AA5083 Hlll）joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength （UTS） of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology （RSM） and the identified optimum FSW welding parameters were reported.

Effects of single and multi-stage solid solution treatments on microstructure and properties of as-extruded AA7055 helical profile

The effects of single-stage solution treatment(SST),enhanced solution treatment(EST),high-temperature pre-precipitation(HTPP)and multi-stage solution treatment(MST)on the microstructure,mechanical properties and corrosion resistance of the as-extruded 7055 aluminium alloy(AA7055)helical profile were investigated using differential scanning calorimetry(DSC),optical microscopy(OM),scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD)and transmission electron microscopy(TEM).It was observed that EST and MST could promote the dissolution of the second-phase particles compared with the traditional SST,and the intergranular phases were distinctly discontinuously distributed after HTPP and MST.There was obvious difference in the main texture type and texture strength for the alloy after different solid solution treatments.HTPP could improve the corrosion resistance of the alloy by regulating the intergranular phases,but the mechanical properties were severely weakened.While the good corrosion resistance of the alloy could be obtained by MST without obvious strength loss.As a result,the MST is an ideal solid solution treatment scheme for AA7055.

铝合金型材挤压弯曲一体化成形技术研究进展

相比于直型材,铝合金弯曲型材更适用于日益复杂的部件形状并能更好地满足轻量化需求,具有提升部件结构强度和刚度、节约空间及增加工业设计自由度等优点,在汽车、高铁和航空航天等领域具有广泛用途。相较于传统冷弯成形技术,挤压弯曲一体化成形技术在生产弯曲型材方面具有流程短、精度高、缺陷少等优点,因而受到广泛关注。重点综述了基于外部弯曲装置和材料差速流动的挤压弯曲一体化成形技术的研究进展,分析并总结了不同挤压弯曲一体化成形技术的原理及发展现状,对比了不同挤压弯曲一体化成形技术的优缺点,最后展望未来发展趋势及其研究方向。

基于固有应变法的中空薄壁铝合金结构件焊接变形及残余应力预测

为提升中空薄壁铝合金结构件焊接变形与残余应力预测精度。基于固有应变法与焊接热输入参数对焊接等效载荷开展求解,利用有限元仿真方式从变形及应力的角度出发,分别对焊接变形及残余应力进行分析,并通过焊接试验进行验证。结果表明:焊缝左右两侧的边缘区域是产生焊接残余应力的主要位置,横向、纵向残余应力分别为275 MPa、181 MPa,结构件上蒙板呈马鞍形分布,焊接所导致的最大变形分布在上蒙板左右两侧,左右两侧仿真最大值分别0.299 mm、0.274 mm,左右两侧试验最大值分别0.37 mm、0.34 mm,试验变形值略大于仿真变形值,两侧变形预测误差率分别为19.1%、19.4%。研究结果可为类似中空薄壁铝合金结构件焊接变形及残余应力预测提供一定参考依据。

2A12T4铝合金型材在苛刻海洋大气环境中的腐蚀规律

采用室内周期性浸泡的模拟试验方法,研究了2A12T4铝合金型材在苛刻海洋大气环境中的腐蚀行为及电化学规律。试验结果表明,在干燥温度为60℃,浸泡在质量分数为3.5%的氯化钠溶液的条件下,随着时间的延长型材出现明显的点蚀现象和较重的层片状剥蚀,腐蚀失重规律符合幂指数规律,腐蚀电位先降低后升高再降低最后趋于稳定。

喷粉铝合金建筑型材耐老化性能紫外灯快速检测方法的研究

为了获得适合工厂对粉末喷涂铝型材耐老化性能进行质量控制的快速检测方法,研究了紫外灯加速老化试验结果与1 000 h氙灯老化试验结果之间的关系,试验样品为含有不同耐候等级的粉末涂料制成的粉末喷涂铝板,分别测试了组合紫外灯加速老化试验与1 000 h氙灯老化试验的光泽及颜色变化,两种试验结果之间的相关系数为0.85~0.89,216 h的组合紫外灯人工加速老化试验可以近似准确模拟1 000 h氙灯老化试验结果,该试验方法可以作为工厂内部质量控制方法使用。

铝合金榫卯结构的几何特征

铝合金材料是一种优秀的轻量化材料,但由于其焊接性能差,限制了其在汽车上的大量应用。文中提出一种新的铝合金型材连接方案,即铝合金榫卯连接结构,并对其几何特点进行了研究:给出了铝合金榫卯结构的构成,即榫头、卯孔和固定结构;分析了铝合金榫卯结构的几何缺陷;定义了7组描述铝合金榫卯结构特点的基本参数;研究了铝合金型材截面轮廓及其内部结构的拓扑规律;归纳了工程中4类实用的铝合金榫卯结构类型。

铝合金挤压型材的拉伸失效行为研究

为了研究挤压速度、预热温度、挤压角度等对铝合金性能的影响,通过熔炼、差压铸造、挤压制备出铝合金型材,用万能试验机完成双向拉伸试验,用扫描电子显微镜观察显微组织,分析差压铸造铝合金经挤压后的拉伸失效行为。结果表明:双向拉伸后,铝合金型材出现较严重的变形,挤压角度为90°时,铝合金挤压型材不易拉断;挤压速度为1.5 mm/s时拉伸损伤概率更低;预热温度为250℃时拉伸后韧窝更密集,不易脆性断裂。

铝合金型材挤压过程能耗优化的研究现状

铝合金挤压型材广泛用于汽车领域。在推动绿色发展的战略背景下,铝合金型材挤压过程的能耗优化问题越来越受到关注。论述了铝合金型材挤压过程能耗优化的重要性,介绍了主要影响因素,并从挤压机能耗和挤压成型能耗两方面分析了铝合金型材挤压过程能耗优化的研究现状。

5E61铝合金壁板型材挤压过程的模拟和试验研究

为研究5E61铝合金壁板型材挤压过程变形的规律,本文通过热模拟压缩试验建立了5E61铝合金本构模型,确定了动态再结晶动力学模型中的相关参数。研究结果表明,模具结构和挤压工艺共同决定了热挤压成形过程中金属的变形,其中模具结构对型材挤出速度场的影响最大,挤压工艺影响不明显,模具结构对型材截面的组织影响较小,型材挤出温度场和应变场共同决定型材截面组织的演变;模具温度和挤出速度对料头形状、型材截面温度场及动态再结晶体积分数的影响最大,挤压筒的影响次之,铸锭温度的影响最小。

基于盲孔法的X7001挤压L型铝材残余应力测试研究

采用盲孔法对3种截面规格的X7001铝合金挤压L型截面型材的纵向残余应力进行试验测量,基于试验结果分析了L型铝材的残余应力分布特点,给出了其残余应力分布建议图。结果表明:L型截面铝材残余应力分布呈对称模式;残余拉应力峰值略大于残余压应力峰值,且均不超过屈服强度的15%;生产工艺对构件残余应力分布模式有一定影响;残余应力系数β与构件宽厚比有关,建议普通L型截面X7001挤压型铝材的残余应力系数β的绝对值取值范围为0.08~0.15。

Horizontal continuous casting process under electromagnetic field for preparing AA3003/AA4045 clad composite hollow billets

A modified horizontal continuous casting process under the electromagnetic field was proposed for preparing AA3003/ AA4045 clad composite hollow billets. To investigate the effect of electromagnetic field on this process, a comprehensive three-dimensional model was developed. Two cases with and without electromagnetic field were compared using the simulations. When rotating electromagnetic stirring is applied, the flow pattern of fluid melt is greatly modified; the mushy zone becomes much wider, the temperature profile becomes more uniform, and the solid fraction decreases for both the external and internal alloy melt layers. These modifications are beneficial for the formation of a bimetal interface and fine and uniform grain structure of the clad composite hollow billet. Experiments conducted using the same electrical and casting parameters as the simulations verify that under the electromagnetic field the microstructure of the clad composite hollow billet becomes fine and the diffusion of the elements at the interface is promoted.

车用6082铝合金型材断裂失效行为研究

基于Gissmo损伤失效模型,采用数值参数反方法得到车用6082铝合金材料的失效参数,并设计铝合金防撞梁准静态三点弯曲试验验证6082铝合金Gissmo损伤失效模型的合理性。通过准静态单轴拉伸试验,得到6082材料的硬化曲线,并采用Swift-Hockett-Sherby(SHS)准则对硬化曲线进行外推;开展不同应力状态下的准静态试验(剪切、单轴拉伸、中心孔、缺口、三点弯曲、杯突),并采用仿真结合试验的数值反求得到Gissmo失效参数;设计6082铝合金防撞梁的准静态三点弯曲试验,验证6082材料失效参数的合理性。结果表明,本研究中提出的参数反求得到的6082铝合金Gissmo损伤失效模型(含硬化曲线、失效应变曲线、失稳曲线、单元尺寸正则化曲线)可以较好地预测防撞梁材料的失效行为。

6005A铝合金型材开裂性缺陷分析

使用直读光谱仪、电子万能试验机等设备,对新能源汽车边梁用6005A铝合金型材发生的开裂性缺陷进行分析,具体包括缩尾和焊合不良。缩尾和焊合不良严重破坏组织的连续性,在一定程度上降低力学性能。可以通过调整模具结构,采用合理的挤压工艺参数来避免开裂性缺陷的产生,并对此进行了分析。

6082铝合金挤压型材黑线缺陷分析

通过宏观检验、微观组织观察和微区成分分析,对6082铝合金挤压型材表面出现黑线缺陷的原因进行分析。结果表明缺陷是以Al为主的氧化物和碳化物非金属类夹杂形式存在;缺陷周围存在粗大的含Mg、Si相,或伴随有过剩析出的Si。通过严格控制原材料质量及挤压和熔铸流程,消除C和O元素,以及通过变质处理和成分过冷等方法来细化含Mg、Si相,可有效消除黑线缺陷。