铝合金交叉筋壁板激光热诱导锥面成形边缘效应的研究

目的 减小铝合金交叉筋壁板激光热诱导锥面成形过程中的边缘效应。方法 利用有限元分析方法,通过对扫描线温度、应力应变分布的分析,得到边缘效应产生的原因;研究激光功率、扫描速度、扫描次数对边缘效应的影响,选择合适参数,采用激光热诱导成形系统,对5A06铝合金交叉筋壁板进行锥面成形试验,并用扫描仪检测成形精度。结果 边缘效应随着扫描速度的减小、激光的功率变大而减小,与单次扫描相比,两次扫描能有效减小边缘效应。试验证明,扫描速度对边缘效应的影响最大,将扫描速度保持在30 mm/s以下,调整激光功率和扫描速度控制能量密度,在保证弯曲角度的同时,也能较好抑制边缘效应。     

筋条外置整体壁板填料滚弯成形工艺研究

以橡胶填料辅助筋条外置整体壁板滚弯成形实验为基础,讨论压下量对壁板筋条和蒙皮弧高值的影响,分析滚弯成形之后壁板的表面质量以及尺寸精度。结果表明:橡胶填料改善壁板的力学状态,使壁板蒙皮和筋条协调变形,提高壁板滚弯成形性;成形之后壁板的表面质量良好,无开裂、失稳等缺陷,尺寸精度满足工艺要求。     

TA2板料激光热应力弯曲成形 及其力学性能研究

用HVS-1000显微硬度测试仪、X-350A型X射线应力测定仪,以2.5 kW SM2000SM快轴流CO2激光器对0.6 mm厚的TA2板料进行扫描,按照正交试验理论安排成形工艺参数,研究了TA2板料弯曲成形时主要工艺参数对弯曲角度的影响,以及试样表面残余应力的分布和试样断面上的显微硬度变化。结果表明：正交试验中的4个工艺参数的作用是不同的,按其变化对弯曲变形量影响的大小排序,依次是扫描次数、光斑直径、激光束功率、扫描速度;成形参数对试样表面的残余应力分布也存在一定的影响;试样变形区断面上的显微硬度变化呈现出一定的规律。     

SLM成形薄壁件尺寸偏差预测与控制研究

目的 针对选区激光熔化成形薄壁件过程中存在的变形较大、精度低等问题,通过获得最优工艺参数区间来减小薄壁件的变形。方法 利用有限元软件分析薄壁件成形过程中温度场和应力场的演化规律;建立形变量预测模型并进行试验验证,研究工艺参数对薄壁件尺寸偏差的影响,得到激光功率、扫描速度与形变量之间的关系,实现对形变量的预测和控制。结果 随着扫描层数的增加,熔池的最高温度和热影响区也随之增大,等温线越密集,温度梯度越大,最终趋于稳定;薄壁件成形过程中,出现两侧壁边缘向内倾斜、上侧边缘出现内凹的现象,薄壁件的最大应力随层数的增加而减小,最大热应力主要分布在薄壁件底层的两端;形变量随激光功率的增大而增大,随扫描速度的增大而减小,薄壁件的形变量最小约为0.02 mm;试验验证所建立的数学模型误差在10%左右,误差较小,可以对形变量进行良好的预测和控制。结论 激光功率100～200 W、扫描速度800～1 000 mm/s为最优参数区间;降低能量密度可以有效降低薄壁件形变量,提高其精度。     

整体壁板增量压弯试验与模拟

采用逐点增量弯曲的方法对网格式带筋整体壁板进行了试验研究,并进行了有限元模拟.研究表明:采用增量压弯成形工艺可以成形出具有一定曲率外形的整体壁板;压弯过程中蒙皮始终处于弹性变形阶段,筋条既有弹性变形产生,又有塑性变形产生;压下量达到一定值时,塑性变形的比率急剧增加.     

数字摄影测量技术在抛物面天线型面精度、重力变形测试中的应用

对大口径抛物面天线而言,自重较大,型面精度会随天线俯仰角度的变化而变化,数字摄影测量技术可以量出天线任意姿态下型面精度,计算天线反射体重力变形数值,根据测量数据进行精度及重力预变形调整。66米口径天线实际应用中,型面调整精度0.25mm。测试结果表明数字摄影测量技术可用于天线重力变形测试和形面精度在位测量、调整。     

网格式整体壁板增量成形有限元模拟

将机加后的平面外形的壁板毛坯成形为具有复杂曲面外形的壁板零件具有很大难度,为此,采用有限元方法进行壁板成形工艺模拟,分析壁板加工过程中的应力应变分布与失稳开裂现象.研究表明:网格式整体壁板增量成形过程中,塑性变形主要集中于筋条处,成形后的壁板主要是由于筋条发生塑性变形而导致壁板外形的改变.在成形过程中,筋条容易出现失稳与开裂现象.采用分段逐点循环模拟的方法,实现了网格式整体壁板结构件增量成形过程的数值模拟.     

20G钢管的电磁校形

采用线圈轴向磁场力对压扁量为11mm的20G钢管进行了电磁校形,并以变形量为评价指标,研究了放电电压、放电次数和线圈电感对钢管校形精度的影响。结果表明：虽然线圈电感和放电次数对校形精度有一定的影响,但放电电压是影响校形精度的决定因素;试验还从各种参数对校形的影响关系得到了较优化的工艺参数,以达到提高校形效果的目的。     

喷丸成形2024铝合金整体带筋壁板变形规律研究

目的 获得2024铝合金在不同喷丸参数下壁板外表面的变形规律。方法 选取喷丸气压、移动速度、预应力3个工艺参数作为正交试验因素进行预应力喷丸成形正交试验,研究在不同参数组合下单筋件的变形规律。结果 工艺参数按对单筋件变形量影响程度从大到小的顺序依次为：移动速度、预应力和喷丸气压。获得了2024铝合金单筋试验件喷丸成形后曲率半径与气压、移动速度和预应力之间的回归方程,其拟合值与试验值偏差小于12.6%。结论 获得了喷丸成形工艺参数对单筋件弯曲变形的影响规律,建立了工艺参数与曲率半径的回归方程,可为今后带筋壁板零件的喷丸成形工艺设计提供参考。     

基于分区扫描策略的激光金属沉积短梁件残余变形有限元模拟

目的 研究分区扫描策略对激光金属沉积TC4钛合金短梁件残余变形的影响,探寻较优的分区扫描策略,以改善成形短梁件残余变形.方法 通过建立激光金属沉积TC4钛合金三维顺序耦合有限元模型,来模拟不同分区尺寸和分区间跳转顺序下短梁件的成形过程,研究成形过程温度场的演变和不同分区扫描策略下成形件短梁件的总变形和z向变形.结果 不同分区扫描策略下成形短梁件和基板的变形趋势相同,均为面向热源的翘曲变形;与分6个子区域和8个子区域相比,每层分16个子区域扫描成形的短梁件残余变形最小,且较6分区减小了约12％;顺序扫描、对角扫描和向外扫描3种分区间跳转顺序下成形的短梁件残余变形相差不大.结论 随着分区尺寸的减小,激光金属沉积短梁件的残余变形逐渐减小,每层分16个子区域,从中间往两侧向外成形的分区扫描策略成形得到的短梁件残余变形最小.     

Prediction of fracture in press bend forming of aluminum alloy high-stiffener integral panels

Aluminum alloy high-stiffener integral panels are widely used on modern aircrafts to meet the demand of light weight and high stiffness. Press bend forming is an important method of producing this structure, of which fracture on stiffeners is a severe forming defect. In this study, a series of ductile fracture criteria that have been successfully applied in the metal forming field are adopted, the constants of which are obtained by tensile tests of different specimens and their corresponded FEM simulations. Then all the criteria are implemented into ABAQUS with user subroutine. A set of press bending dies is designed, with which bend to fracture experiments of single stiffener and multi-stiffener specimens are carried out. By comparative analysis of the experiments and the FEM simulations including many ductile fracture criteria, the most suitable ductile fracture criteria for predicting the fractures in this forming process are determined. The reasons of the usability are also explained based on the mechanics of the fracture.     

2050铝锂合金喷丸成形变形规律试验研究

目的 以某飞机机身壁板为研究对象,采用2050铝锂合金材料开展喷丸成形基础工艺研究,获得其宏观变形规律。方法 采用正交试验法,选取零件厚度、喷丸气压、移动速度、预应力4个喷丸工艺参数作为正交试验因素,对2050铝锂合金进行喷丸成形试验,研究不同工艺参数对喷丸变形的影响规律。结果 随着4个喷丸工艺参数的变化,2050铝锂合金喷丸弯曲半径曲线均呈现出幂函数曲线特征,其中喷丸弯曲半径随着零件厚度和移动速度的增大而增大,随着喷丸气压和预应力的增大而减小。结论 根据正交试验结果可知,各参数对喷丸变形程度的影响顺序为:板材厚度>预应力>移动速度>喷丸气压。通过回归分析建立了喷丸弯曲半径与工艺参数间的幂函数经验方程,为后续开展机身壁板喷丸成形提供了一定的技术支撑。     

The influences of processing parameters on forming characterizations during laser rapid forming

Laser rapid forming experiments were carried out with 316L stainless steel and nickel-base alloy to investigate the influences of the processing parameters on forming characterizations systematically. It is found that the height of a single cladding layer was very important for fabrication accuracy and forming stability of components of laser rapid forming because it was affected by almost all processing parameters and was quite difficult to precisely control. For the system with lateral powder feeding pattern, the powder injection point was the most important factor to the height control of single layer. The variation of the width of single clad, which was mainly affected by laser power, spot diameter and scanning velocity, was similar to that in laser surface melting. The surface quality was another important characterization for laser rapid forming and was remarkably affected by oxidation and the powder adhesion. In order to improve the surface quality, the flow flux of shielding gas should be 10 l min⁻¹ and the powder stream cannot be injected to the tail part of the melt pool. Based on the investigation, some metal components were fabricated.     

折叠纸盒压痕形态与成型质量分析研究

目的 探寻纸盒模切压痕时,盒片模切压痕形态与模切力以及折叠纸盒成型质量之间的相互关联关系,从而对纸盒模切力进行有效标准控制,并最终提高纸盒成型质量及其稳定性。方法 采用三维激光扫描仪对纸盒进行非接触式扫描获得高精度的压痕线扫描点云,在此基础上利用特定算法把压痕线从无序点云中提取出来,随后对测量数据进行分析和计算,分别计算出压痕线的深度和宽度。结果 结果表明采用三维激光扫描技术有效地测量了纸盒压痕深度和压痕宽度等一系列数据。所获得的测试数据与理论计算数据的误差值极小,平均误差在0.01 mm左右,证明了该测量方法的有效性、可靠性及精准性。此外,为了研究硬盒盒片压痕形态与压痕挺度之间的相互关系,并建立较为准确的函数关系模型,也利用该仪器进行了大量测试工作并对测试数据进行了统计分析及曲线拟合,所获得的结果与理论分析高度一致。结论 压痕形态的有效测量以及压痕形态与压痕挺度之间关系模型的建立为纸盒模切质量的有效控制提供了理论基础和数据依据。     

白车身顶盖激光钎焊焊缝装配尺寸控制方法研究

目的研究白车身顶盖与侧围激光钎焊装配尺寸控制方法,提高顶盖侧围激光钎焊焊缝装配精度,降低激光焊缺陷率。方法顶盖与侧围焊接配合形面由传统的面贴合设计更改为线贴合,降低对车身焊接合拼精度的要求;顶盖与侧围模具结构上采用整体整形及压料镶块提升零件的尺寸精度,避免因镶块交接造成的翻边面缺陷而影响激光钎焊质量;顶盖与侧围的成形焊夹具设计成y向浮动以及在激光焊夹具上设计z向夹紧功能,来实现侧围与顶盖装配间隙的调整。结果实际应用表明,侧围与顶盖激光钎焊装配尺寸得到了有效控制,满足激光钎焊的要求。结论顶盖与侧围产品的设计优化、冲压模具工艺和结构的创新和优化以及焊装焊接夹具的柔性化适配功能,可以有效保证白车身顶盖钎焊搭接部位尺寸精度。     

Simulation and experiment of curve irradiated laser bending process of titanium alloy sheet

Abstract

Laser bending along a curve scanning path is a complex 3D forming process. To analyse the deformation behaviour of the process and the effect of process parameters on the bending angle of sheets, numerical simulation becomes indispensable. In this paper, non-linear transient heat transfer and dynamic structural computational models including thermal mechanical coupling analysis, in which the temperature dependence of the thermal and mechanical properties of the material are taken into account, have been developed. The temperature, stress, and strain fields as well as the effect of process parameters on the bending angle were calculated on the basis of models using the finite element method. Meanwhile, an experimental parameter investigation was also carried out. The results showed that, compared with the linear laser bending, curve irradiated laser bending has a significant reduction of the bending angle and the bending angle decreases with increasing path curvature. The bending angle increases with increasing laser power and decreasing spot diameter, and decreases roughly with decreasing scanning velocity. Good correlation was found between the numerically simulated results and the experimental data.     

Measurement techniques for buckling sensitive composite shells

This paper describes a measurement system that was developed for an experimental study on buckling of glass reinforced composite cylinders. An automated non-contact laser device operating inside the test specimen provided a three dimensional scanning system for measuring the deformation of the shell wall. The measurement system was used to obtain the initial geometric imperfections, as well as the deformation under varying control axial displacement. All loading and data acquisition operations were carried out using advanced computer controlled techniques. Due to the large number of measurements undertaken in each test, data collection was followed by processing and reduction techniques, thus delivering the data in a form suitable for finite element analysis and comparative studies. Typical results are presented in order to demonstrate the reliability, accuracy and versatility of the system.