管材激光弯曲的有限元分析

为了研究管材激光弯曲过程中的温度和应力情况,利用有限元软件ANSYS进行分析计算,采用APDL语言编写命令流,生成单元,模拟移动热源载荷.通过分析计算获取温度场,应力应变场的详细信息.分析结果表明管材激光弯曲成形过程中,管材先经历背向激光的弯曲,之后形成面向激光束的弯曲;最后,在加热位置内外表面会发生朝向外侧的凸起变形.     

管材激光成形的工艺参数优化

建立了管材激光弯曲成形工艺优化模型,采用优化软件iSIGHT与有限元模拟软件MSC.Marc相结合,对管材激光弯曲成形工艺参数进行优化,得到成形一定角度并高效成形的最佳工艺参数组合。     

激光辅助加热微器件弯曲研究

在总结了国内外近十多年来微弯曲成形研究现状基础上,提出了基于激光辅助加热的微器件弯曲成形方法,将激光直接加载于难成形的微小工件材料表面,利用激光热作用对工件非接触式加热和热传导,使成形区域温度瞬时达到成形温度,然后通过微弯曲模具对工件施加载荷,实现微弯曲成形,解决了常规的微弯曲方法难以成形的复杂微器件以及难成形材料的成形问题,并采用激光束对工件前后两侧同时加热的方法解决工件加热不均匀问题,设计了激光辅助加热微器件弯曲系统,可以实现微器件的低成本批量化生产.     

工艺参数对管材激光弯曲成形影响规律的研究

管材激光弯曲成形是一种柔性金属塑性成形方法。将连续的激光光斑简化为一间歇跳跃的方形匀强面热源,并考虑材料性能参数与温度的相关性,建立了管材激光弯曲成形的热-机耦合有限元工艺仿真模型,对成形过程进行了数值模拟。有限元模拟结果表明:在其他条件不变的情况下,激光弯曲角度随激光功率的增大而增大,两者基本上成线性关系;弯曲角度随扫描速度的升高而减小,随光斑直径的减小而增大,但当光斑直径减小到一定程度后,弯曲角度开始减小;弯曲角度随扫描包角的增大而增大,当扫描包角为180°时,弯曲角度达到最大,弯曲角度随扫描包角的继续增大而减小;扫描次数与弯曲角度间成近似的线性关系,且第一次扫描管材产生的弯曲角度最大。     

加热弯管有限元分析

建立了加热弯管的数学模型,并系统的分析了加热弯管塑性加工的受力情况,推导出加热弯管弯曲时推力、弯矩、支撑力的5个计算公式,同时分析了加热弯管弯曲成形时管材截面的应力、应变及中性层的位置.通过对加热弯管弯曲成形变形的有限元分析,总结出加热弯管弯曲成形的变形特点,得出加热弯管弯曲成形不仅有助于改善变形区的应力分布,而且有助于防止变形时管材截面的畸变.指出了管材弯曲加工时所出现的缺陷是管材壁厚不均匀及其截面形状畸变引起的.     

采用小弯曲半径弯头反向推直与正向推弯的管坯设计方法

采用数值模拟技术对小弯曲半径弯头（1D）进行反向推直以获得弯头推弯成形时管坯的近似尺寸,并进行优化;在此基础上,采用正向成形法对优化管坯进行推弯模拟与试验验证,最终得到较为精确的管坯尺寸。以管径为32mm×1mm的LF2M铝合金管材进行小弯曲半径弯头成形为例,首先对弯头产品尺寸进行反向推直模拟,获得推直管坯尺寸后,进行优化与正向推弯模拟验证,最终对优化的精确管坯进行推弯成形试验,结果显示：通过反向推直与正向推弯模拟相结合获得小弯曲半径弯头推弯成形管坯尺寸的方法具有较高的可靠性,并得到了管径为32mm×1mm的LF2M铝合金管材进行高难推弯成形时的管坯尺寸与成形零件。     

管材局部加热管壁增厚技术

介绍了几种金属管材弯曲成形工艺及其存在的缺陷,最后得出管壁局部增厚的结论。采用传统弯曲工艺是目前解决管壁变薄强度下降的可行方法,主要叙述了高频感应圈局部加热增厚管壁的机理,对试验装备和操作过程作了较详尽的论述。最后,试验研究了各种工艺参数对成形工艺和管材材质的影响。     

金属微弯曲成形方法的研究

介绍微弯曲成形方法——激光微弯曲成形以及塑性微成形方法。并提出了激光辅助加热微弯曲成形方法。即激光辅助加热待加工件使其达到合适的温度范围后进行微弯曲成形的方法，提高难成形材料的微塑性成形能力和质量。     

管材塑性弯曲成形工艺参数分析与力学仿真

针对管材塑性弯曲成形中影响因素复杂且难以确定的问题,对管材弯曲成形的影响因素进行了划分,分析了可控工艺参数中的重要参数模具压力,并提出基于弯曲力矩的模具压力计算方法。为充分考虑管材材料性能、几何参数等对模具压力的影响,将管材横截面上弯曲变形区划分为弹性区和塑性区,分别计算各区域的弯曲力矩,积分求解管材弯曲所需的总力矩,进而推导了压模压力、助推力的理论近似计算公式,最后构建了管材弯曲有限元模型进行模拟仿真,并与实验结果对比验证了理论公式的有效性。     

TP2管材三维自由弯曲回弹及优化研究

回弹是金属管材在弯曲成形过程中无法避免的现象，它的存在降低了管材的成形质量。以外径12mm，壁厚1.5mm的TP2管材为研究对象，采用显式分析弯曲过程，隐式分析回弹过程。结合有限元数值模拟和实验，通过单因素分析法，探究弯曲模圆角半径和管材与导向机构间隙的变化对管材弯曲回弹的影响规律，分析参数的最优取值以优化管材弯曲成形过程。结果表明：回弹角在弯曲模圆角半径为2mm，管材与导向机构间隙值为0.3mm时最小。优化后的管材回弹角均小于2°，壁厚减薄率均小于2%，模拟结果与实验结果十分接近，优化后的管材成形质量较高。     

Effect of die corner radius on the formability and dimensional accuracy of tube shear bending

Tube shear bending is a beneficial technique to realize considerable small bending radii. The authors have investigated the tube shear bending process of circular tubes experimentally. Moreover, an elastoplastic 3D finite element simulation has been conducted, aimed at clarifying the forming mechanism. Both the experiment and simulation results indicate that, in order to perform successful forming, the value of the applied pushing force on the tube must be appropriate. In this paper, the mechanism of defect generation was clarified. Two failure criteria were introduced and employed to recognize the occurrence of defects in the simulation. The effects of the die corner radius, as the main parameter, on the defect generation of circular A1050 aluminum tubes were investigated both by experiments and numerical simulation. From the results, the formability of tube on dies with different corner radii applying various pushing pressures was clarified. Moreover, the influence of the die radius on the dimensional accuracy of the deformed tube regarding cross-section ovality and thickness changes of the deformed tube was evaluated. The results of this study indicate that, whilst a small bending radius results in high cross-section ovality, increasing the die corner radius raises the wrinkling tendency of the tube. However, the die radius has a small effect on the suitable values of pushing pressure required for a successful shear bending deformation. Moreover, the effect of the die corner radius on the thickness strain of the deformed tube is insignificant.     

铜管弯曲成形加工中确定回弹量的方法

在空调的管路件制作过程中,通过经验公式确定铜管在弯曲成形加工中回弹量的方法,提高铜管弯制工艺质量.     

硅片激光弯曲成形的数值模拟与实验

介绍了一种利用脉冲激光塑性化弯曲单晶硅片的新方法。在分析和描述光脉冲时空特性的基础上,运用有限元分析软件ANSYS对硅片弯曲过程进行建模仿真,得到了脉冲激光弯曲过程中温度场与应力应变的仿真结果。对脉冲激光作用过程中温度场与应力应变的周期性瞬间变化特征进行了描述,指出了脆性材料硅片的脉冲激光弯曲机理不属于简单意义上的温度梯度机理或屈曲机理,而是二种机理共同作用的结果。通过6次扫描试验实现了对硅片的有效弯曲,弯曲角度达6.5º,仿真结果与验证性试验相符。     

Formability evaluation of dimple forming process based on numerical and experimental approach

Exhaust gas recirculation (EGR) cooler consists of a number of heat transfer tubes that have relatively larger net area than that of flat type tubes. The surface of the tubes is made up with lots of grooves and protrusions for enlarging the net heat transfer area. Most tubes are manufactured through forming processes, such as bending, spinning, roll forming, stamping and so on. Therefore, a series of fracture or defect can occur during the various forming processes. In this study, the manufacturing process of a dimple-type rectangular heat transfer tube used for an EGR cooler system is investigated based on the numerical simulation and the experimental approach. A prototype of the tube is designed and modified to a newly designed tube considering the conservation of the net heat transfer area based on the numerical and analytical approach. Formability evaluation of the tube sheet is carried out by using forming limit curves based on the plastic instability conditions. Strain- and stress-based forming limit curves are utilized to ensure the strain path independence. The newly designed tube having a number of dimples on the both sides are manufactured by the press forming process. Thickness distributions for the principal cross-sections are observed from both the simulation and the experiment and compared each other. From the results, it is confirmed that the forming process is robust to manufacture the dimple type rectangular tubes with the comparison of thickness, and application of the forming limit curves.     

矩形截面L形不锈钢弯管冷推弯成形工艺研究

U形管是聚变堆实验中比较重要的一类管件,但其整体成形难度比较大,研究了U形管的一半,即矩形截面L形管件的冷推弯成形.为了防止管坯起皱,在推弯过程中,使用了3种不同的柔性芯棒形式:低熔点合金、轴承滚珠、聚氨酯橡胶.实验结果表明,采用低熔点合金芯棒,在管坯表面润滑、尾部焊接封口的情况下,可获得截面畸变小、尺寸符合、内表面品质良好的矩形截面L形弯管.聚氨酯橡胶作为芯棒的弯管弯头部分出现了内凹现象,轴承滚珠作为芯棒的弯管虽然外表面品质良好,但内表面却出现了很多压痕.     

An investigation on multistage bending of blank sheet into cylindrical tube by experiment and numerical simulation

In this paper, one pair of punch and die was employed to experimentally investigate the pure bending of blank sheet into cylindrical tube by multistage process. The investigated material was hot-rolled HSLA370 with the thickness of 2?mm. Numerical simulation was conducted on bending and springback with LS-DYNA solver. Results showed that multistage bending technique was an alternative way to produce cylindrical tubes. The sequence is described as $ {\text{Blank}}\,{\text{sheet}}\xrightarrow{{{\text{Multistage}}\,{\text{bending}}}}{\text{C - tube}}\xrightarrow[{{\text{Welding}}}]{{{\text{Squeezing}}}}{\text{O - tube}} $ . Gap width and roundness of C-tube (configuration like letter ??C??) were two dominant parameters to evaluate the bending performance. The effects of blank positioning on both of them were investigated by means of numerical simulation. Laser-welded tubes meeting roundness and the tolerance limit of diameter were produced. Simulation revealed that effective plastic strain along circumferential direction was much low, mostly ranging between 0.03 and 0.05. Severe thinning and shape defects were not observed in the finished tubes. A numerical model was developed and its effectiveness was verified by a comparison between the predicted results and the corresponding experiments.     

空间弯管仿真与回弹补偿

回弹是空间弯管成形的主要成形缺陷。为了预测和补偿空间弯管成形中的回弹,通过编写用户幅值子程序（UAMP）,将有限元法应用于空间弯管的成形和回弹分析,提出了一种从仿真结果中提取管材中心线的方法。通过圆柱螺线形弯管成形的仿真计算,建立了管材回弹前后中心轴线曲率、挠率的关系。提出了一种基于求解曲线基本方程的空间弯管模具型面补偿方法,论述了曲线几何补偿的数学依据。通过对曲率和挠率(均为非常值)曲线进行补偿计算和成形仿真,对该方法进行了验证。结果表明该方法能够有效补偿回弹误差,保证弯管精度。