基于 ＵＧ 的五轴数控渐进成形轨迹生成研究

针对金属板材五轴数控渐进成形轨迹生成的需求,研究了基于UG的五轴数控渐进成形轨迹生成方法.为使挤压工具能够按照用户所希望的方向挤压板材,给出了五轴数控渐进成形中基于前倾角和侧倾角的挤压工具姿态定义方法.研究了基于等残留高度的五轴不等层间距等高线轨迹生成方法以及交错运动轨迹生成方法,并给出了五轴数控渐进成形加工轨迹应用实例仿真.     

金属板材单点渐进成形过程的数值模拟

利用有限元软件LS_DYNA模拟金属板材单点渐进成形过程。并利用LS_DYNA的显式求解器分析当压头压下时,不同压头半径条件下,压头与板材接触区域的应力分布。根据对模拟数据的分析比较,讨论不同压头半径对板材成形时的影响。     

板料零件数控渐进成形工艺研究

板料零件数控渐进成形工艺是一种通过数字控制设备 ,采用预先编制好的控制程序逐点成形板料零件的柔性加工工艺。本文就板料零件数控渐进成形工艺的成形过程、变形机理、极限半顶角等方面进行了探讨。认为 ,板料零件数控渐进成形是使板料的厚度减薄 ,表面积增大 ,靠逐次的变形累积产生整体的变形。变形区厚度的变化与成形半顶角有关 ,其中 ,成形极限半顶角是数控渐进成形能否成功的关键 ,它不仅与材料有关 ,而且与板料厚度有关。     

波动加工轨迹驱动的板料锤击渐进成形时间研究

为深入了解工艺参数对波动加工轨迹驱动的板料锤击渐进成形时间的影响规律,选择工具直径、工具进给速度、垂直层进给量、波长以及振幅等5个工艺参数为因素,以成形阶梯型锥杯时间为指标,进行正交实验,并对实验结果进行极差分析和方差分析。研究结果表明:垂直层进给量对成形时间有显著影响,而其他4个工艺参数的影响不显著;成形时间随工具垂直层进给量、工具进给速度、波长和工具直径的增加而减少,随振幅的增加而增加。研究结果为合理选择工艺参数、减少波动加工轨迹驱动的板料锤击渐进成形时间提供了理论依据。     

Experimental investigations and numerical analysis for improving knowledge of incremental sheet forming process for sheet metal parts

The paper is related to the analysis of shape distortions and springback effects arising in single point incremental sheet forming in order to study the use of a FE model based on shell elements to perform simulation of the process. A comparison between numerical and experimental results is made to assess the suitability of the model. The measurements of geometrical profile of a truncated cone and springback of cut rings show that the FE model allows to predict accurate results for a set of well defined process parameters. The deformation mechanism of ISF is taken into consideration to determine the limits of the model studied.     

金属薄板直壁件数字化渐进成形过程的实验研究

金属薄板直壁件的成形是数字化渐进成形技术中的热点和难点之一。本文基于数字化渐进成形的基本原理提出了一种加工金属直壁件的方法,在实验中研究金属薄板直壁件的成形过程,了解直壁成形机理和控制成形过程的工艺措施。     

The mechanics of incremental sheet forming

The deformation mechanism of incremental sheet forming (ISF) is examined experimentally through forming specially prepared copper sheets. Strain distributions through the thickness of the sheets are measured for two configurations of ISF: two-point incremental forming (TPIF) and single-point incremental forming (SPIF), and a comparison is made to pressing. The measurements show that the deformation mechanisms of both SPIF and TPIF are stretching and shear in the plane perpendicular to the tool direction, with shear in the plane parallel to the tool direction. Strain components increase on successive laps, and the most significant component of strain is shear parallel to the tool direction. Increasing stretching and shear perpendicular to the tool direction account for differences between the sine law prediction and measured wall thickness for both SPIF and TPIF. The observed mechanisms of SPIF and TPIF differ from a mechanism of pure shear that has previously been assumed.     

薄板无模分层成形技术

本文介绍了薄板无模分层成形技术的基本原理 ,优点以及工具运动轨迹的生成     

The influence of tool rotation on an incremental forming process

Incremental forming is a sheet metal forming process characterized by high flexibility; for this reason, it is suggested for rapid prototyping and customised products. On the other hand, this process is slower than traditional ones and requires in-depth studies to know the influence of certain process parameters.The purpose of this study is to investigate the influence of tool rotation on an incremental forming process. Pyramid frusta are created for different speeds and both directions of tool rotation, starting with aluminium alloy sheets; a punch with hemispherical head is used as tool.The variation of speed of tool rotation puts into the variation of friction coefficients, so these ones are preliminarily evaluated for different speeds, in order to explain the influence of tool rotation in terms of forming forces, temperatures reached and surface roughness. The evaluation of these quantities highlights the influence of tool rotation, both in terms of speed and direction of rotation, on the components of the forming forces in the sheet plane, whereas neither the heating of the sheet caused by the friction nor the surface finishing feel the effects of this parameter significantly.     

缓面零件单点渐进成形刀具轨迹优化数值模拟

利用有限元软件ANSYS/workbench,以平缓曲面零件为例,模拟零件单点渐进成过程,研究了优化方法中增量角度Δθ对零件厚度、成形精度、等效应变等方面的影响,并与传统固定增量步长方法进行对比。结果表明:加工层数相同时,优化方法更有助于提高板厚,且零件壁厚随着增量角度Δθ的增加而增加;优化方法较明显的提高了零件底部成形精度,无论增量角度Δθ取值多少,零件底部都能充分成形,与实验结果相吻合;加工层数相同时,在相同区域优化方法导致的板料等效应变大于固定增量步长成形方法,Δθ越小应变越均匀,但两种方法最终的等效应变趋于一致。     

Exergy analysis of incremental sheet forming

Research in the last 15 years has led to die-less incremental forming processes that are close to realization in an industrial setup. Whereas many studies have been carried out with the intention of investigating technical abilities and economic consequences, the ecological impact of incremental sheet forming (ISF) has not been studied so far. Using the concept of exergy analysis, two ISF technologies, namely single sided and double sided incremental forming, are investigated and compared to conventional forming and hydroforming. A second exergy analysis is carried out with the purpose of examining the environmental impact of different forming technologies from a supply chain perspective. Therefore, related upstream activities (die set production, aluminum sheet production and energy conversion and supply) are included into the exergy analysis. The entire supply chain is modeled with Matlab/Simulink. The results of both analyses suggest that ISF is environmentally advantageous for prototyping and small production runs.     

In-situ springback compensation in incremental sheet forming

Limited geometric accuracy in incremental sheet forming is a major obstacle for its wide adoption in industry. This paper develops a generic methodology, suitable for arbitrary part geometries and various ISF processes, for addressing one of the main causes of geometric inaccuracy, i.e., in-process springback. The methodology consists of three main elements: determination of key control points to treat geometric complexity, simplified simulation models to predict springback offline, and in-situ toolpath modification during forming. It is shown experimentally that the method provides an efficient and robust solution for various geometries with negligible setup cost.     

The strain path and forming limit analysis of the lubricated sheet metal forming process

Few previous attempts have been made to analyze numerically the strain path and the forming limit in complex lubricated sheet metal forming. Since usual approaches of solving the lubrication model are limited to axisymmetric and plane strain cases only, this paper developed a unified procedure for combining the finite element code of sheet metal forming, the current lubrication/friction model and forming limit theory, to predict the strain path and fracture strains for either a steady or an unsteady three-dimensional process including both axisymmetric and plane strain cases. The availability of the method must be proved by a published problem, and an axisymmetric stretch forming process was therefore adopted as a benchmark. Numerical results showed that the present analysis provides good agreement with the experimental data of the strain path and the fracture strain for various tribological parameters such as lubricant viscosity and composite roughness of tooling and workpiece, and the advantage of the developed model is that it can be applied to solve the complicated 3D geometric problems.     

板料单点渐进成形数值模拟研究

板料单点渐进成形过程变形复杂、影响因素多,工艺参数选择是提高成形质量和成形效率的关键。对单点渐进成形过程进行数值模拟,分析了成形件的应力分布和厚度变化以及成形路径、进给量等工艺参数对成形过程的影响。结果表明:成形件最大应力和最大厚度减薄发生在底面附近;采用螺旋进给方式可有效提高成形质量和成形效率。实验结果显示,实验结果与数值模拟结果基本吻合。     

板料增量成形的研究进展

板料增量成形是采用简单模具对板料进行逐次塑性加工的一种工艺,不需要专用的模具就可以成形较为复杂的零件,同时还具有成形力小、柔性高的特点,特别适合多品种小批量零件的生产方式,因此得到国内外学者的重视。本文重点从板料的增量压弯成形、增量拉深胀形、增量微成形3个方面对板料增量成形的发展进行综述,还对板料增量成形工艺的发展前景进行了展望,指出进行理论创新、开发新的模拟软件、探索新的成形方案、开发增量成形新设备是发展趋势。     

板料点压渐进成形的成形性能研究

板料渐进成形技术作为柔性制造技术,其研究已经取得相当进展。但是在进给轨迹连续的普通渐进成形中,材料在成形过程容易产生沿轨迹方向的推挤,而产生不必要的变形,影响加工能力和加工质量。通过圆弧沟槽实验,对比点压渐进成形和连续渐进成形,发现点压渐进成形可获得的沟槽长度为60.5 mm,大于连续渐进成形中48.9 mm的沟槽长度;破裂位置最大主应变分别为1.212和0.982,说明板料点压渐进成形时的成形性能比连续渐进成形好。通过改变点压渐进成形中正弦波的波长和振幅,说明两参数对成形性能的影响。采用成形性能更好的点压渐进成形,可减少多道次渐进成形的成形道次,拓展渐进成形所能成形的零件结构类型。     

Laser-assisted asymmetric incremental sheet forming of titanium sheet metal parts

Asymmetric Incremental Sheet Forming (AISF) is a relatively new manufacturing process. In AISF, a CNC driven forming tool imposes a localized plastic deformation as it moves along the contour of the desired part. Thus, the final shape is obtained by a sequence of localized plastic deformations. AISF is suitable for small series production of sheet metal parts as needed in aeronautical and medical applications. Two main process limits restrict the range of application of AISF in these fields. These are the low geometrical accuracy of parts made from titanium alloys or high strength steels and, for titanium alloys, the limited formability at room temperature. In this paper a new concept for laser-assisted AISF is introduced including the required components. Furthermore, the CAX tools used for programming the NC path for the forming tool and the laser spot are illustrated. First experimental results show that the formability of the alloy Ti Grade 5 (TiAl6V4), which is usually used in aeronautic applications, can be increased.     

75°锥形件渐进成形路径的参数化

对于渐进成形工艺成形锥形件,当成形角度大于极限成形角时,需采用多道次成形。多道次成形路径设计相对复杂,通过参数化路径可有效简化成形路径设计过程。文章基于ANSYS/LS-DYNA平台建立了金属板料外轮廓支撑渐进成形的有限元模型,以壁厚均匀为目标,通过数值模拟对一定口径和深度的75°锥形件进行路径设计和优化,得到了75°锥形件渐进成形的参数化路径方程,并对其进行实验验证。验证结果表明,该参数化路径在一定范围内可行。     

镁合金板料工具转动渐进成形工艺参数实验研究

用正交试验的方法研究了AZ31镁合金板料工具转动渐进成形过程中工艺参数对板料成形性能的影响,试验采用变角度锥杯模型,并以成形破裂角作为试验指标。结果表明:单一因素对AZ31镁合金渐进成形性能的影响从主到次的顺序为主轴转速Z轴进给量工具头直径进给速度工具材料,主轴转速是影响镁合金板料成形性能的最主要因素,在保证板料成形性能和表面质量的前提下,为节约时间,尽量选用快的进给速度和大的Z轴进给量和工具头直径,工具材料对成形性能影响很小,可以忽略。正交试验中最优工艺参数组合:工具转速4500 r·min-1,进给速度300 mm·min,Z轴进给量0.3 mm,工具头直径Φ12 mm,工具材料HSS4341,成形破裂角为88.25°。     

Springback prediction for incremental sheet forming based on FEM-PSONN technology

In the incremental sheet forming (ISF) process, springback is a very important factor that affects the quality of parts. Predicting and controlling springback accurately is essential for the design of the toolpath for ISF. A three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those from the experiment. The springback angle was found to be in accordance with the experimental result, proving the FEM to be effective. A coupled artificial neural networks (ANN) and finite element method technique was developed to simulate and predict springback responses to changes in the processing parameters. A particle swarm optimization (PSO) algorithm was used to optimize the weights and thresholds of the neural network model. The neural network was trained using available FEM simulation data. The results showed that a more accurate prediction of springback can be acquired using the FEM-PSONN model.