反向弧度变曲率拉弯成型中工艺参数研究分析

针对复杂截面型材的变曲率弯曲成型中的调试时间长、废品率高的问题,对其弯曲成型中工艺参数确定问题进行研究分析。以带有反向弧度变曲率的Ω型防撞梁成型为例,首先对拉弯成型工艺参数进行说明,然后通过理论计算、CAE分析与现场验证相结合的方式,对成型中工艺参数进行研究分析,最后得出了一种拉弯成型工艺参数确定的方法,同时总结各工艺参数之间相互匹配对成型结果的影响规律。该方法对提高调试安全性,缩短调试时间,减少调试废品有重要的意义,为后续类似产品的开发和调试提供借鉴。     

型材扭曲-拉伸-弯曲组合成形工艺研究

在介绍型材拉弯工艺的基础上,依据LWS-12-2000拉弯设备的结构特征和未来产品实现要求,提出了设备性能改进方案,给出了不同工况下成形应力的计算公式.讨论了组合成形工艺的加载顺序和潜在应用前景.     

新型汽车玻璃滑槽拉弯成形工艺

针对汽车玻璃滑槽的拉弯成形工艺,设计开发了一种基于张臂式拉弯机上安装的一次拉弯工装和非标二次拉弯设备相结合的新型加工工艺。该工艺通过二次拉弯工序,利用机械、电气和液压相结合的控制技术,实现了汽车玻璃滑槽的拉弯成形工艺。采用该工艺来加工汽车玻璃滑槽,具有调试简单和产品状态稳定等优点。     

玻璃钢美化通信塔的制造工艺及质量控制

玻璃钢因其优良的特性而在诸多领域得到广泛应用,介绍了玻璃钢美化通信塔的制造成型工艺、材料机械性能及其质量控制方法,提出了以拉挤成型工艺为主、手糊成型工艺为辅的制造方案。     

油田测井车铝合金型材拉弯装置的设计

通过对测井车使用的铝型材煨弯效率低、外观质量差等问题的分析,提出了采用拉弯的方案。对拉弯装置结构设计和工作原理及主要模具的设计作了说明,对拉弯转速、加工工艺和冲压工艺进行了计算和分析。     

电火花加工成型电极的研究

文章在分析带冠弯扭叶片整体涡轮盘加工状况的基础上,提出了采用成型电极靠模加工带冠弯扭叶片整体涡轮盘通道的加工方案,并讨论了该方案中整体涡轮盘通道几何造型、成型电极设计方案和加工工艺,成型电极进给路径确定等着急性技术问题。     

汽车顶盖流水槽辊弯成型工艺

介绍了辊弯成型产品的特点,并以汽车流水槽为典型零件进行了工艺分析,设计出它的成型制度.     

汽车顶盖流水槽辊弯成型工艺

介绍了辊弯成型产品的特点，并以汽车流水槽为典型零件进行了工艺分析，设计出它的成型制度。     

φ800mm鲁奇式加压气化炉壳体的焊接

介绍了先进的鲁奇炉代表型MARK#Ⅳ/4型φ3 800 mm鲁奇式加压气化炉壳体的焊接工艺及相关要求。根据产品的结构特点确定试验方案,在试验的基础上针对产品制造过程中的一些疑难问题进行方案论证和工艺攻关。制订了科学合理的焊接工艺方案,采取一系列措施保证产品质量和控制焊接变形,实现壳体纵环缝焊接采用窄间隙埋弧焊自动跟踪压道焊工艺。成功地解决了鲁奇式φ3 800 mm加压气化炉壳体焊接在质量性能、控制焊接变形等方面存在的难题,获得了满意的焊接效果。该项目的研制成功为承制大型疲劳容器和耐高温、高压的机械传动设备积累了宝贵的经验。     

钢板预弯机工艺参数研究

探讨了目前大口径直缝埋弧焊管JCO预弯成型工艺参数计算中存在的问题,采用幂指数强化弹塑性模型对预弯成型过程进行理论分析,获得了预弯长度、压制行程、成型力等计算公式,并利用VB编程进行了数值计算,通过实际生产验证了理论计算的正确性。实际应用结果表明:该计算方法可以快速准确地制定预弯工艺参数,并能提高成型质量。     

考虑弯曲回弹的拉弯模外形设计方法

拉弯是型材弯曲成形的重要方法,可以有效减少回弹、提高成形精度,在飞机、汽车弯曲件成形中得到广泛应用。采用弯曲回弹理论分析,结合拉弯零件数字化模型,修正拉弯模模具轮廓;采用圆弧样条表示模具轮廓,给出了拉弯模合理外形的计算方法。在理论分析基础上,通过有限元分析方法计算拉弯型材的回弹量,评估拉弯模型面的回弹修正量及拉弯件校形余量的减少情况。为提高汽车和飞机拉弯件的质量和促进工装的数字化设计提供了合理有效的方法。     

管材拉弯工艺及数值模拟分析

拉弯是管材弯曲成形的重要工艺方法,采用有限元分析软件ANSYS/LS-DYNA对不同工艺参数下的管材拉弯成形过程进行了数值模拟,通过改变相对弯曲半径R/D和相对弯曲厚度t/D,分析了拉弯工艺参数对成形过程的影响。研究结果表明:通过增大相对弯曲半径R/D或增大相对弯曲厚度t/D,降低弯曲件的等效应力,可以有效控制弯曲件壁厚的变化,有助于提高管材拉弯成形的质量。     

数字化环境下的拉形模制造

拉形模是成形飞机蒙皮的重要工艺装备。本文通过对拉形模传统制造工艺方法与现代制造工艺方法的比较,探讨了数字化环境下拉形模的设计和制造工艺以及新材料的应用情况。     

Springback prediction and optimization of variable stretch force trajectory in three-dimensional stretch bending process

Most of the existing studies use constant force to reduce springback while researching stretch force. However, variable stretch force can reduce springback more efficiently. The current research on springback prediction in stretch bending forming mainly focuses on artificial neural networks combined with the finite element simulation. There is a lack of springback prediction by support vector regression(SVR). In this paper, SVR is applied to predict springback in the three-dimensional stretch bending forming process, and variable stretch force trajectory is optimized. Six parameters of variable stretch force trajectory are chosen as the input parameters of the SVR model. Sixty experiments generated by design of experiments(DOE) are carried out to train and test the SVR model. The experimental results confirm that the accuracy of the SVR model is higher than that of artificial neural networks. Based on this model, an optimization algorithm of variable stretch force trajectory using particle swarm optimization(PSO) is proposed. The springback amount is used as the objective function. Changes of local thickness are applied as the criterion of forming constraints. The objection and constraints are formulated by response surface models. The precision of response surface models is examined. Six different stretch force trajectories are employed to certify springback reduction in the optimum stretch force trajectory, which can efficiently reduce springback. This research proposes a new method of springback prediction using SVR and optimizes variable stretch force trajectory to reduce springback.     

Study on one-step simulation for the bending process of extruded profiles

Traditional one-step approaches are either based on the membrane element in which bending effects cannot be considered or based on the simplified shell element in which the initial blank is flat and the curvatures are kept unchanged in the one-step iterative computation. They are not suitable for the bending process of extruded profiles. In order to inspect the formability and possible forming defects in profile bending for preliminary designs quickly and to provide an efficient finite element computation for process analysis, a new one-step approach is presented. In this approach, instead of the traditional simplified shell element, the rotation-free basic shell triangular element is introduced to consider bending effects and make the new one-step approach suited to the simulation of profile bending. On the basis of the presented one-step approach, an in-house program named profile bending simulation-one step (PBS-ONESTEP) has been developed to simulate stretch bending of aluminum extrusions and three-point bending of stainless steel extrusions. The algorithm for initial guess solution of extruded profiles is described. Sliding constraint and the penalty method are adopted to treat contacts for the two numerical examples, respectively. The numerical results of PBS-ONESTEP simulation are compared with those of ABAQUS/EXPLICIT incremental analyses and experiments.     

Numerical and experimental study of stretching effect on flexible forming technology

The flexible stretch forming technology (FSFT) is suitable for flexible manufacturing because it affords several advantages including applicability to various forming processes such as sheet metal forming, single curved surface forming, and quadratic curved surface forming. In this study, the formation of a quadratic curved surface with a saddle-type shape by the flexible stretch forming process is systematically investigated through a numerical simulation. A 4-mm-thick Al 3003-H14 aluminum alloy is used as the initial blank material. Urethane pads are defined based on a hyperelastic material model as a cushion for the smooth forming surface. The elastic recovery deformation behavior is also investigated to consider the exact result after the last forming process. The simulation indicates that the stretch forming process can be used to apply more stress to the blank and to reduce the elastic recovery effect. An experiment was then performed to confirm the process formability and reduction of the elastic recovery effect. A comparison of the objective surface between the simulation and the experimental results verified that the stretch forming process reduced the elastic recovery effect. This confirms that FSFT can be feasibly used to manufacture quadratic curved surfaces.     

Sectional finite element analysis of forming processes for aluminum-alloy sheet metals

The sectional finite element analysis of the forming processes for the aluminum-alloy sheet metal known to be planar anisotropic was performed. The two-dimensional rigid-viscoplastic FEM formulation based on the bending augmented membrane theory as well as the anisotropic yield criteria was introduced. For modeling the anomalous behavior of aluminum-alloy sheet metals, Barlat's strain rate potential and Hill's (Journal of the Mechanics and Physics of Solids 1990;38:405–17) non-quadratic yield theory with an isotropic hardening rule were employed. Furthermore, a new method to determine anisotropic coefficients of Barlat's strain rate potential was proposed. For evaluating bending effects in the forming process of aluminum-alloy sheet metals, the bending equivalent forces were calculated in terms of the changes in the interior angle at a node between two linear finite elements and were augmented to the membrane stretch forces. In order to verify the validity of sectional finite element formulation based on the bending augmented membrane theory, the plane strain stretch/draw forming processes of a square cup test were simulated and simulation results are compared with experimental measurements. Friction coefficient was obtained from drawbead friction test. The properties of selected material were obtained from uniaxial tensile tests. Simulation shows good agreement with measurements. For the application of the sectional finite element formulation introduced in this research, the drawing process of a rear seat back upper bracket of passenger cars is simulated assuming plane strain condition. The thinning distribution of the simulation agreed well with that of the measurement, so that the sectional analysis is acceptable in the design and analysis of aluminum-alloy sheet stamping dies.     

Sensitivity of model parameters in stretch bending of aluminium extrusions

Stretch bending is a process of considerable importance for plastic forming purposes. Effective operations in the industry demand sufficient knowledge of how different parameters influence the process as well as the final shape of the product. Numerical simulations are an effective way of investigating these issues. However, the numerical model must be validated in order to obtain reliable results. This paper presents an analysis model in the code LS-DYNA which is shown to represent the behaviour in laboratory tests well. The model is subsequently used to check the influence of certain parameters on the response in a stretch bending process. Simple, analytical methods are also presented. It is shown that the local deformations of the cross-section during bending are primarily controlled by the geometry and tensile force level. The main parameters influencing the springback during unloading are the strain hardening properties of the material, and the tensile force.     

Flexible 3D stretch-bending technology for aluminum profile

As the consumption of fossil energy from the traffic system increases, the need for 3D structural parts which provide the design engineer a lighter, stiffer, and more energy-efficient structure is required. A new flexible 3D stretch bending process (FSB) with multi-points dies (MPD) is thus being developed. This study seeks to find out the relationship between the springback error and the adjustment parameters for the FSB process. At first, the structure of flexible fundamental unit (FFU) with four degrees of freedom (DOF) MPD was designed and implemented. Then the FSB experiments with different bending radius of curvature and materials were carried out based on prototype of the flexible 3D stretch bending equipment. The experiment results show that the springback error increased linearly along the length of the workpiece. Without using the post-stretch force, the springback error declined from 7.90 % to 0.80 % by adjusting the positions of the FFU. Most importantly, the surface defects of the forming parts such as wrinkle and crack can be eliminated in this process.