筒形件磁脉冲辅助冲压成形数值模拟

针对磁脉冲辅助冲压成形过程,提出了基于ANSYS平台的有限元分析程式,通过编制用户子程序,采用重启动分析法,建立了冲压预成形过程显式求解和瞬态磁脉冲成形"松散"耦合分析之间的动态连接,并用于5052-O铝合金圆筒形拉深件磁脉冲辅助冲压成形过程的有限元仿真研究。结果表明,所建立的有限元分析方案,能实现圆筒形件磁脉冲辅助冲压成形连续变形过程的模拟,板坯变形信息体现了准静态冲压变形和高速率磁脉冲成形之间的耦合。有限元模拟结果与实验吻合较好。     

Tooling-integrated sensing systems for stamping process monitoring

In-situ stamping process monitoring plays a critical role in enhancing productivity and ensuring part quality in sheet metal stamping. This paper investigates the realization of two sensing methods to create a tooling-integrated sensing system: mutual inductance-based displacement measurement for sheet draw-in, and distributed contact pressure measurement at the tool–workpiece interface. The two sensing systems are complementary in nature, and together, they significantly enhance the on-line observability of the stamping process. The performance of the draw-in sensor was evaluated using numerical simulations and experiments in a small-scale and a large-scale lab setup, and its effectiveness has been confirmed under the presence of wrinkled sheet. To study the spatial and temporal variations of the tool–workpiece contact pressure in a stamping operation, experiments were conducted on a customized panel stamping test-bed with an array of thin-film force sensors embedded below the die flange and die cavity. The force sensor data were then numerically interpolated to form the contact pressure distribution across the tool–workpiece interface, based on the thin plate spline (TPS) method. Comparison between the interpolated pressure obtained from the surface generation techniques and direct measurement using redundant sensors and a press mounted load cell confirms the validity of the new contact pressure sensing method. The integrated sensing technique provides insight into the stamping process by quantifying process variations and providing a reference base for process control to reduce product disparities. Additionally, new product and process designs can be created based on the quantified and referenced variations.     

Numerical modeling and deformation analysis for electromagnetically assisted deep drawing of AA5052 sheet

Electromagnetic forming(EMF) is a high-velocity manufacturing technique which uses electromagnetic (Lorentz) body forces to shape sheet metal parts. One of the several advantages of EMF is the considerable ductility increase observed in several metals, with aluminum featuring prominently among them. Electromagnetically assisted sheet metal stamping(EMAS) is an innovative hybrid sheet metal processing technique that combines EMF into traditional stamping. To evaluate the efficiency of this technique, an experimental scheme of EMAS was established according to the conventional stamping of cylindrical parts from aluminum and the formability encountered was discussed. Furthermore, a “multi-step, loose coupling” numerical scheme was proposed to investigate the deformation behaviors based on the ANSYS Multiphysics/LS-DYNA platform through establishing user-defined subroutines. The results show that electromagnetically assisted deep drawing can remarkably improve the formability of aluminum cylindrical parts. The proposed numerical scheme can successfully simulate the related Stamping-EMF process, and the deformation characteristics of sheet metal reflect experimental results. The predicted results are also validated with the profiles of the deformed sheets in experiments.     

Experimental Observations of Quasi-Static-Dynamic Formability in Biaxially Strained AA5052-O

To establish the efficacy of electromagnetically assisted sheet metal stamping (EMAS), a series of combined hydraulic bulging and electromagnetic forming (EMF) experiments are presented to evaluate the biaxial quasi-static-dynamic formability of an aluminum alloy (AA5052-O) sheet material. Data on formability are plotted in principal strain space and show an enhanced biaxial formability beyond the corresponding experimental results from conventional forming limit diagram. The plastic strains produced by the combined process are a little larger than or at least similar with those obtained in the fully dynamic EMF process. In addition, the biaxial forming limits of aluminum sheets undergoing both very low and high quasi-static prestraining are almost similar in quasi-static-dynamic bulging process. Limit formability seems to depend largely on the high-velocity loading condition as dictated by EMF. It appears that in quasi-static-dynamic forming, quasi-static loading is not of primary importance to the material’s formability. Based on these observations, one may be able to develop forming operations that take advantage of this formability improvement of quasi-static-dynamic deformation. Also, this could enable the use of a quasi-static preform fairly close to the quasi-static material limits for the design of an EMAS process.     

A comparative study of stamping and hydroforming processes for an automobile fuel tank using FEM

The use of sheet metal in the hydroforming process for hollow bodies is a new manufacturing technology for the automotive industry. In this paper, a comparison is made between the forming processes of sheet hydroforming and conventional stamping for production of an automobile fuel tank using a commercial explicit FEM code. A modeling methodology for correlation between stamping and hydroforming is proposed in order to obtain the optimal process parameters for producing a sound hydroformed fuel tank. The simulation model for a conventional stamping process is also verified by comparison with experiment. Finally, it is concluded that the hydroforming process can produce a fuel tank with a more uniform and sound thickness distribution than the stamping operation.     

板材多点成形与模具成形过程的比较研究

利用有限元方法对板材模具成形和多点成形的变形特点进行了分析,并在此基础上就不同成形方法对起皱的抑制作用进行了对比,确定了不同成形方法起皱开始发生时的临界曲率及临界厚向应变。结果表明：多点压机成形方法能够得到比多点模具成形和整体模具成形时变形程度更大且厚度变化更加均匀的制品。     

基于MSC.Patran几何模拟技术预测板料成形毛坯外形

基于MSC．Patran对冲压成形的计算机辅助技术一几何模拟技术进行了探讨研究。研究了几何模拟的关键技术，同时结合抛物曲面的拉深，在MSC．Patran环境下实现了用几何模拟技术预测毛坯并得到较为满意的毛坯形状和应变分布。     

Reduction of a pre-formed radius in aluminium sheet using electromagnetic and conventional forming

Electromagnetic (EM) forming is a high-speed forming process that uses the forces induced on a conductive workpiece by a transient high frequency magnetic field to form the workpiece into a desired shape. This paper describes the results of a work undertaken to study the reduction of a 20 mm radius to 5 mm in 1 mm AA 5754 sheet by conventional metal forming process and by electromagnetic forming. The combination of conventional and EM forming will be referred to as “hybrid forming”. The 20 mm radius was pre-formed from flat sheet using a conventional die, punch and binder that allowed the material to draw in. The radius was then reduced to 5 mm, with no draw-in allowed for either process. Sheets were studied in the as-received condition and were also pre-strained to 5%, 10% and 15% to simulate strain path effects in a multiple stage forming operation. The process was modelled numerically to gain insight into the stress, strain and strain rate histories. The research indicates that features that are not achievable using traditional stamping techniques can be obtained with the aid of EM forming.     

Research on formability of 5052 aluminum alloy sheet in a quasi-static–dynamic tensile process

In order to establish the efficacy of electromagnetically assisted sheet metal stamping (EMAS), the formability of 5052 aluminum alloy sheet in a quasi-static–dynamic tensile process is experimentally investigated using a combined quasi-static tension and the pulsed electromagnetic forming (EMF) method. Data on the formability of aluminum alloy 5052-O employing this combined loading method is compared with data for traditional quasi-static tensile tests. Results show that the formability of aluminum alloy sheet undergoing a quasi-static–dynamic tensile process is dramatically increased beyond that exhibited in quasi-static tensile tests, and a little higher than or at least similar with that obtained in the fully dynamic EMF process. The forming limits of aluminum samples with both low and high pre-strain levels are almost similar in quasi-static–dynamic tensile process, which makes it possible stretching the sheet to a higher quasi-static pre-strain level without weakening its total quasi-static–dynamic formability. This would enable the use of a quasi-static pre-form fairly close to the quasi-static material limits for design of an EMAS process in manufacturing large aluminum alloy shell parts.     

基于状态空间法的板料成形过程闭环控制系统的建模及仿真

冲压过程中,因材料的性能参数、润滑条件的波动和模具参数的改变,导致冲压件质量的不稳定,因此必须提高冲压件质量的控制鲁棒性。压边力是板料冲压过程的重要工艺参数之一,合理控制压边力的大小,可以避免起皱或破裂等缺陷。文章提出了一种基于结合RBF神经网络和经典状态空间理论的板料成形过程控制策略,并建立了其控制模型。引入时序分析法,将压边力的调整与反映工件成形质量的法兰边的吸入量误差联系起来,同时应用非线性最小二乘法识别出增益系数。仿真结果表明,在加入一噪声后,仍能获得满意的冲压件质量,模型具有较高的控制鲁棒性。     

金属板材冲压成形技术与装备的现状与发展

本文首先介绍了我国金属板材冲压成形行业的生产规模及技术水平现状，简要介绍了一些具有市场发展潜力的板材成形新技术。在此基础上，对板材冲压模具行业的供需现状、模具材料状况等作了介绍。最后，本文以较大篇幅介绍了板材冲压设备行业的发展现状，并对目前板冲行业比较受关注的设备及技术作了介绍，这些设备及技术包括金自动压力机技术、单机联线自动化冲压生产线、多工位压力机系统、多连杆压力机及拉伸垫技术以及伺服压力机、高速压力机等。     

Inverse finite element approach and its application in sheet metal forming

The inverse finite element approach (IFEA) was derived from ideal forming to predict the development blank of sheet metal and the thickness strain distribution according to the geometry of final product. The flange portion of stamping product under blank-holder is a free parameter that is mostly dependent on the shape of the initial flat blank. Based on the IFEA, this paper proposed a node relocation technique to estimate the influence of flange shape and evaluate the final geometry and thickness strain distribution from the prescribed flat blank. The applications of the IFEA cover the backward and forward evaluations: from given product to initial blank and from given initial blank to final product. Those applications make the design of sheet metal forming easy and fast. A door-like product experiment confirmed that the precision of the IFEA satisfied the manufacturing requirement.     

大型薄板冲压液压机的全吨位低噪声冲裁缓冲装置

大型薄板冲压液压机在作冲裁工艺时,噪声大,工作吨位受到限制.利用步进电机驱动皮带轮方法实现了冲裁装置缓冲缸的同步调节,降低了冲裁噪声,实现了全吨位冲裁,提高了液压机的使用效率,延长了寿命,保证了大型汽车覆盖件的冲压质量.     

On-line measurement of contact pressure distribution at tool-workpiece interfaces in manufacturing operations

A new method is proposed for determining the contact pressure distribution (CPD) between the tool and the workpiece in sheet metal forming processes. Contact pressure is measured at discrete points at the tool-workpiece interface by sensors that are structurally embedded beneath the tooling surface. An analytical framework is developed for determining the pressure values between the sensing points through the construction of continuous CPD maps. This is achieved using the Thin Plate Spline (TPS) surface generation method, which creates temporal snapshots of the CPD during a forming process. The effectiveness of this technique is illustrated for a panel stamping operation.     

一种压力机智能检测控制系统的设计

本系统是将智能化检测控制系统与精密压力机结合的新一代机械压力机,由精密压力机、智能监测系统、多级智能控制系统等组成,是一种能对整机状态进行在线检测、故障预警和自适应控制的智能化成形加工设备,适用于各种冲压零件,尤其是引线框、变压器硅钢片等功能性精密冲压零件的生产,可以推广应用于建筑、汽车及电气和电子元器件等行业,提升相...     

板料多步冲压回弹的数值模拟研究

回弹是板料冲压成形过程中一种常见但很难解决的现象。首先研究了板料弯曲变形中卸载回弹的原理,然后以依维柯侧壁上内板为例,采用动态和静态算法相结合的方法,在考虑每道工序板料回弹的基础上,对其进行多步冲压回弹的数值模拟,最后对模拟结果和实验结果进行比较,验证该模拟方法提高回弹计算精度的有效性,为板料冲压成形工艺的制定提供科学依据。     

行李箱内板零件冲压成形分析

在材料力学性能测试和成形极限分析的基础上,采用网格应变分析技术研究了行李箱内板零件冲压过程危险区域的金属流动规律,评价了两种钢板的成形效果。结果表明：行李箱内板危险部位的变形方式为胀形一深拉延变形,r值和n值较高的冷轧薄板具有较高的成形极限,相应地其冲压成形安全裕度也较大。     

Transient dynamical analysis of strain signals in sheet metal stamping processes

On-line monitoring of stamping processes can be carried out based on various sensors, such as force, strain, acceleration, proximity, and acoustic emission sensors. The strain sensor signal is the most favourite because of its effectiveness and acquisition cost as well as it contains rich information about the stamping process. The key problem of stamping monitoring is how to extract features from the strain signal to effectively detect the faults. The strain signal, however, is a transient signal that depends on many factors. In this paper, it is intended to address some new methods to analyse the transient strain signal with the objective of decomposing it in order to understand the dynamics of the stamping process and extract a malfunction signal for fault detection. A latent process model method, which is a combination of a time-varying auto-regression model and a dynamic linear model, is initially presented. Continuous wavelet transforms and a new discrete wavelet transform (maximum overlap discrete wavelet transform) are then addressed to project the transient signal into a time scale plan to represent the dynamical behaviour in a different way. Empirical mode decomposition is finally employed to decompose the transient signal into a finite and often small number of intrinsic mode functions (IMF). The advantage of this new method is that it is adaptive and highly efficient. The performance of the methods employed in this paper is reviewed using two real strain signals in a sheet metal stamping process. It is found that these methods can efficiently provide the energy–frequency–time distribution of the transient strain signal.     

Evaluation of stamping lubricants using the deep drawing test

This paper presents a practical methodology that uses the deep drawing test and finite element (FE) analysis to evaluate stamping lubricants under near production conditions. In stamping operations good lubrication helps to reduce wrinkling, premature fracture, and localized thinning. Furthermore, lubrication also reduces tool wear in large-volume production. Determination of reliable friction data associated with a given lubrication system is also important for successful process design and simulation by FE analysis. In this study, five stamping lubricants (four dry film lubes and one wet lube) were evaluated using the deep drawing test. The performance of the lubricants were evaluated based on: (a) maximum punch force measured, (b) the maximum applicable blank holder force (BHF), (c) the draw-in length, (d) the perimeter of flange after test, (e) the change of surface roughness, and (f) the inspection of surface topography. The coefficient of friction for each lubricant tested was determined through the FE-based inverse analysis by matching the predicted and measured values of the load-stroke curve and the draw-in length. This study showed that one of the tested lubricants was most effective, regardless of test speed and the magnitude of BHF. The methodology used was shown to be effective in evaluating various lubricants for sheet metal forming and accurately differentiating their performances.     

基于板料冲压的有限元数值模拟

以圆筒形件成形过程为例,采用有限元分析软件MSC.Marc建立了数学仿真模型,对板料变形过程中的应力、应变分布、摩擦的分布以及摩擦系数与板厚的关系进行了分析.结果表明,模拟结果与实际情况相符合,说明用MSC.Marc软件可以正确的模拟板料成形过程,显著地提高计算速度及计算精度,对于CAE技术的工程应用有重要价值.