To solve the problem of springback in traditional multi-point forming (MPF), a new multi-point forming process, namely, multi-point forming with individually controlled force–displacement (MPF-ICFD), is proposed. In this manuscript, traditional MPF and MPF-ICFD are compared. Taking the cylindrical surface as the research object, the change in the springback of a plate is analysed by experiments, and the distribution of the strain and wall thickness of the plate is analysed by numerical simulation. Theoretical analysis is used to calculate the forming window for the MPF-ICFD process, and the results from theoretical analysis are verified by experiments and numerical simulation. The results show that the springback of 1060 aluminium alloy and Q295 for MPF-ICFD can be decreased by 73.8% and 45.5%, respectively, compared with traditional MPF. In traditional MPF, the strain uniformity of the plate is poor, and the maximum thinning rate is 4.5%. For MPF-ICFD, the strain is relatively uniform, and the maximum thinning rate is 0.25%. For an aluminium alloy sheet with a wall thickness of 1.5–3 mm, the upper and lower limits of the forming force for a single head are observed to change linearly from 6.3 to 12.6 kN and from 0.5 to 1 kN, respectively.

提出了触变软芯复合锻造成形技术,以某型铝钢双金属标准圆柱直齿轮为成形对象,通过有限元模拟研究了不同钢质层初始壁厚以及初始温度时的双金属协调变形行为.结果表明,铝/钢协调变形行为主要受钢质层初始壁厚与半径的比值影响;铝/钢在协调变形过程中形成机械互锁,钢质层齿顶壁厚增加,齿根壁厚明显减薄,成为开裂危险区;提高钢质层温度有助于改善其流动性,但温度过高时,铝芯接触到钢质层后被快速加热,流动应力大幅降低而流动紊乱.钢管初始温度为1 100℃、初始壁厚为4 mm时,齿轮成形品质较好.基于仿真分析设计了成形试验,获得了成形品质良好的铝钢双金属齿轮,证明触变软芯复合锻造技术可实现复杂铝钢双金属构件近净成形.

采用半固态触变锻造技术成形铝合金构件,容易实现轻量化、低成本、短流程制造,因此在汽车、航空航天等领域应用广泛,但是对于高强铝合金复杂形状构件触变锻造存在半固态坯料制坯工序复杂、制件固液偏析严重和力学性能较弱等问题.基于SIMA制坯方法 ,提出了分级热处理、快速感应重熔和梯度等温处理等重熔工艺以及触变-塑变复合成形等新成形技术,优化了变形铝合金二次重熔半固态组织调控和触变锻造技术,获得了良好的半固态球晶组织并成形出合格的制件,最后提出了铝合金触变锻造成形中仍需解决的问题和发展方向.

采用三段式感应加热研究了半固态7075铝合金挤压棒材的组织演变规律.以某型号尾翼结构件为研究对象,设计了尾翼半固态触变成形模具,研究了7075高强铝合金尾翼半固态触变-塑变复合近净成形的组织.当平均加热速度为4℃/s时,坯料上端最高加热温度为620℃,保温5 min,制件复杂薄壁部位成形完整,尺寸精度高,其纵截面的微观组织为半固态到固态的梯度分布状态.

In order to solve the problem of wrinkling in traditional multi-point forming (MPF), a new multi-point forming process, namely multi-point forming with individually controlled force-displacement (MPF-ICFD), was proposed. The core idea of this process is to impose a full-area normal constraint on the sheet metal during the whole forming process. Therefore, the deformation sequence of the sheet metal is changed from the local constraint and the whole deformation in the traditional MPF to the whole constraint and the local deformation so as to completely eliminate the noncontact region and avoid wrinkling. In this paper, the saddle surface part was taken as the research object. The influence of normal restraint on critical wrinkle stress is studied by mechanical analysis, and the wrinkle restraint mechanism under normal restraint is revealed. The deformation behavior of saddle surface parts was studied by forming experiments, and the wrinkling law of saddle surface parts under different constraints is obtained. The deformation characteristics of saddle surface parts were analyzed by numerical simulation, and the critical stress distribution rules of the sheet metal were given. It is shown that the critical wrinkling stress of the sheet metal is significantly increased in MPF-ICFD compared with that in traditional MPF, and the increased value is proportional to the magnitude of normal constrained force. Besides, the wrinkling phenomenon of saddle surface parts is significantly suppressed, and the surface quality of workpiece is obviously improved. In addition, the stress state change from compressive stress to tensile stress in the core region of the sheet metal was prone to wrinkle.

In order to study the shape accuracy of multi-point forming (MPF) process for sheet metal under normal full constrained conditions, the in-depth analysis of shape accuracy of workpieces in multi-point forming with individually controlled force-displacement (MPF-ICFD) process is conducted in this paper by combining experiment, theoretical analysis and numerical simulation. The influences of normal force, material thickness and material properties on the shape accuracy of the feature surface are studied, and the shape accuracy characteristics of the sheet under different parameters are obtained. Afterwards, the stress and strain characteristics of sheets are obtained by numerical simulation. Finally, the effect of normal force on shape accuracy was revealed by establishing a mechanical model of the sheet metal under normal full constrained conditions. Moreover, the amount of springback reduction in MPF-ICFD is defined quantitatively. Compared with the normal unconstrained conditions, the shape accuracy of sheet metal is improved significantly under normal full constrained conditions. The stress and plastic deformation are more uniform and the amount of springback is smaller. For Q 295 steel plate with thickness of 2.0 mm, the difference between the maximum value and the minimum value of the reaction force of punch decreases from 4515.9 N to 1475 N when the forming force is 2500 N. Besides, the bending moment of the sheet on the unit width decreases from 357.9 N • mm to 328.1 N • mm. The average shape error E rr and the amount of springback Δk decreases by 60.05% and 16.03%, respectively.

目的 对比研究力-位移分控多点弯曲成形的受力和变形特点,揭示力-位移分控多点成形技术改善成形质量的机理.方法 首先设计制造出采用力-位移分控多点成形原理成形的实验装置,并进行圆柱面的实际成形,比较不同成形模式下所获得成形制件的差异,然后采用理论分析和数值模拟等手段,分析对比不同成形模式的受力与变形条件,探讨不同成形模式下的变形特点与规律.结果 从理论上给出了力-位移分控多点成形能有效减小回弹、消除"直边效应"的力学原理,指出了力-位移分控多点成形技术减小回弹的根本原因在于法向约束力的作用,且回弹减小量与法向约束力的大小成正比,并通过数值模拟,从应力和应变分布、支反力变化等方面予以了验证.结论 力-位移分控多点成形从本质上改变了板材的受力和变形条件,能有效提升成形质量.

In order to provide simple and practical experimental equipment for the experiment of forging technology course, based on the impact cylinder, the pneumatic hammer used in experiment of forging process course was developed. According to upsetting deformation energy of the lead specimen and the biggest impact energy of impact cylinder, inner diameter and piston stroke of cylinder were chosen. According to the working principle of impact cylinder, the control circuit of the impact cylinder was designed, the electrical components and control components were selected and used, the support bracket of impact cylinder and the anvil block were designed and manufactured. When air pressure is 0.7 MPa, the switch is pressed, after delay the hammer head moves downward at a high speed. The pneumatic hammer has simple structure, small footprint, low noise and vibration. Its impact energy can meet the need of upsetting deformation of lead specimen with a diameter of 20mm at room temperature.

In order to solve the folded problem in multi-point forming with symmetric punches (SMPF), a new process of multi-point forming with asymmetric punches (AMPF) is proposed in this paper. Experiment and numerical simulation were both used to elaborately analyze the problem of fold. The deformation behaviors of cylindrical surface, spherical surface, and sail surface in two processes were investigated. The characteristics of shape precision of the sheet metal were obtained under different forming parameters. Then, the stress and strain distribution of the cylindrical surface is obtained by numerical simulations. Finally, the mechanisms of folded generation and suppression were revealed by process analysis. It is shown that the surface quality and the forming precision of the workpiece formed by AMPF are improved by AMPF. Besides, the stress fluctuation during the forming process is obviously reduced and the uniformity of stress and strain after forming is enhanced. In addition, under the same loading condition, the average shape error of the cylindrical surface decreases by 17.6%, the stress extremum difference decreases by 5.7%, and the strain extremum difference decreases by 4.3%. The above research indicates that AMPF has a good application prospect in sheet metal forming.

基于冲击气缸研制了用于车架矫形的气锤,可以代替人工抡大锤砸车架.根据冲击气缸的打击能量大于人工抡大锤的打击能量,选用了冲击气缸的缸径和行程.设计了气锤控制电路,选用了控制电路所用的元器件,如开关、继电器和电磁阀等.采用悬挂装置,使气锤沿水平方向冲击车架,使用爪形装置钩住车架,以减少冲击时气锤的后退.采用电动葫芦升降气锤,电动葫芦固定在可以沿导轨行走的门架悬臂上.当气压达到0.5～0.6 MPa时,按下开关,经延时2～3s后,锤头高速水平运动,被撞击的车架钢管发生了塑性变形,达到了矫直的要求.

利用ABAQUS建立了传统多点成形与力-位移分控多点成形两种模式的数值模型,两种模型均可实现压头的随动偏转,计算效率高.在力-位移分控多点成形数值模型中,能够对200个基本体分别施加位移加载曲线和力加载曲线.以1050铝合金为原材料,对半径为200 mm的圆柱面进行成形实验,将实验数据与模拟数据进行比较,结果表明:模拟结果与实验结果具有较好的一致性.

The aim of this study was to analyze the effect of different nozzle sizes on the crystallization and the grain size of 7A09 rapid solidification alloy by melt spinning method. The rapidly solidified ribbons of the 7A09 alloys were produced by melt spinning. The as-quenched microstructures of each rapidly solidified alloy ribbon were investigated by using metallographic microscope,X-ray diffraction(XRD),scanning electron microscope(SEM),etc. A diffraction peak appeared near the X-ray diffraction peak,concluding that substances like amorphous appeared. By reducing the nozzle size,the crystallization ability of the 7A09 alloy can be reduced,thus the grain size of the 7A09 alloy is smaller.

In this paper, a new process of multi-point forming with individually controlled force-displacement (MPF-ICFD) is presented to reduce the springback in the traditional multi-point forming (MPF). An experimental setup was designed and manufactured, and the contrast experiment was conducted to investigate the differences between the traditional MPF and the proposed MPF-ICFD. Furthermore, the stress state and springback mechanism in both processes were analyzed with the plastic forming theory. The differences in springback were also investigated with 1060 aluminum alloy and Q 295 steel. The results showed that the specimens in MPF-ICFD presented an excellent deformation uniformity and are consistent with the target profile. The springback magnitude of 1060 aluminum alloy is 34.63% in MPF while 7.51% in MPF-ICFD, and the springback magnitude of Q 295 steel is 31.16% in MPF while 17.02% in MPF-ICFD. The results demonstrate that the springback can be strongly inhibited by MPF-ICFD.

This paper introduces the modeling and FEM simulation of FDSC Multi-Point Forming based on ABAQUS. Python is used as programming languages to secondary develop the software and to establish a simulation platform. An additional module was developed for the automatic modeling with the functions of: (a) basic parameters input such as material performance, plate size (b) rapid assembly of MPF punches and sheet automatically (c) automatic definition of the analytical step and the output of variables and (d) automatic definition of interaction conditions, loading and meshing.The additional module developed was used to simulate the forming of different curved surfaces to verify its efficiency and accuracy. The results showed that the pre-treatment modeling for FDSC MPF can be established automatically and quickly. The simulation can be accomplished within a receivable speed in ABAQUS. Future more, experimental deformations were carried out and the simulating results are compared with that of experiment. Comparison shows a good consistency between the experimental data and simulation data.

In this paper, Force-Displacement Separated Control Multi-Point Forming technology (FDSC MPF), a new technology of sheet metal forming is proposed. Through controlling displacement by upper die and controlling force by lower die, the technology realizes the separated controlling of displacement and forming force through the forming process. Trough numerical simulation and forming experiment, the discrepancy of the springback between FDSC MPF and MPF are studied. The springback regulars of FDSC MPF are studied as the cylindrical radius and the forming force changed. The results show that in the same condition, the springback of FDSC MPF is much less than that of MPF, the springback decreases with the increase of forming force and the decrease of cylindrical radius.

In this paper, ABAQUS was used to analyze the forming defects during Force-Displacement Separated Control Multi-Point Forming (FDSC MPF) of sphere surface. The numerical simulation model was introduced, and the influence of thickness to springback and crease was analyzed, the reason of crease was confirmed and the solving solution was given. The results show that the smaller of the thickness, the more obvious of crease and wrinkle, the bigger the springback. When the thickness is greater than 2mm, the sheet has no forming defects basically.

It is critical to the success of enterprise systems (ES) assimilation that employees acquire sufficient knowledge and apply the knowledge effectively in routine system use. Drawing from knowledge management and socialization theories, we develop a theoretical model for better understanding how management could exercise socialization tactics to promote the transfer of knowledge, and thus improve the knowledge application outcomes in ES assimilation. We validate the model through survey data from employees in 14 companies which have implemented ES for more than one year in China. We find that socialization tactics strongly impact the properties of knowledge acquisition (depth, breadth, and linkage), which in turn influences knowledge application by users (habitual and extended use). Interesting, while the depth of knowledge impacts the breadth and linkage of knowledge, it does not have a significant direct impact on knowledge application. Theoretical and practical implications of these findings are discussed.

在多点成形中,起皱是影响板材成形质量的重要因素.针对鞍面在力-位移分控多点成形方式下的起皱,以ABAQUS为模拟分析平台,模拟了鞍面的成形过程,并分析了其起皱缺陷.研究结果表明:在鞍面力-位移分控多点成形过程中,当板厚较小(1和1.5 mm)时,板材中心区域发生了较为严重的起皱,且优先变形的方向发生的起皱现象更明显;随着板厚和曲率半径的增大,起皱趋势减小.针对起皱现象探明了起皱的原因,提出了鞍面起皱的抑制方法,并进行了模拟计算和成形试验,结果表明,增大成形力和错位都可以抑制起皱,错位并结合增大成形力可以显著改善板材成形质量.

In order to simulate the forming process and predict the forming result of Multi-Point Forming (MPF), numerical model based on ABAQUS was established in this paper, and the reliability of the model was confirmed by experiments. This model can simulate the forming process of traditional MPF and Force-Displacement-Separated-Controlled MPF, each punch can be given independent motion parameter and the punch's heads can rotate with the deformation of the sheet. The result indicated that the simulation value and experimental value has a good consistency and the model can be used to analyse the forming process of the MPF.