Analysis of the electromagnetic forming process

As a result of the mathematical analysis of the electromagnetic forming process, an approximate solution and a more exact numerical solution of a set of differential equations are presented. Both methods permit the investigation of the influence of a variety of parameters of the discharge unit, the forming coil, and of the workpiece on the attainable forming result. Three conditions for an optimum design of the forming machine are derived from the approximate solution, one of them being an expression for the optimum frequency, for which maximum deformation is achieved. The numerical solution was verified by comparison with selected experimental results.     

Wafer size effect on material removal rate in copper CMP process

Journal of Mechanical Science and Technology - The semiconductor industry has employed the Chemical mechanical planarization (CMP) to enable surface topography control. Copper has been used to...     

成形砂轮磨齿工艺中磨削烧伤缺陷的研究与防止对策

根据成形砂轮磨齿工艺的特点,说明磨削烧伤产生的原因,经过分析研究与实践,给出烧伤缺陷的防止对策.     

连续多点成形中的成形载荷分析

研制了连续多点成形装置来完成三维曲面工件的高效、柔性加工,并对其成形载荷的变化趋势以及不同工艺参数对成形载荷的影响进行了研究.首先,介绍了连续多点成形原理;基于一定的假设条件,建立了成形载荷的理论公式;以双曲率元件为研究对象,建立有限元模型,分析了y方向载荷、z方向载荷以及合成载荷的变化情况.接着,分析了上辊压下量、板材厚度以及柔性辊曲率半径对成形载荷的影响.最后,设计出成形装置并进行实验.结果表明,y方向载荷最大值为6.693 kN,成形载荷的最大值为6.716 kN,成形载荷主要由y方向载荷决定;z方向载荷最大值为1.412 kN,为驱动工件运动的力;随上辊压下量的增加、板材厚度的增加以及柔性辊曲率半径的减小,y方向载荷均增加.成形载荷的变化情况与实际情况吻合,为成形装置的研制提供了指导作用.实验结果证明,连续多点成形是一种连续、高效、柔性的三维曲面成形方法.     

Analysis of plating grain size effect on whisker

Whisker is a single beard-shape crystal filament, and it would be a main cause of producing electrical short circuits. Re-crystallization of both plating grain and base metal grain caused by internal and external stresses affects whisker growth. In this paper, we analyzed effect of grain size and structure of plating on whisker growth through whisker acceleration tests of ICs used in the electronic products. Samples with different package types, base metal, and plating thickness were used in the tests, and both structure and size of plating, and whisker were examined using SEM. From the test results, internal and external stresses produce more grain boundaries of plating when the grain size is smaller. And based on t-test, we found that there is a significant negative correlation between grain size and whisker growth. Therefore, smaller grain size of plating produces higher possibility of whisker occurrence, and whiskers grow in the grain boundaries of plating.     

车轮挡圈成形工艺分析与模具设计

分析了车轮挡圈成形工艺特点,设计了一副缩口、成形两工住模具,介绍了该模具的结构及设计要点和使用要求。实践证明,设计方案可行,模具工作平稳,操作方便,安全可靠,生产效率高,降低了生产成本,满足批量生产的要求。     

Application of flexible forming process to hull structure forming

The conventional line heating method has been applied for the manufacture of various curved blocks used for hull structures in the ship-building industry. However, it has low economical efficiency and productivity because most of its processes are based entirely on the skillful experience of experts. In this study, a flexible forming process is proposed and utilized to substitute for the conventional manual process. In the proposed process, numbers of punches which have round shapes on the contact tip are adopted to configure an equivalent forming surface according to the arbitrarily curved objective surface. A simple punch height determination algorithm that considers the discrete surface and its spatial planar equations is applied to determine the discrete forming surface composed of the adjusted punches. Punch height data are transferred to a numerical simulation model using ANSYS parametric design language, and finite element analysis is conducted to check the formability of the process. Further, experimental investigations are carried out to verify the feasibility of the process using a flexible forming apparatus. Consequently, it is confirmed that a double-curved thick plate could be obtained by the flexible forming process.     

Effects of three parameters on forming force of the single point incremental forming process

This research has examined the effects of three parameter groups on the forming force of single point incremental forming (SPIF) process. The parameters under study include the material types (sheet aluminum, brass and copper), the forming angles (30°, 40° and 50°), and the tool revolution speeds (200, 400 and 600 rpm). The metal forming was carried out using a spherical edge tool which was pressed onto the metal surface to form work pieces of truncated pyramid shape. In the experiment, the forming forces were measured and analyzed to determine an optimal parameter combination, with regard to the material type, forming angle and revolution speed, for the SPIF process. The experimental results showed that all three parameter groups exerted varying influences over the forming force of the SPIF process. The findings indicated that the sheet brass exhibited the highest force value and that the smaller forming angle contributed to the greater forming force. In addition, the higher tool revolution speed resulted in the lower forming force.

     

板料成形中单元大小对回弹的影响研究

板料成形数值模拟的准确性在很大程度上取决于回弹模拟的精度。本文就 DYNAFORM软件中单元尺寸与回弹模拟计算的关系进行了研究 ,得出了相应的结论。     

Research on roll forming process and springback based on five-boundary condition forming angle distribution function

Journal of Mechanical Science and Technology - In the present study, a five-boundary conditional distribution function of the forming angle is proposed. The stress, strain, and springback of a...     

基于一种广义摩擦公式的金属非稳态成型过程弹塑性行为的分析

通过理论分析推导，归纳总结了一个广义摩擦公式。同时应用该公式，对典型金属成型过程非稳态轧制过程进行了三维大变形弹塑性有限元分析。对轧辊与工件之间的接触(摩擦)问题，用这种新的摩擦公式进行了较精确计算。对数值计算结果(包括轧制力、轧制力矩以及界面间的正应力和剪应力)进行了分析讨论。证明广义摩擦公式是切实可行的。     

On the prediction of the effect of process parameters upon forming limit strains in sheet metals

Plasticity analysis of sheet metal forming requires a detailed knowledge of the influence of process parameters on the stress–strain relationships from yielding up to localized necking, for accurate prediction of forming limits. Achievable strain and stress–strain relationships are sensitive to modulations in process parameters, chiefly temperature and strain rate. However, the effects of changes in strain rate and temperature are often complex as they also depend on the levels of strain, strain rate and the temperature employed. Such variations could be either triggered by the process dynamics of the forming operation or imposed for optimal exploitation of the material ductility. In this study, the influence of such process parameter modulations upon formability has been theoretically modelled, following the Sing–Rao prediction approach. The limit strains thus predicted compare favourably with experimental results for a drawing steel, thus validating the present formalism. This approach can also be adopted to accommodate non-linear straining conditions. Thus, theoretical modelling of strain-path-dependent forming limits, which has not been explored adequately so far, now becomes feasible.     

Investigation on the forming force and surface quality during ultrasonic-assisted incremental sheet forming process

The integration of ultrasonic vibration into the incremental sheet forming (ISF) process can significantly reduce the forming force and bring other benefit     

Numerical and experimental approach to reduce bouncing effect in electromagnetic forming process using cushion plate

Electromagnetic forming (EMF) is a high strain rate forming process that uses Lorentz force. In this study, electromagnetic forming with a rectangular block shape in the center of the forming die was examined to determine the possibility and applicability of EMF. However, the high speed of the process in the absence of a medium between the coil and the workpiece results in bouncing of the workpiece, which may result in poor forming. So, in this study, the use of a cushion plate is proposed as a means of reducing the degree of bounce in an EMF process. A 3D electromagnetic numerical model using a spiral forming coil was considered. An RLC circuit, coupled with the spiral coil, was numerically simulated to determine the deformation behavior and design parameters, such as the input current and the magnetic forces. A cushion plate was used between the forming coil and the sheet to be deformed to reduce the extent of bounce. In the numerical simulation, the sheet was found to be well fitted to the objective die with the cushion plate. The simulation results showed that the extent of bounce was drastically reduced because of the velocity direction of the workpiece and the cushion plate. The experiment was performed using 24 kJ to deform Al 1100 with a thickness of 1.27 mm, based on the simulation results. The deformed sheet was well formed, and closely fitted the objective die with a minimum of wrinkling, relative to the results obtained without a cushion plate. As a result, an EMF process with a middle-block die was successfully established both numerically and experimentally to reduce the bouncing.     

瓦楞翅片碾压-铲削成形机理及试验研究

针对由高塑性工业纯铝Al1060制造的散热器翅片,提出碾压-铲削加工成形新工艺.通过工艺试验,研究了刀具前刀角γ、碾压状态、翅片材料等对瓦楞成形的影响,并初步分析了这种瓦楞状凸起的成因,得到了Al1060在低速加工时产生瓦楞状的两个基本条件.     

Research on the forming process of three-dimensional metal parts fabricated by laser direct metal forming

To improve the forming quality of parts fabricated by laser direct metal forming (LDMF), the forming process of three-dimensional parts under open-loop LDMF system was studied in this paper. The influencing rule of scanning space on the forming quality was studied, and the optimal scanning space was derived. The software of control system about scanning style is also optimized, and thus, the forming quality of parts is improved. During fabricating three-dimensional parts, uneven heat distribution caused by multi-overlapping is one of the main factors affecting the sidewall forming quality. To solve the uneven heat distribution, the strategy of changing scanning speed was put forward. The influence of the standoff distance on the height of single-trace cladding layer was studied, and it was suggested that uneven surface of parts was caused by instability of process parameters, which could be compensated automatically in the condition of suitable standoff distance in the process of LDMF. Thus a so-called self-regulation effect is reached. Typical multi-overlapped parts with good forming quality are fabricated using the above-mentioned methods.     

尺寸缺陷对拉伸试验影响的研究

拉伸试验是航天制造领域广泛进行的基本力学试验之一.在拉伸试验过程中试样上的应力变化及最终断裂位置受多种因素影响,其中加工和装配过程中的各种尺寸缺陷对拉伸试验产生的影响是工程界关注的焦点.利用三维实体造型软件SohdWorks和有限元分析软件DEFORM-3D模拟拉伸试验过程,分析研究拉伸试验中出现各种尺寸缺陷时对试样上的应力分布情况及出现失效破坏的位置的影响,为航天制造领域材料试样的形状标准化设计以及进一步的夹具优化设计提供参考数据.     

成形铣齿加工过程中的切削热模型

为了获得铣齿切削时切削区域的温升分布,在分别对铣削热产生和传出的机理,以及刀具和工件之间几何关系分析的基础上,得出包含对应虚拟镜像热源的热源模型。考虑到剪切面热源和刀屑接触面摩擦热源对工件、切屑和刀具的温升作用效果的不同,根据傅里叶导热定律推导出顶刃切削时相应热源的温升计算公式,分别对3者的温升分布进行计算可以获得整个切削区域的温升分布。结果表明,铣削过程中温度随切削的深入而升高,在不改变工件和刀具材料的情况下,进给速度是影响切削温度的主要因素,改变刀盘转速对温升的影响不大。     

Energy efficiency of cold roll forming process

Cold roll forming is an important sheet metal forming process for the mass production of a variety of complex profiles out of a wide spectrum of materials and thicknesses. The energy efficiency of such a continuous bending process may lead to a significant reduction in energy consumption. In this paper, the energy efficiency indicator is introduced for the case of roll forming. In order for this indicator to be calculated, analytical models are proposed and developed for the estimation of the energy consumption and the production rate. An application to a U-section profile and the effects of the process parameters on the energy efficiency indicator are discussed. The overall contribution (in percent) of the main process parameters on the energy efficiency indicator is calculated through a matrix of experiments. The results have shown that the most influential process parameters, on the energy efficiency of the cold roll forming process, are the bending angle concept, the line velocity, and the inter-distance among the roll stations.