Improving geometrical accuracy for flanging by incremental sheet metal forming

Incremental Sheet Forming (ISF) is a manufacturing technology for individualized and small batch production. Among the opportunities this technology provides there is the possibility of a short ramp-up time and to cover the whole production chain of sheet metal parts by using a single reconfigurable machine set-up. Since recent developments proved that manufacturing of industrial parts is feasible, finishing operations such as flanging and trimming gain importance, which are an integral part of manufacturing process chains of many sheet metal parts. This paper analyses the technological capabilities of performing flanging operations by ISF. Due to the localized forming zone and the absence of surrounding clamping devices, ISF exhibits a different material flow than conventional flanging processes. In this paper, the influence of the tool path characteristics, the flange length as well as the flange radius is analysed in order to establish a process window and to compare it to the process limits of conventional flanging operations. Since geometrical deviations occur when flanging operations are performed by ISF, a new adaptive blank holder is developed, which acts in the vicinity of the forming tool and reduces unwanted deformation outside the primary forming zone. The experimental results show the benefits of the adaptive blank holder with respect to geometric accuracy. The established process window and the adaptive blank holder hence contribute to the applicability of incremental flanging operations, such that ISF can be used for all forming and flanging operations along the process chain.     

Capability of iterative learning control and influence of the material properties on the improvement of the geometrical accuracy in incremental sheet forming process

Incremental Sheet Forming (ISF) is a flexible technology that allows the deformation of blank sheets without the need of complex and high cost tools or equipments. One of the main lacks of ISF is the geometrical accuracy which is not comparable with the one achieved by using traditional sheet stamping processes. There are several approaches proposed to enhance this aspect and among them the Authors have developed a method based on an Iterative Learning Control (ILC). ILC consists of a cyclic and progressive error compensation method that improves the quality of the manufactured parts. ILC has been proved to be capable for optimising the production of parts with tight tolerances when dealing with ductile materials (aluminium and steel alloys) and small deformations. In this paper, the method was tested to investigate its capability in a virtual environment. The suggested compensations were checked with Finite Element Method (FEM) so to reduce the number of parts to be manufactured saving time and costs. Moreover, the algorithm was tested considering both a difficult to form material (titanium alloy) and high deformation conditions. The results demonstrated how the precision of ISF processes depends on the blank material properties. Moreover, the capabilities of ILC are shown and discussed.     

Thermo-mechanical fatigue approach to predict tooling life in high temperature metal forming processes

In high temperature metal forming processes, strong mechanical and thermal cyclic loads coexist in the formed material and in the tooling. Such a phenomenon has a negative influence in the tool life cycle. The thermal and mechanical ranges lead to the appearance of cracks on the tool surface because of thermo-mechanical fatigue damage (TMF). The objective of this paper is to present a simplified cumulative thermo-mechanical fatigue model which has been developed in order to study the most critical areas in the forming tools according to the predicted number of cycles up to crack appearance considering multi-axial fatigue and oxidation. This model is based on assumptions of a general cumulative TMF model proposed by Neu and Sehitoglu; and critical plane approaches by Smith, Watson and Topper, and Fatemi and Socie. In general, cumulative TMF approaches three agents are considered: multiaxial-fatigue, oxidation and creep. The developed model has been applied to a specific manufacturing process of seamless steel pipes which includes three basic forming steps: backward extrusion, perforation and Pilger rolling mill. This process transforms a blank, or ingot, into a final seamless steel pipe with specific dimensions and characteristics depending on market requirements. These studies have been carried out in order to improve the tool life. To this end, the forming process has been reproduced by means of coupled thermo-mechanical FE simulations using the ABAQUS/Explicit solver. Moreover, a post-processing subroutine has been incorporated which enables to predict the number of cycles until crack appearance (tool life) according to both the general model of Neu and Sehitoglu, and the specific model developed. Good correlations between predicted and actually observed damage areas have been reached in both cases. The advantage of the hereafter proposed TMF model is that, it takes the most convenient features of general TMF models and it is particularized to a reduced input TMF model in order to analyze high temperature metal forming processes.     

SQL query to increase data accuracy and completeness in PATSTAT

PATSTAT is the worldwide patent statistical database created and maintained by the European Patent Office. Many methods and techniques have been developed to increase its accuracy and completeness. This paper contributes to this body of research. It proposes an allocation procedure which reduces by 44% the number of empty entries concerning the residence country of patentees, and, at the same time, it increases by 22% the accuracy of country code allocation. The procedure consists of a replicable SQL query to be run in PATSTAT. An application of this procedure illustrates that patent analyses based on raw data underestimate the role of China and Japan in the area of climate change mitigation technologies.     

Development of high speed surface transport system (IISST)

Our first electromagnetically levitated, LIM-propelled test vehicle, HSST-01, reached a maximum speed of 307.8 km/h on a 1,300-meter long test track in February, 1978, whereas our second test vehicle, HSST-02, has demonstrated manned test flights successfully covering an aggregate total of about 1,500 passengers since April, 1978. The 1-ton HSST-01, designed for high speed testing incorporates eight electromagnets and a LIM with a maximum thrust of 340 kg. The levitation power supply is taken from the vehicle-borne batteries and the 3-phase variable voltage variable frequency (VVVF) power for the LIM propulsion is supplied from wayside power lines. The 9-seat HSST- 02 has a laden mass of 2.3 tons. Additional functions realized in the 2nd test vehicle include: (1) Improved riding comfort achieved through the provision of a mechanical suspension with the electromagnets mounted on the flexible chassis. (2) A rectified power supply to the LIM enabling continuous levitation. Test results have shown that the predicted performances of the magnets, LIM and power collector system have been satisfactorily established. The design of an 80-seat pre-operational test vehicle is now underway, and its test flight is scheduled to be initiated in 1980 at a cruising speed of 300 km/h.     

32通道高速一体化测时仪研制

基于分布式-嵌入式技术,研制一种集成激励源、测量一体化全数字测时仪器,在信号检测中采用测量回路电流的方法,有效地解决测量过程中的多种干扰问题。该测时仪器将激励源、信号处理、记录、数据传输等功能部件完全集成在一台仪器中,较好地保证信号完整性和系统的方便易用性能,实现32个完全隔离的测试通道、测时范围100 ns~2 s、分辨力3.3 ns、不确定度优于±7 ns的指标,为爆炸外场试验中实现信号抗干扰,增强信号完整性、可信度,缩短测试准备时间等提供有效的技术支撑。     

Development of robust processing routes for powder metallurgy high speed steels

Abstract

This paper reviews progress made in understanding the factors which control the supersolidus liquid phase sintering of high speed steel powders to full density. The correlation between alloy composition and sintering behaviour is discussed for a number of alloy systems. Realising that for complete densification it is necessary for sintering to take place in the liquid +γ+M₆C+MC (or MX) phase region, two approaches have been developed to extend this critical phase field. This enables a scientific development of alloys that are more robust to process variations than currently sintered high speed steels of standard (for wrought materials) compositions. The new alloy systems possess wider process or sintering windows and have lower optimum sintering temperatures. The first approach relies on computer aided alloy design: vacuum sintering windows extending to 30–40 K at temperatures of 1170–1200°C have been achieved for novel Fe–C–4Cr–14Mo(–8Co)systems. The second approach involves sintering vanadium enriched high speed steels (HSSs) in nitrogen rich atmospheres. Such processing promotes the formation of MX carbonitrides in place of the more massive MC carbides. The solidus is lowered and sintering windows of ～30 K at temperatures of 1140–1150°C have been achieved. Compared with wrought HSSs, directly sintered materials have uniform, coarser microstructures. The low levels of residual porosity achieved enable attainment of metal and wood cutting properties comparable to those achieved with wrought and hipped HSSs of similar compositions.     

旋翼翼型高速风洞动态试验装置研制

为弥补国内在旋翼翼型高速风洞动态试验模拟能力和测试精度方面的不足,基于FL-20连续式跨音速风洞,提出采用双端同步驱动旋翼翼型试验模型的方式,设计了一套高速风洞动态试验装置。该装置依托双天平动态载荷测量结合表面动态压力测量的方式,可提高旋翼翼型动态气动载荷的测量精度。风洞试验结果显示：当旋翼翼型试验模型的俯仰振荡幅值为10°时,其振荡频率可达17 Hz,且试验马赫数为0.6,雷诺数达到5×10⁶,处于国际领先水平。所研制的动态试验装置及其相关测试技术具有较高的可靠性,且试验数据可靠、规律合理,具备了开展高速风洞动态试验的能力,可为旋翼翼型动态失速问题的研究以及真实直升机试验参数的模拟提供重要的技术支撑。     

On the use of Back-drawing Incremental Forming (BIF) to improve geometrical accuracy in sheet metal parts

Industrial interest about Incremental Sheet Forming (ISF) process is growing in the last years. Up to a few years ago, two main investigation ways were proposed, the former aimed at analysing the process mechanics, the latter at reproducing some ??case study?? geometries. In industrial applications, if the long cycle-time can be neglected in small batches manufacturing, geometrical accuracy represents a relevant drawback, especially when the product has to be coupled to one another. For this reason, in the opinion of the authors, the low accuracy is the most relevant defect of ISF processes today. Among the techniques already set-up to reduce inaccuracy, the use of different material supports or the use of ??arbitrarily modified?? tool trajectories are probably the most known. In this paper a simple approach is proposed, based on the process self capability to correct inaccuracy when different steps of Incremental Sheet Forming are carried out on both the part surfaces. In particular, it is demonstrated that a relevant increasing in accuracy is obtainable at the second repeated step, while new ones do not reduce the inaccuracy sensitively. The above approach builds a new scenario since it allows to keep the basic equipment (without any support) and does not require any further knowledge concerning the material behaviour after the punch action. These aspects are deeply discussed in the next chapters.     

Experimental investigations on the single point incremental forming of a titanium alloy component combining static heating with high tool rotation speed

The present work focuses the attention on the Single Point Incremental Forming (SPIF) process of a scaled car door shell made by Titanium alloy (Ti6Al4V). The effect of a temperature increase contemporary due to electric static heating and tool rotation speed was investigated.Preliminary tensile tests allowed to define the temperature level to be assured on the sheet in order to determine a consistent flow stress reduction. SPIF tests were carried out adopting rotation speed in the range 800–1600 RPM, while simultaneously changing the pitch value in the range 0.5–1.0 mm. Temperature during the forming process was continuously measured in the central area of the blank using a pyrometer. In addition a digital image correlation system was used for measuring the strain distribution over the formed part.The combination of the two approaches (heating by both electric bands and high tool rotation speed) revealed to be a feasible solution for manufacturing hard to work materials like Ti alloys, since the investigated case study was successfully formed by SPIF. In addition, a positive effect of the tool rotation speed in stabilizing the necking (thus allowing to reach higher level of stretching) was recognised.     

PCIe接口高速数据传输卡的驱动程序开发

结合自行开发的PCI Express接口高速数据传输卡,讨论了一般PCI Express设备驱动程序编写时所面临的主要问题和解决方案,重点从驱动程序、硬件接口以及应用程序等几个方面进行分析阐述,并比较详尽的介绍了使用WinDriver开发具有简单数据传输和DMA传输功能的驱动程序的有效方法.     

Raising the accuracy in determining the geometrical parameters and calibration of vertical cylindrical vessels on checking

Methods are described for making measurements with electronic tacheometers and scanners that allow one to raise the productivity of labor by a substantial factor while increasing the accuracy in determining the geometrical parameters of the vessels. Formulas are given for estimating the geometrical parameters from the coordinates of points on the tank walls, and also estimates of the accuracy obtained by least-squares fitting. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 29–33, March, 2007.     

高速压力机转子-轴承系统的动力学研究

以有限元方法为基础,建立了曲柄压力机的转子-轴承系统的运动方程,通过计算压力机的曲柄连杆之间的作用力,获得主轴转子的径向载荷,并集成建立转子-轴承系统的振动模型;采用Newmark方法进行求解,进行模拟仿真,分析转子-轴承系统的振动响应;对主轴转子的振动特性进行实验研究,验证了转子-轴承系统的振动模型及其模拟仿真,进而为压力机转子-轴承系统的设计提供了数值分析及实验研究依据。     

Towards accuracy improvement in single point incremental forming of shallow parts formed under laser assisted conditions

Single point incrementally formed parts with a low wall angle geometry typically exhibit a manufactured geometry that significantly deviates from the design surface due to accumulated unwanted bulging deformation. Development of the bulge on the bottom of the part might result in wrinkling of the sheet at the bulged region which leads to higher forming forces and can even cease the forming process. In this study, the geometric inaccuracy of low angled parts is investigated by means of both Finite element analysis and an experimental campaign on a conical geometry. Deformation mechanisms in shallow sloped parts have been studied in detail and the tool-sheet contact area has been characterized both for low and high angled geometries. In a second phase, the laser assisted single point incremental forming process and its potential for improving accuracy are investigated. To obtain suitable process parameters for a warm forming condition, a transient heat transfer analysis is developed to simulate the laser movement on the conical geometry. Based on the simulated and experimentally determined tool-sheet contact zone, different laser spot positioning strategies have been used while the accuracy of the part and forming forces were measured. It has been observed that overforming of the cone wall is due to the continuous deformation of the sheet outside the contact zone which changes into underforming upon laser treatment. By selection of a proper laser positioning strategy a reduction of 42 % in bulge height is observed. This shows its effect in reducing radial forming forces.     

高低孔爆破处理高陡边坡的技术分析

针对前期规划不当,大宝山露天矿877 m平台高陡边坡局部存在难以采用预裂爆破技术进行处理的情况,决定采用高低孔爆破处理技术。为了解决这一难题,首先分析了高低孔的相对内涵,并对高低孔孔深计算公式进行了简单推导,然后通过公式计算得到了高低孔的孔深。在施工阶段,为了确保低孔的实施效果,两排低孔分区域使用同段别毫秒延时雷管,晚于高孔起爆。实践表明,处理后的平台平整度良好,坡面较为稳定,对高陡边坡采用高低孔爆破处理具有可行性,效果较好,可为类似边坡处理提供新思路。     

高低孔爆破处理高陡边坡的技术分析

针对前期规划不当,大宝山露天矿877 m平台高陡边坡局部存在难以采用预裂爆破技术进行处理的情况,决定采用高低孔爆破处理技术。为了解决这一难题,首先分析了高低孔的相对内涵,并对高低孔孔深计算公式进行了简单推导,然后通过公式计算得到了高低孔的孔深。在施工阶段,为了确保低孔的实施效果,两排低孔分区域使用同段别毫秒延时雷管,晚于高孔起爆。实践表明,处理后的平台平整度良好,坡面较为稳定,对高陡边坡采用高低孔爆破处理具有可行性,效果较好,可为类似边坡处理提供新思路。