Effect of material scatter on the plastic behavior and stretchability in sheet metal forming

Robust design of forming processes is gaining attention throughout the industry. To analyze the robustness of a sheet metal forming process using finite element (FE) simulations, an accurate input in terms of parameter scatter is required. This paper presents a pragmatic, accurate and economic approach for measuring and modeling one of the main inputs, i.e. material properties and its associated scattering.For the purpose of this research, samples of 41 coils of a forming steel DX54D+Z (EN 10327:2004) from multiple casts have been collected. Fully determining the stochastic material behavior to the required accuracy for modeling in FE simulations would require many mechanical experiments. Instead, the present work combines mechanical testing and texture analysis to limit the required effort. Moreover, use is made of the correlations between the material parameters to efficiently model the material property scatter for use in the numerical robustness analysis. The proposed approach is validated by the forming of a series of cup products using the collected material. The observed experimental scatter can be reproduced efficiently using FE simulations, demonstrating the potential of the modeling approach and robustness analysis in general.     

A 3D forming tool optimisation method considering springback and thinning compensation

In this paper, an enhanced numerical method for forming tool design optimisation in three-dimensional (3D) sheet metal forming applications is presented. The applied procedure enables a determination of appropriate forming tool geometry so that the manufacture of a sheet metal product inside specified tolerances would be ensured. In addition to the springback that occurs in the formed part after removal of the forming tools, the impact of the thinning of the sheet metal during the forming process is considered in the method, and both effects are correspondingly compensated for an iterative procedure. Computational efficiency in the E-DA-3D method is achieved mainly because the improved accuracy of the communicated data established corresponding interrelations between the discretised topologies used in the definition of the prescribed product geometry, the current tool geometry, and on this basis actually computed product geometry which is achieved by means of additional point topology mappings. The potential and effectiveness of the method is demonstrated by considering two cases of the forming tool design optimisation that are also experimentally validated.     

Prediction of fracture in a dual-phase steel subjected to non-linear straining

In this work, selected fracture criteria are applied to predict the fracture of dual-phase steel subjected to non-linear strain paths. Furthermore, the effects of manufacturing history are studied. Four fracture criteria were calibrated in three tests using standard specimens. The fracture criteria were first validated in the circular Nakajima test. A second validation test case was included in order to validate fracture prediction for non-linear strain paths. In this test a sheet metal component was manufactured and subsequently stretched until it fractured. All fracture criteria included in this study predict fracture during the Nakajima test with reasonable accuracy. In the second validation test however, the different fracture criteria show considerable diversity in accumulated damage during manufacturing which caused substantial scatter of the fracture prediction in the subsequent stretching. This shows that manufacturing history influences the prediction of fracture.     

自动化立体仓库系统在飞机钣金模具管理中的应用

通过设计与规划自动化立体仓库管理系统,提出了以满足工段生产需求为目标的物流配送思想,以此思想为导向,优化模具管理流程,理顺内部客户关系,实现了飞机钣金零件模具的高效、准时配送。在飞机钣金模具管理中,与传统的模具仓库管理模式相比,自动化立体仓库系统节省了场地面积,降低了人工成本,提高了零件生产效率。     

基于正确边界条件的宽板弯曲变薄理论

指出了现有的宽板塑性弯曲变薄研究方面存在的问题,引入了应变增量中性层概念,提出了应变增量中性层处的切向应变增量等于零这一正确的边界条件,在此基础上推导出了宽板塑性弯曲变薄的理论解,最后给出了计算实例。     

Development of an analytical 3D-simulation model of the levelling process

Sheet metal often shows shape defects, which is not complying with the increasing requirements for the quality of the products needed to satisfy the highest demands on finer tolerances. Due to the market's high requirements on the quality of products, new high-technology levelling machines were developed. The adjustment of these levellers is very complicated and a successful adjustment depends mainly on the experience of the line operator. As the computational power has developed over the past years, simulation becomes more important in the production process and is used in analysing the effects of leveller adjustments on the unflattened sheet metal. In this study, edge- and centre waves are investigated. In order to find a suitable adjustment of the leveller to reach a flat sheet metal, an analytical 3D simulation model has been developed using the Matlab programming environment. The sheet metal will be firstly analyzed and visualized before and after deformation. A user-friendly interface has been developed to enter the required parameters before starting the simulation. Different methods have been used to investigate the effect of the levelling process on the sheet metal and to calculate the remaining shape defects after levelling. The simulation results were validated by experiments and are represented in this paper.     

A numerical method for the optimal blank shape design

This paper describes a numerical procedure for the blank shape design of thin metallic parts obtained by stamping. The objective is to determine the initial blank shape knowing the geometry of the desired 3D CAD part. The numerical procedure consists of two stages: At first, an estimation of the initial blank shape is given using the one step inverse approach (IA). Then, update of the blank shape is continued by iterations combining optimization algorithms and finite element analysis (FEA). The numerical procedure for the blank shape design is tested in the case of an industrial stamping process where the part is formed using a manual press without blank-holder. The proposed numerical procedure can provide very quickly the optimal blank shape in a few iterations.     

冷轧硅钢片磁性能测量因素的分析

采用硅钢片磁性能测试系统,分析了测试环境温度(10～30℃)、试样质量(642～667 g)和剪切应力(剪切1～5次)对国内外不同牌号0.27～0.50 mm取向和无取向冷轧硅钢片磁性能的影响.结果表明,随环境温度升高,冷轧硅钢片的铁损和磁感降低;随试样质量增加,铁损增加,磁感降低;随剪切次数增加铁损递增,磁感递减.文中归纳出磁性能测量的适合条件和注意事项.     

Enhancement of Drying Rate in Paper Machines with Multi-Functional Radial Jet Reattachment Blow Boxes — Theoretical Analysis

ABSTRACT

Multi-functional radial jet reattachment blow boxes deliver a dry air into the pockets of the dryer section of a paper machine by impinging directly onto the unsuppned sheet in the open diaw. The air flow also maintains or improves the sheet swbility.

The iadial jet reattachment blow box technology pmvides a significant enhancement in drying rates. The theoretical drying results are presented in terms of average drying rates, moisture and temperature pmfiles along the drying section with and without the presence of the multi-functional radial jet reaaachment blow boxes. The thcorclical results indicate that enhancements of drying rates within the range of 8% to 25% are feasible depending on ihe operating conditions and machine configuration.     

LED节能灯的安规要求

根据CTL发布的DSH 0743决议,归纳了LED节能灯测试标准中的要求,主要包含对灯头、防触电、灯头温升、绝缘材料、异常状态、结构的考核,以及灯的光生物学安全考核。