New experimental approach for yield loci determination using a modified Nakajima setup

使用修改后的 Nakajima 设置确定产量位点的新实验方法

基本信息

批准号：
363839128
负责人：
Professor Dr.-Ing. Wolfram Volk
金额：
--
依托单位：
Lehrstuhl für Umformtechnik und Gießereiwesen
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/363839128?language=en
关键词：
New experimental approach yield loci

项目摘要

In the state of the art the Nakajima test is used to determine die forming limit of sheet metal. In the common test setup, consisting of a spherical punch, a die and a blank holder, only the strains in the sheet are measured. The aim of the research project is the development of a method for the experimental determination of stress states by use of a modification of the Nakajima test. For this purpose, different measurement concepts are developed for the detection of the normal pressure between the apex area of the punch and different tailored specimens by means of a simulation and a calibrated test rig. The high strength steel DP600 is used as a test material. On the basis of the experiments as well as the virtual experiments with specimens, which have different widths, a mathematical method is designed for differentiation of the measured normal pressure into the membrane stresses. This approach takes into account the complete punch stroke and thus the entire forming history of the test sheet. By means of the resulting knowledge, it is possible to determine flow curves or yield loci for sheet metal, at different stress states in the first quadrant of the stress space, as well as for each strain state of the deformation history up to the determination of the local necking. The methodology is validated by using of prescale foil, which can measure the pressure, and the bulge test. Finally, experimental yield loci are determined exemplary. The Nakajima tests, which are required in the research project, are determined on the BUP1000 universal sheet metal testing machine procured within the scope of the DFG large instrument application. The new approach to determine the yield locus offers the possibility to understand the plastic material behavior better, to compare numerical material models with actual material parameter, and to develop new yield function approaches. Performing all the necessary tests on one test machine and one experimental setup, which already finds a wide application for the determination of the forming limit, minimizes the extensive effort required for the determination of yield loci.The main objectives of the research project include:1.Construction of measuring concepts and a calibrated test rig2.Derivation of calibration function depending on the different specimen widths3.Development of a mathematical method for the decomposition of the normal pressures in membrane stresses4.Determination of flow curves and yield loci by means of the membrane equation

在最新的状态下，中岛测试用于确定钣金的模具形成极限。在常见的测试设置中，由球形拳，模具和空白支架组成，仅测量纸张中的应变。研究项目的目的是开发一种通过使用中岛测试的修改来实验压力状态的方法。为此，开发了不同的测量概念，以通过模拟和校准的测试钻机来检测打孔器顶部和不同量身定制标本之间的正常压力。高强度钢DP600用作测试材料。基于实验以及具有不同宽度的样品的虚拟实验，数学方法的设计用于将测得的正常压力区分为膜应力。这种方法考虑了完整的打孔冲程，从而考虑了测试表的整个历史记录。通过所产生的知识，在应力空间的第一个象限的不同应力状态以及变形史的每个应变状态下，可以确定钣金的流曲线或产生基因座，直到确定局部颈部。通过使用预先计算箔可以测量压力和凸起测试来验证该方法。最后，确定实验屈服基因座的示例性。在研究项目中需要的Nakajima测试是在DFG大型仪器应用程序范围内采购的BUP1000通用钣金测试机上确定的。确定产量基因座的新方法提供了更好地了解塑料材料行为的可能性，将数值材料模型与实际材料参数进行比较并开发新的产量函数方法。在一台测试机和一项实验设置上执行所有必要的测试，该测试已经为确定形成极限的确定而广泛应用，最大程度地减少了确定产量基因位置所需的广泛努力。研究项目的主要目标包括：1.测量概念和校准测试索具的校准测试措施的校准范围。膜应力的压力。通过膜方程确定流动曲线并产生基因座