Experimental investigation of arbitrary non-linear load paths using a feedback controller in combination with a conventional sheet metal testing machine and a special tool for cruciform specimens

成形性预测是板料成形过程中最重要的工作之一。不断增长的设计需求和不断上升的成本压力意味着对成形极限的进一步开发。非线性负荷路径的预测是一个重要的方面。目前，对任意非线性载荷路径进行实验研究需要多种工具和压力机。实验验证所提出的方法有助于解决这个问题，但由于需要大量的成本和时间，仍然具有挑战性。因此，研究项目的主要目标是在给定的任意非线性载荷路径上使用钣金试验机进行部分自动化的实验研究。利用大型实验和数值数据库，研究了有效拉延头高度与压边力之间的相互关系及其对应变比的影响。另一个目标是设计一个反馈控制器，并将其集成到当前的材料表征实验装置中。结合一个特殊的工具，十字形试样的实验装置能够覆盖非线性载荷路径的实验。因此，可以使用一个试样和一个工具实现相应的模拟非线性载荷路径的经济验证。这为复杂零件成形性的改进预测提供了可能。

The prediction of formability is one of the most important tasks in sheet metal forming. The combination of growing demands on design and rising cost pressures implies the further exploit of forming limits. The prediction of non-linear load paths is a critical aspect. Nowadays, several tools and presses are necessary for the experimental investigation of arbitrary non-linear load paths. The experimental validation of the proposed methods, which help solve the problem, is still challenging because of the high amount of costs and time needed. Therefore, the main goal of the research project is the partly automated experimental investigation of given arbitrary non-linear load paths using a sheet metal testing machine. The interrelationships between the effective drawbead height and the blankholder force and their impact on the strain ratio are carried out using a big experimental and numerical data base. Another objective is the design of a feedback controller and its integration into a present experimental setup for material characterization. In combination with a special tool for cruciform specimens the experimental setup is able to cover non-linear load paths experimentally. Thus an economic validation of corresponding simulated non-linear load paths can be realized using one specimen and one tool. This gives the possibility to make a contribution to an improved prediction of the formability of complex parts.