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

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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.