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Landkammer P.,Institute of Applied Mechanics LTM | Schneider T.,Institute of Manufacturing Technology LFT | Schulte R.,Institute of Manufacturing Technology LFT | Steinmann P.,Institute of Applied Mechanics LTM | Merklein M.,Institute of Manufacturing Technology LFT
Production Engineering | Year: 2016

Inverse form finding aims in determining the optimal material configuration of a workpiece for a specific forming process. A gradient- and parameter-free (nodal-based) form finding approach has recently been developed, which can be coupled non-invasively as a black box to arbitrary finite element software. Additionally the algorithm is independent from the constitutive behavior. Consequently, the user has not to struggle with the underlying optimization theory behind. Benchmark tests showed already that the approach works robustly and efficiently. This contribution demonstrates that the optimization algorithm is also applicable to more sophisticated forming processes including orthotropic large strain plasticity, combined hardening and frictional contact. A cup deep drawing process with solid-shell elements and a combined deep drawing and upsetting process to form a functional component with external teeth are investigated. © 2016 German Academic Society for Production Engineering (WGP)


Suttner S.,Institute of Manufacturing Technology LFT | Merklein M.,Institute of Manufacturing Technology LFT
Materials Today: Proceedings | Year: 2015

Complex parts with sharp corners are on the rise to satisfy increasing customer demands on the design. To realize these parts in single or multistage forming processes the information of the material behavior under linear and non-linear strain paths is essential. As Bauschinger already showed for the material behavior under cyclic loading, a reduction of the subsequent beginning of plastic yielding can be observed. Different research works studied the Bauschinger effect under cyclic proportional loading or non-proportional strain paths mostly with uniaxial pre-straining of the material. In this paper the material behavior under shearing after previous biaxial stretching in the Marciniak test is analyzed for the aluminum alloy AA5182 and the advanced high strength steel DP600. The Marciniak test is suited for biaxial pre-straining due to an almost almost equibiaxial strain state and a homogeneous strain distribution in-plane on the bottom of the specimen up to higher strains than in a biaxial tensile test. The subsequent shear test is realized with a modified shear test specimen according to the ASTM standard. Finally, the influence of biaxal pre-straining on the beginning of plastic yielding under shear condition, the hardening behavior and the maximum reachable shear strain is investigated for a better understanding of the material behavior under non-proportional loading paths. © 2015 .


Merklein M.,Institute of Manufacturing Technology LFT | Suttner S.,Institute of Manufacturing Technology LFT | Schaub A.,Institute of Manufacturing Technology LFT
Key Engineering Materials | Year: 2014

The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling. © (2014) Trans Tech Publications, Switzerland.

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