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Failure Analysis With a New Tool Geometry, X-Die, in Areas With High Tension/Compression Strains

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Author

Editor

  • Jose M. A. Cesar de Sa
  • Abel D. Santos

Summary, in English

Sheet-metal forming involves a complex strain distribution over the part. The strains consist of tension, compression, and a mix of both. A geometry has been developed, the X-Die, in order to gain insight into the strain behavior of different materials. The X-Die enables strain paths far into the tension/compression region, thus creating the possibility to extend the experimental base both for definition and for further extrapolation of the Forming Limit Curve (FLC) in the tension/compression region, as well as to evaluate FE-simulation results for the same region.Today, evaluation of cracks is made by using FLC. In the conventional test methods, the strains only reach 40% compression (true strain) and often much lower percentages. In conventional test methods, the FLC for any region beyond these levels is extrapolated from existing data.The experimental test proposed in this work consists of a geometry, the X-die, which has shown that rates of 70% tension/compression can be reached (point 0.7/−0.7 in the FLC). Thereby, the region for prediction of cracks on the compression side can be extended in the Forming Limit Diagram (FLD). Furthermore, the strain paths are easy to follow and the limits when cracks appear can be evaluated. Furthermore, the experimental results show that the behavior depends on the material quality. Qualities such as Extreme High Strength Steel (EHSS) and Aluminum have a limited tension/compression rate due to failure in plane strain tension. Material qualities with high r-values, e.g. Mild steel and High Strength Steel (HSS), reach high tension/compression rates before failure and have regions with clearly defined strain signatures. This will be favorable for comparison with numerical simulations, especially for strain signatures in the tension/compression region. Furthermore, the experiments did not indicate any limitation in the compression region besides the one defined in the normal procedure in creation of an FLC.This geometry is favorable to calibrate simulation results, in order to analyze prediction of strains located on the left side in an FLD. ©2007 American Institute of Physics

Publishing year

2007

Language

English

Pages

1445-1450

Publication/Series

MATERIALS PROCESSING AND DESIGN; Modeling, Simulation and Applications; NUMIFORM '07; Proceedings of the 9th International Conference on Numerical Methods in Industrial Forming Processes (AIP Conference Proceedings)

Volume

908

Document type

Conference paper

Publisher

American Institute of Physics (AIP)

Topic

  • Materials Engineering

Conference name

9th International Conference on Numerical Methods in Industrial Forming Processes

Conference date

2007-06-17 - 2007-06-21

Conference place

Porto, Portugal

Status

Published

ISBN/ISSN/Other

  • ISSN: 0094-243X
  • ISSN: 1551-7616
  • ISBN: 978-0-7354-0415-1