Experimental identification of characteristic values for forming simulations

© Achim Käflein / Fraunhofer IWM

Precisely understanding material properties and characteristics is an essential requirement in order to achieve reliable forming simulation results. Depending on the forming process, different properties of the sheet material – hardening, anisotropy, temperature, strain rate or damage behavior – will be desired and each of these properties needs to be characterized and utilized in the material model. Here at the Fraunhofer IWM, we perform the following testing for the experimental characterization of sheet metal materials:

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#Mechanical testing

 

  • Standardized tensile testing
    • Stress-strain curve/flow curve
    • r-values (Lankford coefficient)
  • Shear tests
  • Tensile and shear tests at different strain rates
  • Cyclic tension-compression tests
  • Tensile tests at elevated temperatures
  • Testing at various stress-triaxality
  • Thermomechanical testing (More about thermomechanical testing at the Fraunhofer IWM)
    • Under inert gas and in a vacuum

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© Fraunhofer IWM
Technical stress-strain curve of a titanium alloy as a function of temperature.

#Microstructure analysis

(More about microstructure analysis at the Fraunhofer IWM)

  • Metallography/Hardness measurement
  • Scanning Electron Microscope (SEM)
  • Texture analysis using EBSD (Electron backscatter diffraction)
  • EDX for measuring local chemical composition

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#Residual-stress analysis using x-ray

(More about residual-stress analysis at the Fraunhofer IWM)

 

Surface and coating analysis#

(More about Tribology at the Fraunhofer IWM)

  • Determination of friction coefficients
  • Wear measurement

 

Thermophysical characterization#

(More about thermophysical characterization at the Fraunhofer IWM)

  • Thermal expansion coefficients
  • Temperature and thermal conductivity
  • Specific heat capacities
  • Determination of phase transformation

 

Parameter identification and preparation of material cards for FE simulation#

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  • Isotropic hardening models
  • Isotrope-kinematic hardening (Bauschinger)
  • Yield surface models
  • Creep and relaxation models

 

Appropriate material models are selected based on the experimental data; parameters are then adjusted and transferred into the numerical simulation.

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