Material- and failure characteristics for high-speed forming and cutting
Final Report Abstract
The quality of simulation results strongly depends on the material model and its parameters. For conventional forming processes, quasi-static conditions can be assumed as a good approximation and numerical process optimization is state of the art. In the field of material characterization at high strain rates, there is still need for research. For example, in high-speed forming processes, such as electromagnetic forming, two opposing effects influence the yield stress of the material: strain hardening due to high strain rates and thermal softening due to adiabatic heating. The aim of the research project was the development of a method for the characterization of flow and failure parameters for forming speeds of up to 10^5 s^-1. For this purpose, two setups with pneumatic and electromagnetic drive, respectively, were designed and implemented for different speed ranges and an inverse parameter identification was developed. The method was verified for a mild steel and an aluminum alloy proving that the identified material parameters allow numerical modeling of high-speed processes with good accuracy. The determined material parameters for steel show significant differences for different stress states. For specimen geometries with predominantly uniaxial tensile strain at forming speeds in the order of 10^4–10^5 s^-1 the determined yield stress was nearly twice as high compared to shear samples; an effect which does not occur under quasi-static loading. This trend suggests a triaxialitydependent rate dependence, which might be attributed to shear band induced strain localization and adiabatic heating. While the first phase of the project focused primarily on developing the methodology for parameter identification and determining material coefficients, the second phase of the project focused on better understanding the influences by quantifying the adiabatic heating of the workpiece under high-speed loading. For this purpose, uniaxial tensile and shear tests at various high strain rates were analyzed experimentally and numerically. One focus of the analysis was the identification of a characteristic time- and location-dependent forming rate. In addition to measuring force and strain, the experiments also recorded the temperature in the fracture region using a thermal imaging camera and a pyrometer for higher strain rates. Finally, the determined material properties were used for the simulation of deep drawing with strain rates up to 10^2 s^-1 and high-speed shearing in LS-Dyna. The results showed good agreement with the experimental data in terms of the time-dependent force-displacement curve and the maximum occurring temperature.
Publications
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Principle and setup for characterization of material parameters for high speed forming and cutting. Procedia Engineering, 207(2017), 2000-2005.
Tulke, Marc; Scheffler, Christian; Psyk, Verena; Landgrebe, Dirk & Brosius, Alexander
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Characterisation of high strain rate material behaviour for high-speed forming and cutting applications. Journal of Physics: Conference Series, 1063, 012166.
Tulke, M.; Scheffler, C.; Linnemann, M.; Psyk, V.; Landgrebe, D. & Brosius, A.
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Characterization of material parameters for high speed forming and cutting via experiment and inverse simulation. AIP Conference Proceedings, 1960(2018), 110009. Author(s).
Scheffler, Christian; Psyk, Verena; Linnemann, Maik; Tulke, Marc; Brosius, Alexander & Landgrebe, Dirk
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Determination of Material and Failure Characteristics for High-Speed Forming via High-Speed Testing and Inverse Numerical Simulation. Journal of Manufacturing and Materials Processing, 4(2), 31.
Psyk, Verena; Scheffler, Christian; Tulke, Marc; Winter, Sven; Guilleaume, Christina & Brosius, Alexander
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Determination of material and fracture parameters for high strain rate processes, especially considering the local adiabatic heating in the fracture zone of the sample. 9th ICHSF.
Galiev, E., Tulke, M., Psyk, V., Brosius, A. & Kräusel, V.
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Deep drawing of DC06 at high strain rates. IOP Conference Series: Materials Science and Engineering, 1238(1), 012047.
Tulke, M.; Galiev, E.; Psyk, V.; Kräusel, V. & Brosius, A.
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Local Temperature Development in the Fracture Zone during Uniaxial Tensile Testing at High Strain Rate: Experimental and Numerical Investigations. Applied Sciences, 12(5), 2299.
Galiev, Elmar; Winter, Sven; Reuther, Franz; Psyk, Verena; Tulke, Marc; Brosius, Alexander & Kräusel, Verena
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Forming and cutting at high strain rates Part 1: Experimental data and FE-model for an inverse material characterization of DC06 at high strain rates
Tulke, M., Galiev, E., Scheffler, C., Linnemann, M., Psyk, V. & Brosius, A.
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Forming and cutting at high strain rates Part 3: Deep drawing
Tulke, M., Galiev, E., Psyk, V. & Brosius, A.
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Forming and cutting at high strain rates Part 4: High-speed blanking
Galiev, E., Tulke, M., Brosius, A. & Psyk, V.
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Forming at high strain rates Part 2: Analysis of adiabatic heating based on tensile tests of DC06
Tulke, M., Galiev, E., Psyk, V. & Brosius, A.
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Numerical and experimental study of high-speed blanking of DC06 steel. Materials Research Proceedings, 25, 27-34. Materials Research Forum LLC.
Galiev, E.
