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Numerical calibration of material parameters of selected directional distortional hardening models with combined approach using both distorted yield surfaces and stress-strain curves
Hrubý, Zbyněk ; Plešek, Jiří ; Parma, Slavomír ; Marek, René ; Feigenbaum, H. P. ; Dafalias, Y.F.
The plastic strain induced anisotropy is a well-known phenomenon in manufacturing and directional distortional hardening represents a very promising way to capture real plastic behavior of metals. Many papers were published in the past typically extending the von Mises yield criterion with directionally dependent internal variable and defining yield point at the basis of plastic strain offset. Material parameters of these models were typically calibrated at the basis of deformed yield surfaces only, which – as revealed – could lead to certain discrepancies in simple stress-strain response. Presented paper introduces a numerical calibration approach taking both distorted yield surfaces and stress-strain curves information into account. Besides the calibration procedures, innovative applications of experimental techniques such as the acoustic emission for an acquisition of yield inception and plastic straining, convexity of the models, or numerical implementation of these models are discussed.
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Experiments in directional distortional hardening—determination of mechanical properties of the S355J0 grade structural steel
Parma, Slavomír ; Ciocanel, C. ; Seiner, Hanuš ; Hrubý, Zbyněk
In order to carry out comprehensive experiments in the research of directional distortional hardening phenomenon, some basic mechanical properties of S355J0 structural steel are determined. Particularly, attention is payed to the determination of elastic properties of the material, determination of anisotropy of the material induced by the manufacturing technology of specimens, and determination of elasto-plastic behavior of the material. Elastic properties of the material are measured via an ultrasound method, elasto-plastic behavior is analyzed from the tensile and torsional testing. Conclusions of the report are intended for design and evaluation of the comprehensive experiments mentioned.
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Modelling of nanoindentation of modern Nickel-based superalloys for turbofans
Hrubý, Zbyněk ; Plešek, Jiří ; Tin, S.
Stress and strain distribution underneath various types of indentors – spherical, conical, and Berkovich – can be provided by the finite element method. In the presented work, indentation of isotropic aluminium is introduced as a benchmark problem, in which plasticity and contact algorithms are tested. The knowledge obtained in this way passes on to the real-life indentation processes involving orthotropic materials such as FCC metals (Ni-based alloys) in the context of nonlinear continuum and finite strain elasto-plasticity, including homogenization approach on the material microscale.
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Modelling of micro and nano indentation of modern nickel-based superalloys for turbofans
Hrubý, Zbyněk ; Plešek, Jiří ; Tin, S.
Stress and strain distribution underneath various types of indentors – spherical, conical, and Berkovich – can be provided by the finite element method. In the presented work, indentation of isotropic aluminium is introduced as a benchmark problem, in which plasticity and contact algorithms are tested. The knowledge obtained in this way passes on to the real-life indentation processes involving orthotropic materials such as FCC metals (Ni-based alloys) in the context of nonlinear continuum and finite strain elasto-plasticity, including homogenization approach on the material microscale.
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Energeticky konjugované míry napětí a deformace v mechanice kontinua
Hrubý, Zbyněk ; Plešek, Jiří
The energy conjugate measures of stress and strain enter any constitutive relation for the material behaviour description. There are many strain measures in common use, several of them discussed in the text. The main aim of the contribution is to focus on the derivation of a general energy conjugate stress tensor corresponding with a general Lagrangean strain tensor.
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