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Simulation of heat exchange during simple shear of sheet steel

Rusinek A., Gadaj S. P., Nowacki W. K., Klepaczko J. R.

Journal of Theoretical and Applied Mechanics

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2002

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Vol. 40 nr 2

317-337

EN

An original technique to measure the temperature increase in the shear zone during quasi-static loading of a sheet metal is reported. The set-up used to perform such a test has been developed in IPPT-Warsaw (Gadaj et al., 1996). The tested material is a ES sheet steel (Enhanced Formability) used in automotive industry. In addition, several tests have been performed on this material for different strain rates (...) in LPMM-Metz (Nguyen and Nowacki, 1998; Rusinek and Klepaczko, 2001). The experimental results enabled formulation of original visco-plastic constitutive relations (Rusinek and Klepaczko, 2001). Those constitutive relations have been implement into a numerical code to simulate the experimental results and to compare the temperature gradient in the shear band and to calibrate the heat conduction into the surface contact (specimen-grips). The comparison between the experimental and numerical results yielded complete agreement. Thus, the visco-plastic model implemented in this study is well defined for this type of problem. Moreover, the numerical simulations indicated that at a high strain rate, ... , the heat evacuation to the surface contact of the grips seemed to be negligible. In that case the specimen was thermally isolated and the temperature increase took place essentially within the shear zone.

PL

Przedstawiono oryginalną technikę pomiaru przyrostu temperatury w strefie ścinania w trakcie quasistatycznego obciążenia metalowych blach. Stanowisko badawcze do przeprowadzenia takich badań zostało skonstruowane w IPPT PAN w Warszawie. Badano blachy stalowe typu ES (Enhanced Formability), używane we francuskim przemyśle samochodowym. Dodatkowe badania zostały wykonane w LPMM-Metz, dla tego samego materiału dla innych prędkości deformacji, w zakresie ... . Otrzymane wyniki badań pozwoliły na zaproponowanie oryginalnych równań konstytutywnych lepko-plastycznego zachowania się materiału. Zaimplementowano te równania konstytutywne w programie ABAQUS Standart w celu symulacji wyników doświadczalnych i porównaniu gradientu temperatury w strefie ścinania i kalibracji wymiany ciepła na granicy kontaktu próbka-uchwyt. Otrzymano zgodność wyników doświadczalnych i numerycznych. Stwierdzono, że przyjęty model lepko-plastyczny jest przydatny w badaniach rozważanych w pracy problemów ścinania blach. Ponadto stwierdzono, na podstawie symulacji numerycznej, że dla prędkości deformacji większej od ... , przejmowanie ciepła przez uchwyty od próbki może być pomijalne. W tym przypadku próbka jest termicznie izolowana i przyrost temperatury następuje głównie w strefie ścinania.

2

Visco-plasticity of polycrystalline tantalum - rational phenomenology in constitutive modeling

Klepaczko J. R.

Archives of Mechanics

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2002

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Vol. 54, nr 5-6

459-478

EN

Constitutive modeling based on the so-called rational phenomenology (materials science approach) has been applied to take into account strain hardening, strain-rate sensitivity, thermal effects and evolution of microstructure in a polycrystalline tantalum. A wide range of strain rate in shear ... and homologous temperature (0.05 < ... < 0.2) is considered. Behavior of tantalum is understood as an example for BCC polycrystalline metals. The constitutive modeling provided a possibility to determine all material constants via the experimental results obtained on thin tubular specimens using a fast hydraulic machine and a torsion Hopkinson bar. Finally, the model predictions are demonstrated by numerical simulations for different history paths in strain rate and temperature.

3

Remarks on numerical estimation of the critical impact velocity in shear

Klosak M., Łodygowski T., Klepaczko J. R.

Computer Assisted Mechanics and Engineering Sciences

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2001

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Vol. 8, No. 4

579--593

EN

A phenomenon called the Critical Impact Velocity (CIV), which is directly related to material behavior under dynamic loads, is of special interest in this paper. Deformation trapping due to thermoplastic instability caused by the propagation of plastic waves is the main physical reasons for the CIV. This critical value of shear velocity should be considered as a material constant, but it is difficult to estimate due to complicated material response. Analytical approaches may only provide some preliminary estimates, because they are based on simple constitutive relations. On the other hand, experimental techniques are more reliable, but then there exist problems in specimen design. Numerical techniques such as FE method offer a possibility to treat the problem in a more general aspect. Numerical results obtained in the environment of ABAQUS code demonstrate the role to be played by computer simulations as compared to the analytical and experimental findings. The CIV in shear is studied for the case of martensitic steel VAR4340, and the FE models are based on geometry of the Modified Double Shear specimen (MDS). Thus, the principal questions are formulated as follows: to which extent the analytical approach approximate the CIV, what is the role of experimental results and what information can be obtained after numerical simulations.