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1 Computer Methods in Materials Science

1 2007

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Dedicated computer system of aided steel deformation testing procedure near solidus temperature

Głowacki M., Hojny M.

Computer Methods in Materials Science

2007

Vol. 7, No. 1

36-41

Modern engineering requires computer technique and methods. Application of CAE systems results in lowering production costs, shortening manufacturing and technology preparation time etc. The Finite Element Method is the most popular among methods dedicated to numerical engineering systems. Physical simulations of deformation of metals at extra high temperatures performed with the aid of advanced testing machines, for example GLEEBLE simulator, are very expensive. Acceptance of a proper set of process parameters and good analysis of experimental results are some time problematic due to lack of unquestionable interpretation methods for the discussed temperature range. As a consequence, a system for computer aided physical simulations of deformation of metals at extra high temperatures has been developed. The program can be used to predict the shape and dimensions of deformation zone. Due to application of inverse method thermo-physical and mechanical properties of materials can easly be calculated according to tests conducted by variable specimen temperature. The basis of the system is the thermal-mechanical high temperature model developed by authors for simulation of processes which require high accuracy obligatory for both the inverse method and variable density [1-4]. The incompressibility and controlled compressibility conditions are introduced into the model in analytical form. It can help toavoid problems with unintentional specimen volume changes and is important in modelling of thermo-mechanical behaviour of steel in temperature range which is characteristic for the transformation of state of aggregation. Existing steel density changes in the mushy zone can cause volume variations close to those which come from numerical errors. The paper presents the latest version of Def_Semi_Solid system and its abilities. The system is an implementation of the presented model. The previous version of the program was developed by the authors two years ago. It worked under control of the Windows systems. Since that time the programme abilities have reached a more advanced level. The program has been written in two programming languages: the solver in FORTRAN and the graphical part in object oriented C++. This approach enables usability of the program both under Windows and Linux/Unix systems. The latest version of Def_Semi_Solid is equipped with full automatic installation unit and new graphical interface and consists of three independent units: pre-processing, two solvers (resistance heating solver and deformation solver) and post-processing. The system is also equipped with additional tools. The most important among them is the previously mentioned inverse analysis module. The paper consists of both theoretical and experimental part. Apart from presentation of computational results the comparison with physical simulation is published showing good predictive ability and usefulness of the system. REFERENCES [1] M. Glowacki, Z. Malinowski, M. Hojny, D. Jedrzejczyk, The Physical and Mathematical Modeling of Plastic Deformation of Samples with Mushy Zone, Proc. Int. Conf. Inverse Problems, Design and Optimization Symposium, Rio de Janeiro, Brazil, p. 79-86, 2004. [2] M. Glowacki, M. Hojny, The Mathematical Modelling of Strain and Stress Fields in Samples with Mushy Zone, Steel Grips 2, Proc. Metal Forming, p. 559 – 565, 2004. [3] M. Hojny, M. Glowacki, Computer aided testing of metal deformation at extra high temperature, Proc. Int. Conf. Forming, Lednice, Czech Republik, 2005. [4] M. Glowacki, M. Hojny, Computer modelling of deformation of steel samples with mushy zone, Proc. Int. Conf. ECCM, Lisbon, Portugal, 2006.

W parcy zaprezentowano wyniki prac teoretycznych i doświadczalnych prowadzących do modelowania zjawisk towarzyszących odkształcaniu stali w ostatniej fazie procesu krzepnięcia. Symulacje fizyczne odkształcania w takich warunkach z wykorzystaniem nowoczesnych urządzeń (np. symulator GLEEBLE 3800) są kosztowne i bardzo trudne ze względu na równoczesne odkształcenie i krzepnięcie metalu i jego niestabilne zachowanie. Zastosowanie dedykowanego systemu symulacji komputerowej wykorzystującego analizę odwrotną umożliwia procedurę testową i obniża koszty eksperymentu. Autorzy zaprezentowali taki właśnie system uwzględniający zmienną gęstość i warunek nieściśliwości w postaci analitycznej. Podstawowym celem symulacji jest odtworzenie zmian temperatury, odkształceń i naprężeń w próbkach stalowych poddawanych odkształceniu w końcowej fazie krzepnięcia. Zaprezentowany program umożliwia prawidłową interpretację odkształcania w bardzo wysokich temperaturach.