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Research Papers

# The Physical and Computer Modeling of Plastic Deformation of Low Carbon Steel in Semisolid State

[+] Author and Article Information
Marcin Hojny

AGH-University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Polandmhojny@metal.agh.edu.pl

Miroslaw Glowacki

AGH-University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Poland

J. Eng. Mater. Technol 131(4), 041003 (Sep 09, 2009) (7 pages) doi:10.1115/1.3184034 History: Received December 01, 2008; Revised June 12, 2009; Published September 09, 2009

## Abstract

This paper reports the results of theoretical and experimental work leading to the construction of a dedicated finite element method (FEM) system allowing the computer simulation of physical phenomena accompanying the steel sample testing at temperatures that are characteristic for integrated casting and rolling of steel processes, which was equipped with graphical, database oriented pre- and postprocessing. The kernel of the system is a numerical FEM solver based on a coupled thermomechanical model with changing density and mass conservation condition given in analytical form. The system was also equipped with an inverse analysis module having crucial significance for interpretation of results of compression tests at temperatures close to the solidus level. One of the advantages of the solution is the negligible volume loss of the deformation zone due to the analytical form of mass conservation conditions. This prevents FEM variational solution from unintentional specimen volume loss caused by numerical errors, which is inevitable in cases where the condition is written in its numerical form. It is very important for the computer simulation of deformation processes to be running at temperatures characteristic of the last stage of solidification. The still existing density change in mushy steel causes volume changes comparable to those caused by numerical errors. This paper reports work concerning the adaptation of the model to simulation of plastic behavior of axial-symmetrical steel samples subjected to compression at temperature levels higher than $1400°C$. The emphasis is placed on the computer aided testing procedure leading to the determination of mechanical properties of steels at temperatures that are very close to the solidus line. Example results of computer simulation using the developed system are presented as well.

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## Figures

Figure 1

The example photo—equipment used for NST examination

Figure 2

Initial density distribution in cross section of a sample deformed at 1460°C

Figure 3

The main stages realized during experiments—GLEEBLE 3800 thermomechanical simulator

Figure 4

Sample pickled in Oberhoffer reagent—deformation at (a) 1400°C, (b) 1425°C, and (c) 1460°C (magnification of 10X)

Figure 5

The cross section of the sample after mounting and preliminary compression in the GLEEBLE equipment

Figure 6

Comparison between measured and calculated loads at a temperature of 1425°C (tool velocity of 10 mm/s)

Figure 7

Flow stress versus strain at temperature levels of 1425°C, 1450°C, and 1460°C for two values of tool velocity

Figure 8

Influence of deformation temperature on the maximum force recorded during experiment for four variants and for tool velocity: 1 mm/s, 10 mm/s, 20 mm/s, and 100 mm/s

Figure 9

The handle with short contact zone and example sample (with marked position of steering thermocouple TC1) used in the experiment

Figure 10

Comparison between the experimental and theoretical time-temperature curves (indication of steering TC1 thermocouples and deformation at 1460°C)

Figure 11

Initial temperature distribution in the cross section of a sample deformed at 1425°C

Figure 12

Effective strain distribution in the cross section of the sample deformed at 1425°C

Figure 13

Effective strain distribution in the cross section of the sample deformed at 1460°C

Figure 14

Mean stress distribution in the cross section of the sample deformed at 1425°C

Figure 15

Mean stress distribution in the cross section of the sample deformed at 1460°C

Figure 16

Final temperature distribution in the cross section of the sample deformed at 1425°C

Figure 17

Final temperature distribution in the cross section of the sample deformed at 1460°C

Figure 18

Final shapes of the samples after deformation at 1400–1460°C and a tool velocity of 10 mm/s

Figure 19

The comparison between the measured and calculated lengths of the zone, which was not subjected to the deformation—experiments for 1425°C and 1460°C (tool velocity of 10 mm/s)

Figure 20

The comparison of the measured and calculated maximum diameters of the samples—deformation at 1425°C and 1460°C (tool velocity of 10 mm/s)

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