Physical Simulation Papers
The following are abstracts of past papers presented by members of the Dynamic Systems team. If you would like more information about any of these subjects, please contact us.
Development of New Physical Simulation Technology for Continuous Casting and Semi-Solid Rolling
by D. Ferguson, W. Chen and H. Ferguson
Numerical and physical modeling have an important role in materials and thermo-mechanical process development. Numerical modeling popularity has grown with the increasing capabilities of software and computers. The use of physical modeling simulation has also grown in popularity as a tool to provide essential physical property data, boundary conditions for processes and for validation of computer models. In response to increasing demands on researchers to develop new materials and processes, and to lower costs, new physical simulation technology developments continue to be made in several areas. This paper discusses various methods used for continuous casting and rolling simulation and focuses on the development of a new thermo-mechanical physical simulation system for continuous casting and semi-solid rolling. This new simulator contains significant technology advancements in capabilities for melting, solidification and rolling in-situ, thus providing enhanced capabilities for simulation of continuous casting processes followed by direct rolling or semi-solid rolling. A scanning laser allows the measurement of phase transformations in the material after deformation. Specimens of substantial size are used and after simulation, the deformed specimen can be machined for subsequent mechanical property measurements.
An overview of the simulator design and its application will be presented. Comparisons of the design and methods used in the new system with previously used methods for casting and rolling simulation will be shown.

New Developments in the Field of Physical Simulation of Thermomechanical Processing
by D. Ferguson1, W. Chen1, R. Kuziak2, S. Zajac3
1Dynamic Systems Inc., Poestenkill, NY USA 12140
2The Institute for Ferrous Metallurgy, Gliwice, Poland
3Swedish Institute for Metals Research, Stockholm, Sweden
Computer mathematical modeling becomes more and more popular in materials thermomechanical processing thanks to the development of computation technology. However, it must rely on physical modeling and simulation which provides essential physical property data, boundary conditions, and even validation of a computer model itself. Physical modeling technologies have developed significantly over the recent years with the increasing pressure on researchers for new materials and lower production costs. As a result, physical simulation systems have become more capable, accurate, and efficient with higher deformation speeds, more complex stress states, more flexibility in functions, along with easier programming and operation.
This paper will focus on a new experimental technique used in physical simulation and discuss the results obtained. The emphasis will be put on a new generation of thermomechanical simulator that has been developed. This multi-axis hot deformation (MAXStrain) system can subject materials to virtually unlimited strain under precise control of strain, strain rate, and temperature. The deformed specimen can be machined for subsequent mechanical property measurements. The MAXStrain system has been used for ultrafine grain and nanometer materials development. The strength of an ultrafine grain (1 mm) plain carbon steel (AISI 1018) was doubled after multi-axis thermomechanical controlled hot deformation. The strength of an aluminum alloy (AA5083) reached 560 MPa after a strain of 5 imposed at room temperature compared to 290 MPa with no prior deformation.

Development of Ultrafine Grained Materials Using the MAXStrain® Technology
by W. Chen, D. Ferguson and H. Ferguson
Costly processing of fine grain materials and low strain rate superplastic forming has been the bottle-neck for development of the superplastic forming technology. It has been realized that the finer the grain size the faster a complex part can be superplastically formed. Several techniques have been developed to produce the ultrafine grain structures primarily using a severe-plastic-deformation method, such as equal channel angular pressing (ECAP), 3D forging, high pressure torsion (HPT), and accumulative roll bonding (ARB) technique. Recently, a multi-axis restraint deformation technique (MAXStrain® Technology) was developed to achieve extremely large strains. The technology offers the potential to cost-effectively produce industrial-size ultrafine-grained bulk materials, such as aluminum alloys. In this paper, a cost-effective procedure of developing ultrafine-grain structures of a commercial aluminum alloy will be presented. The results show that the MAXStrain® technology is promising in industrial applications, such as making materials for high strain rate superplastic forming.

New Tests for Welding Cracks
by W. Chen
There are over 150 weldability testing techniques to date. In general, they can be classified into two categories as representative (self-restraint) and simulative (augmented restrain) test techniques. The representative test technique usually tells only 'cracking' or 'no-cracking' of a material when an actual welding situation is represented, which can not quantify the cracking susceptibility of the material under different welding conditions. The simulative test can follow a thermomechanical history of a material during welding, and an external strain is usually applied to be able to quantify the cracking susceptibility, i.e., weld metal solidification cracking susceptibility and HAZ cracking susceptibility. Among the simulative tests, the Varestraint test and the Gleeble® hot ductility test are the most widely used in weldability studies.
This presentation will first discuss the solidification cracking susceptibility test and then introduce a new testing procedure in weld metal cracking susceptibilities, i.e., the Strain Induced Crack Opening (SICOTM) procedure. To simulate the fusion process in the weld metal zone, a specimen must be heated to its melting temperature. This fusion process can be controlled by Gleeble® power input. The solidification cracking susceptibility can be studied simply by fixing the jaws during subsequent solidification to examine if it has cracks, or further cooling to different temperatures to pull the specimen apart to measure the hot ductility.
The SICOTM procedure was originally developed for hot workability studies of metals. The critical strain defined as the hoop strain at the onset of cracking during compression is measured to characterize the hot workability. The SICOTM procedure has also been applied to study the solidification cracking susceptibilities. In multi-bead welds of austenitic stainless steels and nickel-base alloys, small cracks (or so-called microfissures) can occur in characteristic sites just below the top layer of the weld. SICOï tests can be used to examine the presence of microfissures in multipass welding process simulation. The critical strain obtained from specimens cut from the top layers showed lower values than that at the bottom layer at given temperatures. The difference in the critical strains indicates the presence of the microfissures in the multi-bead welds.
Four electrode alloys were examined in this study using the SICOTM procedure. The testing procedure complies with the proposed micromechanism of the microfissure formation and is considered to be suitable for microfissure susceptibility studies in multipass welds of high alloy stainless steels and Ni-base alloys.

Multi-Axis Deformation Methods to Achieve Extremely Large Strain and Ultrafine Grains
by W. Chen, D. Ferguson and H. Ferguson
Ultrafine grain size is often achieved by severe plastic deformation. A few techniques have been developed to achieve severe plastic deformation, such as equal channel angular (ECA) pressing/extrusion, torsion straining, and accumulative roll bonding (ARB) techniques. This paper will introduce multiaxis deformation techniques which can achieve extremely large strains with constant deformation volume.
Two different types of multiaxis hot deformation methods, each with a different number of deformation axis, are studied. They are two-axis deformation and three-axis deformation. The two-axis deformation can be fully restrained or unrestrained lengthwise, and the thermal profile and history of the specimen can be readily controlled. The three-axis deformation has no restraint. The bulk volume of multiaxis full restraint compression specimens can be easily machined into mechanical test samples for mechanical property measurements and other studies.
A plain carbon steel (AISI 1018) was studied using the Multi-Axis Restraint Compression System developed at Dynamic Systems Inc. One micron grain size was achieved with the plain carbon steel. The ultimate tensile strength measured doubled, when compared to that of the conventionally hot rolled material.