Abstract
High Pressure Torsion (HPT) is a highly effective super-plastic deformation process for obtaining nano-materials with high performance mechanical properties. In view of its optimization, it is of paramount importance to evaluate the relations between the behavior of the material under the effects of different processing parameters. In this context, this work aims to highlight the plastic strain distribution in the deformed material as a function of the hydrostatic pressure, the torsion angle and the temperature of the material applied during the process. A typical amorphous polymer (Polymethyl-Methacrylate: PMMA) has been tested. Firstly, in order to identify the material parameters of a phenomenological elasto-viscoplastic model compression tests at different temperatures and strain rates have been carried out. Then, the distributions of the effective plastic strain, the equivalent plastic strain rate and the hydrostatic stress were analyzed using finite elements method. Recommendations on process conditions were proclaimed at the end of this work according to the obtained numerical results.
Highlights
There have been extensive investigations over the last two decades into the production of bulk ultrafine-grained (UFG) materials through the application of severe plastic deformation (SPD) [1, 2]
SPD techniques have been used in the modification of microstructure
T o identify the parameters of the elasto-viscoplastic constitutive law presented in the previous paragraph, we used compression tests at different strain rates and different temperatures conducted on polymethyl-methacrylate (PMMA) samples
Summary
There have been extensive investigations over the last two decades into the production of bulk ultrafine-grained (UFG) materials through the application of severe plastic deformation (SPD) [1, 2]. SPD techniques have been used in the modification of microstructure. They made possible to produce nano-crystalline (NC) microstructures out of metallic materials [3, 4]. Such SPD methods include High Pressure Torsion (HPT), Equal Channel Angular Pressing (ECAP), Accumulative Roll Bonding (ARB), Multiple Forging, Twist Extrusion (TE) and some others. Among the various SPD techniques, Equal-Channel Angular Pressing (ECAP) and High Pressure Torsion (HPT) are the most common [5]. To date, processing by HPT has proven to be the most effective of all the SPD methods in producing bulk nanostructured materials [6]. Different materials have been tested experimentally [14] and theoretically [15] through the application of HPT process such as aluminum alloys [8, 16], nickel [17], copper [15], titanium alloys [3, 18], polymers [19], zirconium [20, 21], Magnesium alloys [22], aluminum-zinc alloys [23], intermetallics [24, 25] and others (see [26, 27])
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