Abstract
Friction stir extrusion (FSE) is a novel solid-phase processing technique that consolidates and extrudes metal powders, flakes, chips, or billets into high-performance parts by plastic deformation, which has the potential to save substantial processing time and energy. Currently, most studies on FSE are experimental and only a few numerical models have been developed to explain and predict the complex physics of the process. In this work, a meshfree simulation framework based on smoothed particle hydrodynamics (SPH) was developed for FSE. Unlike traditional grid-based methods, SPH is a Lagrangian particle-based method that can handle severe material deformations, capture moving interfaces and surfaces, and monitor the field variable histories explicitly without complicated tracking schemes. These aspects of SPH make it attractive for the FSE process, where in situ evolution of field variables is difficult to observe experimentally. To this end, a 3-D, fully thermomechanically coupled SPH model was developed to simulate the FSE of aluminum wires. The developed model was thoroughly validated by comparing the numerically predicted material flow, strain, temperature history, and extrusion force with experimental results for a certain set of process parameters. The validated SPH model can serve as an effective tool to predict and better understand the extreme thermomechanical conditions during the FSE process.
Highlights
Friction stir extrusion (FSE) is a solid-phase processing technique that is used to consolidate and extrude highperformance wires, rods, and tubes from metal powder, chips, Varun Gupta: Contributed to work while at Pacific Northwest National Laboratory (PNNL).flakes, or a solid billet in a single step
The evolutions of the material flow, strain, temperature, and extrusion force were predicted to gain a better understanding of the extreme thermomechanical conditions during the FSE process
3.1 Smoothed particle hydrodynamics (SPH) method In smoothed particle hydrodynamics (SPH), a continuous function f (x) and its spatial derivative ∇ · f (x) at point x in a continuous domain can be approximated as f (x) and ∇ · f (x), respectively, by a convolution integral based on the information of its neighboring particles as follows: In this study, the FSE process was performed by a one-of-kind Shear Assisted Processing and Extrusion (ShAPE) machine designed by PNNL
Summary
Friction stir extrusion (FSE) is a solid-phase processing technique that is used to consolidate and extrude highperformance wires, rods, and tubes from metal powder, chips, Varun Gupta: Contributed to work while at PNNL. Baffari et al [5] developed a 3-D, Lagrangian, thermomechanical model in Design Environment for FORMing (DEFORM)® software to simulate FSE of AZ31 milling chips They showed that the distributions of material strain, strain rate, microstructure, and temperature can be predicted well by the model. As an ideal method to simulate solid-phase processing problems, SPH was first used to predict the material flow and temperature in FSW by Tartakovsky et al [38] using the fluid-based approach. A coupled, thermomechanical, solid-based SPH model was implemented to predict the temperature, stress, strain, damage, and defect formation during the process. The evolutions of the material flow, strain, temperature, and extrusion force were predicted to gain a better understanding of the extreme thermomechanical conditions during the FSE process. The methodologies used for marker wire insertion and strain calculation can be found in greater detail in Li et al [44]
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