In this work, the effect of processing parameters on the resulting microstructure and mechanical properties of magnesium alloy WE43 processed via Additive Friction Stir Deposition (AFSD), a nascent solid-state additive manufacturing (AM) process, is investigated. In particular, a parameterization study was carried out, using multiple four-layer deposits, to identify a suitable process window for a structural 68-layers bulk WE43 deposition. The parametric study identified an acceptable set of parameters with minimal surface defects and excellent consolidation for the fabrication of a bulk WE43 deposition. Microstructural, tensile, and fatigue life characterization was conducted on the bulk WE43 deposition and compared to commercially available wrought material to elucidate the process-structure-property-performance (PSPP) relationship of the AFSD process. This study shows that the bulk WE43 deposit exhibited a refined homogenous microstructure and a texture shift relative to the wrought material. However, a reduction in hardness and tensile behavior was observed in the as-deposited WE43 compared to the wrought control. Additionally, fatigue specimens extracted from the bulk deposition exhibited a decrease in life in the low-cycle regime but performed comparably to the wrought plate in the high-cycle regime. The outcomes of this study illustrate the potential of the AFSD process in additively manufactured structural load-bearing components made with magnesium alloy WE43 in the as-built condition.

In recent years, additive manufacturing (AM) has gained prominence in rapid prototyping and production of structural components with complex geometries. Magnesium alloys, which have a strength-to-weight ratio that is superior compared with steel and aluminum alloys, have shown potential in lightweighting applications. However, commercial beam-based AM technologies have limited success with magnesium alloys due to vaporization and hot cracking. Therefore, as an alternative approach, we propose the use of a near net-shape solid-state additive manufacturing process, additive friction stir deposition (AFSD), to fabricate magnesium alloys in bulk. In this study, a parametric investigation was performed to quantify the effect of process parameters on AFSD build quality including volumetric defects and surface quality in magnesium alloy AZ31B. In order to understand the effect of the AFSD process on structural integrity in the magnesium alloy AZ31B, in-depth microstructure and mechanical property characterization was conducted on a bulk AFSD build fabricated with a set of acceptable process parameters. Results of the microstructure analysis of the as-deposited AFSD build revealed bulk microstructure similar to wrought magnesium alloy AZ31 plate. Additionally, similar hardness measurements were found in AFSD build compared with control wrought specimens. While tensile test results of the as-deposited AFSD build exhibited a 20% drop in yield strength (YS), nearly identical ultimate strength was observed compared with the wrought control. The experimental results of this study illustrate the potential of using the AFSD process to additively manufacture Mg alloys for load bearing structural components with achieving wrought-like microstructure and mechanical properties.

This study presents a coupled mathematical surrogate modeling and finite element analysis to quantify the risk of brain injury resulting from contact between a soccer ball and a player's head. Our approach implements a previously developed and validated regulation size finite element soccer ball and a 50th percentile adult male head model to inform the surrogate models regarding the positioning of the soccer ball's impact, inbound velocity, and the role of the activation of the neck musculature. Surrogate models are developed using injury metrics such as HIC15 and BrIC, which can be correlated to clinical assessments. The surrogate models predict occipital-temporal impacts as the highest risk of injury along a perpendicular axis and highlight the risk of increased velocity and passive neck musculature. The surrogate model predicts the worst-case scenarios to produce HIC15 and BrIC values of approximately 80 and 0.65, which correlate to 4.27% of a minor head injury (AIS1) and 71% of a moderate head injury (AIS2), respectively. These models are also used to develop a graphical user interface that may be used to supplement existing clinical knowledge of soccer headings to improve the head health of athletes participating in the game of soccer.

This work examines a bulk deposition of additive friction stir deposition (AFS-D) of AZ31 Mg Alloy. The AFS-D process was used to fabricate a 4” by 4” by 1/4” tall deposition of AZ31 Mg alloy using a differentiating raster pattern. The effect of the bulk deposition on material properties was examined using microstructure characterization and mechanical testing. Electron