Abstract

Additive Friction Stir Deposition (AFSD) is a friction stir based process that includes the addition of material extruding through a bore in the center of the rotating tool. The deformation of the material from the tool rotation and high pressures result in fully dense depositions printed at very high rates with forged like mechanical properties. While deposition properties of varying alloys have been increasingly published, little work has been done investigating control of the process and as with all additive processes, consistency and predictability are of significant concern before implementation can occur. One common control method implemented in Friction Stir Welding (FSW) is temperature control. This method involves a thermocouple inserted into the tool ending near the face of the tool contacting the substrate. Data from this is relayed to the controller where a PID controller outputs varying process parameters (typically torque or RPM) to control the temperature. Temperature control in FSW has been shown to help find optimum parameters for best post weld properties, improved consistency of those properties along the weld and also to increase the repeatability of each weld. Chapter two of this work investigates if the same temperature control programs can be implemented to AFSD and if there are different requirements due to its multi pass nature. It was found that by using an auto tuner to identify PID constants, process temperatures in AFSD could achieve control to within ±3 °C by 1 cm of linear traverse distance. Furthermore, this study found that varying PID constants values according to different layers or thermal boundary conditions does not appreciably impact control. This is beneficial for the technology as it simplifies the control system requirements. Chapter three of this work investigates the impacts of temperature control on the material properties of Al 7050 T7451 substrates repaired via AFSD. Hardness in the deposited material is found to increase with the process temperature but so does the HAZ size in the substrate being repaired. Variating deposition temperature had no effect on the minimum hardness value, tensile or tensile fatigue strengths. Active cooling increased the minimum hardness value, and tensile strength of the substrate. Repairing a damaged component (simulated as a dog bone with a divot) increased fatigue life of the damaged coupon at a fixed loading condition. The further work needed to determine the feasibility of AFSD repair of Al 7050 is outlined.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Manufacturing Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-04-24

Document Type

Thesis

Keywords

AFSD, temperature control, friction stir processing, Al 7050

Language

english

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Engineering Commons

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