Experimental studies and asymptotic scaling for the development of engineering tools to predict coupled heat transfer and plastic deformation in Friction Stir Welding (FSW)

• Author / Creator

  Tsui, Jordan A.

• A study of temperature, force, and torque was performed using a set of ten different friction stir welding (FSW) tools. It was observed that pin diameter had the most significant effect on steady state welding temperature followed by shoulder diameter having a smaller but measureable effect. Pin threading caused the smallest change, increasing welding temperature only a few degrees higher than a smooth surface pin. Comparisons between temperatures measured from the FSW tool and the base material showed that material deformation during welding often causes thermocouple position in the substrate to move which can result in inaccurate readings. Additionally, thermocouples located in the substrate failed to fully capture temperature changes caused by increases in the tool shoulder diameter. Forces measured along the x, y, and z axis were all directly related to the size of the pin and shoulder diameter with the pin having a greater influence. As pin or shoulder diameter were increased, forces along the three axes increased and vice versa. However, once pin diameter became large enough the addition of pin threading caused measured force to decrease due to increased welding temperature which softened the base material. Torque was also directly related to the size of the pin and shoulder diameter (i.e. as pin/shoulder diameter increased, measured torque increased). The one exception was for tools with small pin diameter which experienced high torque due to their inability to generate enough frictional heating which led to low welding temperature. Experimental results of welding temperature and torque were compared to an existing model of coupled heat transfer and plastic deformation. Analyzing a single material with the model yielded the best results, and the accuracy of theoretical welding temperature and torque for aluminum alloy 5059 was 94% and 85%, respectively. Accounting for the size of the tool shoulder in a correction function for the model improved predicted values of temperature and torque by ~5% over previous results that did not account for shoulder diameter.

• Subjects / Keywords

  • FSW
  • Friction Stir Welding
  • Welding Torque Model
  • Effects of Tool Geometry
  • Welding Temperature Analysis
  • Welding Force Analysis
  • Welding Temperature Model

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3736MC73

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.