Context: explanation of the Friction Stir Welding process. In the fourth sentence I don't understand why there are two 〜により.
What is that is causing the process? The movement of the tool or the gradual plastic flow? My translation attempt:
Thanks to the movement of the tool the joining surfaces become agitated and unite thanks to the gradual plastic flow.
Also, in the sentence ツールの回転に引きずられる形で塑性流動 could you explain if 引きずられる refers the plastic flow being caused by the rotation of the tool or if it refers to the rotating tool being dragged? Thank you for your help!