A model relating tool torque and its associated power and specific energy to rotation and forward speeds during friction stir welding/processing

Abstract Torque ( M ) is a very important quantity in the friction stir welding (FSW) process but a satisfactory model relating M to the two major FSW parameters, rotation speed ( ω ) and forward speed ( v ), has not been well developed. In this work, a better model of the form, M = f ( ω , v ), was sought. Experimentally, FSW of an aluminium alloy was conducted over a wide range of ω and v values and M was measured. An exponential decay function has been found to fit all the M versus ω data well and is meaningful for any ω value. The effect of v on M can approximately be accounted for through linearly relating the model parameters to v . The model allows for a detailed evaluation of the sensitivity of M to changes in ω and v . The model decay and the pre-exponential parameters need to be adjusted to make predictions for different aluminium alloys in the low ω range. Both the model and experimental data demonstrate a diminishing alloy effect on material flow resistance as ω increases. Furthermore, models of tool power ( P Tool ) and specific energy ( E s ) can be derived from the model for M and give predictions that are also meaningful over the entire range of ω values. Finally, the dependences of P Tool and E s on ω and v and the relationship between E s and the processing zone temperature will be discussed.