Modelling of heat generation in linear friction welding using a small strain finite element method

Heat generation in linear friction welding of Ti alloy was modelled with a computationally efficient finite element analysis. This was achieved by using multiple small strain analyses during one quarter cycle of workpiece oscillation, giving a snapshot of the average heat dissipation rate in a single complete cycle. This mechanical model for heat generation in a single cycle was then repeated at intervals throughout the equilibrium phase of welding. A separate continuous thermal model of the process (Jedrasiak et al., 2018), provided the spatial temperature field as an input to each mechanical analysis. The values of instantaneous power from the mechanical model agreed well with the power history used in the thermal model, independently inferred from thermocouple data. Axial shortening of the weld geometry required particular attention, and was handled by discarding thin layers of elements at discrete intervals to match the flash expulsion rate. The predicted distributions of plastic strain and heat generation were concentrated within narrow windows of temperature and flow stress, corresponding to a layer of material at the interface less than 1 mm thick, consistent with weld micrographs.