The effect of micro - swinging on joint formation in linear friction welding

Abstract

A 3D Eulerian numerical model was developed to investigate the effect of micro-swing on joint formation during workpiece oscillation in linear friction welding (LFW). The temperature field and axial shortening history for different amplitudes of micro-swing have been studied. Results show that the amplitude of micro-swing influences flash morphology and axial shortening. The micro-swing contributes to the extrusion of viscoplastic metal and the formation of flash during the LFW process. Flash volume and axial shortening increase as the amplitude of micro-swing becomes larger. When the amplitude of micro-swing is more than a critical value, a sudden change of axial shortening (different from the period of the oscillation cycle) would occur at certain welding time, which change would also have a periodic nature. Although different amplitudes of micro-swing affect joint morphology, the inner temperature field and the highest temperature of joints remain constant. The high temperature region inside the joints remains about the same, when the amplitude of micro-swing is constant. This indicates that the heat generated through plastic deformation could maintain the welding process, and so that the welding process would enter the equilibrium phase.

3D modelling of Ti–6Al–4V linear friction welds

“…Sorina-Müller et al [20] developed a 3D model to compare the weld temperatures of a ‘prismatic’ and a ‘blade-like’ geometry for Ti–6Al–2Sn–4Cr–6Mo; the larger prismatic geometry had a higher interface temperature. Li et al [21] analysed high-speed photography of the LFW process and noted that the workpieces do not oscillate in a rigid manner. In fact, it was noticed that the workpieces can move in the tooling, which generates a ‘micro swing’ effect.…”

“…The models showed that the burn-off rate increased with larger angles of micro-swing, which was due to one workpiece digging further into the other and extruding more material per cycle. According to Li et al [21], the different micro-swinging angles had negligible effect on the interface temperature at the centre of the weld. Bikmeyev et al [22] used a 3D model to investigate the mechanisms behind the formation of the plasticised layer (start of phase 2).…”

The effects of forging pressure and temperature field on residual stresses in linear friction welded Ti6Al4V joints

“…The temperature during the process does not reach the melting point of the parent material (PM), thus, solidification problems (e.g., hot cracking, porosity, segregation) are avoided [3,5]. A number of additional advantages such as no spatter, no need for filler material and gas protection [6][7][8], have made LFW an important technology to manufacture and repair blisks in aeroengines [9,10]. Furthermore, LFW has been demonstrated to be effective in welding similar or dissimilar joints of titanium alloys, steels, nickel alloys and aluminum alloys [11][12][13][14].…”

Role of oscillation frequency and amplitude on the microstructure and properties of linear friction welded nickel aluminium bronze joints

“…The plastic region expands when frictional heat is directed away from the contact, extruding material as a flash out from the interface. The final step is the deceleration or forge phase, in which the materials are made to rest once the necessary shortening has been achieved [21]. The aviation engine industry's desire to develop titanium alloy blisks, which offer lower weight and improved performance than traditional slotted blade/disk combinations, has fueled most of LFW's advancement [22][23][24].…”