Ultrasonic welding of metals

Ultrasonic metal welding of AA 6022‐T4 lap joints: Part I – Technological characterisation and static mechanical behaviour

“…23 The reason why these studies observed local fusion could be the wrong selection of technological parameters, for example a initial interface condition; b interface after oxides and contaminants disruption 2 Formation of ultrasonically spot welded joint 3 Joint transversal section micrograph after Barkel low values of clamping force produce a 'friction type' welding and a strong heat formation. 6,24 In any case, it is commonly accepted that USMW can count on a great advantage compared with fusion welding because it seems that no wide heat affected zones (HAZs) take place. In order to experimentally check the validity of this statement, a spot welded joint (made of AA 6022-T4 aluminium alloy and obtained using the best technological parameters described in the next sections) was sectioned along the longitudinal direction and subjected to a series of nanoindentations on both the base material and the spot weld, so to derive the local profile of the Vickers hardness HV.…”

Role of friction on the thermal development in ultrasonically consolidated aluminum foils and composites

“…The prescribed amplitude of oscillation and fixed frequency are regulated using feedback control built into the welder. The frequency used, 20 kHz, is, as reported by Neppiras' (1965) investigation of the physical mechanisms involved in ultrasonic welding, typical to ultrasonic welding. The clamping force is controlled with a pressure regulated pneumatic cylinder.…”

“…It is also known that the bonding mechanisms of ultrasonic welding are heat-assisted. Though not required, the application of additional heat (pre-heating) facilitates the welding process as reported by Neppiras (1965). Plastic deformation occurs from friction, the applied load, and thermal and acoustic softening.…”

“…It has been suggested that diffusion and plastic deformation aid in the bonding process as theorized by Neppiras (1965) and discussed by Hazlett and Ambekar (1970). Janaki Ram et al (2007) attributed flow lines to plastic deformation which permitted the embedment of fibers during UC.…”

A model for weld strength in ultrasonically consolidated components

“…This action breaks up surface contaminants and oxides to permit metal -metal contact [2,3] at regions within the weld interface (termed 'contact points'). As welding continues, the scrubbing action produces elastic -plastic deformation, within the weld interface, across which diffusion and plastic flow take place [4]. Depending on the traverse speed of the sonotrode, oxides and surface contaminants continue to break up and may be displaced within the vicinity of the interface and along the weld zone [5,6] resulting in solid-state metallurgical bonds and no noticeable external deformation of the specimen [7,8].…”