Ultrasonic Welding
Ultrasonic welding is a welding process in which ultrasonic waves or vibrations are used to generate heat for welding. Ultrasonic means those vibration waves which have frequency above the normal hearing range. It is about 20000 to 30000 Hz. It is a solid state welding process. Solid state welding is a welding process in which no external heat is added for welding.
Transducer is a device which can convert high frequency electric signal into high frequency mechanical vibration. This is connected with the welding head. The converter or piezoelectric transducer used in this welding process.
It works on the basic principle of energy of ultrasonic wave. Ultrasonic vibration creates a dynamic shear stress between the contacts of two work piece. Due to local plastic deformation and heat generate due to friction between contact surfaces, joint formation will take place at the interface.
At the start, high frequency current passes through a piezoelectric transducer. This transducer converts high frequency electrical signal into mechanical vibration. This vibration further supplied to the booster which amplify its frequency. The amplified high frequency vibration passes through horn which is in contact with welding plate. This welding creates lap joint. One plant of the weld is fixed into fixture and other one is in direct contact with horn. These plates are fixed under moderate pressure force. The horn supply high frequency mechanical vibration to the welding plate. Due to this vibration, oscillation shear force act at the interface between welding plates which result elestoplastic deformation at interface. It also create a localize temperature rise due to mechanical force and friction. This heat helps in plastic deformation at interface and makes a strong joint without melting of work piece or using filler metal.
Applications
This welding is used in fabrication of nuclear reactor components.
It is used in automotive industry for key, head lamp parts, button and switches etc.
Ultrasonic is used in electronic industries like armature winding, switches etc.
This is clean welding process so it is used in medical industries to make parts like filters, masks etc.
