Ultrasonic welding has applications in many areas of the composite industry. So how does it work?
Ultrasound is a mechanical vibration similar to that produced by musical instruments. They are called ultrasound because their frequency is above the hearing range of the human ear (greater than 16 kHz).
In an acoustic assembly, these pressure waves are produced by a generator. This sends an alternating current of the same frequency as the converter (or transducer).
Then the converter, which is made of piezoelectric ceramics, transforms this energy into mechanical vibrations.
In ultrasound, a voltage is sent to the ceramic and it lengthens or shortens depending on the polarity of the voltage.
Finally, once the vibration is produced, it is amplified and transmitted to the parts to be a welded by the sonotrode. The vibrations generated create heat by friction and melting of the surfaces to be welded.
The generator converts the mains network (50/60 Hz) electrical frequency into a corresponding high frequency electrical energy, in this diagram, to 20,000 Hz.
The piezoelectric converter (or transducer) transforms the electrical 20,000 Hz frequency into mechanical vibrations of the same frequency. The energy is then mechanical.
The booster, or amplitude amplifier, is used to increase or reduce the amplitude produced by the converter.
The last element in the acoustic chain, the sonotrode transmits ultrasound energy to the welding workpiece.
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