It is easy to cut foam with an ultrasonic knife, but when the material gradually hardens, from cardboard, rubber, wood to hard plastic, the ultrasonic knife can cut smoothly.
What is an ultrasonic knife? How does it cut everything? To understand the ultrasonic knife, you must first know what ultrasound is?
When the vibration generated by the sound-emitting body propagates in the air or other substances, the waves generated are called sound waves. Different sound waves have different vibration frequencies. Everything has a frequency. The frequency is measured in hertz. Scientists call the number of vibrations per second the frequency of sound, but not all humans can hear this frequency. So in order to help divide, people call sound waves below 20 Hz infrasound waves, sound waves above 20,000 Hz ultrasonic waves, and sound waves between 20 Hz and 20,000 Hz are the sound waves that can be heard by the human ear.
Sound waves are a mechanical wave that transmits energy in the form of waves. Ultrasonic waves have many characteristics due to their high frequency, such as high power, high energy, short wavelength, and good directivity. These excellent characteristics make them used in many places. Ultrasonic knife is one of them. What is the cutting principle of ultrasonic knife? Since the manifestation of sound waves is vibration, ultrasonic knife also uses its vibration principle.
Common ultrasonic knives are mainly composed of ultrasonic generators, transducers, amplitude modulators and cutting knives. Among them, the ultrasonic generator is responsible for converting ordinary power into alternating current with high-frequency voltage, and then the transducer converts this part of high-frequency electricity into mechanical vibration of the same frequency, and then the mechanical vibration is transmitted to the cutting knife through the amplitude modulator that can change the amplitude, so that the blade extends the length direction and vibrates with an amplitude of ten to 70 microns and 40,000 repetitions per second.
However, since this amplitude is quite small, it cannot be observed by the naked eye. The huge energy of ultrasonic waves is concentrated on the cutting part where the blade contacts the material during the layer-by-layer transmission, which increases its temperature, melts the material, greatly reduces its strength, and the cutting is carried out smoothly.
So in summary, the principle of ultrasonic knife is to transfer the energy of ultrasound to the blade in the form of high-speed vibration, and use the generated high temperature to cut the material. In addition to ultrasonic knife, what other applications does ultrasound have in life?
Common ultrasonic cleaning is to put three rust-colored cylinders in the cleaning liquid, and then turn on the cleaning mode. With the generation of fine ripples on the water surface, the transparent liquid is quickly filled with red rust particles, and these rusts are emitted from the cylinders.
As for its cleaning principle, it actually uses the energy transfer of ultrasound in the liquid, but this process has an additional empty role, because the sound wave is transmitted longitudinally according to the sine curve, that is, one strong and one weak are transmitted in sequence. When a weak signal acts on the liquid, it will produce a certain negative pressure on the liquid, that is, low pressure. On the contrary, a strong signal brings high pressure. Therefore, the high and low pressures of the cleaning liquid will be converted to each other during the propagation of ultrasound in the liquid.
At low pressure, the liquid produces a large number of fine and tiny bubbles, which is the cavitation phenomenon. At the high pressure stage, the bubbles are squeezed inwards and burst rapidly. At this time, the shock wave generated by the burst will instantly increase the pressure around the bubbles to more than 1000 standard atmospheres, accompanied by high temperatures in the local area. The mechanical force generated by this repetitive process will continuously impact the surface of the object in all directions, so that the attached dirt will quickly fall off, thereby achieving the purpose of cleaning.