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    2019-8-28 19:20:30
    When an object vibrates, it makes a sound. Scientists call the number of vibrations per second the frequency of sound (hertz). The frequency of sound waves that human ears can hear ranges from 16 HZ to 20 KHz (kilohertz). Therefore, when the vibration of an object exceeds a certain frequency, that is, the threshold value of the human ear, the human can not hear it. This kind of sound wave is called "ultrasound". Ultrasound frequency, usually used in medical diagnosis, ranges from 1 to 5 MHz.
    Although humans can't hear ultrasound, many animals can hear it. They can use ultrasound to "navigate", track food or avoid dangerous objects. You may have seen many bats flying around the yard on summer nights. Why don't they get lost without light? The reason is that bats emit ultrasound between 20 and 100,000 hertz, like an active "radar station". Bats use this radar to identify insects or obstacles in front of them.

    It was not until World War I that we humans learned to use ultrasound. Ultrasound uses the principle of "sonar" to detect objects and their states in water, such as the position of submarines. At this time, a series of different frequencies of ultrasonic waves are sent to the water, and the reflected echoes are recorded and processed. According to the characteristics of the echo signal, the range, shape and dynamic change of the detected target can be estimated. The earliest medical application of ultrasound was in 1942, when Austrian doctor Dusk first used ultrasound technology to scan brain structures; then in the 1960s, doctors began to use ultrasound to detect abdominal organs. Ultrasound scanning technology has become an indispensable tool for modern medical diagnosis.


    The working principle of medical ultrasound examination is similar to that of sonar, that is, ultrasound is transmitted to human body through sound wave. When it encounters an interface in the body, it will be reflected and refracted, and may be absorbed and attenuated by human tissues. Because of the different shapes and structures of human tissues, they can reflect and refract ultrasonic waves and absorb them to varying degrees. In addition, combined with anatomical knowledge, normal and pathological changes, we can diagnose whether the organs examined are diseased or not.
    Sound waves above 20 Hz. A branch of acoustics, which studies the generation, transmission, reception and application of ultrasound, is called ultrasound. There are mechanical ultrasonic generators (such as air flute, air flute, liquid flute). The electroacoustic generators are made of electromagnetic induction and electromagnetic interaction principle. The electroacoustic transducers are made of piezoelectric crystals and ferromagnetic materials by electrostrictive effect.
    Welding Principle
    The principle of ultrasonic plastic welding is that the generator generates 20KHz (or 15KHz) high-voltage and high-frequency signals. Through the energy conversion system, the signals are converted into high-frequency mechanical vibration and added to the plastic parts.
    Temperature transfer to the interface increases through friction between the surface and molecules of the workpiece. When the temperature reaches the melting point of the workpiece itself, the workpiece interface melts rapidly, and then fills the gap between the interfaces.
    When the vibration stops, the workpiece is cooled and formed under certain pressure.
    Perfect welding has been achieved.
    The new 15KHz ultrasonic plastic welding machine has unique welding effect on soft PE, PP materials and large diameter and long length plastic welding parts, which can meet the needs of various products.
    It can contribute to the production efficiency and product grade of users. For more information, please visit the website: http://www.spn-biz.com.
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