超声波探伤英文资料.doc

Ultrasonic flaw detection Ultrasound is a mechanical wave, mechanical vibrations and fluctuations in the physical basis of ultrasonic testing.Reciprocating cyclic movement of an object along a straight line or curve in a near equilibrium position, known as the mechanical vibration. Propagation of vibration, known as volatility. Fluctuations into mechanical waves and electromagnetic waves two categories. Mechanical wave propagation of mechanical vibrations in an elastic medium. The ultrasound is a mechanical wave. The main parameters of the mechanical wave wavelength, frequency and wave velocity. Wavelength ?: the distance between the same two adjacent oscillation phase of the same wave line particle known as the wavelength, source or medium, any one particle to complete a full vibration wave just forward a wavelength distance, commonly used in meters (m); frequency f: fluctuations in the process, he served as a given point in one second, adopted by the number of complete wave is called frequency, commonly used in units of hertz (Hz); wave velocity C: fluctuations in the wave per unit time transmitted the distance is called the wave velocity, the common units of meters / second (m / s). Wavelength and wave velocity is proportional to and inversely proportional to frequency; when the frequency is fixed, the wave velocity the greater the wavelength the more long; wave velocity when the frequency lower, the more long wavelength available by the above definition: C = ?* f. Sub-sonic, sonic and ultrasonic mechanical wave propagation in an elastic medium, the propagation velocity in the same medium. Their difference mainly due to different frequencies. Frequency between 20 ~ 20000Hz can cause people to hearing the mechanical wave is called sound waves at frequencies below 20Hz mechanical waves known as infrasonic, frequencies above 20000Hz of mechanical waves called ultrasound. Infrasonic, ultrasound can not be heard.The freque