超声波简介及其应用外文翻译

襄樊学院毕业设计(论文)英文翻译题 目超声波简介及其应用专 业机械设计制造及其自动化班 级机制0712姓 名刘康学 号07116201指导教师职 称李梅副教授2011年5月25日Introduction and application of ultrasonicUltrasonic is a mechanical waves which frequency above 20,000 Hz. Ultrasonic inspection commonly used in the frequency of 0. 55 MHz. The mechanical waves in the material spread in a certain speed and directions, acoustic impedance different heterogeneous interfaces such as defect is encountered or the bottom surface of the object being tested, will reflections. This reflection phenomenon can be used to ultrasonic testing , most common is pulse echo testing method testing , pulse oscillator issued of voltage plus in probe with pressure electric ceramic or quartz chip made of detection components , probe issued of ultrasonic pulse by sound coupled media such as oil or water , entered material and in which spread , encountered defects , part reflection energy along original way returns probe , probe will change it in electric pulse , by instrument zoom and display in oscilloscope tubes of screen . Depending on where the flaw echo on the screen and amplitude of reflection wave with artificial defects in a reference block rate compared to defect location and approximate dimensions. Apart from Echo method, and use another probe to the other side of the workpiece to accept signal penetration method. When use ultrasonic detection the physical properties of materials, also often take advantage of ultrasonic in sound velocity, attenuation and resonance characteristics of workpiece.Ultrasonic characteristics: 1, ultrasonic beam to focus on a specific direction, along the straight lines in the media, has a good point. 2, ultrasonic wave propagation in the media, attenuation and scattering occurs. 3, ultrasonic wave on the interface of heterogeneous media will make reflection, refraction and mode conversion. Using these features, you can get the defective interface from reflected reflection, so as to achieve the purpose of detecting defects. 4, ultrasonic energy is power than sonic. 5, the ultrasonic loss is very small in solid transmission , probe depth, as occurs in the hetero - interface by ultrasonic phenomena such as reflection, refraction, especially not by gas - solid interface. If the metal air holes, flaws and layer defects such as defects in a gas or a mixture, when defects at the interface of ultrasonic propagation to the metal and on all or part of the reflection. Reflected ultrasonic probe received, handled through circuits inside the instrument, on the screen of the instrument will show a different height and have a certain pitch waveform.Based on waveform characteristics of determine defect depth, location, and shape of the workpiece.Non - destructive testing is not damaged parts or raw materials subject to the status of the work, a means of detection of surface and internal quality checks, Nondestructive Testing abbreviations short for NDT. Ultrasonic testing is also called ultrasonic, ultrasonic flaw detector, is a type of non - destructive testing. UT is on industrial ultrasonic testing non - destructive testing methods. Ultrasonic enters objects when a defect is encountered, some sound waves produce reflection, transmit and receive an analysis of the reflected wave, exception can accurately gauge the flaws. And is able to display the location and size of internal defects, determination of material thickness.Advantages of ultrasonic inspection is to detect thickness, high sensitivity, high speed, low cost, is harmless to human body, can be positioned and quantitative defects. Display of ultrasonic detection on defects are not intuitive, testing of technical difficulty, vulnerable to subjective and objective factors, and inspection results are not easy to hold, ultrasonic testing requirements on the work surface smooth, requiring experienced inspectors to identify defects types, suitable for the part of considerable thickness inspection, ultrasonic inspection has its limitations.Variety of ultrasonic flaw detector, but most widely application of pulse - echo ultrasonic flaw detector. In general, in uniform material, presence of defect will create material discontinuity, this often acoustic impedance of the discontinuity is inconsistent , by the reflection theorem we know that, in two different acoustic impedance by ultrasonic reflection on the interface of media occurs. Size and interface on both sides of the reflected energy media differences in acoustic impedance and orientation, relative to the size of the interface. Pulse - echo ultrasonic flaw detector is designed according to this principle. Most of pulse - echo ultrasonic flaw detector is a scan, the so-called A-scan display is the way the display of ultrasonic detection in materials is the horizontal coordinate of transmission time or distance, the ordinate is the amplitude of ultrasonic reflected wave. Such as , in a workpiece in the ex