转换距离英寸conversion distance inch 入射反射折射incident .ppt

Testing Techniques * * * * * * * * * 2.1.3 Unit II NDT Method 2.1 UT Pulse echo normal beam ultrasonic test 直束脉冲反射检测法 转换 距离 英寸 conversion distance inch rugged 粗糙的，高低不平的 入射 反射 折射 incident / incidence reflect / reflection refract / refraction A pulse-echo ultrasonic normal beam test can determine the location of a discontinuity with a part or structure by accurately measuring the time required for a short ultrasonic pulse generated by a transducer to travel through a thickness of the material. 通过精确测量探头产生的超声脉冲穿过工件需要的时间，直束脉冲反射检测可以发现工件中的不连续性。 Then it reflects from the back or surface of a discontinuity and is returned to the transducer. 超声波从工件底面或不连续性的表面反射回探头。 The ultrasonic tester graphs a peak of energy whenever the transducer receives a reflected wave. 只要探头接收到反射波，超声仪就会显示波形能量图。 Right when the initial pulse of energy is sent from the tester, some is reflected as the ultrasonic waves go from the transducer into the couplant. 当超声仪发送初始脉冲信号，超声波从探头进入到异质界面将会有部分能量发生反射。 The first peak is therefore said to record the energy of the initial pulse. 第一个波就是初始脉冲信号。 The next peak in a material with no defects is the backwall peak. 如果工件中没有缺陷，第二个波就是底波。 This is the reflection from waves changing between the bottom of the test material and the material behind it, such as air or the table it is on. 由于工件和底座材质的差异，譬如空气和桌子，因此超声波传播到工件底面就会产生反射波。 The back wall peak will not have as much energy as the first pulse, because some of the energy is absorbed by the test object and some into the material behind it. 底波能量小于初始脉冲，这是由于部分能量被工件吸收了，还有部分能量传播到工件底面外了。 The amount of distance between peaks on the graph can be used to locate the defects. 显示器上波与波之间的距离用于缺陷的定位。 If the graph has 10 divisions and the test object is 2 inches thick, each division represents 0.2 inches. 如果显示器分成10个分格，检测件2英寸厚，那么每个分格表示0.2英寸。 If a defect peak occurs at the 8th division, we know the defect is located 1.6 (0.2*8) inches into the test object. 如果在第8个分格上出现一个反射波，这说明该缺陷位于1.6英寸深度的位置。 Since it reflected energy sooner than the back wall,