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对材料进行超声波探伤时,表征缺陷特性的主要因素之一就是讯一杂比。此间,讯号应理解为缺陷的回波脉冲,杂音应理解为结构的混响杂音。压电元件的直径和反射体(缺陷)的尺寸对由缺陷反射的超声波能量都有影响,因为随着它们尺寸的变化,指向性图表也相应变化,卽图案上相对应的能量也随之改变。在发射功率一定时,结构杂音的强度与发射的方向性无关。当波长和晶粒度之比一定时,对于粗晶材料存在一个可使讯一杂比最好的最佳频带。随着压电探
Ultrasonic flaw detection of materials, the characterization of defects in one of the main factors is the information mixed. Here, the signal should be understood as defective echo pulse, noise should be understood as the structure of reverberation noise. The diameter of the piezoelectric element and the size of the reflector (imperfections) have an influence on the ultrasonic energy reflected by the defects because the directivity charts change correspondingly as their dimensions change and the corresponding energies on the pattern change accordingly . The intensity of structural noise has nothing to do with the directivity of the emission at a certain transmission power. When the ratio of wavelength to grain size is constant, there is an optimum frequency band for the coarse-grained material to make the best signal-to-noise ratio. With piezoelectric probe