Acoustical Imaging Techniques—Theoretical and Experimental Results
Ultrasonic evaluation of materials has experienced tremendous growth in recent years- especially for composite materials in the automotive and aerospace industries. Of special interest is the ability to precisely identify small defects or faults at various depths inside the material. The range resolution is inherently limited by the transmitting pulse width and operating frequency. Improvement can be made by using large amplitude narrow pulses. However, a very narrow pulse is difficult to produce in practice, besides which its instantaneous ultrasonic intensity could cause damage to the transmitting transducer and/or the target. In addition to the range resolution limitation, we observed that the typical acoustic imaging system has some range accuracy problems related to the limited coherence of trigger time from the microprocessor controlled ultrasonic pulse transmission. This has caused a range inaccuracy of as much as one millimeter in water at an operating frequency of 2.25 MHz.
KeywordsTrigger Time Attenuation Property Boundary Reflection Attenuation Imaging Ultrasonic Evaluation
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