Measurement Models for Ultrasonic Arrays

Abstract

In the previous two chapters we showed how the response of a pair of send-receive array elements can be modeled in terms of two components: (1) a system function that describes all the electrical and electromechanical parts of the elements and their driving/receiving sub-systems, and (2) an acoustic/elastic transfer function that describes all the acoustic and elastic wave propagation and scattering fields present between the sending/receiving elements. As seen in Chap. 10, the system functions can be measured directly in a calibration experiment where the acoustic/elastic transfer functions are known. If the same array elements and settings for the phased array instrument that are used in the calibration experiment are present when the array is used in an ultrasonic flaw measurement then the system functions remain unchanged. This is also true if the elements are part of separate sending and receiving arrays. Thus, if the acoustic/elastic transfer functions in the flaw measurement can also be expressed in terms of fields that can be modeled then one can determine the voltage signals received from the flaw from every element pair in the array(s).