Phased Array training Course Module 1: Basic on Phased Array Patchbook n° 415 / 1 Document 3| Rev. 4 16 July 2012 – PC 18 Campus & PC Dott. Certo Structure of a linear PHA probe backing Connection to the instrumentation Single element in piezoelectric material Adaptation layer gap between elements Element width Step between elements Ultrasound beam generated by a PHA probe with constant time excitattion Array probe with 8 elements Excitation pulses at constant delay time Cylindrical wave fronts generated by each probe element Overall wave front as the envelope of the wave front generated by the probe elements Ultrasound beam generated by a PHA probe with linear time delay variation of excitation Array probe with 8 elements Excitation pulses with a linear time delay variation Overall wave front as envelope of the single wave fronts generated by each probe elements Parameters influencing the orientation angle of the generated ultrasonic beam increasing the delay time in excitation pulses, the beam angle increases; increasing ultrasonic velocity, the beam angle increases; increasing the step between probe elements, the beam angle decreases. Parameters necessary to allow correct computing of angle beam In order to allow the instrumentation to correctly compute the desired angle beam, it’s necessary to communicate to the instrumentation the following parameters: ultrasound velocity in the material; the step between probe elements the total number of elements. Ultrasound beam generated by a PHA probe with linear time delay variation of excitation (I) Ultrasound beam generated by a PHA probe with linear time delay variation of excitation (II) Ultrasound beam generated by a PHA probe with linear time delay variation of excitation (III) Main Parameter of PHA probe The main parameters of a PHA probe can be summarized as follow: 1. Ultrasound working frequency; 2. Total element number Nt which are in the array; 3. Element step and width. The Code Case 2557 of ASME Boiler and Pressure Vessel Code includes the above mentioned parameters to be mandatory reported in the inspection procedure. Crack detection at different angle beam angle with single crysrall probe (left) and phased array (right). Cracks with different orientation can be detected more easily with Phased Array probe which is able to electronically controls the beam angle while the single crystals probe has a fixed beam angle. Selection of ultrasound beam angle in receiving Echo signal received from each probe element Cylindrical wave front adder Output signal punto riflettente P Delay lines electronically programmed in order to compensate the delays of echo indications coming from point P Main component of PHA instrumentation Electronic apparatus for phased array probe menager Computer Phased array probe scanner/encoder Wave type selection: longitudinal wave With the same probe it is possible to produce and receive longitudinal wave with an angular field ranging nominally from -90° to +90° Wave type selection: shear wave Using a perspex wedge allows to obtain with the same probe the production and reception of shear wave with an angular field ranging from 30° to 80° Definition of irradiation field for contact probe (longitudinal) and with wedge (shear/longitudinal). Wedge parameters to be setup on the instrumentation diffusor element n° 1 Height of 1th element from inspection surface Distance of 1° element from diffusor distance of 1° element from the front side of the wedge
