Telechargé par deniz alici

# 1-Basic on Phased Array

publicité
```Phased Array training Course
Module 1:
Basic on Phased Array
Patchbook n&deg; 415 / 1
Document 3| Rev. 4 16 July 2012 – PC 18 Campus &amp; PC Dott. Certo
Structure of a linear PHA probe
backing
Connection to the instrumentation
Single element in
piezoelectric material
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
probe element
Cylindrical wave front
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&deg; to +90&deg;
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&deg; to 80&deg;
Definition of irradiation field for contact
probe (longitudinal) and with wedge
(shear/longitudinal).
Wedge parameters to be setup on the
instrumentation
diffusor
element n&deg; 1
Height of 1th
element from
inspection surface
Distance of 1&deg; element
from diffusor
distance of 1&deg; element
from the front side of the
wedge
```