T.O. 33B-1-1
5-20
R
Z
Z
Z
Z
=
-
+
2
1
2
1
2
100
Where:
R = percentage of energy reflected at the interface.
Z2 =
acoustic impedance of the discontinuity
Z1 = acoustic impedance of the test material
Example: A tungsten inclusion is found in a piece of titanium. How much energy will be reflected at the
interface if 100% of the sound energy strikes the tungsten?
Known from: Table 5-2
Acoustic impedance of tungsten (Z2) = 14.20 (104 lb/in2 - sec)
Acoustic impedance of titanium (Z1) = 3.94 (104 lb/in2 - sec)
Solution:
R
=
-
+
=
=
=
=
14
20
3
94
14
20
3
94
100
10
26
18
14
100
0
5656
100
0
32
100
32%
2
2
2
.
.
.
.
.
.
( .
)
.
Therefore, 32% of the energy will be reflected at the interface by the tungsten inclusion. A crack would
reflect virtually 100% of the energy because it is filled with air.
SECTION II
ULTRASONIC EQUIPMENT AND MATERIALS
5.2
ULTRASONIC EQUIPMENT AND MATERIALS.
5.2.1
Basic Ultrasonic Instruments.
5.2.1.1
General Description.
All ultrasonic instruments basically perform the functions of generating, receiving and displaying pulses of electrical
energy that have been converted to and from pulses of ultrasonic energy by a transducer/search unit attached to an
instrument. By properly adjusting an instrument an operator can measure the amplitude of displayed pulse signals and
determine the time/distance relationships between generated and received signals. Detailed instructions for operation
of individual models shall be obtained by consulting the operating and maintenance manual for the specific instrument
being used.
5.2.1.2
Physical Characteristics of Instrument Controls.
The physical nature of the instrument controls varies with the type and age of the instrument. Older instruments have
rotary knobs for fine adjustments, slide switches for coarse adjustments and screwdriver rotary controls for infrequent
adjustments of waveform position and visibility. Newer instruments have push buttons or a sealed membrane keypad
both to select the desired control from a displayed menu and to make the respective adjustments (see Figure 5-20).
Alternatively, some menu driven instruments have a single rotary ("smart") knob for making adjustments after a
control has been selected from the menu.
