A Guide To Sound Velocities - Cygnus 1 Operation Manual

A GUIDE TO SOUND VELOCITIES

Table of Sound Velocities
Velocities can vary according to the precise grade and processing conditions.
This table is included as a guide only.
Wherever possible, the Gauge should always be calibrated on the material under test.
These Velocities are given in good faith and are believed to be accurate within the limits
described above.
No liability is accepted for errors.
Velocities given are the compressional wave velocity c
Reading Conversion
In some circumstances it may not be possible to Calibrate the Gauge :
If there is no test-sample available for the Material which is to be measured
And : if the Velocity of Sound for the Material to be measured is not currently known
To allow uncalibrated measurements to be made, use this procedure :
When measuring :
the Gauge should be initially calibrated for Mild Steel, by selecting Mild Steel from the
Materials List - see : Calibration by Named Material, page 36
Later, when preparing a report :
Choose the actual material from the Table of Sound Velocities, or otherwise find out
the Velocity of Sound
convert the readings by multiplying each reading by by the Conversion Factor for
the material being measured - see : Table of Sound Velocities, page 44
Example – if the Gauge is calibrated for Mild Steel [5920 m/s], and a reading is being taken
on Copper [4700 m/s] :
T = t x V
thus : T = t x f
where : T = true thickness of Copper being measured
t = actual reading obtained
f = Conversion Factor
V
V
Conversion Factor f :
Conversion Factor is given for various materials in the Table of Sound Velocities, page
44
If the Material does not appear in the Table, but the Velocity of Sound, V
known for the Material : calculate conversion factor, f = V
/ V
COPPER
= Sound Velocity in Copper
COPPER
= Sound Velocity in Steel
STEEL
= t x 4700 / 5920 = t x 0.794
STEEL
Measuring with the Gauge
.
l
: 4700 m/s
: 5920 m/s
/ V
MATERIAL STEEL
is
MATERIAL,
43