Dakota Ultrasonics MINI--MAX - Manual (Page 104)

Dakota Ultrasonics
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8) Apply a drop of couplant to the bolt or transducer, and attach it to one
end of the bolt. Rotate the transducer clockwise and counter clockwise
applying a small amount of pressure to eliminate any excess couplant
between the transducer and bolt. Measure and record the Ultrasonic
Length at Load 2 “L
U2
”for the current sample bolt.
9) Increase the applied load to approximately the maximum load, which is
to be placed on the bolt under actual working conditions. Using the
mechanical measuring device, measure and record the Mechanical
Length at Load 3 “L
M3
” for the current sample bolt.
10) Apply a drop of couplant to the bolt or transducer, and attach it to one
end of the bolt. Rotate the transducer clockwise and counter clockwise
applying a small amount of pressure to eliminate any excess couplant
between the transducer and bolt. Measure and record the Ultrasonic
Length at Load 3 “L
U3
” (Maximum) for the current sample bolt.
11) Repeat Steps 5 – 10 for the remaining bolts.
12) Calculate the value of the Sonic Stress Factor at each load on each
sample bolt.
0 1
0 1
1 1
U U
M M
L B
L L
L L
SSF
−
−
=
0 2
0 2
2 1
U U
M M
L B
L L
L L
SSF
−
−
=
0 3
0 3
3 1
U U
M M
L B
L L
L L
SSF
−
−
=
13) Determine the average value of the Sonic Stress Factor by dividing the
sum of all SSF values divided by the total number of SSF values.
10.4 Temperature factor calibration
The thermal expansion of the fastener and the ultrasonic velocity change with
temperature are two separate effects. However, for the purpose of the MINI-
MAX they are combined into a single factor known as the Temperature Factor.