20
en
10.3.1 Notes
Before you begin:
•
Calibrate (zero) the gauge - see “Measuring System Zero - Using Calibration Bars or Triple Sided
Glass Block” on page 14.
•
Calibrate the velocity - see “Velocity calibration” on page 18.
•
Soak the sample bolts in the controlled temperature environment for a period of not less than 24 hours.
Care must be taken throughout the measurement process to avoid significant change in the bolt
temperature due to handling of the sample bolts, or the process of applying load.
•
The mechanical apparatus for measurement of length must be calibrated in accordance with
governing quality procedures. The device should be configured so that minimum handling of the
sample bolts will be required during the measurement process.
10.3.2 Procedure
Note: The following steps assume that you have performed the steps in the previous section and calibrated
the velocity. Therefore, the velocity has been adjusted, approximate length already entered, and the gauge
is currently setup and ready to measure in elongation mode.
1.
Using the mechanical measuring device, measure and record the Mechanical Length at Zero Load
for each sample bolt.
2.
Apply the transducer and couplant to the bolt and record the Ultrasonic Length at Zero Load
.
3.
Repeat step 2 for each sample bolt.
4.
Place the first sample bolt in the loading apparatus. Apply approximately 1/3 of 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 1
for the current sample bolt.
5.
Apply the transducer and couplant to the bolt and measure and record the Ultrasonic Length at Load 1
.
6.
Increase the applied load to approximately 2/3 of 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 2
for the current sample bolt.
7.
Apply the transducer and couplant to the bolt and measure and record the Ultrasonic Length at Load 2
.
8.
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
for the current sample bolt.
9.
Apply the transducer and couplant to the bolt and measure and record the Ultrasonic Length at Load 3
.
10. Repeat steps 4 to 9 for the remaining sample bolts.
11. Calculate the value of the Sonic Stress Factor at each load on each sample bolt.
12. Determine the average value of the Sonic Stress Factor by dividing the sum of all Sonic Stress Factor
values by the number of bolts sampled.
L
M
0
L
U
0
L
M
1
L
U
1
L
M
2
L
U
2
L
M
3
L
U
3
SonicStressFactor
Bolt
1
L
1
L
M
1
L
M
0
–
L
U
1
L
U
0
–
--------------------------
=
SonicStressFactor
Bolt
1
L
2
L
M
2
L
M
0
–
L
U
2
L
U
0
–
--------------------------
=
SonicStressFactor
Bolt
1
L
3
L
M
3
L
M
0
–
L
U
3
L
U
0
–
--------------------------
=
