Operating Manual

Chapter 2: Fastener Preparation
Page 14 Guide to Ultrasonic Inspection of Fasteners
maximum-amplitude waveform may change. If the
maximum-response location has changed, adjust the
position of the transducer to the new location on the bolt
head. This assures the optimum sound path is being
used, both before and after tightening.
Step 5: Position the transducer in the marked location
(or at the newly identified maximum-amplitude location)
to continue recording tensioned readings.
2.2.2 Fixtures for Non-Magnetic Fasteners
When fasteners are made of non-magnetic materials,
fixtures are sometimes used to hold the transducer in
place. Note that the fit between the transducer and the
head of the bolt is extremely critical, and some provision
must be made in the fixture to allow the transducer to
“float” while finding the position where contact is at its
best.
NOTE: Ultrasonic inspection techniques evaluate the
change in length of a fastener. Fastener elongation
occurs when a significant portion of the fastener
(known as the effective length) is exposed to tensile
loading. However, ultrasonic techniques are not ef-
fective when only a small percentage of the fastener’s
length experiences tensile loading (such as a screw
holding a piece of sheet metal) or where load levels
are below 10% of ultimate tensile stress.