22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-4.5.2
NON DESTRUCTIVE ASSESSMENT OF THE RADIAL CLEARANCE OF THE BOLTED JOINTS IN AIRCRAFT STRUCTURES
T. B. Ryzhova
Central Aerohydrodynamic Institute (TsAGI), Russia
Keywords: non destructive testing, bolted joints, aircraft structures, radial clearance
Within the nearest ten years bolted and boltriveted
joints will be still most often used in
aluminium alloy airframes. One of the ways of
increasing fatigue strength of bolted joints is the
creation of large radial (diameter) clearance.
Capability of estimating radial clearance in joints
after assembly offers great practical prospects.
This paper considers the results of
research on non-destructive control of
clearance in standard bolted and bolt-riveted
joints of airframes.
It describes the test facility, with the help of
which dependencies between the value of radial
clearance and the ultrasonic signal were
determined for conical models of joints with
clearance. Typical areas where there were
revealed changes of ultrasonic signal that
correspond to the areas of elastic, elasto-plastic
and plastic deformation of materials. Contact
pairs of materials typical for airframe joints
(steel-aluminium, titanium-aluminium) were
used for joint imitation.
The field of the method application was
determined. There was introduced a concept of
the limit value of clearance, which corresponds to
the upper boundary of the area of unambiguous
ultrasonic estimation of clearance.
Influence of axial clearance on the results of
radial clearance estimation by ultrasonic waves is
investigated. The required minimum of ultrasonic
measurements for estimating clearance in bolted
joint is determined.
The results of ultrasonic control of
clearance in bolted joints of a full-scale panel of
the passenger aircraft wing are given. The
results of panel service life testing confirm the
reliability of ultrasonic control of clearance in
bolted joints of airframes.
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