<DOC>
<DOCNO>
640
</DOCNO>
<TITLE>
the design of structures to resist jet noise fatigue .
</TITLE>
<AUTHOR>
b. l. clarkson
</AUTHOR>
<BIBLIO>
j. royal aero. soc. 66, oct. 1962
</BIBLIO>
<TEXT>
the design of structures to resist jet noise fatigue demands a
knowledge of a wide range of subjects from pure acoustics at one
hand to metal physics at the other . at the present time the various
aspects of the problem are not sufficiently well know quantitatively
for a purely theoretical design study to be made . nevertheless
a knowledge of the behaviour of typical forms of construction
in noise environments can be used with a limited
amount of theoretical work to indicate tne most efficient types of
structure . this approach to the problem is adopted in this
lecture as it seems to be the most promising one available at the
moment . it must be emphasized, however, that although some
progress has been made in dicsovering the behaviour of a
structure subjected to noise it is not possible to estimate the life
of any component at the drawing board stage . some prototype
strain measurements and proof testing are therefore essential if
one is to prove the integrity of the design .
     within the structural limits of single skin construction set in
this lecture the main conclusion to be reached is that no reasonable
estimate of fatigue life can yet be made in the drawing
board stage of a structure . nevertheless, a study of the form of
behaviour of typical structures has led to a theoretical simplification
of the problem of skin vibration . from this it has been
possible to suggest an optimum deisgn for a skin stiffened by
stringers . a suggestion for an optimum design of skin and rib
for control surfaces to minimise stresses at the rib-skin intersection
is put forward but no experience can check this yet .
     the most resonable basis for the future estimation of
fatigue life of a component appears to be the /random/ s-n
curve and consierable effort should be made to obtain the
necessary test data .
     the life expectation of a new design will be uncertain and
some proof testing is essential if the integrity of structure in high
noise levels (150 db) is to be guaranteed .
</TEXT>
</DOC>
