Ap. Parker et Jh. Underwood, STRESS INTENSITY, STRESS-CONCENTRATION, AND FATIGUE-CRACK GROWTH ALONG EVACUATOR HOLES OF PRESSURIZED, AUTOFRETTAGED TUBES, Journal of pressure vessel technology, 118(3), 1996, pp. 336-342
The geometry analyzed consists of a thick-walled cylinder having a sma
ll-diameter evacuator hole penetrating radially through the wall. The
loading involves pressure acting on the i.d, of the tube and all or pa
rt of this pressure acting on the evacuator hole. In addition, the tub
e may be fully or partially autofrettaged. Total hoop stress concentra
tions are determined for a range of radial locations along the evacuat
or, as are stress intensity factors along a crack emanating from the e
vacuator hole. Fatigue crack growth rates, and hence crack profiles, a
re predicted at each of the radial locations. These predictions indica
te that the critical location for the crack in a nonautofrettaged tube
is at the i.d., whereas in a fully autofrettaged tube it is located a
pproximately halfway through the wall thickness. Taking account of the
influence of stress ratio, sigma(min)/sigma(max), has a significant i
nfluence an crack shape in autofrettaged tubes, but a limited effect u
pon lifetime. The effect upon fatigue lifetime of axial residual stres
ses due to the autofrettage process is described and it is demonstrate
d that an insignificant reduction in lifetime results from the presenc
e of such stresses. Finally the predicted profiles are compared with e
xperimental observations of fatigue cracked evacuator holes and a limi
ted comparison of predicted and actual lifetimes is presented. Agreeme
nt is considered good.