ABSTRACT
The numerical study presents a procedure to determine the optimum autofrettage
pressure for a given operating pressure, so as to achieve the longest fatigue service life
of thick-walled cylinders. The study investigates the fatigue life of pressurized cylinders
under the effect of applied cyclic internal operating pressure. The cylinders had
previously undergone a process of optimum autofrettage to induce a minimum total
equivalent stress under the operating pressure. A nonlinear material property with a
kinematic hardening was used. Experiments were carried out to validate the numerical
results of residual stress where strain gages provided the strain values used to find the
hoop stresses present on the outer surface. There was good agreement between the
FE simulation and the strain measurement in obtaining residual stresses. The
performance of the cylinders was evaluated in terms of fatigue damage accumulation
for various levels of autofrettage. The results clearly indicate the importance of
autofrettage in increasing the fatigue life. In increasing the autofrettage level, the fatigue
life increases first, reaches a maximum optimum level and then decreases. In
conclusion, optimum autofrettage level leads to an optimum fatigue life.