A finite element simulation and an experimental study of autofrettage for strain hardened thick-walled cylinders

The effect of the autofrettage process on high pressure cylinders has been investigated. Both numerical and experimental techniques have been used for the investigation. It was observed that the best autofrettage pressure for raising the pressure capacity of the cylinder was the pressure Py2 which is just sufficient to bring the outer surface of the cylinder to yielding. Pressures higher than Py2 will have the inverse effect. It was found that the number of autofrettage stages has no effect on pressure capacity. It was also shown that to reduce the flow stress within the wall of the cylinder, the autofrettage pressure must be greater than the working pressure. For pressures lower than working pressure, the flow stress remains unchanged. A close agreement was found between the Py2 calculated from the Xioying and Gangling relation and with those obtained from experiments and numerical simulations.