The above equations yield hoop and radial stress distributions throughout the cylinder wall typically of the form shown in Fig. 3.30.

Fig. 3.30. Stress distributions under autofrettage pressure.

Residual stress distributions

Residual stress after unloading can then be obtained using the procedure introduced in ยง3.9 of elastic unloading, i.e. the autofrettage loading pressure is assumed to be removed (applied in a negative sense) elastically across the whole cylinder, the unloading elastic stress distribution being given by eqns. (10.5) and (10.6)+ as:

Superposition of these distributions on the previous loading distributions allows the two curves to be subtracted for both hoop and radial stresses and produces residual stresses of the form shown in Figs. 3.31 and 3.32.

Fig. 3.31. Determination of residual hoop stresses by elastic unloading.

Residual stresses

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