PSI - Issue 37

7

Carl Fällgren et al. / Procedia Structural Integrity 37 (2022) 948–955 Carl Fällgren / Structural Integrity Procedia 00 (2019) 000 – 000

954

Figure 6: Comparison of experimentally obtained data and calculated results for the thicker specimen geometry h/d = 2.5 made of W360.

All experimentally obtained data are shown with green, filled dots. Results for crack initiation are marked with x, results for endurance limit pressure ranges for crack-arrest are marked with diamonds and corresponding ranges for crack propagation calculated with the strip yield model are marked with circles. In Fig. 7, the comparison is shown for the thicker specimen geometry h/d = 2.5. For the maximum autofrettage pressure of 1700 MPa (=17000 bar), the experimentally obtained value for the endurance limit pressure range could be even higher than shown in the figure. As it can be seen in Fig. 6, for these specimens no pressure high enough to cause failure could be applied during the pulsating inner-pressure experiments. For the crack initiation lives it can be seen, that the calculated results for the non-autofrettaged specimen match the experimental results very well. The calculated results for crack propagation overestimate the endurable pressure range. In Fig. 8 the results for the thinner specimens are shown. As more of these specimens were subjected to a wider range of autofrettage pressures, more information on the endurance limit increase due to the process could be gained.

Figure 7: Comparison of experimentally obtained data and calculated results for the thinner specimen geometry h/d = 2.0 made of W360.

Here it can be seen, that the results for crack initiation are overestimated for the less autofrettaged specimens. The calculated results for crack propagation lives obtained with the strip yield model and the results obtained from linear elastic fracture mechanics match the experimental data passably well.