PSI - Issue 72

Dražan Kozak et al. / Procedia Structural Integrity 72 (2025) 270 – 277

273

= (1+√1+ 2 ℎ )

(3)

The calculated dynamic deflection is 4.72 mm. By expressing force F using equation (2) and incorporating calculated dynamic deflection, the impact force of a stone falling freely from a height of 2000 mm into a pipe was computed. The calculated force is 130320 N. Since the calculation of the impact force is not the primary focus of this article and involves significant complexity, it is recommended that future research verifies the calculated force using an alternative approach and compares the results. 3. Analysis of fatigue strength caused by the impact of stones on the diverter pipe The objective of this analysis is to determine the number of cycles to failure that the pipe can endure. The pipe is loaded with a cyclic alternating load with R=0 and a force of 130320 N. The boundary condition at the point where the pipe connects to the channel is defined such that the displacement is equal to zero on all sides. This is because the pipe will be fixed with a lever externally to ensure it remains stationary. The fatigue strength of the pipe, due to the impact of stones, was calculated numerically using the finite element method in the ANSYS 19.0 software package. The defined boundary conditions and loads are shown in Figure 3.

Fig. 3. Defined boundary conditions and loads.

To solve this problem, a mesh of tetrahedral finite elements with intermediate nodes was used. The mesh consists of 17712 elements and 35512 nodes. Goodman's dynamic strength criterion was applied, as it is considered more conservative than Gerber's and Soderberg's criteria. The calculated maximum equivalent stress is 262.44 MPa, which is below the material's yield strength of 346 MPa. The number of cycles until fatigue failure occurs is shown in Figure 4.