PSI - Issue 72

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

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1. Introduction Material fatigue refers to the gradual damage that materials undergo due to long-term exposure to periodic variable loads. This phenomenon primarily occurs in structures subjected to dynamic stresses. When steel materials are dynamically loaded, they can fracture at stress levels significantly lower than both their maximum tensile strength and yield strength. Such fractures are known as fatigue fractures. The fatigue process involves three stages: the initiation of a crack, the propagation of that crack until it reaches a critical size, and finally, the fracture of the remaining cross section. A fatigue strength analysis was conducted on the limestone diverter pipe located in the channel between the sieve and the reinforced concrete silo for stones at the stone quarry. The silo is divided into two chambers by a partition wall. To connect these chambers to the main channel and to control the filling process, an additional channel was necessary. This regulation is accomplished by inserting a specific number of pipes that divert the stones. The arrangement of the channel between the sieve and the silo, along with the diverters, is illustrated in Figure 1.

Fig. 1. (a) reinforced concrete silo for stone storage with a channel behind the sieve; (b) 3D model of a channel between sieve and silo with added diverters in view; (c) 3D model of a channel between sieve and silo with added diverters in cross-section. 2. Dimensioning of the stone diverter pipe and calculation of the dynamic force of the stone impacting the pipe Four thick-walled pipes are specified, each with a length of 950 mm, an outer diameter of 88.9 mm, and a wall thickness of 12.5 mm. The material used is structural steel S355 and according to BS EN 10025:2004 has the mechanical properties shown in Table 1.

Table 1. Mechanical properties of structural steel S355 Mechanical properties Modulus of Elasticity, E

200 GPa

Poisson’s ratio, ν Yield strength, R e Tensile strength, R m

0.3

346 MPa 560 MPa

The pipes are supported at both ends, with zero displacement assumed at the points of support on the channel. It was necessary to calculate the impact force of a stone striking the pipe. Limestone has a density of 2705 kg/m³, and