PSI - Issue 42

Chmelko et al. / Procedia Structural Integrity 42 (2022) 315–320 Chmelko,V. at all: / Structural Integrity Procedia 00 (2022) 000–000

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in a pressure-loaded pipe in the presence of a corrosion defect. The small corrosion defect considered has a dimension of 30x30 mm and its depth is gradually increased in the simulations. The influence of shape deviations is significant in the elastic region, over the yield strength is this influence is still significant in the strain region, although the stress increment decreases due to the strain hardening of the material.

Fig. 4. Effect of shape inaccuracy on stresses in a DN500 diameter pipe, t=10mm with corrosion defect depth.

3. Influence of additional bending Additional bending on piping systems can only be caused by external influences in operation. A common case is the subsidence of the subsoil during prolonged rainfall, which causes additional bending in the vertical direction. Pipelines laid on a slope may be subjected to a landslide causing bending in the lateral direction. When a section of pipe is exposed, thermal expansion caused by heating from the sun may cause the pipe to deviate from its axis due to the resulting compressive forces. An assessment of the integrity of a pipeline with an additional bending at an existing corrosion defect can be made by computer simulation. For the credibility of the results, the modelling procedure of the geometry, fit and loading of the pipeline must be verified [8]. The integrity criterion of the pipeline is the burst pressure. Its magnitude is also influenced by the material model used and the failure criterion. The experimental verification of the burst pressures in a pipeline and the methodology for their simulation using a bilinear material model is described in detail in [9, 10]. The definition of the destruction criterion is also an important parameter in the simulations.

Fig. 5. FEM simulation of a burst pressure: a) spot reaching the ultimate strength; b) plastic flow until the break of pipe shell integrity