Effects on a bending pipe behaviour via simple pre-loading for considering functional limitations of piping in industrial facilities

Sugiura, Ayumu*; Takito, Kiyotaka ; Furuya, Osamu*; Nakamura, Izumi*; Okuda, Yukihiko  

The authors has been studied the effect of initial plastic deformation on the load displacement relationship of elbow of different wall thicknesses made of carbon steel. Specifically, the authors conducted load testing for elbow when three cycles of sinusoidal input with frequency of 0.02 Hz were applied to one end of the test specimen. In the load testing, for investigating effect of difference of wall thickness and initial deformation, three types of test specimens with different wall thicknesses were loaded under three different initial deformation. Next, in the finite element analysis (FEA), the same conditions are applied in the analyses that were performed for three types of piping with different wall thicknesses before and after plastic deformation. The effect of initial displacement on the load - displacement relationship was confirmed by loading test, and analytical investigations were also considered. Thus, in this paper, the authors show the two mainly obtained results as organizations of the some issues to improve the accuracy of the analysis with large deformation. Firstly, from the comparison of the test and analytical results confirmed that the load - displacement relationship, the results could be shown as an initial plastic deformation caused not only decreasing in primary stiffness but also decreasing maximum load, on all load testing cases. And then, relative errors in the maximum loads between load testing and FEA results were observed that the errors on maximum loads of tension were larger than those of compression. Secondly, focusing on the wall thickness, the trends of relative errors of the maximum load could be shown when the wall thickness increase the errors on maximum loads of compression. However the trends of the errors on maximum loads of tension were shown completely different.