Three finite element analysis of semi-elliptical crack in high density poly-ethylene pipe subjected to internal pressure

Abstract

The principal objective of this work is to analyze the severity of semi-elliptical crack defects and to study the degree of damage in the equipment under internal pressure during the crack propagation. The semi-elliptical cracks are considered in this work located in different position in the wall of poly-ethylene pipe. The tree finite element method based on the computation of the J integral was used to analyze the fracture behaviour of these structures. The effect of the position shape and size of the crack on the J integral was highlighted. The effects of strain rate and the temperature on the J integral values were also examined. The obtained results show that, whatever the material (strain rate) for a semi-elliptical crack, the J integral value has not an important variation with respect to the crack size. However, the energy for axial crack is more important compared to circumferential crack. The effect of the depth of the crack becomes important when the ratio ( a/ t) reaches a critical value of 0.6 ( a/ t = 0.6), especially when the ratio a/ c is weak (semi-elliptical crack). We recall finally, that the temperature effect on circumferential cracks behaviour is more important compared to the axial cracks. It is also shown that in the wall of pipe, the internal cracks are more dangerous than the external cracks.