CRACK INFLUENCE ON A PIPE WITH DOUBLE SLOPE UNDER INTERNAL PRESSURE: NUMERICAL SIMULATION WITH XFEM

This work analyses the effect of elliptical cracks on a pipe with double slope thickness transition, using the extended finite element method (XFEM), level sets were defined to describe the three-dimensional (3D) cracks. The Computation of the stress intensity factors (SIFs) of cracks is performed. The values of SIFs are compared between straight pipes and pipes with a double (single) slope thickness transition. The results show that the XFEM is an effective tool for modelling cracks in pipes. A pressurized pipe with double slope thickness transition is more sensitive to the defect in comparison with another type of pipe. Parameters of the transition zone have an effect on stress intensity factors, precisely, the parameters of the first thickness transition are more influential on the gravity of the defect compared to the second thickness transition.ABSTRAK: Kajian ini menganalisa kesan retakan elips pada paip dengan peralihan ketebalan cerun berganda, menggunakan kaedah elemen terhingga dipanjangkan (XFEM), set tahap ditentukan bagi menentukan keretakan tiga dimensi (3D). Pengiraan faktor intensiti tekanan (SIF) retakan dilakukan. Nilai SIF dibandingkan antara paip lurus dan paip peralihan ketebalan cerun berganda (tunggal). Hasil kajian menunjukkan bahawa XFEM adalah alat yang berkesan bagi memodel keretakan paip. Paip bertekanan mengikut peralihan ketebalan cerun berganda, lebih sensitif terhadap kecacatan berbanding paip lain. Parameter zon peralihan mempunyai pengaruh terhadap faktor intensiti tegangan, tepatnya, parameter peralihan ketebalan pertama lebih mempengaruhi pada graviti kecacatan berbanding dengan peralihan ketebalan kedua.