Simulation of the propagation of cracking by finite element code calculation of a supermartensitic stainless steel pipe
K.SLIMANI1,2, M. Hassani2 , S. TLILI1,3, C.E. RAMOUL1, T. HAZEM1.
1Research Center in Industrial Technologies CRTI, P.O.Box 64, Cheraga 16014 Algiers Algeria,
2Metal Forming Laboratory, University of Badji Mokhtar Annaba, BP 12 Annaba, Algeria
3University of Badji Mokhtar Annaba,Foundry Laboratory, BP 12 Annaba, Algeria k.slimani@crti.dz, khairo23s@gmail.com
ABSTRACT
The biggest concern of industrial manufacturers is the sustainability of their equipment and facilities.
In the oil sector, for example, cylindrical pipe for the energy transportation to suffer corrosion damage or corrosion stress cracking is a complex problem since it requires to follow the geometry of the crack over time. Many numerical methods are applied to the propagation of fatigue cracks that require conditions to correct limitations in loading term to get results close to reality. The method of Finite Elements is a way to simulate crack propagation. However, it presents two major difficulties, the first is the use of a very fine mesh around the crack tip and the second difficulty is the explicit representation of the crack that the problem of cracking path during the simulation of propagation.
Indeed, let the mesh is constructed with a priori knowledge of the route or it is changed every time the crack advance. In this context, we studied law cracking of internal pressure pipe of super martensitic stainless steel 13% Cr and 5% Ni 2% Mo by a simulation using a finite element code "ANSYS " with a calculation of the stress intensity factor and prediction of the lifetime.
Keywords: Simulation, Finite Elements, Crack, pipe, super martensitic stainless steel.
Introduction:
The crack is defined as the area locally separating a solid into two parts, the displacement field is discontinuous across this surface, the objective of the fracture mechanics is the study of changes in the surface (crack propagation) according to the applied loads and the
characteristics of the constituent material. [1]
In our case we will use "ANSYS 14.5 release" that can handle a large number of mechanical problems of breakage and cracking of the structure.il offers powerful tools for analysis in two and three dimensions.
1. Geometry Data: cylinder thickness 6 mm and the external diameter 80mm.
We introduced a barrel length 300mm backs to reduce the computation time and the crack inside is visible. figure 1
Figure 1: Geometry of a half cylinder.
2. Materials:
The material forming the sections of the tubing is a martensitic stainless steel number
UNS S41426 category of 13-5-2 (Cr-Ni-Mo) and grade 95. This steel quality is the shade of S13Cr S95 grade according to API 5CT / ISO11960 and API5CRA / ISO13680.
Table.1: Chemistry of super martensitic stainless steel:
Teneur en éléments chimiques en % massique Code
échantillon
C Mn Si P S Cr Ni Cu Mo
Acier inox 0,018 0,411 0,215 0,011 0,004 11,845 5,452 0,245 1,945
Tableau.2: Results of tensile tests and bending stainless steel
Code échantillons
Caractéristiques de traction Pliage
Re (MPa)
Rm (MPa)
A
(%) Re/Rm Endroit Envers
TN1 701,6 784,1 23,5 0,89 Satisfaisant Satisfaisant
TN2 690,6 779,3 21,5 0,88 Satisfaisant Satisfaisant
Taking the 207GPa Young modulus and Poisson's ratio 0,3.
3. Mesh type:
Figure2 : mesh type:
The method used is the tetrahedral mesh method and the literature it gives good results in the field of fracture mechanics. [3, 4].
4. RESULTS:
Figure3: Results of the equivalent stress.
Figure3: Results of the rupture Conclusion
In this work the propagation of a crack in a cylindrical tube was simulated for the oil transportation our primary results shows the propagation and the coefficient of stress intensity in hand we still have validated our model with literature or with a real case if possible and do many other simulation by varying several parameters such as pressure and the shape and size of the crack.
References
[1] H. Khoramishad , Majid Reza "finite element analysis of a semi-elliptical external crack in aburied pipe"2009.
[2] Thomas Elguedj,"Simulation numérique de la propagation de fissure en fatigue par la méthode des éléments finis étendus : prise en compte de la plasticité du contact-frottement"
2011.
[3] B. Barthelemy, Notion pratique de la mécanique de rupture, EYROLLES, Paris 1980.
[4] Rupture d’un oléoduc, rapport d’enquête sur accident de pipeline, Canada, 27 février 1996.
[5] M. Lemaire, A. Chateauneuf et J.C. Mitteau, Fiabilité des Structures, Couplage Mécano- Fiabiliste Statique, Hermès Science Publication, ISBN, 2005.
[6] John M. Barsom, Stanley T. Rolfe, Fracture and fatigue control in structures-applications of fracture mechanics, ASTM International (1999), P150.
[7] D. ZELMATI. Ténacité des pipes API-X70 sous sollicitations dynamiques, publication 2006.
[8] A.benhamouda "etude du comportement des fissures dans les tubes sous pression interne
" 2010
