PSI - Issue 5

Amr A. Abd-Elhady et al. / Procedia Structural Integrity 5 (2017) 123–130

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4 Amr A. Abd-Elhady et al. / Structural Integrity Procedia 00 (2017) 000 – 000 = 1 ̅ ( 2 + 2 ) + 2 1 2 (1) Where E̅ = E is modulus of elasticity and G = modulus of rigidity. The energy release rate is calculated directly in ABAQUS/Standard. 2.4 Mesh The mesh refinement process was carried out to assure that results are not dependent upon the elements size. A typical mesh of a composite repaired steel pipe model is shown in Fig. 2. Each component (i.e., the pipe and repair) is meshed by using eight-node linear brick, reduced integration elements (C3D8 in ABAQUS) because these elements are compatible with the XFEM domain integral method.

Fig. 2. Finite element model.

2.5 Methodology of the present work

The present work is sequenced as: 

Determine the critical thickness of composite repair  Determine the fracture parameters such as: J -integral and mode I, II SIF of stationary incline crack in steel pipe  Determine the crack path emanating from inclined stationary crack in steel pipe with different inclined crack angle with/without composite repair  Illustrate the effects of composite repair in steel pipe on the value of J -integral of inclined stationary crack in steel pipe with different inclination angle and different fiber orientation of composite repair

3. Result and discussion

3.1 Preliminary study

In this section, the sufficient thickness of composite repair for reducing the harmful effects of the damage to steel pipe has been checked. ASME has incorporated composite repairs for damaged pipes, by recently developing the ASME Post Construction Repair Standard- PCC2 (ASME 2006). This standard has set a critical FRP repair thickness to be applied to damaged pipelines, which can be computed by the following equation: = 1 ∗ ( 2 − ( ) ) (2) where: E c and  c are the tensile modulus and allowable hoop strain of the composite in the hoop direction respectively, and t s is the minimum remaining wall thickness in the pipe. The present thickness of composite repair equals 16 mm, which is greater than t crepair .