J integral computation and Limit load analysis of bonded composite repair in cracked pipes under pressure (original) (raw)
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Fracture Mechanics Analysis of Repairing a Cracked Pressure Pipe with a Composite Sleeve
NATO Science for Peace and Security Series
Pressure pipes may be externally damaged in different ways: corrosion or notch due to diving machines. These defects may initiate a fatigue crack, which will be first part-through, then through the thickness. This results in a weakened region of the tube, then in leak of the pressure fluid contained in the pipe. There are several ways to repair the tube: changing the portion of tube, welding of extra metal in the defect, putting a welded metal sleeve, or gluing a composite sleeve. This last solution seems to be the easiest and the cheapest. The advantage is that the repairing sleeve is made on site and can be put with a given pre-tension. The work presented here is the numerical study of the fracture mechanics parameters of a part-through crack in a tube submitted to internal pressure and repaired with a composite sleeve. As there is a transfer of loading from the cracked tube to the repairing sleeve, the fracture mechanics parameters of the crack such as J-integral or opening of the crack lips will be modified. The study can be used as a design procedure for such repairing sleeves.
Investigating the effects of pipe live pressure on the design of composite overwrap repairs
Pipelines are widely used in oil and gas industry both in offshore and onshore applications. After several years of operation, steel pipelines typically suffer from internal or external metal loss due to erosion and/or corrosion. More than 60% of the oil and gas transmission pipelines around the world are more than 40 years old and in urgent need of rehabilitation in order to re-establish their maximum operating capacity. Different repair methods are available for pipeline rehabilitation; the most recent method exploits the special characteristics of fibre-reinforced polymer (FRP) matrix composite material for rehabilitation. The corroded part of a pipeline is reinforced by wrapping composite material around the pipe. In 2006, two international codes ISO-24817 (International Organization for Standardization 2006) and ASME PCC-2 (The American Society of Mechanical Engineering 2011) were published in order to assist engineers in designing reliable composite overwrap repairs. For the case when the corroded pipe contributes to the load carrying capacity, the codes calculate the repair thickness based on the pipe diameter, remaining wall thickness, pipe and composite material properties, composite allowable strain, design pressure and the live pressure, which is the internal pressure in the pipe at the time of repair application. In this study, a range of design scenarios are modelled using analytical equations and Finite Element method to assess the validity of including live pressure in the design. Results indicate that the repair thickness is independent of the live pressure and hence an appropriate modification is proposed to the existing design equation.
Iranian Journal of Oil and Gas Science and Technology, 2019
The purpose of this study is to investigate bending moment and the axial load capacity of a pressurized pipe suffering from a through-wall circumferential crack repaired by a composite sleeve. The three-dimensional finite element method (FEM) was adopted to compute the results, and the failure assessment diagram (FAD) was employed to investigate the failure behavior of the repaired pipe. The findings revealed that, for the investigated range of applied loads and angles of the crack, the interaction of brittle and ductile failure modes is negligible. Additionally, the yield strength of the cracked pipe was considered as reference stress to achieve a conservative design. Two cases of the combined loading state consisting of internal pressure/bending moment and internal pressure/axial tensile force were investigated. Repairing the crack under combined loadings using carbon-epoxy composites was studied where the influences of various parameters, including internal pressure, crack angle,...
Pipeline repair by composite patch under temperature and pressure loading
Frattura ed Integrità Strutturale
In this study, the three-dimensional finite element method is used to analyze an API 5L X70 steel cylindrical pipeline subjected to an internal pressure load by calculating the stress intensity factors and the integral J at the peak of crack in elastic and elastoplastic behavior. The effectiveness of composite patch repair bonded to the cracked surface is highlighted. The effects of the geometrical and mechanical properties of the composite patch and the adhesive on the effectiveness of the repair were highlighted. The variation of the stress intensity factor at the crack tip is used to evaluate the repair performance. The results obtained show that the residual heat stress significantly increases the stress intensity factor at the bottom of the crack, which reduces the effectiveness of the repair.
Optimization of the geometrical parameters of bonded composite wrap for repairing cracked pipelines
In this study the finite element method is used to analyze the performances of bonded composite wrap repair of cracked steel pipelines. Parametric analysis was performed in order to highlight the effects of the geometrical properties on the repair efficiency. The experimental design method is used to explore the effects of wrap dimensions (length, angle and thickness) in order to optimize the repair process. We showed in using the MOODE.5 software the most dominant geometrical parameters on stress intensity factor at the crack front which to determine the most important parameters on the repair efficiency. This optimization can help the composite wrap designers to improve the repair performance and rehabilitation.
Mechanical behaviour of adhesively repaired pipes subject to internal pressure
International Journal of Adhesion and Adhesives, 2017
Pipes can crack over time, particularly in areas with pipefittings and joints subject to high pressure and unsteady temperatures. Repair of these cracks requires labour, time, and expense and the cracked pipes are currently repaired with two methods. The first method is cutting out the damaged section of the pipe and adding an additional joint, which requires much time and labour. The second method is replacing the damaged pipe, which requires expensive materials. The aim of this study is to propose an alternative method that reduces or eliminates the use of labour, time, and materials, in order to quickly reactivate pipelines. For this purpose, the cracked steel pipes were repaired by using an adhesive, and the mechanical behaviours of the repaired pipes were investigated experimentally and numerically. In the first step of the study, artificial cracks were created on the pipes and the cracked pipes were repaired using adhesive and galvanized steel patches with different overlap lengths, overlap angles and thicknesses. Then, the repaired pipes were subjected to internal pressure in order to evaluate the effects of patch thickness, overlap angle and overlap length on the joint strength. Finally, the numerical analyses and experimental results show that the variation of the patch thickness, overlap length and overlap angle will change the stress distributions and strength of the adhesively repaired pipes.
Bonded composite repair of metallic pipeline using energy release rate method
Journal of Adhesion Science and Technology, 2019
A methodology of repair in pipes involving bonded joints, manufactured through the wrappage of a composite around the pipe, is becoming a common practice in the industry for a series of associated advantages. The prediction of failure pressure in bonded repaired pipes is vital to guarantee a good quality of adhesion in this type of repair. Nowadays, the failure pressure is usually evaluated using hydrostatic tests that demand complex preparation to pressurize a section of the pipe and that are also dangerous for possible debris during rupture. With this fact in mind, this research purpose is to verify a simpler and more efficient methodology to predict the failure pressure applying energy release rate concepts. Double Cantilever Beam (DCB) and Width Tapered Double Cantilever Beam (WTDCB) tests were used to obtain the energy release rate of dissimilar specimens constituted with the same material as the most common repairs (steel/glass fiber reinforced polymer). Through a design equation that relates the energy release rate and the failure pressure presented in Standards ISO/PDTS 24817 and ASME PCC-2, it is possible to predict a value of failure pressure using DCB and WTDCB energy release rate results. The failure pressure predicted value was compared with the experimental hydrostatic tests results and analyzed. Results showed a good agreement between these two values, indicating that the methodology developed in this research might be used, in the future, to predict the failure pressure in bonded repaired pipes.
2013
In this work, the finite elements method is used for the determination of the stress intensity factor (SIF) and stresses (radial and circumferential) with and without patch. This study is aimed, to compare the design of single composite patch and without patch for repairing cracked API X65 pipeline. The obtained results show that, when the 5 and 65 mm longitudinal crack are applied, the single patch presents lower stress intensity factor for the entire crack tip. Furthermore, the radial and circumferential stresses are higher for the case of the single patch then without patch. The procedure eventually, given by the single patch technique, can be very significant and this method depends on the patch geometry and the adhesive characteristics.
Frattura ed Integrità Strutturale
The purpose of this article is to present the stress intensity factors (SIF) solutions for semi-elliptic crack in pipelines under internal pressures, the stress intensity factors are calculated by the three-dimensional finite element method (FEM) for cracked pipelines and repaired pipe by composite patch. The distribution of normalized stress intensity factors (KI, KII and KIII) along the crack front for different crack lengths, crack depth, crack geometry, lap length and composite thickness was obtained by nodal calculations. Our results show the presence of three failure modes along the semi elliptical crack front and has three zones in which the stress intensity factor in mixed mode (KII) the higher-values comparing to KI and KIII. It can also be noted that the composite repair reduces the SIF KI by 46% and the KII by 55% and the KIII by 72% near the outside diameter of the pipe in each zone. However, the reduction of the SIF K I is more significant for the rectangular crack than for the semi-elliptic crack, from which it is concluded that the composite repair is very effective for a rectangular crack with respect to the semi-elliptic crack. Thereby, the fracture behavior of the semi-elliptic crack is governed by the three modes of failure and not only by mode I.