Validation of Crack Growth for an Finite Element Based ECA Procedure for Reel-Laid Pipelines With Under-Matching Girth Welds

2015 ◽  
Author(s):  
T. Sriskandarajah ◽  
Daowu Zhou ◽  
Lingjun Cao
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Large Scale ◽  
Limit Load ◽  
Bending Test ◽  
Offshore Pipelines ◽  
Reference Stress ◽  
Trial Test ◽  
3D Fea ◽  
Girth Welds

There is a concern on the fracture integrity of the partially over-matching or under-matching weld during reel-lay installation where there is large plastic strain in the pipe. Conventional ECA procedures such as BS7910 and DNV-OS-F101 are applicable for fully over-matching welds only, due to limitations in the reference stress solution (or limit load solutions). The ECA procedure based on 3D finite element (FE) analysis was developed for partially over-matching welds or under-matching. The methodology has been successfully applied to several projects of industry-wide significance, with partially over-matching welds in offshore pipelines. This paper provides a case study validating the crack growth from FE based ECA methodology against the large scale bending trial test where the pipe containing the notched defect was pre-strained under a series of straining cycles. A comparison of the crack growth between 3D FEA and the large scale bending test was presented.

Analysis of Ductile Crack Growth in Pipe Test in STYLE Project

2012 ◽  
Author(s):  
Shengjun Yin ◽  
Paul T. Williams ◽  
Hilda B. Klasky ◽  
B. Richard Bass
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Large Scale ◽  
Structural Integrity ◽  
Bending Test ◽  
Ductile Crack ◽  
Oak Ridge ◽  
Integrity Assessment ◽  
Ductile Crack Growth ◽  
Bending Load

The Oak Ridge National Laboratory (ORNL) is conducting structural analyses, both deterministic and probabilistic, to simulate a large scale mock-up experiment planned within the European Network for Structural Integrity for Lifetime Management – non-RPV Components (STYLE). The paper summarizes current ORNL analyses of STYLE’s Mock-Up3 experiment to simulate/evaluate ductile crack growth in a cladded ferritic pipe. Deterministic analyses of the large-scale bending test of a ferritic surge pipe, with an internal circumferential crack, are being simulated with a number of local micromechanical approaches, such as Gurson-Tvergaard-Needleman (GTN) model. Both FEACrack [1] and ABAQUS [2] general purpose finite element programs are being used to predict the failure load and the failure mode, i.e. ductile tearing or net-section collapse, as part of the pre-test phase of the project. Companion probabilistic analyses of the experiment are utilizing the ORNL developed open-source Structural Integrity Assessment Modular - Probabilistic Fracture Mechanics (SIAM-PFM) framework. SIAM-PFM contains engineering assessment methodologies such as the tearing instability (J-T analysis) module developed for inner surface cracks under bending load. The driving force J-integral estimations are based on the SC.ENG1 or SC.ENG2 models. The J-A2 methodology is used to transfer (constraint-adjust) J-R curve material data from standard test specimens to the Mock-Up3 experiment configuration. The probabilistic results of the Mock-Up3 experiment obtained from SIAM-PFM will be compared to those generated using the deterministic finite element modeling approach. The objective of the probabilistic analysis is to provide uncertainty bounds that will assist in assessing the more detailed 3D finite-element solutions and to also assess the level of confidence that can be placed in the best-estimate finite-element solutions.

J-Integral Analysis of Surface Cracks in Round Bars under Bending Moments

2011 ◽  
Vol 52-54 ◽  
pp. 43-48 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Crack Tip ◽  
Bending Moment ◽  
Limit Load ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Reference Stress ◽  
Proposed Model

This paper presents a non-linear numerical investigation of surface cracks in round bars under bending moment by using ANSYS finite element analysis (FEA). Due to the symmetrical analysis, only quarter finite element (FE) model was constructed and special attention was given at the crack tip of the cracks. The surface cracks were characterized by the dimensionless crack aspect ratio, a/b = 0.6, 0.8, 1.0 and 1.2, while the dimensionless relative crack depth, a/D = 0.1, 0.2 and 0.3. The square-root singularity of stresses and strains was modeled by shifting the mid-point nodes to the quarter-point locations close to the crack tip. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under remotely applied bending moment was assumed to follow the Ramberg-Osgood relation with n = 5 and 10. J values were determined for all positions along the crack front and then, the limit load was predicted using the J values obtained from FEA through the reference stress method.

scholarly journals Prediction of Residual Stresses in a Multipass Pipe Weld by a Novel 3D Finite Element Approach

2018 ◽  
Author(s):  
Hui Huang ◽  
Jian Chen ◽  
Blair Carlson ◽  
Hui-Ping Wang ◽  
Paul Crooker ◽  
...  
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
High Performance ◽  
Large Scale ◽  
Graphics Processing Unit ◽  
Computational Cost ◽  
Three Dimensional ◽  
Processing Unit ◽  
Girth Welds ◽  
Welding Processes

Due to enormous computation cost, current residual stress simulation of multipass girth welds are mostly performed using two-dimensional (2D) axisymmetric models. The 2D model can only provide limited estimation on the residual stresses by assuming its axisymmetric distribution. In this study, a highly efficient thermal-mechanical finite element code for three dimensional (3D) model has been developed based on high performance Graphics Processing Unit (GPU) computers. Our code is further accelerated by considering the unique physics associated with welding processes that are characterized by steep temperature gradient and a moving arc heat source. It is capable of modeling large-scale welding problems that cannot be easily handled by the existing commercial simulation tools. To demonstrate the accuracy and efficiency, our code was compared with a commercial software by simulating a 3D multi-pass girth weld model with over 1 million elements. Our code achieved comparable solution accuracy with respect to the commercial one but with over 100 times saving on computational cost. Moreover, the three-dimensional analysis demonstrated more realistic stress distribution that is not axisymmetric in hoop direction.

A Modified Engineering Critical Assessment Approach for Offshore Pipelines

2018 ◽  
Author(s):  
Colum Holtam ◽  
Rajil Saraswat ◽  
Ramgopal Thodla ◽  
Feng Gui
Keyword(s):  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Fatigue Loading ◽  
Critical Assessment ◽  
Offshore Pipelines ◽  
Static Crack ◽  
Production Environments ◽  
Assessment Approach ◽  
Girth Welds ◽  
Crack Growth Rates

Environmentally assisted sub-critical static crack growth can occur in offshore pipelines exposed to aggressive production environments. Recent advances in fracture mechanics testing methods have shown that slow static crack growth rates can be reliably measured in sweet and sour environments under constant stress intensity factor (K) conditions. This has potential implications for the engineering critical assessment (ECA) of pipe girth welds subject to low cycle fatigue loading with long periods of operation under constant static load between cycles, e.g. lateral buckling. This paper demonstrates the influence of including static (i.e. time dependent) crack growth as well as fatigue crack growth in a modified pipeline ECA approach.

Recent Advances for J Simplified Assessment in RSE-M Code

2003 ◽  
Author(s):  
Bruno Michel ◽  
Jean-Philippe Sermage ◽  
Philippe Gilles ◽  
Bruno Barthelet ◽  
Patrick Le Delliou
Keyword(s):  
Large Scale ◽  
Surface Defects ◽  
Complex Loading ◽  
Limit Load ◽  
Assessment Method ◽  
Reactor Power ◽  
Pressurized Water ◽  
Reference Stress ◽  
Recent Advances ◽  
Wide Range

The RSE-M Code [1] provides rules and requirements for in-service inspection of French Pressurized Water Reactor power plant components. Non mandatory guidance is given in the Code for analytical flaw evaluation in a wide range of situations. In Appendix 5.4 of the Code, influence coefficients are provided to calculate stress intensity factors in pipes and shells containing semi-elliptical surface defects. The J assessment method is based on the reference stress concept with two options for reference loads evaluation: “CEP elastic plastic stress” and “CLC modified limit load”. In this paper recent advances concerning J assessment under mechanical loading for a crack located in a pipe-elbow junction are presented. Reference stress evaluation with “CLC” option is developed and mechanical foundations of the equation of large scale yielding under complex loading (pressure, in-plane and out-of-plane bending) are presented.

Mode I Ductile Crack Growth of 1TCT Specimen Under Large Cyclic Loading: Part III

2019 ◽  
Author(s):  
Kiminobu Hojo
Keyword(s):  
Cyclic Loading ◽  
Crack Growth ◽  
Large Scale ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Mode I ◽  
Piping System ◽  
Ductile Crack ◽  
Reference Stress ◽  
Ductile Crack Growth

Abstract Fitness for service rules and a calculation method for ductile crack growth under large scale plastic cyclic loading have not been established even for Mode I. In a paper presented at the PVP2018 conference the authors presented methods to establish how to determine the parameters of the combined hardening plasticity rule and applied it to simulate the ductile crack growth behavior of 1TCT specimens of the different load levels. Also, ΔJ calculations using the reference stress method, and a ΔJ-basis fatigue crack growth rate derived from that on ΔK-basis according to JSME rules for FFS were applied to estimate the crack growth under cyclic loading in excess of yield. Since in the 2018 paper identified some gaps were found between experiments and the predicted crack growth behavior, several equations of the reference stress method are evaluated in the present paper. Additionally, the prediction procedure using the ΔJ calculation by the reference stress method and the da/dN−ΔJ curve based on the JSME rules for FFS are applied to pipe fracture tests under cyclic loading. Their applicability is discussed for the case of an example piping system.

Plastic Limit Loads for Slanted Through-Wall Cracks in Cylinder and Plate Based on Finite Element Limit Analyses

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Doo-Ho Cho ◽  
Young-Hwan Choi ◽  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Jae-Boong Choi
Keyword(s):  
Finite Element ◽  
Crack Opening ◽  
Limit Load ◽  
Correction Factors ◽  
Plastic Limit ◽  
Opening Displacement ◽  
Limit Loads ◽  
Axial Tension ◽  
Reference Stress ◽  
Plastic Limit Load

The plastic limit load solutions for cylinder and plate with slanted through-wall cracks (TWCs) are developed based on the systematic three-dimensional (3D) finite element (FE) limit analyses. As for loading conditions, axial tension, global bending, and internal pressure are considered for a cylinder with slanted circumferential TWC, whereas, axial tension and internal pressure are considered for a plate and a cylinder with slanted axial TWC. Then, the verification of FE model and analysis procedure employed in the present numerical work was confirmed by employing the existing solutions for both cylinder and plate with idealized TWC. Also, the geometric variables of slanted TWC which can affect plastic limit loads were considered. Based on the systematic FE limit analysis results, the slant correction factors which represent the effect of slanted TWC on plastic limit load were provided as tabulated solutions. By adopting these slant correction factors, the plastic limit loads of slanted TWC can be directly estimated from existing solutions for idealized TWC. Furthermore, the modified engineering estimations of plastic limit loads for slanted TWC are proposed based on equilibrium equation and von Mises yield criterion. The present results can be applied either to diverse structural integrity assessments or for accurate estimation of fracture mechanics parameters such as J-integral, plastic crack opening displacement (COD) and C*-integral for slanted TWC based on the reference stress concept (Kim, et al., 2002, “Plastic Limit Pressure for Cracked Pipes Using Finite Element Limit Analyse,” Int. J. Pressure Vessels Piping, 79, pp. 321–330; Kim, et al., 2001, “Enhanced Reference Stress-Based J and Crack Opening Displacement Estimation Method for Leak-Before-Break Analysis and Comparison With GE/EPRI Method,” Fatigue Fract. Eng. Mater. Struct., 24, pp. 243–254; Kim, et al., 2002, “Non-Linear Fracture Mechanics Analyses of Part Circumferential Surface Cracked Pipes,” Int. J. Fract., 116, pp. 347–375.)

Limit Load and Reference Stress for Curved Wide Plates

2010 ◽  
Author(s):  
Stijn Hertele´ ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Jeroen Van Wittenberghe ◽  
Matthias Verstraete
Keyword(s):  
Experimental Validation ◽  
Limit Load ◽  
Plastic Collapse ◽  
Test Results ◽  
Finite Element Analyses ◽  
Flat Plates ◽  
Stress Equation ◽  
Reference Stress ◽  
Plate Curvature ◽  
Girth Welds

Curved wide plates are a valuable tool in the assessment of defective pipeline girth welds under tension. Throughout the years, Laboratory Soete collected an extensive database of curved wide plate test results. In an effort to investigate these results through FAD analysis, the authors recently developed a reference stress equation for curved plates. The approach followed is similar to the development of the Goodall and Webster equation for flat plates. This paper elaborates finite element analyses of the equation’s capability to predict plastic collapse. It is found that, although overestimated, the influence of plate curvature is correctly predicted in a qualitative way. For all simulations, the curved plate reference stress equation produced conservative estimations. This indicates that the proposed equation is suited to safely predict the plastic collapse of defective pipeline girth welds. An experimental validation is underway.

scholarly journals Inherent possibilities and limitations of finite element modelling of defective girth welds

2010 ◽  
Vol 1 (1) ◽  
pp. 127-135
Author(s):  
Stijn Hertele ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Matthias Verstraete
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Experimental Research ◽  
Finite Element Modelling ◽  
Experimental Validation ◽  
Stable Crack Growth ◽  
Worst Case ◽  
Element Modelling ◽  
Numerical Research ◽  
Girth Welds

Welds unavoidably show defects, which can negatively affect the integrity of the entire structureand, worst case, result in a failure. Defects of a considerable size should therefore be detected, assessedand, if necessary, repaired. The assessment of a defect requires a procedure which allows a conservativeestimation of the acceptability of the defect. To develop such procedure, both experimental and numericalresearch is performed. This paper describes the inherent possibilities and limitations of numerical researchthrough finite element modelling, as compared to experimental research. Summarizing all arguments, itbecomes clear that numerical research is a highly powerful tool, but a thorough experimental validation is ofparamount importance. Moreover, some specific weld-related problems are highly difficult to address,namely the presence of stable crack growth and material heterogeneity. More research is needed toachieve a description of these phenomena, under a set of conservative assumptions.

Limit Load Analysis of Pressurized Containers

2014 ◽  
Author(s):  
C. Sklorz ◽  
F. Otremba ◽  
F. Reich
Keyword(s):  
Finite Element ◽  
Flow Stress ◽  
Yield Strength ◽  
Large Scale ◽  
Limit Load ◽  
Experimental Results ◽  
Small Scale ◽  
Finite Element Calculations ◽  
Load Analysis ◽  
Design Pressure

Limit load analysis is a well known method to calculate the allowable design pressure of container components. A limit load of a pressurized container is achieved, when the stress of a wall and the flow stress are equal. In the following paper the transferability of limit load analysis from small scale tank containers up to large scale containers (railway tank) are investigated. Finite element calculations are carried out and compared with experimental results. It can be concluded that the limit load analysis works very well. Furthermore, the yield strength of the material should be used as flow stress.

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