Finite Element Simulation of a Circumferential Through-Thickness Crack in a Cylinder

2014 ◽  
Author(s):  
Sutham Arun ◽  
Andrew H. Sherry ◽  
Mike C. Smith ◽  
Mohammad Sheikh
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Structural Integrity ◽  
Mouth Opening ◽  
Element Model ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Integrity Assessment ◽  
Final Extent ◽  
Welded Pipe

This paper presents the results of a structural integrity assessment of a large-scale test undertaken as part of the EU programme STYLE on a repair welded pipe containing a circumferential through-thickness crack. The pipe was manufactured from two Esshete 1250 stainless steel pipes joined by a girth weld containing a deep repair. A through-thickness circumferential pre-crack was introduced to the centre of the repair prior to testing in four-point bend. The assessment used a finite element model created in Abaqus, with the weld residual stress introduced by an iterative technique. Linear elastic fracture mechanics was used to evaluate the stress intensity factor KI for the defect and elastic-plastic analyses were performed to characterise the crack driving force J along the crack front. The predicted crack mouth opening displacement as a function of load was compared with the test results and the derived variation in J used to predict crack initiation and growth. The results predicted the global behaviour of the test to within approximately 7% at final load, and the position of maximum crack growth. However, the final extent of crack extension is under-predicted. Reasons for this underprediction are suggested.

Validation of a Finite Element Toolbox for Studying Flaw Interaction

2020 ◽  
Author(s):  
Harry E. Coules
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Large Scale ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Integrity Assessment ◽  
Linear Elastic ◽  
Wide Range ◽  
Parametric Studies ◽  
Elastic Crack

Abstract Structural integrity assessment often requires the interaction of multiple closely-spaced cracks or flaws in a structure to be considered. Although many procedures for structural integrity assessment include rules for determining the significance of flaw interaction, and for re-characterising interacting flaws, these rules can be difficult to validate in a fracture mechanics framework. int_defects is an open-source MATLAB toolbox which uses the Abaqus finite element suite to perform large-scale parametric studies in cracked-body analysis. It is designed to allow developers of assessment codes to check the accuracy of simplified interaction criteria under a wide range of conditions, e.g. for different interacting flaw geometries, material models and loading cases. int_defects can help analysts perform parametric studies to determine linear elastic crack tip stress field parameters, elastic-plastic parameters and plastic limit loads for simple three-dimensional cracked bodies relevant to assessment codes. This article focusses on the validation of int_defects using existing fracture mechanics results. Through a set of validation examples, int_defects is shown to produce accurate results for a very wide range of cases in both linear and non-linear cracked-body analysis. Nevertheless, it is emphasised that users of this software should be conscious of the inherent limitations of LEFM and EPFM theory when applied to real fracture processes, and effects such as constraint loss should be considered when formulating interaction criteria.

Statistical modeling for deformation analysis of concrete arch dams with influential horizontal cracks

2018 ◽  
Vol 18 (2) ◽  
pp. 546-562 ◽  
Author(s):  
Jiang Hu ◽  
Suhua Wu
Keyword(s):  
Large Scale ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Deformation Analysis ◽  
Downstream Face ◽  
Thermal Crack ◽  
Crack Mouth ◽  
Opening Displacement ◽  
Time Model ◽  
Arch Dams

Several concrete dams all over the world exhibit severe cracks. It is very important to investigate the influence of cracks on the long-term behavior of dam structures to ensure safe operation. The interpretation of measured dam displacements is usually based on statistical hydrostatic-seasonal-time and hydrostatic-thermal-time models. The main purpose of this article is to present a statistical hydrostatic-thermal-crack-time model to interpret displacements of concrete arch dams with influential horizontal cracks. The hydrostatic-thermal-crack-time model is applied to analyze the Chencun dam, an arch–gravity dam with a large-scale horizontal crack on the downstream face. The crack stretches horizontally across most of the dam blocks. Its crack mouth opening displacement had been continually increasing even after reinforcement treatment, accompanied by abnormal deformation characteristics of the arch–cantilever system. A three-dimensional finite element model, containing the pre-existing crack using special gap elements, is built to reproduce the structural response, assess the contribution of the crack on the registered movements, and obtain the relationship between the crack mouth opening displacement and the dam crest displacement. Based on this, the hydrostatic-thermal-CMOD-time model considering crack mouth opening displacement is developed. Compared with the traditional models, the hydrostatic-thermal-crack-time model is expected to provide a better fit accuracy. The results also show that the crack and the corresponding reinforcement measure have a significant effect on the deformation behavior of the dam. This can provide some useful indications for concrete structures with similar problems.

Estimation Procedures for J and CTOD Fracture Parameters Experimental Evaluation Using Homogeneous and Mismatched Pin-Loaded SE(T) Specimens

2010 ◽  
Author(s):  
Gabriel P. de Oliveira ◽  
Gustavo H. B. Donato
Keyword(s):  
Experimental Evaluation ◽  
Fracture Resistance ◽  
Structural Integrity ◽  
Mouth Opening ◽  
Pressure Vessels ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
J Integral ◽  
Opening Displacement ◽  
Conceptual Background

Experimental evaluation of geometry-dependent material’s fracture resistance using constraint-designed SE(T) specimens has proved to be an accurate option to assess the structural integrity of pipelines and pressure vessels reducing excessive conservatism. In this context, this work presents procedures for experimental J-integral and CTOD (δ) evaluation using the eta (η) method applied to tension pin-loaded SE(T) specimens made of homogeneous materials and also containing mismatched joints. Initially, the conceptual background is presented, followed by the description of the refined non-linear finite element models developed, which provide the necessary evolution of load with increased load-line and crack mouth opening displacement. As results, are presented η factors for J-integral estimation and CTOD calculations, which are not available in current standardized procedures. The main objective is to allow fracture resistance experimental evaluation using specimens of different a/W-ratios, material flow properties, weld joint configurations and levels of weld strength mismatch. The main motivation is the possibility of enhancing accuracy of pressure vessels and piping integrity assessments, since these later present very close fracture conditions if compared to SE(T) specimens. The present results, when taken together with previous developments, extend the knowledge about the use of pin-loaded SE(T) specimens. The reader should enhance the studies about the topic with the complimentary paper with the same title beginning but involving clamped SE(T) specimens.

The Effect of Concrete Quality on the Acoustic Emission Parameters during Three-Point Bending Fracture Test

2014 ◽  
Vol 897 ◽  
pp. 149-152 ◽  
Author(s):  
Michal Matysík ◽  
Libor Topolář ◽  
Petr Daněk ◽  
Tomáš Vymazal ◽  
Iveta Plšková
Keyword(s):  
Acoustic Emission ◽  
Large Scale ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Fracture Test ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Fracture Tests ◽  
Stress Behaviour ◽  
Bending Fracture

Acoustic emission is an experimental tool well suited for monitoring fracture processes. The paper presents experiment focused on analysing acoustic emission signals captured during three-point bending fracture test of specimens of concrete. Quantitative acoustic emission techniques were used to measure micro fracture properties. For three different concrete mixtures typical acoustic emission patterns were identified in the acoustic emission records to further describe the under-the-stress behaviour and failure development. If we have a better understanding of the relationships between micro structural events and macroscopic behaviour we can better formulate predictive models for large-scale structural performance and reliability. An understanding of microstructureperformance relationships is the key to true understanding of material behaviours. Three-point bending fracture tests were conducted on these specimens and load versus crack mouth opening displacement (Load-CMOD) diagrams were recorded during the testing.

Finite Element Analysis of Flaw Growth History

2010 ◽  
Author(s):  
Nader Yoosef-Ghodsi ◽  
Da-Ming Duan ◽  
Qishi Chen ◽  
Randy Petersen ◽  
Chengye Fan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Peak Load ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Element Analysis ◽  
Family Of Curves ◽  
Growth History ◽  
Unloading Compliance

Finite element models of curved wide plate (CWP) samples were used to generate a family of load-deformation curves, where each curve corresponds to a flaw with a constant depth. This family of curves was then compared to the test results to find the flaw depth corresponding to each load step using two techniques. One technique is based on mapping the crack mouth opening displacement (CMOD) response obtained from finite element analysis (FEA) and tests, while the other one is based on FEA and experimental unloading compliance data. Both the CMOD mapping and unloading compliance techniques were applied to six CWP specimens and the results from the two techniques were compared. The CWP specimens included flaws either at the centreline of the girth weld or at the heat affected zone (HAZ). Nominal flaw sizes were 3 or 5 mm deep by 25, 50 or 75 mm long. For all specimens, testing continued until either maximum load was reached or specimen rupture occurred. Failure strain, defined as the remote strain at peak load, ranged from 1.1% to 4.1%. The flaw growth history curves from the CMOD mapping and unloading compliance techniques for a given specimen were generally found to be in close agreement. The prediction of flaw growth at failure for the specimens with flaw in the weld was closer to the experimental flaw growth at failure than for the specimens with flaw in the HAZ. The average FEA to test ratio of the flaw growth at failure for these two groups of specimens was 0.95 and 0.6, respectively. Additional analyses were carried out to study the effect of HAZ softening and the shape of the input stress strain curves beyond the onset of necking.

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.

Estimation Procedures for J and CTOD Fracture Parameters Experimental Evaluation Using Homogeneous and Mismatched Clamped SE(T) Specimens

2010 ◽  
Author(s):  
Felipe C. Moreira ◽  
Gustavo H. B. Donato
Keyword(s):  
Experimental Evaluation ◽  
Fracture Resistance ◽  
Structural Integrity ◽  
Mouth Opening ◽  
Pressure Vessels ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
J Integral ◽  
Opening Displacement ◽  
Conceptual Background

Experimental evaluation of geometry-dependent material’s fracture resistance using constraint-designed SE(T) specimens has proved to be an accurate option to assess the structural integrity of pipelines and pressure vessels reducing excessive conservatism. In this context, this work presents procedures for experimental J-integral and CTOD (δ) evaluation using the eta (η) method applied to tension clamped SE(T) specimens made of homogeneous materials and also containing mismatched joints. Initially, the conceptual background is presented, followed by the description of the refined non-linear finite element models developed, which provide the necessary evolution of load with increased load-line displacement and crack mouth opening displacement. As results, are presented a variety of η factors for J -integral and CTOD calculations, which are not available in current standardized procedures. The main objective is to allow fracture resistance experimental evaluation using specimens of different a/W-ratios, material flow properties, weld joint configurations and levels of weld strength mismatch. The main motivation is the possibility of enhancing accuracy of pressure vessels and piping integrity assessments, since these later present very close fracture conditions if compared to SE(T) specimens. The present results, when taken together with previous developments, extend the knowledge about the use of clamped SE(T) specimens. The reader should enhance the studies about the topic with the complimentary paper with the same title beginning but involving pin-loaded SE(T) specimens.

Assessment of Fracture Integrity for Trawl Impact of the Ormen Lange SFD Pipelines

2009 ◽  
Author(s):  
Erlend Olso̸ ◽  
Ba˚rd Nyhus ◽  
Erling O̸stby ◽  
Morten Hval ◽  
Hans Olav Knagenhjelm
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Structural Integrity ◽  
Element Model ◽  
Gas Field ◽  
Finite Element Program ◽  
Field Development ◽  
Integrity Assessment ◽  
Element Program ◽  
Pipeline Design

Ormen Lange Southern Field Development (SFD) is part of the phase 2 development of the Ormen Lange gas field located about 120 km offshore the coast of Norway. The SFD includes an 8 slot template, two 16 inch infield flowlines, one 6 5/8 inch MEG line and one umbilical located at about 850 m water depth. Although there are presently no fishing activities at the development area, the pipeline design has included a design case with evaluation of the structural integrity and potential for failure caused by future interaction with fishing gear such as trawl impact/pull-over and hooking. In contrast to the MEG line and the umbilical, which will be trenched and buried along the whole pipeline route, the 16 inch production flowlines will be left exposed on the seabed and may therefore be subjected to interference with trawl equipment in the future. It was therefore decided that pipeline engineering shall document that impact from trawl equipment during operation will not cause detrimental damage to the exposed flowlines, resulting in leakage of hydrocarbons to the environment and/or high cost of repair. In the event of impact from trawl equipment, it is likely that the pipe will be operating and thus be in a state of internal overpressure. Recent research has shown that the effect of internal pressure can be detrimental to the fracture response of pipelines with circumferential flaws subjected to bending or tensile loading. Today’s analytical equations that are the basis for most engineering critical assessments (ECA) are not capable of accounting for the effect of internal pressure when elastic-plastic fracture mechanics is considered. LINKpipe, which is a special purpose finite element program for assessing the fracture integrity of pipelines, is capable of accounting for the effect of internal pressure and was therefore chosen for the fracture integrity assessment. The flowline was analyzed for a range of defect sizes and material stress-strain behaviors. The finite element model was subjected to bending while under internal pressure, and both surface breaking defects and embedded defects have been assessed to ensure that the Ormen Lange SFD flowlines are capable of withstanding impact from trawl equipment during operation. The analyses were used to determine safe operational windows regarding acceptable defect sizes for both surface breaking and embedded defects for the parameters analyzed.

Modelling the Complex Manufacturing History of a Pipework Joint and Assessment of Its Through Life Creep-Fatigue Damage Using Finite Element Based Methods

2010 ◽  
Author(s):  
D. P. Bray ◽  
R. J. Dennis ◽  
R. A. W. Bradford
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Structural Integrity ◽  
Element Model ◽  
General Purpose ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Creep Fatigue ◽  
History Of ◽  
Manufacturing History

The work reported in this paper investigates the complex manufacture and through-life operation of a pipework joint in a UK AGR boiler. Residual stresses resulting from the fabrication process can be a key driver for creep and creep-fatigue damage. The calculation of creep-fatigue damage for assessment purposes is typically undertaken within the framework of an appropriate assessment code (such as British Energy’s R5). The standard assessment approach usually requires the undertaking of elastic finite element analysis followed by Neuber construction to convert elastic stress ranges into elastic-plastic stress and strain ranges prior to the calculation of creep-fatigue damage. A combination of explicit and implicit finite element methods are employed in order to simulate a range of manufacturing processes which influence the material state for a branched pipework joint. The solution is effectively obtained within one finite element model, with re-meshing performed where necessary. This solution then feeds into a finite element based structural integrity assessment. The methods utilise the principles outlined in the British Energy R5 assessment code but utilise the inelastic strains calculated directly from analysis. The methods are based around the general purpose finite-element code Abaqus enhanced by the use of user-defined subroutines CREEP and UVARM. This paper describes analyses performed to simulate the complex manufacturing history of a branched pipework component, and to estimate its subsequent in service creep-fatigue damage using finite element based methods.

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