STYLE Project: A Large Scale Ductile Tearing Experiment on a Cladded Ferritic Pipe

2014 ◽  
Author(s):  
Dominique Moinereau ◽  
Patrick Le Delliou ◽  
Elisabeth Keim ◽  
Tomas Nicak
Keyword(s):  
Crack Growth ◽  
Base Metal ◽  
Ferritic Steel ◽  
Large Scale ◽  
Bending Test ◽  
Test Facility ◽  
Outer Diameter ◽  
Ductile Tearing ◽  
Wide Range ◽  
Scale Experiment

Within the framework of the FP7 European project STYLE, a large scale experiment has been performed at EDF on a cladded ferritic pipe. The objective of such an experiment was to investigate transferability of material properties from small specimens to large scale components. The large scale experiment involves applying 4-point bending under displacement control at room temperature to a clad ferritic steel pipe with an internal surface crack. The goal of the experiment is to initiate ductile crack growth and track the resulting stable crack growth until the surface flaw fails by producing a through-wall crack. The test specimen is representative from a surge line consisting of a clad ferritic pipe with an outer diameter of 420 mm, length of 520 mm, and base metal wall thickness of 31 mm, with an internal austenitic stainless steel cladding layer of thickness 5 mm. The base metal is a low alloy 20MnMoNi55 steel (corresponding to the specifications of an SA 508 Grade 3, Class 1 steel), and the necessary extensions are made of a high strength ferritic steel. A wide range of instrumentation was implemented to provide data for mock-up behavior understanding and detect the ductile tearing initiation during the test. The test has been conducted with full success on the EDF 4 point bending test facility. After the experiment, samples have been taken from the mock-up for full SEM fractographic examinations of the fracture surface for identification of failure modes. The present paper describes the large scale experiment and presents the main experimental results and data. A synthesis of SEM fractographic examinations is also presented, to better understand the rupture behavior during the test.

STYLE Project: Assessment of Transferability of Fracture Material Properties From Specimens to Large Components by Local Approach to Fracture

2014 ◽  
Author(s):  
Patrick Le Delliou ◽  
Dominique Moinereau ◽  
Elisabeth Keim ◽  
Tomas Nicak
Keyword(s):  
Crack Growth ◽  
Base Metal ◽  
Material Properties ◽  
Large Scale ◽  
Material Behavior ◽  
Experimental Results ◽  
Outer Diameter ◽  
Local Approach ◽  
Inner Surface ◽  
Scale Experiment

Within the framework of the FP7 European project STYLE, a large scale experiment was performed at EDF R&D on a cladded ferritic pipe (Mock-Up 3). The objective of this experiment was to investigate the transferability of material properties from small specimens to large scale components. The large scale experiment involved applying 4-point bending under displacement control at room temperature to a clad ferritic steel pipe with an inner surface crack. The goal of the experiment was to initiate ductile crack growth and track the resulting stable crack growth until the surface flaw breaks through the wall. The pipe was representative of a surge line, consisting of a clad ferritic pipe with an outer diameter of 424 mm, and base metal wall thickness of 31 mm, with an austenitic stainless steel cladding layer 5 mm thick on the inner surface. The base metal is a low alloy 20 MnMoNi 5 5 steel (corresponding to the specifications of an SA 508 Grade 3, Class 1 steel). The pipe test was conducted in 2012 in the EDF R&D 4-point bending frame. Following the experiment, various specimens were taken from the mock-up to identify the material behavior and provide data to investigate the transferability of the material fracture properties. This paper recalls briefly the large scale experiment results and presents the main experimental results from the specimens. Then the results of the local approach finite element computations with the Rousselier model are presented and compared with the experimental results.

scholarly journals European Project ATLAS+: Small and Large Scale Ductile Tearing Experiments on Ferritic Steel WB36 to Study Transferability of Material Ductile Properties

2019 ◽  
Author(s):  
Anna Dahl ◽  
Dominique Moinereau ◽  
Patrick Le Delliou ◽  
Willy Vincent
Keyword(s):  
Ferritic Steel ◽  
Large Scale ◽  
Structural Integrity ◽  
Assessment Tools ◽  
Test Facility ◽  
Small Scale ◽  
Feed Water ◽  
Ductile Tearing ◽  
Integrity Assessment ◽  
European Project

Abstract The 4-years European project ATLAS+ (Advanced Structural Integrity Assessment Tools for Safe long Term Operation) has been launched in June 2017. One of its objectives is to study the transferability of material ductile properties from small scale specimens to large scale components and validate some advanced tools for structural integrity assessment. The study of properties transferability is based on a wide experimental programme which includes a full set of fracture experiments conducted on conventional fracture specimens and large scale components (mainly pipes). Three materials are considered in the programme : a ferritic steel WB36 typical from secondary feed water line in German PWR reactors, an aged stainless steel austenitic weld representative of EPR design and a typical VVER austenitic dissimilar weld (DMW). This paper describes the experimental work conducted on the ferritic steel WB 36 (15NiCuMoNb5) and summarizes the experimental results available after 2 years of work. Numerous mechanical tests have been conducted on a wide panel of fracture mechanics specimens for a full characterization of the ferritic steel: Tensile properties, Hardness, Charpy Energy, pre-cracked Charpy PCC, Master curve on CT and SENT specimens, ductile tearing properties on CT and SENT specimens. In parallel, it is planned to test three 4PB large scale tests on pipings (FP1, FP2 and FP3) at room temperature on the EDF test facility with 3 configurations (shape, size and location) of cracks: through wall crack (TWC), internal and external ½ elliptical cracks. Progress of these large scale experiments is described including first results.

Four Points Bending Test on an EPR Type DMW Pipe Containing a Through-Wall Defect: Experimental and Numerical Analysis From Small Specimens Until Pipe Scale

2014 ◽  
Author(s):  
M. Bourgeois ◽  
S. Chapuliot ◽  
S. Marie ◽  
O. Ancelet ◽  
Y. Kayser
Keyword(s):  
Numerical Analysis ◽  
Ferritic Steel ◽  
Large Scale ◽  
Bending Test ◽  
Small Scale ◽  
Narrow Gap ◽  
Fracture Test ◽  
Ductile Tearing ◽  
Four Point Bending ◽  
Four Point Bending Test

Within the framework of European project STYLE [1], a fracture test on a pipe containing a through wall crack in a narrow gap Inconel Dissimilar Metals weld (welds named hereafter DMW) has been performed. The work is focusing on the Inconel - ferritic steel interface which is the weakest area of such welded pipes in front of ductile tearing. The study temperature is 300°C, which covers typical temperatures in components like hot pipes in the primary coolant system of pressurized water reactors. The four point bending test was carried out by the French Atomic Energy Commission and Alternative Energies (CEA), in order to study the mechanical properties and integrity of component such as the DMW pipes provided and designed by AREVA France. The observations made post-mortem showed a small 2.5 mm ductile tearing at the interface of Inconel and ferritic steel, and after this point, a large crack that has deviated from the interface to propagate in the Inconel and then in the stainless steel. The DMW Mock-up is presented with previous results concerning the mechanical characterizations of his constitutive materials. The second part of this paper is devoted to the four point bending test at 300°C: procedure, instrumentation and interpretation of large-scale test in terms of initiation and propagation of cracks. A comparison is made with tests performed at a smaller scale on multi-material CT specimens. The third part deals with first numerical analysis of fracture test. The results are interpreted on a small scale using finite element analysis to obtain the parameters of damage models that are needed for global approach. Finally, numerical approaches is presented and applied to simulate the fracture of the large-scale pipe. The aim of this paper is to propose and discuss the validity of new assessment methods of ductile propagation in a large scale pipe containing a through wall crack in a narrow gap dissimilar metal weld.

STYLE: Mock-Up3 Design—FE Simulation of Crack Growth in a Cladded Ferritic Pipe

2010 ◽  
Author(s):  
Tomas Nicak ◽  
Herbert Schendzielorz ◽  
Elisabeth Keim ◽  
Gottfried Meier ◽  
Dominique Moinereau ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Large Scale ◽  
Assessment Tools ◽  
Bending Test ◽  
Test Facility ◽  
J Integral ◽  
Material Data ◽  
Porous Plasticity ◽  
Micromechanical Models

This paper describes numerical analyses performed in connection with the design of a large scale mock-up test planned within the European project on structural integrity STYLE. There are three large scale mock-up tests planned in STYLE, each of them dedicated to investigate specific effects. Mock-up3 (cladded ferritic pipe with an outer diameter of 420 mm) is foreseen to investigate transferability of material data, including fracture mechanics properties. Usually, material data are obtained by testing small specimens, which are subsequently used for the assessment of large scale structures (real components). The Mock-Up3 is an original part of a surge line made of low alloy steel 20MnMoNi55 (similar to SA 508 Grade 3, Cl. 1). The test will be performed on a 4 point bending test facility provided by EDF under displacement control at room temperature. The goal of the test is to obtain the stable crack growth of an inner surface flaw until a break through the wall occurs. The range of assessment tools applied within STYLE includes assessment of component failure by fracture mechanics analyses using methods based on fracture mechanics parameters (e.g K1 or J-Integral) as well as methods based on local micromechanical models (e.g. Gurson’s porous plasticity model and its variations). Micromechanical models have some advantages compared to those based on single term fracture parameters, especially if one considers designing a large scale mock-up test. The precise description of the entire damage process, beginning from with initiation on brittle particles, their growth leading to the crack initiation and finally to the macroscopic crack growth, can be seen as the most valuable attribute of these methods. Such methods make it possible to perform a set virtual tests prior to the real one, on which different test conditions can be investigated. A comparison of the common assessment method based on J-Integral with a local approach method, based on the Gurson’s porous plasticity theory, will be presented in this paper. Details on the Gurson model calibration will also be provided. Moreover, influence of boundary conditions on the large scale test will be discussed.

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.

ORNL Pre-Test Analyses of a Large-Scale Experiment in STYLE

2011 ◽  
Author(s):  
Paul T. Williams ◽  
Shengjun Yin ◽  
Hilda B. Klasky ◽  
B. Richard Bass
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Probabilistic Analysis ◽  
Alternative Assessment ◽  
Large Scale ◽  
Structural Integrity ◽  
Nuclear Industry ◽  
Work Package ◽  
Scale Experiment

Oak Ridge National Laboratory (ORNL) is conducting a series of numerical analyses to simulate a large scale mock-up experiment planned within the European Network for Structural Integrity for Lifetime Management – non-RPV Components (STYLE). STYLE is a European cooperative effort to assess the structural integrity of (non-reactor pressure vessel) reactor coolant pressure boundary components relevant to ageing and life-time management and to integrate the knowledge created in the project into mainstream nuclear industry assessment codes. ORNL contributes “work-in-kind” support to STYLE Work Package 2 (Numerical Analysis/Advanced Tools) and Work Package 3 (Engineering Assessment Methods/LBB Analyses). This paper summarizes the current status of ORNL analyses of the STYLE Mock-Up3 large-scale experiment to simulate and evaluate crack growth in a cladded ferritic pipe. The analyses are being performed in two parts. In the first part, advanced fracture mechanics models are being developed and performed to evaluate several experiment designs taking into account the capabilities of the test facility while satisfying the test objectives. Then these advanced fracture mechanics models will be utilized to simulate the crack growth in the large scale mock-up test. For the second part, the recently developed ORNL SIAM-PFM open-source, cross-platform, probabilistic computational tool will be used to generate an alternative assessment for comparison with the advanced fracture mechanics model results. The SIAM-PFM probabilistic analysis of the Mock-Up3 experiment will utilize fracture modules that are installed into a general probabilistic framework. The probabilistic results of the Mock-Up3 experiment obtained from SIAM-PFM will be compared to those results generated using the deterministic 3D nonlinear 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.

ATLAS PLUS: Design of Large Scale Fracture Mechanics Tests on a Ferritic Pipe

2018 ◽  
Author(s):  
Tomas Nicak ◽  
Tobias Bolinder ◽  
Elisabeth Keim ◽  
Alexander Eriksson ◽  
Patrick Le Delliou ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Large Scale ◽  
Crack Tip ◽  
Bending Test ◽  
Test Facility ◽  
Small Scale ◽  
Integrity Assessment ◽  
Design Calculations ◽  
Crack Tip Constraint ◽  
Large Scale Tests

This paper summarizes the design calculations performed by Framatome, EDF, KIWA INSPECTA and VTT for three large scale tests on ferritic pipes made of material WB 36 (15 NiCuMoNb 5). The large scale tests will be performed on a 4-point bending test facility provided by EDF under displacement control at room temperature. The overall goal of the planned large scale tests is to demonstrate the effect of the crack tip constraint on the fracture toughness at the component level. Results of those tests will be utilized to develop and validate advanced tools for structural integrity assessment within WP 3 particularly with respect to the transferability of material properties from small scale specimens to large scale components as well as for the development and validation of a procedure for the determination of component fracture resistance curves. Three configurations of the initial defect with different constraint conditions (one through-wall and two surface cracks) are considered. The design calculations are divided into two parts. In the first part an optimization of three different crack shapes is performed on basis of the standard fracture mechanics approach (based on J-Integral) without consideration of the constraint effect. In the second part a quantification of the crack tip constraint for the selected crack configurations from part I is performed. The effect of the constraint on the crack initiation and propagation for the selected crack configurations shall be assessed and compared between each other. Based on these calculations the final flaw configuration for each large scale experiment is selected.

Mechanistic Prediction of Fracture Processes in Ferritic Steel Welds Within the Transition Temperature Regime

1998 ◽  
Vol 120 (4) ◽  
pp. 328-337 ◽  
Author(s):  
E. P. Busso ◽  
Y. Lei ◽  
N. P. O’Dowd ◽  
G. A. Webster
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Crack Growth ◽  
Cleavage Fracture ◽  
Temperature Regime ◽  
Ferritic Steel ◽  
Crack Tip ◽  
Ductile Tearing ◽  
Steel Welds ◽  
Fracture Processes

This work examines the fracture behavior of ferritic steel welds in the transition temperature regime, where failure can occur either by ductile tearing or cleavage fracture. A computational and probabilistic-based mechanistic approach to cleavage fracture and ductile crack growth is adopted to model the fracture processes. The softening effect of ductile damage close to the crack tip is described by a Gurson-type material model. A statistical approach linked to both the Weibull stress and the initial void volume fraction is employed to determine the probability of cleavage fracture and the coupling between both fracture mechanisms. Finite element results are relied upon to interpret experimental fracture toughness data for the welds and to examine the effects of near crack tip damage and crack growth on the cleavage failure probabilities and cleavage and ductile fracture toughness distributions. The scatter in the weld experimental fracture toughness data is well reproduced by the proposed cleavage and ductile tearing models.

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.

Modelling the Tearing Crack Growth in a Ductile Ferritic Steel Using X-FEM Elements

2011 ◽  
Author(s):  
A. Simatos ◽  
B. Prabel ◽  
S. Marie ◽  
M. Ne´de´lec ◽  
A. Combescure
Keyword(s):  
Crack Growth ◽  
Ferritic Steel ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Crack Tip ◽  
Internal Variable ◽  
Integration Scheme ◽  
Gauss Point ◽  
Ductile Crack Growth ◽  
Crack Position

eXtended Finite Element Method (X-FEM) is used to model a cracked structure without meshing explicitly the crack. Indeed, the crack is represented by a discontinuity of the displacement field through additional degrees of freedom using Heaviside type function or derived from the Irwin’s singular fields. Initially, the stress integration in the XFEM framework supposed to divide the cut elements into subtriangles that are conform to the crack. This was motivated in order to integrate the behaviour accurately on both sides of the crack in particular at proximity of the crack tip where singular enrichments are present. This strategy induces field projections from the usual Gauss point configuration to a variable new one that depends on the crack position in the element. For ductile fracture modelization, this approach is not applicable, because in presence of large scale yield, the projection of internal variable fields is not conservative, in particular at proximity of the crack tip. In order to circumvent this problem, a new integration strategy was proposed by B. Prabel. It consists in using 64 Gauss points that are placed without regards to the crack position. This simple integration scheme permits to take implicitly into account the crack position and the fields in the element in an accurate and consistent way. This strategy was used in problem calculation for which the plastic radius remained small. It allowed introducing the overintegrated elements in the probable propagation zone, just before plastification. In the case of ductile tearing, the plasticity is not confined near the crack tip and an improvement of the proposed strategy is made. This is then used to model large ductile crack growth in a ductile ferritic steel. To validate the predictions, the modelization is compared to a second F.E. calculation using the node release technique for the crack propagation. It is then shown that the two predictions are strictly equivalents.

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