Simulations of a Large-scale Four Point Bending Experiment; Influence of Residual Stresses from a Repair Weld

ADIMEW (Assessment of Aged Piping Dissimilar Metal Weld Integrity) was a three-year collaborative research programme carried out under the EC 5th Framework Programme. The objective of the study was to advance the understanding of the behaviour and safety assessment of defects in dissimilar metal welds between pipes representative of those found in nuclear power plant. ADIMEW studied and compared different methods for predicting the behaviour of defects located near the fusion boundaries of dissimilar metal welds typically used to join sections of austentic and ferritic piping operating at high temperature. Assessment of such defects is complicated by issues that include: severe mis-match of yield strength of the constituent parent and weld metals, strong gradients of material properties, the presence of welding residual stresses and mixed mode loading of the defect. The study includes the measurement of material properties and residual stresses, predictive engineering analysis and validation by means of a large-scale test. The particular component studies was a 453mm diameter pipe that joins a section of type A508 Class 3 ferritic pipe to a section of type 316L austentic pipe by means of a type 308 austentic weld with type 308/309L buttering laid on the ferritic pipe. A circumferential, surface-breaking defect was cut using electro discharge machining into the 308L/309L weld buttering layer parallel to the fusion line. The test pipe was subjected to four-point bending to promote ductile tearing of the defect. This paper presents the results of TWI contributions to ADIMEW including: fracture toughness testing, residual stress measurements and assessments of the ADIMEW test using elastic-plastic, cracked body, finite element analysis.

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Additive Manufactured 316L Stainless-Steel Samples: Microstructure, Residual Stress and Corrosion Characteristics after Post-Processing

Metals ◽

10.3390/met11020182 ◽

2021 ◽

Vol 11 (2) ◽

pp. 182

Author(s):

Suvi Santa-aho ◽

Mika Kiviluoma ◽

Tuomas Jokiaho ◽

Tejas Gundgire ◽

Mari Honkanen ◽

...

Keyword(s):

Residual Stress ◽

Residual Stresses ◽

Sample Surface ◽

Post Processing ◽

Magnesium Chloride Solution ◽

Manufacturing Method ◽

Four Point Bending ◽

Traditional Manufacturing ◽

Processing Steps ◽

Compressive Residual Stresses

Additive manufacturing (AM) is a relatively new manufacturing method that can produce complex geometries and optimized shapes with less process steps. In addition to distinct microstructural features, residual stresses and their formation are also inherent to AM components. AM components require several post-processing steps before they are ready for use. To change the traditional manufacturing method to AM, comprehensive characterization is needed to verify the suitability of AM components. On very demanding corrosion atmospheres, the question is does AM lower or eliminate the risk of stress corrosion cracking (SCC) compared to welded 316L components? This work concentrates on post-processing and its influence on the microstructure and surface and subsurface residual stresses. The shot peening (SP) post-processing levelled out the residual stress differences, producing compressive residual stresses of more than −400 MPa in the AM samples and the effect exceeded an over 100 µm layer below the surface. Post-processing caused grain refinement and low-angle boundary formation on the sample surface layer and silicon carbide (SiC) residue adhesion, which should be taken into account when using the components. Immersion tests with four-point-bending in the heated 80 °C magnesium chloride solution for SCC showed no difference between AM and reference samples even after a 674 h immersion.

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Investigation of Residual Stress/Strain and Texture in a Large Dissimilar Metal Weld Using Synchrotron Radiation and Neutrons

Materials Science Forum ◽

10.4028/www.scientific.net/msf.772.193 ◽

2013 ◽

Vol 772 ◽

pp. 193-199 ◽

Cited By ~ 1

Author(s):

Carsten Ohms ◽

Rene V. Martins

Keyword(s):

Synchrotron Radiation ◽

Neutron Diffraction ◽

Residual Stresses ◽

Large Scale ◽

High Energy ◽

X Ray Diffraction ◽

Butt Weld ◽

X Ray ◽

Component Size ◽

Thin Slice

Bi-metallic piping welds are frequently used in light water nuclear reactors to connect ferritic steel pressure vessel nozzles to austenitic stainless steel primary cooling piping systems. An important aspect for the integrity of such welds is the presence of residual stresses. Measurement of these residual stresses presents a considerable challenge because of the component size and because of the material heterogeneity in the weld regions. The specimen investigated here was a thin slice cut from a full-scale bi-metallic piping weld mock-up. A similar mock-up had previously been investigated by neutron diffraction within a European research project called ADIMEW. However, at that time, due to the wall thickness of the pipe, stress and spatial resolution of the measurements were severely restricted. One aim of the present investigations by high energy synchrotron radiation and neutrons used on this thin slice was to determine whether such measurements would render a valid representation of the axial strains and stresses in the uncut large-scale structure. The advantage of the small specimen was, apart from the easier manipulation, the fact that measurement times facilitated a high density of measurements across large parts of the test piece in a reasonable time. Furthermore, the recording of complete diffraction patterns within the accessible diffraction angle range by synchrotron X-ray diffraction permitted mapping the texture variations. The strain and stress results obtained are presented and compared for the neutron and synchrotron X-ray diffraction measurements. A strong variation of the texture pole orientations is observed in the weld regions which could be attributed to individual weld torch passes. The effect of specimen rocking on the scatter of the diffraction data in the butt weld region is assessed during the neutron diffraction measurements.

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Design of crack arrestors for ultra high grade gas transmission pipelines: simulation of crack initiation, propagation and arrest

International Journal Sustainable Construction & Design ◽

10.21825/scad.v2i2.20528 ◽

2011 ◽

Vol 2 (2) ◽

pp. 307-319

Author(s):

F. Van den Abeele ◽

M. Di Biagio ◽

L. Amlung

Keyword(s):

Crack Initiation ◽

Crack Propagation ◽

Large Scale ◽

Large Diameter ◽

Pipe Material ◽

High Grade ◽

Gas Pipelines ◽

Ductile Crack ◽

Reinforced Plastics ◽

Four Point Bending

One of the major challenges in the design of ultra high grade (X100) gas pipelines is the identification of areliable crack propagation strategy. Recent research results have shown that the newly developed highstrength and large diameter gas pipelines, when operated at severe conditions, may not be able to arrest arunning ductile crack through pipe material properties. Hence, the use of crack arrestors is required in thedesign of safe and reliable pipeline systems.A conventional crack arrestor can be a high toughness pipe insert, or a local joint with higher wall thickness.According to experimental results of full-scale burst tests, composite crack arrestors are one of the mostpromising technologies. Such crack arrestors are made of fibre reinforced plastics which provide the pipewith an additional hoop constraint. In this paper, numerical tools to simulate crack initiation, propagationand arrest in composite crack arrestors are introduced.First, the in-use behaviour of composite crack arrestors is evaluated by means of large scale tensile testsand four point bending experiments. The ability of different stress based orthotropic failure measures topredict the onset of material degradation is compared. Then, computational fracture mechanics is applied tosimulate ductile crack propagation in high pressure gas pipelines, and the corresponding crack growth inthe composite arrestor. The combination of numerical simulation and experimental research allows derivingdesign guidelines for composite crack arrestors.

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

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2018-85044 ◽

2018 ◽

Cited By ~ 1

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.

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Hybrid-laser welding-induced distortions and residual stresses analysis of large-scale stiffener panel

Ocean Engineering ◽

10.1016/j.oceaneng.2021.110411 ◽

2022 ◽

Vol 245 ◽

pp. 110411

Author(s):

M. Hashemzadeh ◽

Y. Garbatov ◽

C. Guedes Soares

Keyword(s):

Residual Stresses ◽

Laser Welding ◽

Large Scale

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Development of residual stresses in fatigue-stressed joints subjected to four-point bending

Welding International ◽

10.1080/09507116.2011.592692 ◽

2011 ◽

pp. 1-9

Author(s):

V. Dattoma ◽

M. De Giorgi ◽

R. Nobile

Keyword(s):

Residual Stresses ◽

Four Point Bending

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Measurement and Modelling of Residual Stresses in Fracture Toughness Specimens Extracted From Large Components

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2008-61348 ◽

2008 ◽

Author(s):

S. J. Lewis ◽

S. Hossain ◽

C. E. Truman ◽

D. J. Smith ◽

M. Hofmann

Keyword(s):

Fracture Toughness ◽

Residual Stress ◽

Residual Stresses ◽

Driving Force ◽

Large Scale ◽

Structural Integrity ◽

Mechanical Load ◽

Crack Driving Force ◽

Neutron Diffraction Technique ◽

Fracture Specimens

A number of previously published works have shown that the presence of residual stresses can significantly affect measurements of fracture toughness, unless they are properly accounted for when calculating parameters such as the crack driving force. This in turn requires accurate, quantitative residual stress data for the fracture specimens prior to loading to failure. It is known that material mechanical properties may change while components are in service, for example due to thermo-mechanical load cycles or neutron embrittlement. Fracture specimens are often extracted from large scale components in order to more accurately determine the current fracture resistance of components. In testing these fracture specimens it is generally assumed that any residual stresses present are reduced to a negligible level by the creation of free surfaces during extraction. If this is not the case, the value of toughness obtained from testing the extracted specimen is likely to be affected by the residual stress present and will not represent the true material property. In terms of structural integrity assessments, this can lead to ‘double accounting’ — including the residual stresses in both the material toughness and the crack driving force, which in turn can lead to unnecessary conservatism. This work describes the numerical modelling and measurement of stresses in fracture specimens extracted from two different welded parent components: one component considerably larger than the extracted specimens, where considerable relaxation would be expected as well as a smaller component where appreciable stresses were expected to remain. The results of finite element modelling, along with residual stress measurements obtained using the neutron diffraction technique, are presented and the likely implications of the results in terms of measured fracture toughness are examined.

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Investigation of Interlaminar Defects and their Influence on Interlaminar Strength

Advanced Composites Letters ◽

10.1177/096369359600500404 ◽

1996 ◽

Vol 5 (4) ◽

pp. 096369359600500

Author(s):

J Ziao ◽

J Tao

Keyword(s):

Tensile Strength ◽

Large Scale ◽

Peel Strength ◽

Test Method ◽

Bending Test ◽

Four Point Bending ◽

Transverse Tensile ◽

Interlaminar Shear ◽

Transverse Tensile Strength ◽

Set Up

In this paper, we directed our attention to the interlaminar defects and their influence on the interlaminar strengths. With the aid of a S-570 scanning electron microscope, the morphology and distribution of interlaminar defects were inspected and documented. According to their shape, size and cause of formation, the defects were classified into five types: flakiness void, irregular shaped debond, local imperfectly cured resin, debond in two multi-directional plies, and inhomogeneous fibers and the large scale debond by these fibers. The cause of defects formation was discussed by analyzing the manufacturing process of composites. The influence of defects on the interlaminar strength and its mechanism was analyzed experimentally and theoretically. The results indicate that these defects, with different effects, decrease the interlaminar strength because they form interlaminar cracks, and the interlaminar shear strength is less affected than interlaminar tensile strength, which is measured according to GB4944 test method. To comprehend defects distribution effect, a four-point-bending test method was introduced to measure the interlaminar peel strength, and a discussion was made on the correlation between the interlaminar tensile strength, interlaminar peel strength and in-plane transverse tensile strength. Finally the concept of interlaminar defect coefficient, which can be used to characterize the defects, was set up and the formula to calculate it was proposed.

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