X-Ray Diffraction Study of Microstructural Changes During Fatigue Damage in Steel Pipelines

2012 ◽  
Author(s):  
Bianca Pinheiro ◽  
Jacky Lesage ◽  
Ilson Pasqualino ◽  
Noureddine Benseddiq ◽  
Edoardo Bemporad
Keyword(s):  
Fatigue Damage ◽  
Fatigue Behavior ◽  
Ion Beam ◽  
Fatigue Tests ◽  
X Ray Diffraction ◽  
Microstructural Changes ◽  
X Ray ◽  
Steel Pipes ◽  
Damage Initiation ◽  
Three Stages

Steel pipes used for oil and gas exploitation undergo the action of cyclic loads that can cause their failure by fatigue. A consistent evaluation of the fatigue behavior should take into account the micromechanisms of fatigue damage initiation, which precede macroscopic cracking and macrocrack propagation. In this work, microstructural changes in terms of variations in microdeformations and residual stresses (macrostresses) are evaluated by X-ray diffraction in real time during alternating bending fatigue tests performed on samples taken from an API 5L X60 grade steel pipe. Three stages of microstructural changes are detected. It is found that their amplitudes and durations are proportional to the level of alternating stress applied. Changes in density and distribution of dislocations are observed by transmission electron microscopy combined with the technique of focused ion beam. To understand the role of the initial dislocation structure, fatigue tests on annealed samples are performed under the same test conditions. Again, three stages of changes are observed, but with an increase in microdeformations during the first stage instead of a decrease as found for as-machined samples, suggesting the influence of the initial state of the dislocation network. The results obtained are very encouraging for the consideration of microstructural evolutions in the development of an indicator of fatigue damage initiation in steel pipes.

X-Ray Diffraction Study of Microstructural Changes During Fatigue Damage Initiation in Steel Pipes

2012 ◽  
Author(s):  
Bianca Pinheiro ◽  
Jacky Lesage ◽  
Ilson Pasqualino ◽  
Noureddine Benseddiq ◽  
Edoardo Bemporad
Keyword(s):  
Residual Stresses ◽  
Fatigue Damage ◽  
Fatigue Tests ◽  
X Ray Diffraction ◽  
Peak Displacement ◽  
Microstructural Changes ◽  
X Ray ◽  
Steel Pipes ◽  
Damage Initiation ◽  
Grade Steel

The present work aims to evaluate the microstructural mechanisms associated with the initiation of fatigue damage in steels used in the petroleum industry. Microdeformations and residual stresses (macrostresses) are evaluated by X-ray diffraction in real time during alternating bending fatigue tests performed on samples taken from an API 5L X60 grade steel pipe. Microdeformations are evaluated from measurements of the full width at half maximum (FWHM) of the diffraction peak and residual stresses are estimated from the peak displacement. The evolution of microdeformations shows three regular successive stages of changes. The amplitude of variation of each stage is intensified with increasing stress amplitude, while the duration is reduced. A similar evolution is found for residual stresses, whose stages of changes have nearly the same durations as those of microdeformations. Changes in density and distribution of dislocations are observed by transmission electron microscopy combined with the technique of focused ion beam. To understand the role of the initial structure, fatigue tests on annealed samples are performed under the same test conditions. Again, three stages of changes are observed, but with an increase in microdeformations instead of a decrease during the first stage due to the initial state of the dislocation network. The results are very encouraging for the consideration of microstructural changes measured by X-ray diffraction in the development of a future indicator of fatigue damage initiation in API 5L X60 grade steel pipes.

X-ray diffraction study of microstructural changes during fatigue damage initiation in steel pipes

2012 ◽  
Vol 532 ◽  
pp. 158-166 ◽  
Author(s):  
B. Pinheiro ◽  
J. Lesage ◽  
I. Pasqualino ◽  
N. Benseddiq ◽  
E. Bemporad
Keyword(s):  
Diffraction Study ◽  
Fatigue Damage ◽  
X Ray Diffraction ◽  
Microstructural Changes ◽  
X Ray ◽  
Steel Pipes ◽  
Damage Initiation

Assessment of Fatigue Damage Initiation in Oil and Gas Steel Pipes

2011 ◽  
Author(s):  
Bianca Pinheiro ◽  
Jacky Lesage ◽  
Ilson Pasqualino ◽  
Noureddine Benseddiq
Keyword(s):  
Fatigue Damage ◽  
Oil And Gas ◽  
Fatigue Behavior ◽  
Diffraction Method ◽  
Fatigue Tests ◽  
Uniaxial Tensile ◽  
Good Prediction ◽  
Steel Pipes ◽  
Damage Initiation ◽  
Grade Steel

Steel pipe structures used in oil and gas industry, such as drill pipes, rigid risers and pipelines, undergo the action of cyclic loadings that can cause their failure by fatigue. These structures are made of high strength steels, such as API 5L grades X for instance. A consistent evaluation of the fatigue behavior should fundamentally be based on a local approach, in the dislocation scale, and take into account the micromechanisms of fatigue damage initiation, including microdeformations and microstructural changes, which precede the macrocrack propagation leading to final failure. In this work, the microstructural mechanisms of fatigue damage initiation in API 5L X60 grade steel pipes are investigated. Material properties of API 5L X60 steel are estimated according to chemical composition analyses, microscopic analyses, uniaxial tensile tests and Vickers micro-hardness tests. Samples are submitted to fatigue tests with reversed stress bending loadings. Microdeformations and residual stresses are measured with the aid of the X-ray diffraction method in real-time during fatigue tests. A numerical model is developed to reproduce the fatigue test loadings. The aim of the work is to provide ground for the development of a microstructural criterion for fatigue damage initiation in API 5L X60 grade steel pipes from the obtained experimental results. This criterion could allow a good prediction of the residual life of steel pipes previously submitted to fatigue loadings, before macroscopic cracking, and help to increase the reliability of oil and gas pipes.

scholarly journals High Cycle Fatigue Damage Evaluation of Steel Pipelines Based on Microhardness Changes During Cyclic Loads

2017 ◽  
Author(s):  
Geovana Drumond ◽  
Bianca Pinheiro ◽  
Ilson Pasqualino ◽  
Francine Roudet ◽  
Didier Chicot ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Steel Structures ◽  
Material Surface ◽  
Cyclic Loads ◽  
X Ray Diffraction ◽  
Microstructural Changes ◽  
X Ray ◽  
Microcrack Initiation ◽  
Non Destructive

Fatigue is a major cause of failures concerning metal structures, being capable of causing catastrophic damage to the environment and considerable financial loss. Steel pipelines used in oil and gas industry for hydrocarbon transportation, for instance, are submitted to the action of cyclic loads, being susceptible to undergo fatigue failures. The phenomenon of metal fatigue is a complex process comprising different successive mechanisms. In general, four stages can be identified, representing microcrack initiation (nucleation), microcracking, macrocrack propagation, and final fracture. Fatigue damage prior to nucleation of microcracks is primarily related to localized plastic strain development at or near material surface during cycling. The microhardness of the material shows its ability to resist microplastic deformation caused by indentation or penetration, and is closely related to the material plastic slip capacity. Therefore, the study of changes in material surface microhardness during the different stages of fatigue process can estimate the evolution of the material resistance to microplastic deformations and, consequently, provide relevant information about the cumulated fatigue damage on the surface. The present work is part of a research study being carried out with the aim of proposing a new method based on microstructural changes, represented by a fatigue damage indicator, to predict fatigue life of steel structures submitted to cyclic loads, before macroscopic cracking. In a previous work, the X-ray diffraction technique was used to evaluate these changes. This technique presents several advantages, since it is non-destructive and concerns the surface and subsurface of the material, where major microstructural changes take place during fatigue. The most important parameter obtained by this technique is the full width at half maximum (FWHM) of the diffraction peak, which can provide information about the dislocation network density and estimate microdeformations. It was found that the evolution of this parameter with cycling presents three different stages, associated to the mechanisms of microcrack initiation, microcracking, macrocrack propagation, respectively. Here, the fatigue damage of pipeline steels is evaluated through microhardness testing. Different stages of changes in microhardness are also found and they are correlated to those observed with the X-ray technique and also with transmission electron microscopic (TEM) images from experimental tests performed with a similar material. This correlation can help to corroborate the X-ray diffraction results previously obtained and recommend then this non-destructive technique as the base of the method for predicting fatigue life of steel structures proposed here.

Toward a Fatigue Life Assessment of Steel Pipes Based on X-Ray Diffraction Measurements

2015 ◽  
Author(s):  
Bianca Pinheiro ◽  
Jacky Lesage ◽  
Ilson Pasqualino ◽  
Noureddine Benseddiq ◽  
Edoardo Bemporad
Keyword(s):  
Residual Stresses ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Petroleum Industry ◽  
Fatigue Tests ◽  
Material Behavior ◽  
Life Assessment ◽  
Initial Structure ◽  
X Ray Diffraction ◽  
X Ray

The present work aims to evaluate the microstructural mechanisms associated with the initiation of fatigue damage of steels used in the petroleum industry. Microdeformations and residual stresses (macrostresses) are evaluated by X-ray diffraction in real time during alternating bending fatigue tests performed on samples taken from an API 5L X60 grade steel pipe. Samples under two different conditions are considered: as-machined and annealed. Microdeformations and residual stresses are estimated from measurements of the full width at half maximum (FWHM) and displacement of the diffraction peak, respectively. The evolution of microdeformations shows three distinct stages (Stages 1–3). Increasing stress amplitude accentuates variations in FWHM and reduces the duration of each stage. Similar variations are observed for the residual stresses. The results from annealed samples allow the comprehension of the role of the initial structure. Changes in the density and distribution of dislocations are observed by transmission electron microscopy using the technique of focused ion beam. Cyclic uniaxial tests are carried out in order to evaluate the material behavior, in both as-machined and annealed conditions, under cyclic loadings. The cyclic material behavior is correlated to the evolution of microdeformations observed during the fatigue bending tests.

Mev Ion Beam Synthesis of Well-Defined Buried 3C-Sic Layers in Silicon

1995 ◽  
Vol 396 ◽  
Author(s):  
J.K.N. Lindner ◽  
B. Götz ◽  
A. Frohnwieser ◽  
B. Stritzker
Keyword(s):  
Electron Diffraction ◽  
Depth Distribution ◽  
Ion Beam ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ion Beam Synthesis ◽  
Post Implantation

AbstractWell-defined, homogenous, deep-buried 3C-SiC layers have been formed in silicon by ion beam synthesis using MeV C+ ions. Layers are characterized by RBS/channeling, X-ray diffraction, x-sectional TEM and electron diffraction. The redistribution of implanted carbon atoms into a rectangular carbon depth distribution associated with a well-defined layer during the post-implantation anneal is shown to depend strongly on the existence of crystalline carbide precipitates in the as-implanted state.

Characterization of Natural and Synthesized FeTiO3 Crystals With RBS/PIXE/XRD

1997 ◽  
Vol 07 (03n04) ◽  
pp. 265-275
Author(s):  
R. Q. Zhang ◽  
S. Yamamoto ◽  
Z. N. Dai ◽  
K. Narumi ◽  
A. Miyashita ◽  
...  
Keyword(s):  
Single Crystals ◽  
Ion Beam ◽  
Pressure Control ◽  
Floating Zone ◽  
X Ray Diffraction ◽  
X Ray ◽  
Beam Analysis ◽  
Ppm Level

Natural FeTiO 3 (illuminate) and synthesized FeTiO 3, single crystals were characterized by Rutherford backscattering spectroscopy combined with channeling technique and particle-induced x-ray emission (RBS-C and PIXE). The results obtained by the ion beam analysis were supplemented by the x-ray diffraction analysis to identify the crystallographic phase. Oriented single crystals of synthesized FeTiO 3 were grown under the pressure control of CO 2 and H 2 mixture gas using a single-crystal floating zone technique. The crystal quality of synthesized FeTiO 3 single crystals could be improved by the thermal treatment but the exact pressure control is needed to avoid the precipitation of Fe 2 O 3 even during the annealing procedure. Natural FeTiO 3 contains several kinds of impurities such as Mn , Mg , Na and Si . The synthesized samples contain Al , Si and Na which are around 100 ppm level as impurities. The PBS-C results of the natural sample imply that Mn impurities occupy the Fe sublattice in FeTiO 3 or in mixed phase between ilmenite and hematite.

Formation and Thermal Stability of Nd0.32Y0.68Si1.7 Layers Formed by Channeled Ion Beam Synthesis

1998 ◽  
Vol 514 ◽  
Author(s):  
M. F. Wu ◽  
A. Vantomne ◽  
S. Hogg ◽  
H. Pattyn ◽  
G. Langouche ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Ion Beam ◽  
Hexagonal Structure ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Good Crystalline Quality ◽  
Ion Beam Synthesis ◽  
Thermal Stability Of

ABSTRACTThe Nd-disilicide, which exists only in a tetragonal or an orthorhombic structure, cannot be grown epitaxially on a Si(111) substrate. However, by adding Y and using channeled ion beam synthesis, hexagonal Nd0.32Y0.68Si1.7 epilayers with lattice constant of aepi = 0.3915 nm and cepi = 0.4152 nm and with good crystalline quality (χmin of Nd and Y is 3.5% and 4.3 % respectively) are formed in a Si(111) substrate. This shows that the addition of Y to the Nd-Si system forces the latter into a hexagonal structure. The epilayer is stable up to 950 °C; annealing at 1000 °C results in partial transformation into other phases. The formation, the structure and the thermal stability of this ternary silicide have been studied using Rutherford backscattering/channeling, x-ray diffraction and transmission electron microscopy.

Sign in / Sign up

Export Citation Format

Share Document