A Damage Criterion to Predict the Fatigue Life of Steel Pipelines Based on Indentation Measurements

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Geovana Drumond ◽  
Francine Roudet ◽  
Didier Chicot ◽  
Bianca Pinheiro ◽  
Ilson Pasqualino
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Steel Structure ◽  
Steel Structures ◽  
Initial State ◽  
Damage Criterion ◽  
Microstructural Changes ◽  
Pertinent Data ◽  
Indentation Tests ◽  
Number Of Cycles

Abstract A study was conducted to investigate the effects of surface microhardness on different phases of fatigue damage. This helps to estimate the evolution of the material resistance from microplastic distortions and gives pertinent data about cumulated fatigue damage. The objective of this work is to propose a damage criterion, associated with microstructural changes, to predict the fatigue life of steel structures submitted to cyclic loads before macroscopic cracking. Instrumented indentation tests (IIT) were conducted on test samples submitted to high cycle fatigue (HCF) loads. To evaluate the role of the microstructure initial state, the material was considered in two different conditions: as-received and annealed. It was observed that significant changes in the microhardness values happened at the surface and subsurface of the material, up to 2 µm of indentation depth, and around 21% and 7% of the fatigue life for as-received and annealed conditions, respectively. These percentages were identified as a critical period for microstructural changes, which was taken as a reference in a damage criterion to predict the number of cycles to fatigue failure (Nf) of a steel structure.

High Cycle Fatigue Damage Evaluation of Steel Pipelines Based on Microhardness Changes During Cyclic Loads: Part II

2018 ◽  
Author(s):  
Geovana Drumond ◽  
Bianca Pinheiro ◽  
Ilson Pasqualino ◽  
Francine Roudet ◽  
Didier Chicot
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Steel Structures ◽  
New Method ◽  
Microplastic Deformation ◽  
Surface Phenomenon ◽  
Cyclic Loads ◽  
Cycle Fatigue ◽  
Indentation Tests

The hardness of a material shows its ability to resist to microplastic deformation caused by indentation or penetration and is closely related to the plastic slip capacity of the material. Therefore, it could be significant to study the resistance to microplastic deformations based on microhardness changes on the surface, and the associated accumulation of fatigue damage. 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. Here, Berkovich indentation tests were carried out in the samples previously submitted to high cycle fatigue (HCF) tests. It was observed that the major changes in the microhardness values occurred at the surface of the material below 3 μm of indentation depth, and around 20% of the fatigue life of the material, proving that microcracking is a surface phenomenon. So, the results obtained for the surface of the specimen and at the beginning of the fatigue life of the material will be considered in the proposal of a new method to estimate the fatigue life of metal structures.

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.

scholarly journals Experimental study on fatigue performance of Q420qD high-performance steel cross joint in complex environment

2021 ◽  
Author(s):  
Haigen Cheng ◽  
Cong Hu ◽  
Yong Jiang
Keyword(s):  
Fatigue Life ◽  
High Performance ◽  
Steel Structure ◽  
Steel Structures ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Corrosive Media ◽  
Joint Connection ◽  
High Performance Steel ◽  
The Cross

AbstractThe steel structure under the action of alternating load for a long time is prone to fatigue failure and affects the safety of the engineering structure. For steel structures in complex environments such as corrosive media and fires, the remaining fatigue life is more difficult to predict theoretically. To this end, the article carried out fatigue tests on Q420qD high-performance steel cross joints under three different working conditions, established a 95% survival rate $$S{ - }N$$ S - N curves, and analyzed the effects of corrosive media and high fire temperatures on its fatigue performance. And refer to the current specifications to evaluate its fatigue performance. The results show that the fatigue performance of the cross joint connection is reduced under the influence of corrosive medium, and the fatigue performance of the cross joint connection is improved under the high temperature of fire. When the number of cycles is more than 200,000 times, the design curves of EN code, GBJ code, and GB code can better predict the fatigue life of cross joints without treatment, only corrosion treatment, and corrosion and fire treatment, and all have sufficient safety reserve.

Application of Surface Roughness Parameters to the Evaluation of Low Cycle Fatigue Damage in Austenitic Stainless Steel

2013 ◽  
Author(s):  
Nao Fujimura ◽  
Takashi Nakamura ◽  
Hiroyuki Oguma
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Crack Detection ◽  
Low Cycle Fatigue ◽  
Roughness Parameter ◽  
Strain Range ◽  
Maximum Height ◽  
Roughness Parameters ◽  
Number Of Cycles

Changes in the surface roughness of SUS316NG during cyclic loadings were investigated, and the relations between those changes and the crack initiation and propagation processes are discussed on the basis of microscopic observations and cellulose acetate replica observations. Strain-controlled fatigue tests were conducted at three constant strain ranges. Surface roughness was measured periodically during the tests, and three roughness parameters were calculated: arithmetic mean roughness Ra, surface profile maximum height Rmax, and maximum valley depth Rv. Until the middle of fatigue life, all three increased linearly with the number of cycles regardless of the strain range, and their rates of increase became smaller with decreasing strain range. Surface observation revealed that small cracks initiated very early in fatigue life, propagated slowly until the middle of fatigue life, and then grew rapidly. Changes in surface roughness are therefore sensitive to fatigue loading even when cracks are very small and crack detection is difficult. The results suggest that surface roughness can probably be used to assess fatigue damage because until the middle of fatigue life it increases linearly with the number of cycles. The definition of each roughness parameter and the changes show that Rmax and Rv are suitable for damage assessment.

On the Quantification of Robustness of Structures

2006 ◽  
Author(s):  
Michael H. Faber ◽  
Marc A. Maes ◽  
Daniel Straub ◽  
Jack Baker
Keyword(s):  
Service Life ◽  
Fatigue Damage ◽  
Steel Structure ◽  
Steel Structures ◽  
Risk Assessments ◽  
Structural Systems ◽  
Engineering Systems ◽  
Type Steel ◽  
Damage And Failure ◽  
Generic Framework

The paper first reviews different interpretations of robustness. On this basis objectives facilitating the quantification of robustness of engineering systems are formulated. Thereafter a generic framework for risk assessments of engineering systems is presented in which robustness is related to the ability of the system to sustain damages. This framework is then applied to quantify robustness of structural systems and to develop a robustness index facilitating a consistent ranking of structures according to their robustness. The proposed approach to the assessment of robustness principally takes into account the effect of redundancy, ductility, damage and failure consequences as well as strategies for condition control and intervention during the service life of structures. Finally, a simple example illustrates the use of the framework for the assessment of the robustness of a jacket steel structure subject to fatigue damage. The example shows that presently used indicators for the robustness of jacket type steel structures such as the RIF only capture part of the picture and illustrates the merits of a risk based framework for robustness assessments.

Effect of Electropulsing on the Fatigue Behavior and Change in the Austenite Steel Structure

2017 ◽  
Vol 906 ◽  
pp. 26-31 ◽  
Author(s):  
Sergey V. Konovalov ◽  
D.A. Kosinov ◽  
I.A. Komissarova ◽  
V.E. Gromov
Keyword(s):  
Fatigue Life ◽  
Dynamic Recrystallization ◽  
Dislocation Substructure ◽  
Fatigue Behavior ◽  
Steel Structure ◽  
Grain Structure ◽  
Local Dynamic ◽  
Initial State ◽  
Electron Microscopic ◽  
Austenite Steel

The tests were carried out to identify the influence of electropulse treatment on austenite steel ((mass %) 0.44С, 16.50Mn, 0.26Cr, 0.08Ni, 0.34Si, 2.74Al, 0.002S, 0.017P, Fe – balance). The fa-tigue life is reported to increase by 1.8 times. Electron microscopic research into the dislocation structure of the steel was conducted under diverse fatigue conditions with the purpose to give rea-sons for the identified effect. The dislocation chaos substructure, reticular and fragmented dislocation substructures were found in the steel in the initial state. Fatiguing leads to the change in the dis-location substructure parameters. The subsequent electropulse treatment furthers transformation of the grain structure since grains arise and grow due to evolving local dynamic recrystallization and partial transformation of the dislocation substructure and occurrence of a great number of microtwins. The increase in the fatigue life is associated with the mentioned above transformations resulting from electropulse treatment of the steel structural state.

scholarly journals Balance Fatigue Design of Cast Steel Nodes in Tubular Steel Structures

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Libin Wang ◽  
Hui Jin ◽  
Haiwei Dong ◽  
Jing Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Cast Steel ◽  
Steel Structure ◽  
Steel Structures ◽  
Crack Size ◽  
Initial Crack ◽  
Fatigue Design ◽  
Joint Application ◽  
Mechanical Performances

Cast steel nodes are being increasingly popular in steel structure joint application as their advanced mechanical performances and flexible forms. This kind of joints improves the structural antifatigue capability observably and is expected to be widely used in the structures with fatigue loadings. Cast steel node joint consists of two parts: casting itself and the welds between the node and the steel member. The fatigue resistances of these two parts are very different; the experiment results showed very clearly that the fatigue behavior was governed by the welds in all tested configurations. This paper focuses on the balance fatigue design of these two parts in a cast steel node joint using fracture mechanics and FEM. The defects in castings are simulated by cracks conservatively. The final crack size is decided by the minimum of 90% of the wall thickness and the value deduced by fracture toughness. The allowable initial crack size could be obtained through the integral of Paris equation when the crack propagation life is considered equal to the weld fatigue life; therefore, the two parts in a cast steel node joint will have a balance fatigue life.

Fatigue Life Extension Procedure for Subsea Wells Based on Pressure Testing

2021 ◽  
Author(s):  
Arne Fjeldstad ◽  
Torfinn Hørte ◽  
Gudfinnur Sigurdsson ◽  
Anders Wormsen ◽  
Espen Berg ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Hot Spots ◽  
Fatigue Cracks ◽  
Load Test ◽  
Life Extension ◽  
Case Examples ◽  
Pressure Test ◽  
Number Of Cycles

Abstract This article presents a fatigue life extension procedure for subsea wells based on fracture mechanics. It makes use of the outcome of an internal pressure test to determine a safe period for drilling and completion. The pressure test is used as a load test and can only reveal deep fatigue cracks. The safe operational period is estimated as the number of cycles required to grow a fatigue crack from the largest fatigue crack that remains stable after the pressure test until it becomes unstable due to an accidental load. The procedure takes into account the probability of the presence of the fatigue crack that can be revealed by the pressure test. This is used to determine design fatigue factors for the procedure. The design fatigue factor is formulated in terms of the (S-N based) accumulated fatigue damage for historical operations. The procedure is illustrated with two case examples (fatigue hot spots) for illustrating the procedure in more detail: wellhead extension girth weld and wellhead profile. Conditions for use are given at the end of the article.

Effects of Regular and Nano Sized Hydrated Lime Fillers on Fatigue and Bond Strength Behavior of Asphalt Mastic

2018 ◽  
Vol 2672 (28) ◽  
pp. 31-41 ◽  
Author(s):  
Aditya Kumar Das ◽  
Dharamveer Singh
Keyword(s):  
Fatigue Life ◽  
Bond Strength ◽  
Fatigue Damage ◽  
Asphalt Binder ◽  
Hydrated Lime ◽  
Moisture Damage ◽  
Test Results ◽  
Asphalt Mastic ◽  
Asphalt Mastics ◽  
Number Of Cycles

The present study evaluates effects of regular sized hydrated lime (RHL) and nano sized hydrated lime (NHL) on fatigue and bond strength of asphalt mastic. The asphalt mastics were produced in the laboratory using AC-30 binder with different combinations of basalt–RHL, and basalt–NHL fillers. The dosages of RHL and NHL were selected as 0%, 5%, 10%, 15%, and 20% by weight of asphalt binder, and the percentage of basalt filler was adjusted accordingly. Filler to binder (F/B) ratio was selected as 0.8 (by mass ratio) for all mastic sample preparation. The fatigue damage behavior (number of cycles to fatigue damage/failure) of asphalt mastic was evaluated using a linear amplitude sweep (LAS) test. Further, the interfacial bond strengths of asphalt mastic and aggregate samples were evaluated using the bitumen bond strength (BBS) test. Overall test results indicate that mineralogy, surface area, and interaction properties of RHL and NHL fillers have a significant effect on fatigue, bond strength, and moisture damage performance of asphalt mastic. The results from the LAS test showed that NHL filler predominantly enhanced the fatigue life of asphalt mastic as compared with RHL filler. BBS test results imply that the contribution of NHL filler is significant over RHL filler in improving the bond strength and moisture damage resistance of asphalt mastic. Overall asphalt mastic with 20% NHL filler had better fatigue life, bond strength, and moisture damage performance over mastic with other percentages of RHL or NHL fillers.

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