scholarly journals Prediction of Corrosive Fatigue Life of Submarine Pipelines of API 5L X56 Steel Materials

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1031 ◽  
Author(s):  
Xudong Gao ◽  
Yongbo Shao ◽  
Liyuan Xie ◽  
Yamin Wang ◽  
Dongping Yang
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Shape Factor ◽  
Bohai Sea ◽  
Paris Law

Corrosive fatigue failure of submarine pipelines is very common because the pipeline is immersed in a sea environment. In Bohai sea, many old pipelines are made of API 5L X56 steel materials, and it is necessary to provide an accurate method for predicting the residual life of these pipelines. As Paris law has been proven to be reliable in predicting the fatigue crack growth in metal materials, the two constants in Paris law for API 5L X56 steel materials are obtained by using a new proposed shape factor based on the analysis of experimental data measured from fatigue tests on compact tension specimens immersed in the water of Bohai sea. The results of the newly proposed shape factor show that, for a given stress intensity factor range (ΔK), the fatigue crack growth rate (da/dN) in seawater is 1.6 times of that that in air. With the increase of fatigue crack growth rate, the influence of seawater on corrosive fatigue decreases gradually. Thereafter, a finite element model for analyzing the stress intensity factor of fatigue crack in pipelines is built, and the corrosive fatigue life of a submarine pipeline is then predicted according to the Paris law. To verify the presented method, the fatigue crack growth (FCG) behavior of an API 5L X56 pipeline with an initial crack under cyclic load is tested. Comparison between the prediction and the tested result indicates that the presented method is effective in evaluating the corrosive fatigue life of API 5L X56 pipelines.

Numerical Determination of Paris Law Constants for Carbon Steel Using a Two-Scale Model

2022 ◽  
pp. 1-15
Author(s):  
M. Mlikota
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Scale Model ◽  
Numerical Determination ◽  
Paris Law

For most engineering alloys, the long fatigue crack growth under a certain stress level can be described by the Paris law. The law provides a correlation between the fatigue crack growth rate (FCGR or da/dN), the range of stress intensity factor (ΔK), and the material constants C and m. A well-established test procedure is typically used to determine the Paris law constants C and m, considering standard specimens, notched and pre-cracked. Definition of all the details necessary to obtain feasible and comparable Paris law constants are covered by standards. However, these cost-expensive tests can be replaced by appropriate numerical calculations. In this respect, this paper deals with the numerical determination of Paris law constants for carbon steel using a two-scale model. A micro-model containing the microstructure of a material is generated using the Finite Element Method (FEM) to calculate the fatigue crack growth rate at a crack tip. The model is based on the Tanaka-Mura equation. On the other side, a macro-model serves for the calculation of the stress intensity factor. The analysis yields a relationship between the crack growth rates and the stress intensity factors for defined crack lengths which is then used to determine the Paris law constants.

Mechanisms of Fatigue Crack Growth in WC-Co Cemented Carbides

2005 ◽  
Vol 297-300 ◽  
pp. 1120-1125 ◽  
Author(s):  
Myung Hwan Boo ◽  
Chi Yong Park
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Ratio ◽  
Cemented Carbides ◽  
Stress Intensity Factor Range

In order to study the influence of stress ratio and WC grain size, the characteristics of fatigue crack growth were investigated in WC-Co cemented carbides with two different grain sizes of 3 and 6 µm. Fatigue crack growth tests were carried out over a wide range of fatigue crack growth rates covering the threshold stress intensity factor range DKth. It was found that crack growth rate da/dN against stress intensity factor range DK depended on stress ratio R. The crack growth rate plotted in terms of effective stress intensity factor range DKeff still exhibited the effect of microstructure. Fractographic examination revealed brittle fracture at R=0.1 and ductile fracture at R=0.5 in Co binder phase. The amount of Co phase transformation for stress ratio was closely related to fatigue crack growth characteristics.

Fatigue Damage Analysis on Crack Growth and Fatigue Life of Welded Bridge Members with Initial Crack

2006 ◽  
Vol 324-325 ◽  
pp. 251-254 ◽  
Author(s):  
Tai Quan Zhou ◽  
Tommy Hung Tin Chan ◽  
Yuan Hua
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Initial Crack ◽  
Traffic Loading

The behavior of crack growth with a view to fatigue damage accumulation on the tip of cracks is discussed. Fatigue life of welded components with initial crack in bridges under traffic loading is investigated. The study is presented in two parts. Firstly, a new model of fatigue crack growth for welded bridge member under traffic loading is presented. And the calculate method of the stress intensity factor necessary for evaluation of the fatigue life of welded bridge members with cracks is discussed. Based on the concept of continuum damage accumulated on the tip of fatigue cracks, the fatigue damage law suitable for steel bridge member under traffic loading is modified to consider the crack growth. The proposed fatigue crack growth can describe the relationship between the cracking count rate and the effective stress intensity factor. The proposed fatigue crack growth model is then applied to calculate the crack growth and the fatigue life of two types of welded components with fatigue experimental results. The stress intensity factors are modified by the factor of geometric shape for the welded components in order to reflect the influence of the welding type and geometry on the stress intensity factor. The calculated and measured fatigue lives are generally in good agreement, at some of the initial conditions of cracking, for a welded component widely used in steel bridges.

Fatigue Algorithm for Modeling Many Weld Toe Cracks Propagating at Welded Joints

2016 ◽  
Author(s):  
Kin Shun Tsang ◽  
John H. L. Pang ◽  
Hsin Jen Hoh
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Welded Joints ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Paris Law ◽  
Weld Toe

Fatigue crack growth at welded joints often propagates from as many as tens to hundreds of small weld toe cracks along the weld toe line in offshore welded structures. This paper will present a fatigue algorithm for modeling many small weld toe cracks propagating from a welded joint. Cracks usually initiate at the weld toe region of the structures and propagate as surface cracks at the stress concentration regions of the weld-toe line. The presence of such weld defects or crack-like flaws can have a severe detrimental effect on their fatigue life and fracture resistance. Currently, there is a lack of studies that considers the effects of multiple cracks and their distribution density in welded joints. This work focuses on the fatigue analysis and modeling of multiple weld toe cracks, specifically in T-butt joints. Fatigue crack growth prediction is usually determined by the stress intensity factor range and crack propagation rate through Paris law. To predict the Stress Intensity Factor (SIF) of a weld toe crack, the magnification (Mk) factor was used. The Mk factor is influenced by the size of the welded attachment, as well as the size and depth of the weld toe crack. Simplified solutions for practical prediction of Mk factors were determined from 3D extended finite element method (XFEM) by modelling a semi-elliptical weld toe crack in a T-butt weld for cracks of different dimensions. The accuracy of the Mk factor solutions was verified by comparison to HSE fatigue data on 16 mm thick tubular joints. The Mk factor solutions were used to predict the growth of fatigue cracks using a model based on Paris Law and SIF solutions by Newman and Raju with plastic zone size corrections. Fatigue life was predicted for plates with and without attachments. It could be seen that the predicted life of a weld toe crack was severely reduced with the addition of a welded attachment. The model was extended to the multiple surface cracks commonly observed at the weld toe, where each crack is treated as independent, following established code procedures. The multiple cracks will coalesce as they propagate, until a single dominant crack emerges and fracture occurs. In this paper, the relationship between the fatigue life and the number and density distribution of the initial cracks was investigated. Fatigue life was predicted for plates with attachments with 1, 2, 10 and 100 cracks initially. The results show that as the number of cracks increases, the predicted fatigue life decreases.

Negative R Fatigue Crack Growth Rate Testing on Austenitic Stainless Steel in Air and Simulated Primary Water Environments

2018 ◽  
Author(s):  
Norman Platts ◽  
Ben Coult ◽  
Wenzhong Zhang ◽  
Peter Gill
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
High Temperature ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Laws

Light water reactor coolant environments are known to significantly enhance the fatigue crack growth rate of austenitic stainless steels. However, most available data in these high temperature pressurized water environments have been derived using specimens tested at positive load ratios, whilst most plant transients involve significant compressive as well as tensile stresses. The extent to which the compressive loading impacts on the environmental enhancement of fatigue crack growth, and, more importantly, on the processes leading to retardation of those enhanced rates is therefore unclear, potentially leading to excessive conservatism in current assessment methodologies. A test methodology using corner cracked tensile specimens, and based on finite element analysis of the specimens to generate effective stress intensity factors, Keff, for specimens loaded in fully reverse loading has been previously presented. The current paper further develops this approach, enabling it to be utilized to study a range of positive and negative load ratios from R = −2 to R = 0.5 loading, and provides a greater understanding of the development of stress intensity factor within a loading cycle. Test data has been generated in both air and high temperature water environments over a range of loading ratios. Comparison of these data to material specific crack growth data from conventional compact tension specimens and environmental crack growth laws (such as Code Case N-809) enables the impact of crack closure on the effective stress intensity factor to be assessed in both air and water environments. The significance of indicated differences in the apparent level of closure between air and water environments is discussed in the light of accepted growth laws and material specific data.

A Probabilistic Approach to Fatigue Crack Growth Rate

1980 ◽  
Vol 102 (3) ◽  
pp. 300-302 ◽  
Author(s):  
Akira Tsurui ◽  
Akito Igarashi
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Probabilistic Model ◽  
Probabilistic Approach

A probabilistic model for fatigue crack growth proposed by K. P. Oh is modified in some respects. Under more natural assumptions than Oh’s it is derived that the rate of fatigue crack growth is proportional to some power of the range of the stress intensity factor. It is also shown that the exponent ranges from 2 to 4.

Background of Addition of Fatigue Crack Growth Rate Factors for Intermediate Strength Ferritic Steels in KD-4 of ASME Section VIII Division 3

2021 ◽  
Author(s):  
Susumu Terada ◽  
Toshio Yoshida
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Threshold Value

Abstract In Table KD-430 and KD-430M of ASME Section VIII Division 3 (hereinafter called ASME Div. 3), there were no fatigue crack growth rate factors and threshold value of stress intensity factor range for carbon and low alloy steels with yield strength less than or equal to 620 MPa. These fatigue crack growth rate factors and threshold value of stress intensity factor range for ferritic steels with intermediate strength were also necessary for designing ASME Div. 3 vessels. We investigated the fatigue crack growth rates given in various standards. Especially Bloom’s paper related to ASME Sec. XI was investigated in detail. The test results on fatigue crack growth rate under various stress intensity range ratio in Bloom’s paper were compared with test results in other references. An equation for fatigue crack growth corrected by the stress intensity factor ratio was developed based on our investigation. The equation developed for fatigue crack growth was confirmed to agree with the test data in Bloom’s paper for negative and positive R ratios. Hence this equation, which was appropriate for a wide range of positive and negative R ratios, was proposed for ASME Div. 3. The addition of the threshold value of the stress intensity factor range for intermediate strength ferritic steels was also proposed. The fatigue crack growth rate factors at room temperature were provided in Table KD-430 and KD-430M of ASME Div. 3. As the operating temperature is higher than room temperature, the temperature correction is necessary for calculating fatigue crack growth. The temperature correction method in KD-4 of ASME Div. 3 was also proposed. These proposed changes except minimum threshold value were approved by Board in 2018 and they were reflected in 2019 Edition. The minimum threshold value was approved by the Board in 2021. It will be reflected in 2021 Edition. The background of these proposed changes is shown in this paper.

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