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.

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.

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.

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.

Full-Scale Fatigue Testing of Crack-in-Dent and Framework Development for Life Prediction

2020 ◽  
Author(s):  
Udayasankar Arumugam ◽  
Ming Gao ◽  
Ravi Krishnamurthy ◽  
Mures Zarea
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Life Prediction ◽  
Full Scale

Abstract Dents containing crack fields (colonies) were often observed in liquid pipelines. A recent PRCI research “Study of the Mechanism for Cracking in Dents in a Crude Oil Pipeline” showed evidence of corrosion fatigue cracking mechanism in dents and estimated the crack growth rate as a function of stress intensity factor using the measured spacings of fatigue striations from fracture surfaces based on the assumption that the formation of fatigue striations on a cycle-by-cycle basis. However, due to the lack of full-scale fatigue crack growth data, the success was limited in this study. This gap prompted PRCI to launch a full-scale experimental investigation of cracks-indents under cyclic pressure load in the simulated groundwater (NS4 solution) environment. The objective of the study is to determine the crack growth rate in dent as a function of stress intensity factor, the number of cycles to failure, and the failure modes of crack-in-dent. The investigation is aimed at establishing a framework for the remaining fatigue life prediction of cracks-in-dents in liquid pipelines. This framework would benefit liquid pipeline operators to manage the integrity of dents associated with corrosion fatigue cracking exposed to groundwater in a timely manner. A total of six pipe samples containing cracks in shallow dents excavated from a 24-inch diameter liquid transmission pipeline were selected for full-scale fatigue tests. The test system developed under the project consisted of (1) a computer-controlled hydraulic pressure cycling system, (2) an environment chamber containing NS4 solution mounted on the dent region to provide a simulated field environment condition, (3) real-time crack growth monitoring systems including direct current potential drop (DCPD) system, Clip gage, and Strain gage, and (4) a data acquisition system. The cyclic pressure range used in the fatigue test was between 78 psig (7.2%SMYS, minimum) and 780 psig (72%SMYS, maximum) with R = 0.1, which was based on historical operational pressure fluctuation data. A constant frequency of 0.0526 Hz was selected for the testing to ensure the frequency requirement for corrosion fatigue was met. In this paper, the objective, along with the background of this research, is discussed first. Then, the pipe sample preparation, experimental setup, and test results are presented. The fatigue crack growth rate as a function of the stress intensity factor is then discussed. Following this, the fatigue crack growth coefficients were estimated using the full-scale test data and FEA. Finally, the fatigue test results are summarized and presented the framework for the life prediction of corrosion fatigue cracks in shallow dents.

The Role of Three-Dimensional Effects in Constant Amplitude Fatigue Crack Growth Testing

1980 ◽  
Vol 102 (4) ◽  
pp. 341-346 ◽  
Author(s):  
J. J. McGowan ◽  
H. W. Liu
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 ◽  
Mean Stress

An accurate knowledge of the dependence of the fatigue crack growth rate (da/dN) on the stress intensity factor range (ΔK) is necessary to perform a safety analysis of any structure. Fatigue crack growth tests are normally performed on simple, two-dimensional finite thickness specimens to determine this dependence. Certain anomalies in this dependence have been observed when specimen thickness and mean stress have been varied. The thickness effect and the mean stress effect on the fatigue crack growth rate are related to the variation in crack closure and the local stress intensity factor along the crack front. A simple model incorporating both of these two effects is proposed. The model is applied to fatigue crack growth data for a nickel-base super alloy (IN-100) with very good success.

Sign in / Sign up

Export Citation Format

Share Document