Recharacterization of Subsurface Flaw to Surface Flaw Based on Equivalent Fatigue Crack Growth Rate

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Valery Lacroix ◽  
Yinsheng Li ◽  
Bohumir Strnadel ◽  
Kunio Hasegawa
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Point Of View ◽  
Surface Flaw ◽  
Aspect Ratios ◽  
Crack Growth Rates ◽  
Factor Interaction

A subsurface flaw located near a component surface is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The recharacterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the criteria of the recharacterizations are different among the FFS codes. In addition, the proximity factors in the rules are generally defined by constant values, irrespective of flaw aspect ratios. This paper describes the stress intensity factor interaction between the subsurface flaw and component free surface and proposes a proximity factor from the point of view of fatigue crack growth rates.

Re-Characterization of Subsurface Flaw to Surface Flaw Based on Equivalent Fatigue Crack Growth Rate

2015 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Valery Lacroix ◽  
Bohumir Strnadel
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Point Of View ◽  
Surface Flaw ◽  
Aspect Ratios ◽  
Crack Growth Rates ◽  
Factor Interaction

A subsurface flaw located near a component surface is transformed to a surface flaw in accordance with a flaw-to-surface proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the criteria of the re-characterizations are different among the FFS codes. In addition, the proximity factors in the rules are defined by constant values, irrespective of flaw aspect ratios. This paper describes the stress intensity factor interaction between the subsurface flaw and component free surface, and proposes a proximity factor from the point of view of fatigue crack growth rates.

An Investigation of the Effects of Microstructure on Fatigue Crack Growth in Ti-6242

2005 ◽  
Vol 127 (1) ◽  
pp. 46-57 ◽  
Author(s):  
F. McBagonluri ◽  
E. Akpan ◽  
C. Mercer ◽  
W. Shen ◽  
W. O. Soboyejo
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Surface Crack ◽  
Rate Data ◽  
Aspect Ratios ◽  
Crack Growth Rates

Surface and subsurface crack nucleation and growth mechanisms are elucidated for equiaxed (microstructure 1), elongated (microstructure 2), and colony (microstructure 3) microstructures of Ti6242. Prominent cleavage facets, indicative of a Stroh-type dislocation-pile phenomenon characterize the nucleation sites. Beachmarking and scanning electron microscopy (SEM) techniques are used to study fatigue crack growth rates and crack shape evolution in the short and long crack regimes. The studies reveal that surface crack growth rate data are generally comparable to the through-crack growth rate data in the long crack growth regime. However, the depth crack growth rates are somewhat slower than the through-crack growth rates. Surface crack evolution profiles are shown to exhibit a tendency towards “Preferred Propagation Paths” (PPPs). However, the magnitudes of the aspect ratios along the PPPs are different from those reported for square or rectangular cross sections subjected to cyclic tension or bending loads. Finally, the measured crack lengths and aspect ratios are compared with predictions obtained from a fracture mechanics model.

Fatigue Crack Growth Calculations for Pipes Considering Subsurface to Surface Flaw Proximity Rules

2015 ◽  
Author(s):  
Genshichiro Katsumata ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Valery Lacroix
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Surface Flaw ◽  
Rule Based ◽  
Aspect Ratios ◽  
Inner Surface ◽  
Crack Growth Rates

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the re-characterizations are different among the FFS codes. Recently, the authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rates. In this study, fatigue crack growth calculations were carried out for pipes with subsurface flaws, using the proposed subsurface-to-surface flaw proximity rule and the current proximity rule provided in the current JSME and ASME Section XI. Different pipe sizes, flaw aspect ratios and ligament distances from subsurface flaws to inner surface of pipes were taken into account. As the results, the current proximity rule gives less conservative fatigue lives, when the aspect ratios of the subsurface flaws are small.

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.

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.

Remaining Lives of Fatigue Crack Growths for Pipes With Subsurface Flaws and Subsurface-to-Surface Flaw Proximity Rules

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Genshichiro Katsumata ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Valery Lacroix
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Flaw ◽  
Japan Society ◽  
Rule Based ◽  
Aspect Ratios ◽  
Inner Surface ◽  
American Society

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed into a surface flaw in accordance with a subsurface-to-surface flaw proximity rule. The recharacterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes. However, the specific criteria of the recharacterizations are different among the FFS codes. Recently, the authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rate calculations. In this study, fatigue crack growth calculations were carried out for pipes with subsurface flaws, using the proximity rule provided in the current ASME (American Society of Mechanical Engineers) Section XI and JSME (The Japan Society of Mechanical Engineers) codes and the proposed subsurface-to-surface flaw proximity rule. Different pipe sizes, flaw aspect ratios, and ligament distances from subsurface flaws to inner surface of pipes were taken into account. The results indicate the current proximity rule gives less conservative fatigue lives, when the aspect ratios of the subsurface flaws are small.

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.

Fatigue Crack Growth Behavior of Titanium Alloy Ti-6Al-4V and Weldment

2001 ◽  
Vol 123 (3) ◽  
pp. 141-146 ◽  
Author(s):  
Mamdouh M. Salama
Keyword(s):  
Growth Rate ◽  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Growth Rates ◽  
Offshore Structures ◽  
Crack Growth Rates

Optimization of weight, cost, and performance of deepwater offshore structures demands the increased utilization of high strength, light weight, and corrosion resistant materials such as titanium alloys. Titanium alloy Ti-6Al-4V has been considered for several critical components such as risers and taper joints. Because of the novelty of use of titanium alloys in the offshore industry, there is currently no standard governing design of titanium components for offshore structures. Since these structural components are subjected to a complex spectrum of environmental loading, assessment of defect tolerance using fatigue crack growth analysis is generally considered an important design parameter. In this paper, more than 60 crack growth data sets from 20 independent laboratories were collected and analyzed to develop crack growth rate equations for use in defect assessment. These data include the results of fatigue testing of both base material and welded joints in air and seawater with and without cathodic protection and at different R-ratios and test frequencies. The results suggest that for crack growth rates above 10−7 in./cycle, crack growth of Ti-6Al-4V appears to be independent of testing condition and materials processing. At the low crack growth rate (below 10−7 in./cycle), the review revealed that data are very limited. These limited data, however, suggest that the crack growth threshold is dependent on the R-ratio and slightly dependent on material processing. Comparison between crack growth rates of steel and titanium alloy (Ti-6Al-4V) showed that the two materials have very similar behavior.

Fatigue Crack Growth in Type 316 Stainless Steel at High Temperature

1971 ◽  
Vol 93 (4) ◽  
pp. 976-980 ◽  
Author(s):  
P. Shahinian ◽  
H. H. Smith ◽  
H. E. Watson
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
316 Stainless Steel ◽  
Arrhenius Relation ◽  
Crack Growth Rates

The dependence of fatigue crack growth rates on range of stress intensity factor (ΔK) in Type 316 stainless steel was investigated over the temperature range of 75 to 1100 deg F. The data for the most part could be described by a power law relationship. An increase in temperature generally increased crack growth rate for a given ΔK and decreased fatigue life. The dependence of crack growth rate on temperature is not described adequately by an Arrhenius relation over the range investigated. On the other hand, by normalizing ΔK with respect to Young’s modulus, E, the crack growth rates for the various temperatures tend to fall within a single band.

A Superposition Approach for Time-Dependent Fatigue Crack Growth

2012 ◽  
Author(s):  
Fashang Ma
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Time Dependent ◽  
Crack Growth Rates ◽  
Time Dependent Crack Growth

High temperature fatigue crack growth is a combination of fatigue, creep and environmental attack, which greatly enhance fatigue crack growth. In order to understand the damage mechanisms and develop a physically based crack growth model, systematic experimental research has been conducted under various loading conditions for different specimen geometries made from a high strength nickel alloy. Test results from this work showed that time-dependent fatigue crack growth rates differ significantly from those observed in conventional fatigue crack growth tests. Crack geometry and loading history significantly affect fatigue crack growth rate. These results suggest the need for a change in the K based superposition approach for time-dependent crack growth modeling. A phenomenological model has been developed to predict time-dependent crack growth under various loading histories and crack geometries. In this model an effective stress intensity factor is defined to account for the effects of constraint loss of fracture mechanics due to crack-tip plasticity, and the creep stress relaxation on stress intensity factor. It is found the model can accurately predict the dwell crack growth rates for different crack geometries under various loading conditions.

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