Corrosion Fatigue Mechanisms and Fracture Mechanics Based Modelling for Subsea Pipeline Steels

2017 ◽  
Author(s):  
Ankang Cheng ◽  
Nian-Zhong Chen
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Corrosion Fatigue ◽  
Fatigue Cracking ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Propagation Time ◽  
Loading Frequency ◽  
Pipeline Steels ◽  
Driving Mechanisms

Subsea structures such as pipelines are vulnerable to environment-assisted crackings (EACs). As a type of EAC, corrosion fatigue (CF) is almost inevitable. For such a process, stress corrosion (SC) and hydrogen-assisted cracking (HAC) are the two mainly driving mechanisms. And it was further pointed out that slip dissolution (SD) and hydrogen embrittlement (HE) should be responsible for SC and HAC respectively. Based on such a fact, a two-component physical model for estimating the CF crack propagation rate was proposed. The proposed model was built in a frame of fracture mechanics integrated with a dissolution model for C-Mn steel and a newly established model by the authors accounting for the influence from HE upon crack propagation. The overall CF crack propagation rate is the aggregate of the two rates predicted by the two sub-individual models, and then the crack propagation time is calculated accordingly. The model has been proven to be capable of capturing the features of HE influenced fatigue cracking behaviour as well as taking mechanical factors such as the loading frequency and stress ratio into account by comparison with the experimental data of X42 and X65 pipeline steels.

Mechanisms and Mechanics of Fatigue Crack Propagation in Zr-Based Bulk Metallic Glass

2008 ◽  
Vol 378-379 ◽  
pp. 317-328 ◽  
Author(s):  
Yoshikazu Nakai ◽  
Makoto Seki
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Metallic Glass ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Loading Frequency ◽  
Stress Intensity Range ◽  
Intensity Range

In the present study, the fatigue crack propagation tests of Zr-based metallic glass were conducted in laboratory air, and the fracture surface was observed to clarify the effects of loading frequency and the stress ratio. In spite of being brittle material, the metallic glass showed stable fatigue crack propagation behaviour, and the relationship between the crack propagation rate, da/dN, and the stress intensity range, K, can be divided into three regions as well as conventional crystalline metals. The crack propagation rate can be expressed as a function of the stress intensity range by Paris law in the middle region. The power in Paris law was 1.4, and it is considerably smaller than the value for conventional crystalline metals. The threshold stress intensity range, Kth, was 1.8 MPam1/2. The effects of the stress ratio and the loading frequency were not observed on the relationships, da/dN-K and da/dN-Keff. Then, the fatigue crack propagation of the metallic glass is cycle dependent in laboratory air.

Evaluation of Corrosion Fatigue Crack Propagation Characteristics of TMCP Steel in Synthetic Seawater under Cathodic Protection

2007 ◽  
Vol 26-28 ◽  
pp. 1145-1148 ◽  
Author(s):  
Won Beom Kim ◽  
Jeom Kee Paik
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Cathodic Protection ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Synthetic Seawater ◽  
Corrosion Fatigue Crack

In this research, corrosion fatigue tests using tensile strength of 490MPa TMCP steel were performed in synthetic seawater condition to investigate the corrosion fatigue crack propagation characteristics. The influence of cathodic protection at -800mV vs. SCE on the corrosion fatigue crack propagation behavior was investigated. Relationships between da/dN versus ΔK for the material were obtained by two types of test specimens. In the present study, F(α,β) versus α(= 2a/W) relationship for the CCT specimen was calculated by J integral approach, while that for the CT specimen was determined from ASTM E647. It is found that the fatigue crack propagation rate of TMCP steel in synthetic seawater condition is faster than that in air condition at least twice. Also, it is observed that the fatigue crack propagation rate of steel with cathodic protection is in between those of seawater condition without cathodic protection and air condition.

Effects of Hydrogen Concentration, Specimen Thickness and Loading Frequency on the Hydrogen Enhanced Crack Propagation of Low Alloy Steel

2011 ◽  
Vol 465 ◽  
pp. 519-522
Author(s):  
Yoshiyuki Kondo ◽  
Koshiro Mizobe ◽  
Masanobu Kubota
Keyword(s):  
Crack Propagation ◽  
Alloy Steel ◽  
Hydrogen Concentration ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Specimen Thickness ◽  
Loading Frequency ◽  
Low Alloy Steel ◽  
Diffusible Hydrogen ◽  
Thin Specimen

Crack propagation of SCM440H low alloy steel under varying load is enhanced by absorbed hydrogen. Substantial acceleration of crack propagation rate up to 1000 times was observed compared with that of uncharged material. The role of factors affecting enhanced acceleration was investigated by changing hydrogen concentration absorbed in metal, specimen thickness and loading frequency. Results are as follows. (1) 0.2 mass ppm diffusible hydrogen in metal was enough to cause enhanced acceleration. The predominant fracture mode showing acceleration was quasi cleavage. (2) In the case of thin specimen thinner than 0.8mm, the tri-axiality of stress is weak, and the enhanced crack propagation did not appear. However, the introduction of side-groove to 0.8mm specimen in order to increase the tri-axiality resulted in enhanced acceleration. (3) Lower loading frequency resulted in higher crack propagation rate in cycle domain. The crack propagation rate in time domain was almost constant irrespective of loading frequency. Enough concentration of hydrogen, tri-axiality and low loading frequency resulted in enhanced acceleration of fatigue crack propagation.

Electron Microfractography Applied to Large Pipe Bending Fatigue Tests

1968 ◽  
Vol 26 ◽  
pp. 424-425
Author(s):  
Ursula E. Wolff
Keyword(s):  
Crack Propagation ◽  
Wall Thickness ◽  
Nuclear Reactor ◽  
Fatigue Cracking ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Practical Aspect ◽  
Fatigue Tests ◽  
Study Program ◽  
Bending Fatigue

Among the different causes of pipe failures, fatigue cracking has to be considered in any design program. Since the integrity of nuclear reactor piping is of particular importance, an AEC pipe study program includes a task to assess quantitatively the crack propagation rate through pipes for cracks originating at surface flaws. This problem has been attacked theoretically by the use of fracture mechanics, and practically by striation measurements on fracture surfaces produced by full-scale bending fatigue tests. This paper deals with the practical aspect of applying electron microfractography to such fractures as a means to determine crack propagation rates in pipes of different dimensions and materials, and with different flaw locations.Six-inch diameter pipes with a wall thickness of 7.5, 10.8, or 18 mm were notched inside or outside and failed in reverse bending fatigue by growing a crack through the wall thickness. The crack front was marked at intervals by reducing the strain amplitude for a number of cycles.

Corrosion–fatigue crack propagation of aluminum alloys for high-speed trains

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744009 ◽  
Author(s):  
Lin Shen ◽  
Hui Chen ◽  
Xiaoli Che ◽  
Lidong Xu
Keyword(s):  
Fatigue Crack ◽  
Aluminum Alloys ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
High Speed ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Corrosion Fatigue Crack

A modified single-edge notch tension (SENT) specimen exposed to saline environment was utilized to investigate the corrosion–fatigue crack growth behaviors of 5083, 6005 and 7N01 aluminum alloys. The fatigue crack propagation life, corrosion–fatigue crack rate ([Formula: see text]) were tested. The microstructures and fracture surfaces of specimens were examined by optical microscopy and scanning electron microscopy (SEM). The results showed that fatigue crack propagation rate of 7N01 in 3.5% NaCl was significantly higher than 6005 and 5083 alloys. The mechanisms of anodic dissolution and hydrogen embrittlement are used to explain the results.

Applicability of Fracture Mechanics Parameters to Crack Propagation Under Creep Condition

1977 ◽  
Vol 99 (4) ◽  
pp. 298-305 ◽  
Author(s):  
R. Koterazawa ◽  
T. Mori
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Thin Plate ◽  
High Stress ◽  
Creep Condition ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Critical Examination ◽  
J Integral ◽  
Creep Crack

A critical examination was made of the applicability of fracture mechanics parameters to crack propagation under creep condition with 304 stainless steels for a variety of specimen geometries at relatively high stress levels. The creep crack propagation rate could not be described in terms of elastic stress intensity factor but it could be in terms of net section stress for all dimensions of thin plate specimen. The net section stress, however, could not explain the difference between crack propagation rates of thin plate specimens and those of notched round bar specimens. This difference could be ascribed to the plastic constraint around the crack tip. Applicability of the modified J-integral to creep crack propagation was also examined and the results showed that this parameter was better for predicting the creep crack propagation rate at a high stress level. In the case of speicmens of similar geometries, the net section stress could be used in place of the modified J-integral provided that crack propagation rate was divided by the characteristic length of the specimen.

scholarly journals Mode I Crack Propagation Experimental Analysis of Adhesive Bonded Joints Comprising Glass Fibre Composite Material under Impact and Constant Amplitude Fatigue Loading

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4380
Author(s):  
Alirio Andres Bautista Villamil ◽  
Juan Pablo Casas Rodriguez ◽  
Alicia Porras Holguin ◽  
Maribel Silva Barrera
Keyword(s):  
Crack Propagation ◽  
Structural Integrity ◽  
Crack Propagation Rate ◽  
Fatigue Loading ◽  
Propagation Rate ◽  
Operating Conditions ◽  
Impact Testing ◽  
Mode I ◽  
Mode I Crack ◽  
Constant Amplitude

The T-90 Calima is a low-wing monoplane aircraft. Its structure is mainly composed of different components of composite materials, which are mainly bonded by using adhesive joints of different thicknesses. The T-90 Calima is a trainer aircraft; thus, adverse operating conditions such as hard landings, which cause impact loads, may affect the structural integrity of aircrafts. As a result, in this study, the mode I crack propagation rate of a typical adhesive joint of the aircraft is estimated under impact and constant amplitude fatigue loading. To this end, effects of adhesive thickness on the mechanical performance of the joint under quasistatic loading conditions, impact and constant amplitude fatigue in double cantilever beam (DCB) specimens are experimentally investigated. Cyclic impact is induced using a drop-weight impact testing machine to obtain the crack propagation rate (da/dN) as a function of the maximum strain energy release rate (GImax) diagram; likewise, this diagram is also obtained under constant amplitude fatigue, and both diagrams are compared to determine the effect of each type of loading on the structural integrity of the joint. Results reveal that the crack propagation rate under impact fatigue is three orders of magnitude greater than that under constant amplitude fatigue.

scholarly journals Crack Propagation Behavior of a Ni-Based Single-Crystal Superalloy during In Situ SEM Tensile Test at 1000 °C

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1047
Author(s):  
Wenxiang Jiang ◽  
Xiaoyi Ren ◽  
Jinghao Zhao ◽  
Jianli Zhou ◽  
Jinyao Ma ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Tensile Test ◽  
Single Crystal ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Single Crystal Superalloy ◽  
Propagation Path ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

An in situ scanning electron microscope (SEM) tensile test for Ni-based single-crystal superalloy was carried out at 1000 °C. The stress displacement was obtained, and the yield strength and tensile strength of the superalloy were 699 MPa and 826 MPa, respectively. The crack propagation process, consisting of Model I crack and crystallographic shearing crack, was determined. More interestingly, the crack propagation path and rate affected by eutectics was directly observed and counted. Results show that the coalescence of the primary crack and second microcrack at the interface of a γ/γ′ matrix and eutectics would make the crack propagation rate increase from 0.3 μm/s to 0.4 μm/s. On the other hand, crack deflection decreased the rate to 0.05 μm/s. Moreover, movement of dislocations in front of the crack was also analyzed to explain the different crack propagation behavior in the superalloy.

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