Corrosion Fatigue Crack Propagation Research Articles

Influence of hot corrosion on thermal fatigue behavior of Ni-based single crystal superalloy: Invisible and accelerated crack

As an important failure model for single crystal materials in service, with the increasing complexity of working environments, the thermal corrosion fatigue failure needs to be studied urgently. In this study, the thermal corrosion fatigue crack initiation and propagation behaviors of an Ni-based single crystal superalloy in both air and hot corrosion environments at 25–900 °C were studied by using a designed precise thermal fatigue test device. The microstructure characteristics and crack composition were analyzed by SEM, TEM and EDS, and the internal stress and recrystallization during thermal fatigue were characterized by EBSD. Moreover, the detailed and comprehensive crack morphology was characterized with different surface treatments. The results showed that the crack morphology was invisible in the hot corrosion environment, which is worthy of being highlighted. The initiation and propagation of thermal fatigue cracks were also accelerated in the hot corrosion environment, which contributed to the sufficient thermal stress, the accelerated material degradation of the inner/outer layers in the crack region, and the rapid forward diffusion of O2 in the inner crack layer. Finally, the influence mechanism of hot corrosion on the thermal fatigue behavior of the Ni-based single crystal superalloy is proposed.

Effect of corrosion on the fatigue crack propagation properties of butt weld with G20Mn5QT cast steel and Q355D steel in 3.5‐wt% NaCl solution

AbstractThe corrosion fatigue crack propagation (FCP) of the butt weld with G20Mn5QT cast steel and Q355D steel in 3.5‐wt% NaCl solution was investigated experimentally. Considering the influences of stress ratio and loading frequency, the corrosion FCP rate curve was obtained. The results indicated that the corrosion FCP rate in the corrosion environment is three times that in air. Increasing the stress ratio or decreasing the loading frequency will increase the corrosion FCP rate. The fracture morphology of the specimens in the corrosion environment had more corrosion pits and intergranular characteristics due to anodic dissolution than that in air. Anodic dissolution and hydrogen embrittlement jointly promoted the corrosion FCP of butt weld in simulated seawater. The corrosion FCP rate model was established considering the effects of stress ratio and loading frequency.

Study on crack propagation life of corrosion fatigue in orthotropic steel deck in steel bridges

The study of the corrosion fatigue life of steel bridges is of much significance. The remaining life of corrosion fatigue crack propagation is found to be lesser than fatigue crack propagation. The finite element model is established, the key points are meshed in small size, and the fatigue crack damage of local components is analyzed.The crack propagation life evaluation method of corrosion fatigue in orthotropic steel deck structure bridges is obtained based on the multi-scale finite element method. Stress intensity and corrosion are the main factors that affect the crack propagation life of corrosion fatigue. The stress intensity factor was analyzed by diaphragm spacings, diaphragm thickness, and roof thickness,It is understood that the thickness of the diaphragm has a great influence on the stress strength factor. Temperature, humidity and morphological characteristics of corrosion pits affect the rate of corrosion when exploring the influence of corrosion factors.The analysis of corrosion fatigue crack growth process shows that corrosion has a great influence on the remaining life of fatigue crack propagation.

Effect of 0.1 wt% Nb on the microstructure and corrosion fatigue performance of high strength steels

In this manuscript, the effect of 0.1% Nb addition on the corrosion fatigue behavior of the marine engineering steel has been studied through corrosion fatigue experiments, electrochemical hydrogen charging, and a series of microscopic characterization methods. The results show that BM steel has a high corrosion fatigue sensitivity in the marine environment. Compared to BM steel, the corrosion fatigue sensitivity of 0.1 Nb steel is reduced by 8% in the marine environment, and it reduced by 40% in the hydrogen charging environment. 0.1% Nb adding inhibits hydrogen concentration in local areas by forming irreversible hydrogen traps NbC and by improving the microstructure, and it lowers the diffusible hydrogen content and total hydrogen content inside the steel by inhibiting electrochemical hydrogen evolution reaction to hold back the corrosion fatigue crack initiation and propagation, thereby improving the ability of resisting corrosion fatigue cracking for the marine engineering steel.

Effect of Microstructure on the Corrosion Fatigue Crack Growth of Low and Medium Steels

This article studies the effect of microstructure on the corrosion fatigue crack growth behavior of low and medium carbon steels. 45 steel and 15CrMo were selected and five typical microstructures were obtained by different heat treatment processes. The microstructures of 45 steel and 15CrMo after annealing and normalizing are both ferrite and pearlite, but the proportions of ferrite and pearlite in the four microstructures are different. The quenching and tempering microstructure of 45 steel is tempered fine pearlite. Corrosion fatigue tests were conducted on specimens with different microstructures of the two materials. Expressions of corrosion fatigue crack growth rate and da/dN∼ΔK fitting curves of different microstructures were obtained. Comparison of da/dN∼ΔK curves of 45 steel shows that tempered fine pearlite has the best resistance to corrosion fatigue crack growth, and the content of pearlite has a great impact on the corrosion fatigue crack growth behavior for specimens with the microstructure of ferrite and pearlite. In the low ΔK region, the corrosion factor plays a dominant role in fatigue crack growth, and the corrosion resistance of pearlite is weak, which leads to a higher da/dN in the normalized state. In the high ΔK region, fatigue factor dominants, since the fatigue resistance of pearlite is strong, da/dN of the annealed state is higher. The experimental results of 15CrMo showed the same crack growth rate change regulation as that of 45 steel, which further proves the effect of pearlite on the corrosion fatigue crack propagation behavior.

Corrosion fatigue crack propagation of 7XXX series aluminum alloys from key components of high-speed train

The corrosion fatigue cracks propagation behavior of A7N01P-T4 and A7N01S-T5 aluminum alloys in 3.5 wt.% NaCl solution and air were studied by single side notch corrosion fatigue tests (SNET). The crack growth rate (da/dN) was measured and the crack propagation mechanism was analyzed by scanning electron microscopic analysis. The results showed that the corrosion fatigue cracks growth rate of A7N01S-T5 alloy in air and 3.5 wt.% NaCl solution is faster than that of A7N01P-T4 alloy. The crack propagation follows a mixed intergranular and transgranular mode. The anodic dissolution and hydrogen embrittlement accelerate the propagation of corrosion fatigue crack of 7-series Al alloy in 3.5 wt.% NaCl solution. The corrosion resistance and fatigue crack propagation are related to the strength of the alloys and the density of grain boundaries.

Predicting Corrosion Fatigue Crack Propagation Behavior of HRB400 Steel Bars in Simulated Corrosive Environments

AbstractThis paper systematically performed fatigue crack propagation (FCP) tests to investigate the corrosion fatigue crack propagation (CFCP) behavior of HRB400 steel bar. The fatigue loading sch...

Experimental study and residual fatigue life assessment of corroded high-tensile steel wires using 3D scanning technology

Fatigue damage of bridge suspender is a serious problem under long-term environmental erosion and repeated vehicle loads. This paper quantifies the effects of corrosion on the residual fatigue life of steel wires in bridge suspender. A predictive model was proposed to estimate the fatigue life of corroded steel wires based on the equivalent initial flaw size method, in which both corrosion growth stage and fatigue crack propagation stage were considered. The pitting corrosion-induced stress concentration was incorporated into the stress intensity factor model. The theoretical residual fatigue life can be obtained by integrating the fatigue crack growth model from the equivalent initial crack size to a critical crack length. The effects of corrosion on the fatigue performance of steel wires with various corrosion degrees were investigated by fatigue loading tests. The fracture morphology of the steel wires after fatigue was observed using scanning electron microscopy. The relationships between corrosion degrees and fatigue lives of the steel wires were provided. The surface morphology of corroded steel wire was scanned by 3D scanning technology, and a three-dimension model was established. A finite element model of corroded steel wires was established after the scanning model was processed by the Geomagic software. Following that, the relationship between stress concentration factor and corrosion degree was analyzed. A fatigue life prediction method based on the equivalent initial crack size was verified by the experimental observation of various corroded steel wires and the data in open literature.

Corrosion fatigue crack propagation behavior of A7N01P‐T4 aluminum alloy welded joints from high‐speed train underframe after 1.8 million km operation

AbstractUsing the potentiodynamic polarization analysis, the fatigue crack propagation behavior of A7N01P‐T4 aluminum alloy metal inert gas welded joints cut from a high‐speed train underframe after 1.8 million km operation was studied in air and in a 3.5 wt% NaCl solution. The fracture surface and crack growth path were analyzed using optical microscopy, scanning electron microscopy, and electron backscattered diffraction. The results reveal that the corrosion fatigue crack growth rate of an A7N01P‐T4 welded joint in a 3.5 wt% NaCl solution is higher than that in air. Furthermore, the corrosion fatigue crack growth rate is noted to be the fastest in the heat‐affected zone, followed by the base metal, whereas it is the slowest in the weld metal, which is consistent with the corrosion resistance of the A7N01P‐T4 joints. The second phase is observed to exhibit a significant influence on the corrosion fatigue crack propagation path. The cracks are noted to grow toward the soft orientation and have obvious plastic deformation during the propagation process, which indicates that the anodic dissolution is the main cause of the corrosion fatigue crack growth.

Corrosion-fatigue behavior of micro-arc oxidation coated 6061-T6 Al alloy

The corrosion-fatigue response of Al alloys becomes an important consideration for qualifying them for aerospace and other structural applications, the MAO coatings with three different thicknesses namely 10 µm, 50 µm and 90 µm were provided on peened (SP + MAO) and un-peened (Plain MAO) substrates. Further, the corrosion (potentiodynamic polarization) tests in 3.5 wt% NaCl solution and corrosion-fatigue tests at 5-different maximum alternating stress levels were evaluated for each material condition. In addition, the surface roughness, surface and cross-sectional coating morphologies in as deposited and corroded conditions; fractured morphology and corrosion-fatigue crack propagation features were evaluated; correlated with the corresponding corrosion rates and corrosion-fatigue life. The results obtained highlight the role of corrosion medium in significant degradation of corrosion-fatigue life as compared to the plain-fatigue life of both bare substrate and MAO coated conditions. A new parameter namely the normalized corrosion-fatigue life index (NCFI) provides a quicker insight and possible benchmarking of the coating’s ability to withstand the damaging action of simultaneous corrosion and fatigue. A 50 µm thick SP + MAO coating was identified as a candidate choice to withstand diverse degradation modes namely the simple corrosion, plain-fatigue and corrosion-fatigue.

Probabilistic Life Prediction for Reinforced Concrete Structures Subjected to Seasonal Corrosion-Fatigue Damage

The coupled effect of corrosion and fatigue deteriorates the performance of reinforced concrete (RC) structures. This paper proposes a novel framework for the probabilistic life prediction of aging RC structures under seasonal corrosion-fatigue damage based on the fracture mechanics and equivalent initial flaw size concept. A series of fatigue crack growth tests of steel bars in air and solution environments are conducted to simulate the fatigue crack growth behavior of rebar in different seasons. The framework includes three critical deterioration stages: corrosion initiation–pure fatigue crack growth, competition between corrosion pit growth and fatigue crack propagation, and structural failure. The chloride ingress, cyclic load, corrosion pit growth, concrete cracking, seasonal environmental variation, and corrosion pit-induced stress concentration are considered. Following that, an uncertainty model is established to incorporate various uncertainties associated with the load and environment. The characteristics of different stages are discussed. A parametric analysis is also performed to illustrate the influence of stress concentration, concrete severe cracking, and seasonal environmental variation on the life prediction results. Several conclusions are drawn and future work is discussed based on the proposed study.

Corrosion Fatigue Crack Propagation Mechanism of High-Strength Steel Bar in Various Environments

AbstractThis paper investigated the corrosion fatigue crack propagation mechanism of high-strength steel bar HRB400 in various corrosive environments. Fatigue crack growth (FCG) tests were conducte...

Effect of loading frequency on corrosion fatigue crack growth rate of 7N01 aluminum alloy

The fatigue damage of engineering structures is mostly caused by cyclic stress and external environmental factors. Therefore, the study of corrosion fatigue crack propagation is of great significance to the safety and durability of structures. The effects of different loading frequencies (10Hz, 1Hz and 0.1Hz) on fatigue crack growth rate of 7N01 aluminum alloy in humid air were studied by using load control method. The results show that the corrosion fatigue crack growth rate is basically the same at 10Hz and 1Hz, When the loading frequency decreases to 0.1Hz, the corrosion fatigue crack growth rate is slightly higher than 10Hz and 1Hz.

Microstructural evolution and oxidation behaviour of CF8A austenitic stainless steel during corrosion fatigue in a simulated pressurised water reactor environment

The microstructural evolution and oxidation behaviour of CF8A stainless steel during corrosion fatigue (CF) crack initiation and propagation were investigated in a simulated pressurised water reactor environment. Under the action of alternating loads, the near-surface properties of the specimens deteriorate due to the formation of Cr-depleted zones and slip bands (SBs), and CF cracks tend to initiate from SBs on the surface of the specimens. As the CF cracks propagate, dynamic interactions are present between the stress state and the oxidation behaviour at the crack tip due to intense anodic dissolution and the redistribution of stresses and strains.

A review study on Corrosion Fatigue and its related testing methodologies

Corrosion Fatigue is the mechanical degradation of a material under the joint action of damage mechanisms corrosion and fatigue. Corrosive nature of the seawater puts severe durability requirements on materials of which are often exposed to corrosion fatigue and abrasive conditions simultaneously. Therefore, identification of the combined effects of both corrosion and fatigue damage mechanisms is necessary to improve predictive models for the corrosion fatigue phenomenon. Present article is the result of a desktop study (scientific literature and standards) with the aim of study the feasibility of designing and manufacturing of a corrosion fatigue testing set-up that would allow the designer to compare the performance of different materials exposed to corrosion fatigue, permitting also the comparison with results from dry fatigue testing. The corrosion fatigue mechanism is described in more detail and a short presentation of some typical lab-scale corrosion fatigue test setups is given. This is followed by illustration of international standards and guidelines which will be used to design a new corrosion fatigue test set-up for evaluating the fatigue behavior of material in seawater environment. Finally the experimental techniques for corrosion fatigue crack detection and propagation along with the fundamental basic of corrosion fatigue modeling are illustrated.

Corrosion fatigue crack propagation behavior of S135 high–strength drill pipe steel in H2S environment

Abstract Corrosion fatigue crack propagation (CFCP) tests were employed to investigate the behavior of S135 low carbon high−strength drill pipe steel under different strain rates in a simulated H2S containing drilling environment. Results revealed that the CFCP rate curve of the S135 steel has the characteristics of stress corrosion and corrosion fatigue (CF), which can be divided into near threshold, platform and rapid propagation zone. H2S has an obvious acceleration effect on the CFCP rate of S135 steel, the propagation rate of S135 steel in H2S solution is about 10 times more than that of in air. The stress ratio R has different effects on rapid propagation and near threshold zone. In the rapid propagation zone, the order of CFCP rate from high to low is R = 0.1 > R = 0.3 > R = 0.5, while the order of near threshold zone just shows the opposite. In the near threshold zone, the CFCP rate increases with the increasing of the stress ratio R. Based on the proposed Corrosion–Passivation–Fracture model and elastic fracture mechanics, the CFCP rate expression of S135 steel in H2S solution is d a d N cf = 1.927 × 10 ‐ 9 Δ K − 6.15 1 − R 0.59 2 , which can be used to predict the CFCP life in practical engineering. Fracture analysis results shows that the CFCP of S135 steel in H2S solution is mainly controlled by anodic dissolution and hydrogen embrittlement.

Numerical analysis of pitting corrosion fatigue in floating offshore wind turbine foundations

The mooring system of offshore floating wind foundations, which anchors the floating foundations to the seabed, sustains large dynamic loads during operation. The mooring chains are connected to the floating foundation below the water level through fairleads and chain-stoppers. The corrosive marine environment and the cyclic loading make the mooring connection prone to corrosion pitting and fatigue crack initiation and propagation from the pits, particularly in the weld zones. In this study, a finite element analysis of the crack growth from corrosion pits has been performed and the results are presented in order to provide an estimate of the extent of damage after the crack is detected. A Python script have been developed which generates the pit profiles based on a non-uniform random distribution of pit dimensions. 3D pits and elliptical cracks are embedded at critical points of weldment on the mooring point and analysed using ABAQUS XFEM. The Walker’s model has been applied in the model to examine the effect of realistic R ratios in floating structures on pitting corrosion fatigue crack propagation along with direct cyclic solver. The numerical results obtained from this study are discussed in terms of the corrosion pitting effects on fatigue crack propagation behaviour in Spar-type floating offshore wind turbine foundations.

Corrosion fatigue life prediction for steel bar in concrete based on fatigue crack propagation and equivalent initial flaw size

A new corrosion fatigue life prediction approach for steel bar in concrete based on fatigue crack propagation and equivalent initial flaw size (EIFS) was proposed, coupling corrosion growth and fatigue crack propagation together. By using fracture mechanics method and introducing the concept of EIFS, theoretical approach for corrosion fatigue life prediction was discussed, and the corresponding mechanical model was presented. Through accelerated corrosion test of reinforced concrete (RC) beams, the quantitative relation between corrosion pit depth and corrosion degree expressed by mass loss was established. Fatigue loading test of corroded RC beams was carried out, and the quantitative relation between EIFS and corrosion degree was presented according to the test results of corrosion fatigue life. The corrosion fatigue fracture of steel bar obtained by fatigue loading test was observed, and it is found that corrosion has no substantial effect on the critical crack size. Finally, the proposed corrosion fatigue life prediction model was validated by comparing with the existing experimental results, and the predicted values were in acceptable agreement with the test results. The findings of this study can be used to predict the fatigue life of aging corroded RC beams under corrosive environment.

Corrosion Effects on the Fatigue Crack Propagation of Giga-Grade Steel and its Heat Affected Zone in pH Buffer Solutions for Automotive Application

Corrosion fatigue crack propagation test was conducted of giga-grade steel and its heat affected zone in pH buffer solutions, and the results were compared with model predictions. Pure corrosion effect on fatigue crack propagation, particularly, in corrosive environment was evaluated by means of the modified Forman equation. As shown in results, the average corrosion rate determined from the ratio of pure corrosion induced crack length to entire crack length under a cycle load were 0.11 and 0.37 for base metal and heat affected zone, respectively, with load ratio of 0.5, frequency of 0.5 and pH 10.0 environment. These results demonstrate new interpretation methodology for corrosion fatigue crack propagation enabling the pure corrosion effects on the behavior to be determined.

Corrosion fatigue of a magnesium alloy under appropriate human physiological conditions for bio-implant applications

This paper presents investigation of fatigue strength of a common magnesium (Mg) alloy, AZ91D, in air and Hanks’ solution under appropriate mechano-chemical conditions (namely, properly simulated loading and frequency, and in the presence of bovine serum albumin (BSA) at 37 °C). Fatigue cracks initiated from inclusions when tested in air and from corrosion pits when tested in Hanks’ solutions. However, at constant stress levels lower than fatigue limit in air, the alloy tested in Hanks’ solution + BSA indicated longer fatigue strength than the alloy tested in the plain Hanks’ solution which was attributed to the influence of adsorbed BSA on corrosion and corrosion fatigue (CF) crack propagation of the alloy.