Fatigue crack growth rates for offshore wind monopile weldments in air and seawater: SLIC inter-laboratory test results

Materials selection for XL wind turbine support structures : a corrosion-fatigue perspective

Waveform and frequency effects on corrosion-fatigue crack growth behaviour in modern marine steels

This paper presents a critical assessment of the effect of microstructure on the fatigue crack growth rate (FCGR) in ferrite-pearlite (α-P) steels in air and marine environment. This was done by evaluating the resistance of three subgrades of S355 steel, produced by normalized-rolling, NR (S355J2+N) and thermo-mechanical control process, TMCP (S355G8+M and S355G10 + M), to fatigue crack growth (FCG) in air and seawater. The data from the tests were then compared with results of several studies on α-P steels of similar compositions and microconstituents in the literature. It was found that microstructure strongly affected the Paris region of the da/dN vs. ΔK sigmoidal curve in both media. This is contrary to the current belief that microstructure has little or a negligible effect in the linear region of the FCGR curve in air. TMCP and quenched-and-tempered (QT) steels offered better resistance to FCG than NR steel in both media. TMCP steel offered the highest resistance to FCG. The crack path was non-planar with a complex crack front. The tendency for crack deviation, branching, wedging action by metal crumbs and perhaps interlocking majorly explained why the FCGRs of the TMCP and QT steels are lower than that of NR. The result also suggests that ductility and yield stress do not have a strong retarding effect on FCG in α-P steels at low stress intensity factor range (SIFR). This finding has a fundamental implication for analytical and numerical models that wholly depend on the mechanical properties of the steel and assumes plane horizontal crack propagation front in predicting FCGR in steels. Such models are likely to fail in predicting FCGR even in a subgrade of the same grade of steel.

Critical assessment of the fatigue crack growth rate sensitivity to material microstructure in ferrite-pearlite steels in air and marine environment

Effect of pre hot corrosion on high cycle fatigue behavior of the superalloy IN718 at 600 °C

The world is rapidly adopting renewable energy alternatives at a remarkable rate to address the ever-increasing environmental crisis of CO2 emissions. Renewable Energy Systems (RES) offers enormous potential to decarbonize the environment because they produce no greenhouse gases or other polluting emissions. However, the RES relies on natural resources for energy generation, such as sunlight, wind, water, geothermal, which are generally unpredictable and reliant on weather, season, and year. To account for these intermittencies, renewable energy can be stored using various techniques and then used in a consistent and controlled manner as needed. Several researchers from around the world have made substantial contributions over the last century to developing novel methods of energy storage that are efficient enough to meet increasing energy demand and technological breakthroughs. This review attempts to provide a critical review of the advancements in the Energy Storage System (ESS) from 1850–2022, including its evolution, classification, operating principles and comparison. 

Energy storage systems: A review

Corrosion fatigue phenomenon involves the time dependent corrosion and cycle dependent fatigue loading. The intention of this study is to develop a test method to evaluate the crack growth rate of a material in a corrosive environment at low frequencies. The effect of cyclic frequency on crack growth rate of a Mn–Ni–Cr steel in lab air and 3.5% NaCl solution is evaluated using frequency shedding method where the cyclic frequency is decreased exponentially as a function of crack length at a constant stress intensity factor range. A Zn sacrificial anode coupled to the specimen slows down the rate of crack growth.

Effect of low cyclic frequency on fatigue crack growth behavior of a Mn–Ni–Cr steel in air and 3.5% NaCl solution

Corrosion fatigue-crack growth characteristics are important for the design of marine and off-shore structures Design of critical components requires data on fatigue-crack growth rate at very low frequencies of the order of 10−2 to 10−3 Hz Experiments at low frequencies pose practical difficulties of enormous test duration To address this, it is proposed to estimate corrosion crack growth characteristics using a frequency shedding method where the frequency is shed with crack advance using an exponential law Fatigue-crack growth rate tests have been conducted on Ni–Mn–Cr steel at a constant ΔK range of 18 MPa√m (lower Paris regime) under lab air conditions as well as 35 % NaCl solution Crack growth rate data plotted as a function of test frequency presents a straight-line trend in log–log scale for a frequency range of 1–01 Hz; however, there is a change in trend when the frequencies are dropped further, which could be due to domination of corrosion mechanism To understand the role of crack closure, crack closure estimates were obtained at periodic intervals of crack length and the effective stress intensity graphs suggest acceleration in crack growth rate due to corrosion as the frequency is reduced

Estimation of Corrosion Fatigue-Crack Growth through Frequency Shedding Method

Nickel based super-alloys when exposed to a combination of high temperature and low melting point fused corrosion products, result in early fatigue failure compared to their response in high temperature benign environment. The high cycle fatigue (HCF) (at 550 and 625°C) as well as fatigue crack growth (at 550°C) behavior of a nickel based super alloy 718 in hot corrosive environment (Na2SO4+NaCl salt coating), typical of marine engine environment, is presented in this paper. At least an order of magnitude decrease in fatigue life is noticed when the temperature is changed from 550 to 625°C at stress levels below 450 MPa. The statistical analysis of scatter in fatigue lives at different stress levels is performed and a Weibull–Inverse power law model is fitted to the stress–fatigue life data of alloy 718 in hot corrosive environment. Fracture surface examination of hot corrosion fatigue failures showed higher crack growth rates compared to uncoated high temperature HCF fracture surfaces. Fatigue crack growth rate at 550°C in a hot corrosive environment increases by an order of magnitude at 0.5 Hz in the Paris region compared to crack growth kinetics at 2 Hz in lab air environment at the same temperature. The fracture surface shows a mix of transgranular and intergranular mode of crack in the propagation region at 0.5 Hz. A fatigue failure diagram is proposed combining the thresholds of maximum stress level from endurance tests and maximum stress intensity factor from fatigue crack growth tests to demarcate the regions of propagating and non-propagating cracks during hot corrosion fatigue. The complexities in incorporating the effect of loading frequency in fatigue failure diagram are highlighted.

Fatigue Behavior of Nickel Based Super Alloy 718 in a Hot Corrosive Environment

Fatigue crack growth behavior at low loading frequencies for a Mn–Ni–Cr steel immersed in 3.5 % NaCl solution, with and without cathodic polarization, is investigated and presented in this paper. Frequency shedding method is used to estimate fatigue crack growth rate over a range of frequencies between 0.01 and 5 Hz at a constant stress intensity factor range of 15 MPa √m. The effectiveness of cathodic potential of −900 mV SCE in containing corrosion contribution to crack growth is estimated by comparing with published data on fatigue crack growth rate in lab air and 3.5 % NaCl solution without cathodic polarization. It is noted that there are three regions of crack growth rate as a function of applied frequencies when the data is plotted in log–log scale: linear crack growth rate, plateau crack growth rate, and high crack growth rate. The crack growth rate of steel in 3.5 % NaCl solution at 15 MPa √m is scanned for different cathodic potentials between −760 mV SCE and 1150 mV SCE at 0.01 and 0.1 Hz. The potentials at which the crack growth rates are the maximum and the minimum are found to be −760 and −950 mV, respectively. The optimum cathodic protection potential for the minimum corrosion fatigue crack growth rate ranges between −900 and −950 mV. This optimum potential for the minimum corrosion crack growth rate is more negative than the cathodic potential required for restraining the corrosion effects on fatigue strength of steel to normal ambient air behavior.

Sampath Dhinakaran

Papers

Energy storage systems: A review

Effect of low cyclic frequency on fatigue crack growth behavior of a Mn–Ni–Cr steel in air and 3.5% NaCl solution

Estimation of Corrosion Fatigue-Crack Growth through Frequency Shedding Method

Fatigue Behavior of Nickel Based Super Alloy 718 in a Hot Corrosive Environment

Understanding Fatigue Crack Growth Behavior at Low Frequencies for a Mn–Ni–Cr Steel in 3.5 % NaCl Solution Under Controlled Cathodic Potential