scholarly journals Corrosion-Fatigue Evaluation of Uncoated Weathering Steel Bridges

2019 ◽  
Vol 9 (17) ◽  
pp. 3461 ◽  
Author(s):  
Yu Zhang ◽  
Kaifeng Zheng ◽  
Junlin Heng ◽  
Jin Zhu
Keyword(s):  
Crack Propagation ◽  
Fatigue Limit ◽  
Corrosion Fatigue ◽  
Weathering Steel ◽  
Faraday’S Law ◽  
Critical Flaw ◽  
Initiation Stage ◽  
Fatigue Evaluation ◽  
Corrosive Environments ◽  
Propagation Stage

Uncoated weathering steel (UWS) bridges have been extensively used to reduce the lifecycle cost since they are maintenance-free and eco-friendly. However, the fatigue issue becomes significant in UWS bridges due to the intended corrosion process utilized to form the corrodent-proof rust layer instead of the coating process. In this paper, an innovative model is proposed to simulate the corrosion-fatigue (C-F) process in UWS bridges. Generally, the C-F process could be considered as two relatively independent stages in a time series, including the pitting process of flaw-initiation and the fatigue crack propagation of the critical pitting flaw. In the proposed C-F model, Faraday’s law has been employed at the critical flaw-initiation stage to describe the pitting process, in which the pitting current is applied to reflect the pitting rate in different corrosive environments. At the crack propagation stage, the influence of pitting corrosion is so small that it can be safely ignored. In simulating the crack propagation stage, the advanced NASGRO equation proposed by the NASA is employed instead of the classic Paris’ law, in which a modified fatigue limit is adopted. The fatigue limit is then used to determine the critical size of pitting flaws, above which the fatigue effect joins as a parallel driving force in crack propagation. The model is then validated through the experimental data from published articles at the initiation stage as well as the whole C-F process. Two types of structural steel, i.e., HPS 70W and 14MnNbq steel, have been selected to carry out a case study. The result shows that the C-F life can be notably prolonged in the HPS 70W due to the enhancement in fatigue strength and corrosion resistance. Besides, a sensitivity analysis has been made on the crucial parameters, including the stress range, stress ratio, corrosive environment and average daily truck traffic (ADTT). The result has revealed the different influence of the above parameters on the initiation life and propagation life.

Crack Growth Rates and Corrosion Fatigue of Austenitic Stainless Steels in High Chloride Solutions

2011 ◽  
Vol 488-489 ◽  
pp. 97-100 ◽  
Author(s):  
Clemens Vichytil ◽  
G. Mori ◽  
Reinhard Pippan ◽  
M. Panzenböck ◽  
Rainer Fluch
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Limit ◽  
Corrosion Fatigue ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Propagation Rate ◽  
Corrosive Environment

Purpose: Applications for highly corrosive environments and cyclic loading are often made out of austenitic stainless steels. Corrosion fatigue and crack propagation behaviour has been studied to determine failure processes and damage mechanisms. Approach: CrNiMo stabilized austenitic stainless steel and CrMnN austenitic stainless steel in solution annealed and cold worked condition are compared. S/N curves and crack propagation rate curves are recorded in 43 wt% CaCl2solution at 120 °C, which resembles most severe potential service conditions. For comparison these experiments are also performed in inert glycerine. Additionally, the electrochemical behaviour of these materials has been studied. Findings: The CrMnN steels have excellent mechanical properties but are very susceptible to stress corrosion cracking in the test solution. The fatigue limit as well as the threshold for long crack growth are significantly reduced in corrosive environment. Moreover these steels exhibit a remarkable increase in the propagation rate, which is extremely pronounced in the near threshold region. This effect is enhanced by cold working. CrNiMo steels also show a reduction in the fatigue limit, but it is less pronounced compared to CrMnN steels. The threshold is significantly reduced in corrosive environment, but propagation rate is lower in corrosive environment compared to inert glycerine. Possible explanations of this surprising behaviour are discussed.

The investigation of low-cycle fatigue crack propagation of 16 Mn eccentric bar based on the acoustic emission technique

2020 ◽  
pp. 095440542097008
Author(s):  
Yujian Ren ◽  
Yuanzhe Dong ◽  
Jingxiang Li ◽  
Fei Zhao ◽  
Shengdun Zhao ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Cross Section ◽  
Low Cycle Fatigue ◽  
Loading Frequency ◽  
Cycle Fatigue ◽  
The Cross ◽  
Initiation Stage ◽  
Propagation Stage

Compared to the traditional cropping technology, low-cycle fatigue cropping can reduce load and improve cross-section quality. Geometric factors of V-shaped notch and processing parameters (such as load amplitude and load frequency) influence the cropping efficiency and section quality. By changing the factors, the sufficient efficiency of cropping and quality of cross-section get together. However, the influences of material defects, geometric parameters, loading frequency and other factors are different in each stage of the whole cropping process. If the effects of the parameters on the each stage of cropping process are clear, the higher productivity and the better cross-section quality will be obtained by applying suitable parameter on each stage of cropping process. To investigate the effects of eccentric ratio on each stage of low –cycle fatigue cropping process, a suitable monitoring method is needed. This study proposes acoustic emission (AE) technique to detect the low-cycle fatigue cropping process of 16 Mn eccentric bar (The bar prefabricated eccentric notches. The prefabricated notch improve the efficiency of cropping). The parameters of signals such as counts and kurtosis during the low–cycle fatigue process are obtained. According to the counts changes over time, the process of the 16 Mn metal bar cropping can be divided into three stages: the crack initiation stage, the crack propagation stage, and the fracture stage. Based on the cumulative counts, the eccentric ratio’s influence on the time of each cropping process stage is obtained. The time of the crack initiation stage and the final fracture stage doesn’t increase with the eccentric ratio. The time of the propagation stage influenced by the eccentric ratio greatly. Besides, the eccentric ratio’s influence on the cross-section quality is studied by using an advanced optical microscope system. The cross-section quality was influenced by the eccentric ratio significantly. The results of the paper indicate the acoustic emission (AE) monitoring technique is a useful method to detect the process of low-cycle fatigue cropping. Especially, it provide effective information to investigate the effects of the notch eccentric ratio during the low-cycle fatigue cropping process. The eccentric ratio’s effects on each stage of low-cycle fatigue cropping process offer guidance to improve low-stress fatigue cropping efficiency and cross-section quality.

The Use of Classification Zones for Fatigue Behavior in Steels

1977 ◽  
Vol 99 (1) ◽  
pp. 23-25 ◽  
Author(s):  
M. P. Weiss
Keyword(s):  
Phase Diagram ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Evaluation Criteria ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Initiation Stage ◽  
Definition Of ◽  
Fatigue Evaluation

Numerous studies on fatigue damage and fatigue crack propagation in the past dealt with these problems, either by a cumulative damage approach, or using crack propagation equations based on linear elastic fracture mechanics. Although these two approaches are not compatible, each is useful for predicting fatigue behavior correctly, but only within defined limits. This study introduces the “fatigue phase diagram”, which classifies different combinations of stresses and crack lengths in a given specimen, as zones in which different fatigue evaluation criteria, and possibly different fatigue mechanisms govern. Furthermore, a definition of the “threshold crack length” is proposed for consideration as the end of the crack initiation stage. It is suggested that most stress-intensity-range-threshold studies in the literature, were performed with stress range under the fatigue limit of the material, and therefore no crack initiation or propagation could have been measured. Any additional study should specify the zone of the tests on the fatigue phase diagram, so that correlations between different tests could be done with the proper data only.

scholarly journals Corrosion Fatigue Characteristics of 316L Stainless Steel Fabricated by Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1046
Author(s):  
Balachander Gnanasekaran ◽  
Jie Song ◽  
Vijay Vasudevan ◽  
Yao Fu
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Fatigue Properties ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Corrosion Properties ◽  
Powder Bed ◽  
Fatigue Characteristics

Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 316L stainless steels (SS) in 3.5 wt.% NaCl solution have been investigated using an electrochemical method, high cycle fatigue, and fatigue crack propagation testing. The LPBF 316L SSs demonstrated significantly improved corrosion properties compared to conventionally manufactured 316L, as reflected by the increased pitting and repassivation potentials, as well as retarded crack initiation. However, the printing parameters did not strongly affect the pitting potentials. LPBF samples also demonstrated enhanced capabilities of repassivation during the fatigue crack propagation. The unique microstructural features introduced during the printing process are discussed. The improved corrosion and corrosion fatigue properties are attributed to the presence of columnar/cellular subgrains formed by dislocation networks that serve as high diffusion paths to transport anti-corrosion elements.

Fatigue Strength Assessment of a Structure Considering Corrosion Wastage and Corrosion Fatigue

2018 ◽  
Author(s):  
Norio Yamamoto ◽  
Tomohiro Sugimoto ◽  
Kinya Ishibashi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Corrosion Fatigue ◽  
Life Assessment ◽  
Actual State ◽  
Corrosive Environment ◽  
Corrosion Fatigue Crack ◽  
Long Life

It is known that the fatigue strength decreases in corrosive environment and many experiments were carried out to comprehend the decrease in fatigue strength in corrosive environment. In order to comprehend the actual state, a cycle speed of fatigue test loads should correspond to a wave frequency. Therefore, an experiment in the long life region is practically difficult, then the corrosion fatigue data available for the life assessment of the structure is quite limited. In this study, the fatigue strength of the welded joints in long life service was evaluated according to the calculations of corrosion fatigue crack propagation subjected to the random loadings which followed an exponential distribution. In the crack propagation calculations, the progress of corrosion wastage from the plate surface and the resultant stress increase were considered simultaneously. In the high stress and the short life region, the decrease in fatigue strength due to the accelerated crack propagation in corrosive environment was dominant because the progress of corrosion wastage was little. On the other hand, in the low stress and the long life region, the decrease in fatigue strength became dull as longer the fatigue life because the corrosion fatigue crack propagation was suppressed by the corrosion wastage, but after that the fatigue strength showed the precipitous decrease due to the increase in stress resulted by the progress of corrosion wastage.

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