scholarly journals Investigation of the Self-Heating of Q460 Butt Joints and an S-N Curve Modeling Method Based on Infrared Thermographic Data for High-Cycle Fatigue

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 232
Author(s):  
Wei Wei ◽  
Cheng Li ◽  
Yibo Sun ◽  
Hongji Xu ◽  
Xinhua Yang
Keyword(s):  
Entropy Production ◽  
Fatigue Limit ◽  
Survival Probability ◽  
Damage Accumulation ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Likelihood Method ◽  
Entropy Production Rate ◽  
Cycle Fatigue ◽  
Probability Rate

In this study, we investigated the fatigue behavior of Q460 welded joints using tensile fatigue tests. Furthermore, real-time temperature profiles of the examined specimens were recorded by infrared thermography. Based on the obtained thermographic data, we calculated the entropy production rate of the specimens under different stress amplitudes. Hypothetically, the entropy production during high-cycle fatigue (HCF) could be divided into two parts. The first is induced by inelastic behavior that corresponds to damage accumulation, and the second originates from anelasticity associated with recoverable non-damaging microstructural motions. The turning point of entropy production under different stress levels represents an index for fatigue limit estimation. Then, considering the average damage threshold that exists during HCF, the entropy production related to damage accumulation (cumulative damage entropy) is obtained by testing three specimens under the same stress amplitude above the fatigue limit. Finally, a rapid three-parameter S-N curve with a survival probability rate of 50% is obtained. Then, combined with the maximum likelihood method, the 5% and 95% survival probability rate S-N curves are established. Most of experimental data are distributed in the area between S-N curves that correspond to 5% and 95% survival probability rate, indicating good accordance with the test data.

High Cycle Fatigue Properties of Modified 9Cr-1Mo Steel at Elevated Temperatures

2012 ◽  
Author(s):  
Yoshiaki Matsumori ◽  
Jumpei Nemoto ◽  
Yuji Ichikawa ◽  
Isamu Nonaka ◽  
Hideo Miura
Keyword(s):  
Fatigue Strength ◽  
Fatigue Limit ◽  
Room Temperature ◽  
Structural Reliability ◽  
High Cycle Fatigue ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Cyclic Softening ◽  
Fatigue Properties ◽  
Cycle Fatigue

Since high-cycle fatigue loads is applied to the pipes in various energy and chemical plants due to the vibration and frequent temperature change of fluid in the pipes, the high-cycle fatigue behavior of the alloys used for pipes should be understood quantitatively in the structural reliability design of the pipes. The purpose of this study, therefore, is to clarify the high-cycle fatigue strength and fracture mechanism of the modified 9Cr-1Mo steel at temperatures higher than 400°C. This material is one of the effective candidates for the pipes in fast breeder demonstration reactor systems. A rotating bending fatigue test was applied to samples at 50 Hz in air. The stress waveform was sinusoidal and the stress ratio was fixed at −1. The fatigue limit was observed at room temperature and it was about 420 MPa. This value was lower than the 0.2% proof stress of this alloy by about 60 MPa. This decrease can be attributed to the cyclic softening of this material. The limited cycles at knee point was about 8×105 cycles. All fracture was initiated from a single surface crack and no inclusion-induced fracture was observed in the fracture surface by SEM. Thus, the high-cycle fatigue design based on the fatigue limit may be applicable to the modified 9Cr-1Mo steel at room temperature. The fatigue limit of about 350 MPa was also observed at 400°C, and it appeared at about 107 cycles, while it appeared at around 106 cycles at room temperature. Thus, it was confirmed that the fatigue strength of this alloy decrease with temperature. However, the fatigue limit didn’t appear at 550°C up to 108 cycles. The fatigue limit may disappear in this alloy at 550°C. It is very important, therefore, to evaluate the ultra-high cycle fatigue strength of this alloy at temperatures higher than 400°C.

High-Cycle Fatigue P-S-N Curve Estimating Method Based on Maximum Likelihood Method for Turbine Coupling Bolt Materials

2014 ◽  
Vol 541-542 ◽  
pp. 592-598 ◽  
Author(s):  
Yu Jiong Gu ◽  
Tie Zheng Jin ◽  
Hai Dong Zu ◽  
Jing Xu ◽  
Dong Chao Chen
Keyword(s):  
Maximum Likelihood ◽  
Fatigue Limit ◽  
High Cycle Fatigue ◽  
Maximum Likelihood Method ◽  
Fatigue Tests ◽  
Likelihood Method ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Modified Method ◽  
Tensile Fatigue

The tensile fatigue tests and S-N curve fitting results of the coupling bolt material 25CrMo were given in this paper. It has been proved that the high-cycle fatigue properties of the bolt material can be accurately described by the three-parameter exponential S-N curve model by comparing the fitting results based on different S-N curve models. The fatigue limit of the high-cycle P-S-N curve calculated by the traditional maximum likelihood method was proved to have a high probability of being higher than the accurate fatigue limit. Therefore, a modified method based on maximum likelihood method was proposed so as to calculate the high-cycle P-S-N curve more accurately. The P-S-N of 25CrMo calculated using the modified method was given in this paper.

High Cycle Fatigue Behavior of Magnesium Alloys under Corrosive Environment

2008 ◽  
Vol 378-379 ◽  
pp. 131-146 ◽  
Author(s):  
Yoshiharu Mutoh ◽  
M. Shahnewaz Bhuiyan ◽  
Zainuddin Sajuri
Keyword(s):  
Fatigue Strength ◽  
Fatigue Limit ◽  
Magnesium Alloys ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Simultaneous Action ◽  
High Humidity ◽  
Corrosive Environment ◽  
Cycle Fatigue ◽  
Low Humidity

The high cycle fatigue characteristics of magnesium alloys under low humidity, high humidity (80% RH) and sprayed 5%NaCl solution environments have been introduced. Fatigue limit of bulk magnesium alloy was significantly reduced even under high humidity condition, while other structural materials such as steel and aluminum alloy showed no influence of humidity on fatigue limit. The reduction of fatigue limit under 5% NaCl environments was much larger than that under high humidity environment. The remarkable reduction of fatigue limit under corrosive environments was attributed to the formation of corrosion pit, which was induced by simultaneous action of mechanical loading and corrosive environment. To improve the reduced fatigue strength under corrosive environment, coating used to apply on the surface. Non-chromium chemical conversion coating showed superior effect on the improvement of fatigue strength under corrosive environment compared to anodized coating. Fatigue strengths of the coated and painted AZ61 alloy under high humidity and 5%NaCl environments showed almost the same fatigue strength as bulk material under low humidity.

scholarly journals Influence of warm caliber rolling on tensile response and high cycle fatigue behavior of hypereutectoid steel

2021 ◽  
Vol 10 ◽  
pp. 205-215
Author(s):  
Kyu-Sik Kim ◽  
Young-Kyun Kim ◽  
Hyeon-Jin Kim ◽  
Jeoung Han Kim ◽  
Kee-Ahn Lee
Keyword(s):  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Hypereutectoid Steel ◽  
Tensile Response

The Effect of HFPD Thermally Sprayed WC-Co Coatings on the Fatigue Behavior and Deformation of Al 2024-T4

2000 ◽  
Author(s):  
A. Ibrahim ◽  
C.C. Berndt
Keyword(s):  
High Frequency ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Pulse Detonation ◽  
Deformation Behaviors ◽  
Life Distributions ◽  
Thermally Sprayed ◽  
Al 2024 ◽  
Frequency Pulse

Abstract The effect of high frequency pulse detonation (HFPD) and HVOF thermally sprayed WC-Co coatings on the high cycle fatigue (HCF) behavior of 2024-T4 aluminum was investigated. The fatigue life distributions of specimens in the polished and coated conditions are presented as a function of the probability of failure. The monotonic and cyclic deformation behaviors of the as-received and as-coated specimens were investigated. The conclusions show that, (i) the HFPD sprayed specimens exhibited slightly higher fatigue lives compared to the uncoated specimens, (ii) the HVOF sprayed specimens exhibited significantly higher fatigue lives compared to the uncoated specimens, and (iii) the as-coated specimen was cyclically stable.

Effect of corrosion and sandblasting on the high cycle fatigue behavior of reinforcing B500C steel bars

2017 ◽  
Author(s):  
Marina C. Vasco ◽  
Panagiota Polydoropoulou ◽  
Apostolos N. Chamos ◽  
Spiros G. Pantelakis
Keyword(s):  
Mass Loss ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Salt Spray ◽  
Fatigue Tests ◽  
Tensile Behavior ◽  
Loading Frequency ◽  
Reinforcing Steel ◽  
Cycle Fatigue ◽  
Steel Bars

In a series of applications, steel reinforced concrete structures are subjected to fatigue loads during their service life, what in most cases happens in corrosive environments. Surface treatments have been proved to represent proper processes in order to improve both fatigue and corrosion resistances. In this work, the effect of corrosion and sandblasting on the high cycle fatigue behavior reinforcing steel bars is investigated. The investigated material is the reinforcing steel bar of technical class B500C, of nominal diameter of 12 mm. Steel bars specimens were first exposed to corrosion in alternate salt spray environment for 30 and 60 days and subjected to both tensile and fatigue tests. Then, a series of specimens were subjected to common sandblasting, corroded and mechanically tested. Metallographic investigation and corrosion damage evaluation regarding mass loss and martensitic area reduction were performed. Tensile tests were conducted after each corrosion exposure period prior to the fatigue tests. Fatigue tests were performed at a stress ratio, R, of 0.1 and loading frequency of 20 Hz. All fatigue tests series as well as tensile test were also performed for as received steel bars to obtain the reference behavior. The results have shown that sandblasting hardly affects the tensile behavior of the uncorroded material. The effect of sandblasting on the tensile behavior of pre-corroded specimens seems to be also limited. On the other hand, fatigue results indicate an improved fatigue behavior for the sandblasted material after 60 days of corrosion exposure. Martensitic area reductions, mass loss and depth of the pits were significantly smaller for the case of sandblasted materials, which confirms an increased corrosion resistance.

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