Discussion of “Impact of Heavy Freight Railcar on the Remaining Fatigue Life of Centenarian Railway Bridges” by Peng Lou, Hani Nassif, and Dan Su

The effective stress range (ESR) and the number of stress cycles (NSC) are two key parameters in fatigue damage evaluation. The inaccuracies in predicting remaining fatigue life can be attributed to either one of these two parameters. A sensitivity analysis is described to address the effects of four cycle-counting methods on ESR and NSC for various fatigue details, which including rain-flow counting (RF), mean-crossing-peak counting (MCP), level-crossing counting (LC) and simple-range counting (SR). Using field monitoring data under normal traffic of Wei River Bridge, the comparative results of four methods showed that RF was more conservative than MCP and SR. The relationships between RF and other three counting methods were determined in the form of a correlation coefficient and a linear regression line. Therefore, values obtained for ESR and NSC by MCP, LC and SR can be converted to values for RF, which is used for comparison and transformation of fatigue life evaluation results using different cycle-counting methods.

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Stochastic Remaining Fatigue Life Assessment Considering Crack Inspection Results

Journal of the Society of Naval Architects of Korea ◽

10.3744/snak.2020.57.1.001 ◽

2020 ◽

Vol 57 (1) ◽

pp. 1-7

Author(s):

Myong-Jin Park ◽

Yooil Kim

Keyword(s):

Fatigue Life ◽

Life Assessment ◽

Fatigue Life Assessment ◽

Remaining Fatigue Life

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S-N Curve Characterisation for Composite Materials and Prediction of Remaining Fatigue Life Using Damage Function

Journal of Composites Science ◽

10.3390/jcs5030076 ◽

2021 ◽

Vol 5 (3) ◽

pp. 76

Author(s):

Ho Sung Kim ◽

Saijie Huang

Keyword(s):

Fatigue Life ◽

Composite Materials ◽

Loading Rate ◽

Theoretical Method ◽

Damage Function ◽

Simple Method ◽

Arbitrary Choice ◽

Number Of Cycles ◽

First Time ◽

Remaining Fatigue Life

S-N curve characterisation and prediction of remaining fatigue life are studied using polyethylene terephthalate glycol-modified (PETG). A new simple method for finding a data point at the lowest number of cycles for the Kim and Zhang S-N curve model is proposed to avoid the arbitrary choice of loading rate for tensile testing. It was demonstrated that the arbitrary choice of loading rate may likely lead to an erroneous characterisation for the prediction of the remaining fatigue life. The previously proposed theoretical method for predicting the remaining fatigue life of composite materials involving the damage function was verified at a stress ratio of 0.4 for the first time. Both high to low and low to high loadings were conducted for predicting the remaining fatigue lives and a good agreement between predictions and experimental results was found. Fatigue damage consisting of cracks and whitening is described.

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