Spectrum Loading and Crack Growth

1972 ◽  
Vol 94 (1) ◽  
pp. 181-186 ◽  
Author(s):  
O. E. Wheeler
Keyword(s):  
Cyclic Loading ◽  
Crack Growth ◽  
Crack Tip ◽  
Experimental Results ◽  
Load History ◽  
Variable Amplitude ◽  
Yield Zone ◽  
First Order ◽  
Analytical Device ◽  
Spectrum Loading

An analytical device for improving the accuracy of crack growth predictions in metal subjected to variable amplitude cyclic loading is presented. A modification to the linear cumulative growth idea is proposed which incorporates a consideration of prior load history by taking into account the yield zone ahead of the crack tip. Correlation between analysis and experimental results for six different cases shows that the scheme, even though only a first order improvement on the Miner idea, is sound and can be used with confidence for design and analysis.

Application of the Strip Yield Model to Crack Growth Predictions for Structural Steel

2010 ◽  
Vol 57 (1) ◽  
pp. 1-20
Author(s):  
Małgorzata Skorupa ◽  
Tomasz Machniewicz
Keyword(s):  
Structural Steel ◽  
Crack Growth ◽  
Model Calibration ◽  
Load History ◽  
Yield Model ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Constraint Factors ◽  
Strip Yield Model ◽  
Closure Mechanism

Application of the Strip Yield Model to Crack Growth Predictions for Structural SteelA strip yield model implementation by the present authors is applied to predict fatigue crack growth observed in structural steel specimens under various constant and variable amplitude loading conditions. Attention is paid to the model calibration using the constraint factors in view of the dependence of both the crack closure mechanism and the material stress-strain response on the load history. Prediction capabilities of the model are considered in the context of the incompatibility between the crack growth resistance for constant and variable amplitude loading.

A Modified Compliance Method for Automatically Measuring Fatigue Crack Growth In Situ during Spectrum Fatigue Testing

2014 ◽  
Vol 891-892 ◽  
pp. 732-738
Author(s):  
Wyman Zhuang ◽  
Qian Chu Liu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Operating Conditions ◽  
Loading Conditions ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Marker Band ◽  
Spectrum Loading

The fatigue critical structures of military aircraft are generally subjected to variable amplitude flight spectrum loading. Maintaining aircraft structural integrity to ensure safe operation of the fleet is critically dependent on accurate analysis and reliable prediction of fatigue crack growth in those structures under service operating conditions. To achieve this goal, laboratory experimental methods that can accurately measure and monitor fatigue crack growth under variable amplitude loading are required. This can be challenging as no test standard exists to guide the process of fatigue crack growth measurement under variable amplitude loading conditions to ensure the accuracy of the test results. This challenge was addressed by developing a modified compliance method as described in this paper. The results presented employed a modified compliance method complemented with a travelling microscope technique and marker band loads. The modified compliance method developed is able to measure in-situ, fatigue crack growth of standard compact-tension specimens under a fighter flight spectrum loading. The marker band loads and microscope readings were used to assist the post-test validation using quantitative fractography. The results from this study have demonstrated that the modified compliance method can produce consistent and accurate fatigue crack growth data under variable amplitude loading conditions.

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