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Predictions of Crack Growth Rates, R-Ratio and Overload Effects Based on Smooth Specimen LCF Data and the Moving Plastic Stress Field Ahead of the Crack Tip
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Mark Hardy
Materials, Volume: 19, Issue: 11, Pages: 2411 - 2411
Swansea University Authors:
STEPHEN WILLIAMS, Mark Whittaker
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DOI (Published version): 10.3390/ma19112411
Abstract
The use of the stress intensity factor K to characterize the severity of crack tip stress fields is widespread throughout engineering. The relationship between K and the crack growth rate is then usually represented empirically by a straight line Paris law relationship on logarithmic axes. This stud...
| Published in: | Materials |
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| ISSN: | 1996-1944 |
| Published: |
MDPI AG
2026
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| Online Access: |
Check full text
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa72080 |
| Abstract: |
The use of the stress intensity factor K to characterize the severity of crack tip stress fields is widespread throughout engineering. The relationship between K and the crack growth rate is then usually represented empirically by a straight line Paris law relationship on logarithmic axes. This study develops an analytical relationship between the two by linking crack growth to the accumulation of fatigue damage ahead of the moving crack tip. A stress-based fatigue model was used, with inputs from plastic 2D plane stress FE analyses representing an edge crack by a sharp semi-circular notch. Stress–distance profiles ahead of the crack tip were extracted at the maximum and minimum points of a range of fatigue loading cycles. These were then used with data from smooth specimen LCF tests to predict the build-up of fatigue damage at regularly spaced locations ahead of the crack tip and hence crack growth rates. Full da/dN–ΔK curves were generated for the nickel-based superalloy RR1000 at 20 °C with loading R-ratios of 0, −1 and 0.5. The R = 0 and R = −1 crack growth rate predictions agreed well with experimental data, as did the steeper growth rate slope calculated at R = 0.5. The method was then extended to predict overload behaviour. |
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| Keywords: |
crack growth; LCF; strip yield models; plasticity; R-ratio effects; overloads |
| College: |
Faculty of Science and Engineering |
| Funders: |
The work was carried out as part of an EPSRC-funded iCASE Ph.D. programme under project EP/V519601/1 with top-up funding from Rolls-Royce plc. |
| Issue: |
11 |
| Start Page: |
2411 |
| End Page: |
2411 |