Increases in Fatigue Crack Growth Rate and Reductions in Fatigue Strength due to Periodic Overstrains in Biaxial Fatigue Loading
Bibliographic record
Abstract
Fatigue crack growth under biaxial constant amplitude straining (CAS) and a strain history having periodic compressive overstrains (PCO) were investigated. A comparison of the growth of fatigue cracks under constant amplitude straining and under strain histories having periodic compressive overstrains revealed that the morphology of the fracture surface near the crack tip and the crack growth rate changed dramatically with the application of the compressive overstrains. When the magnitude of the compressive overstrains was increased, the height of the fracture surface irregularities was reduced as the increasing overstrain progressively flattened fracture surface asperities near the crack tip. The reduced asperity height was accompanied by drastic increases in crack growth rate and decreases in fatigue strength. Crack opening stress measurements for biaxial fatigue cracks made using confocal scanning laser microscopy (CSLM) image processing of the crack profile, showed that the biaxial cracks were fully open at zero internal pressure for block strain histories containing in-phase periodic compressive overstrains of yield point magnitude. Therefore, for the shear strained samples there was no crack face interference and the strain intensity range was fully effective. For PCO tests with biaxial strain ratios of -0.625, and +1, effective strain intensity data were obtained from tests with positive stress ratios for which cracks did not close. The strain intensity factor ranges derived from popular fatigue life parameters were used to correlate fatigue crack growth rates for the various strain ratios investigated. These parameters all involved the shear strain range, and the normal strain range acting on the maximum shear strain plane. For various biaxiality ratios, the ratios of the effective strain intensity factor range to the constant amplitude strain intensity factor range at the threshold were found to be close to the ratios of the closure free fatigue limit obtained from effective strain-life to the constant amplitude fatigue limit.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".