Evaluation of surface modifications introduced by shot peening of aluminum alloy 2024-T351
Bibliographic record
Abstract
Shot peening is a cold working mechanical deformation process consisting of bombarding a metallic surface with small spherical media, called shots, at velocities commonly in the range of 10 to 100 m/s. Upon impact, the shots generate a near-surface deformed layer containing local hardening as well as compressive residual stresses, resulting in an improved fatigue resistance. However, the dependence of shot velocity and percentage of the total area covered by shot impacts on the surface modification introduced by shot peening are not well understood.The hardness and residual stress profiles beneath shot peened surfaces were investigated using nanoindentation experiments for the situations of three different average shot velocities, corresponding to 35 m/s, 54 m/s and 66 m/s, and two surface coverages, corresponding to a single shot peening impingement and full coverage (100%). For the situation (i) of a single impingement, a new polishing procedure was developed allowing locating an isolated single impingement, verifying that the impingement was produced by a shot that impacted at normal incidence, as well as preparing the surface such that nanoindentation could be performed on the impingement's cross-section. It was demonstrated that both hardness and compressive residual stresses increased with an increase in shot velocity. The experimental residual stress results were compared to those from numerical simulations that utilized the same peening parameters as the experiments. It was observed that the experimental results demonstrated similar behavior and were of the same order of magnitude as those predicted numerically. The main difference was that the experimental results demonstrated a maximum compressive residual stress that was independent of shot velocity.For the situation (ii) of full coverage, channelling contrast imaging in a scanning electron microscope revealed that there were recrystallized grains adjacent to the shot peened edge. Additionally, the hardness and compressive residual stresses were observed to increase with an increase in shot velocity. Similarly to the single impingement, the location of maximum compressive residual stress was independent of shot velocity.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 teacher head, 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".