Deformation mechanisms and impact attenuation characteristics of thin-walled collapsible air chambers used in head protection
Bibliographic record
Abstract
Head injuries are a major cause of morbidity and mortality worldwide, many resulting from sporting activities. There is a constant need in the head protection industry for improved methods to manage impacts and to reduce the risk of mild and severe head injuries. Contemporary head protection primarily consists of foam with several inherent disadvantages, including a limited ability to provide effective energy absorption under both low and high impact velocities. Recently, thin-walled collapsible chambers were engineered to address this problem and have been implemented into sport helmets. The chambers consist of four engineering elements which define their dynamic performance: geometry, air volume, material, and venting system. This research analysed the contribution of air flow through an orifice to the chamber's management of impact energy. The objective of this study was to determine the effect of the chamber's vent diameter and material stiffness on peak force and venting rate during an impact. Two material stiffnesses (thermoplastic polyurethane 45D and thermoplastic polyurethane 90A) and five vent diameters (1 mm, 2 mm, 3 mm, 4 mm, and 5 mm) were tested at three inbound velocities (1.3 m/s, 2.3 m/s, and 3.0 m/s). Each chamber was impacted ten times using a monorail drop system. Analysis of the results revealed that the material stiffness, vent diameter, and inbound velocity all had a significant effect on peak force and venting rate (p < 0.001). Under low inbound velocities the largest vent diameters transmitted a lower force than the smallest vent, while this relationship reversed at high inbound velocities. Under low velocities the air flowrate was negatively correlated and the flow duration was positively correlated to the peak force. Under high velocities, the air flowrate was positively correlated and the duration was negatively correlated to the peak force. This suggested that, under low velocities, chambers performed optimally when air was dissipated quickly, for a short duration; however, as the chamber approached a critical failure region, the increased duration and decreased velocity of air released prevented higher peak forces. This research confirmed that the differences in vent diameter and material stiffness significantly affected the impact force characteristics of engineered thin-walled collapsible chambers.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.000 | 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".