Design and testing of a high frequency hydraulic mechanical jackhammer
Bibliographic record
Abstract
Concrete has been used as a building material for thousands of years.The material has continued to evolve in parallel with our growing understanding of internal structural stresses.As one of the primary building materials in urban centres, concrete is routinely poured, repaired, and demolished.Expansive agents, hydraulic splitting, hydraulic demolition and mechanical demolition breakers are common methods of concrete removal, as documented by Abudayyeh, Sawhney et al. in 1998.Mechanical demolition breakers, known as jackhammers, are commonly used within the industry as they provide a versatile platform for the reduction in size of large quantities of material.The first patent for a pneumatic jackhammer was granted to Charles King in 1894.This design depicts a machine with an internal hammer that is pushed back and forth by compressed air.On the downward stroke the hammer contacts a chisel which transfers the impact energy into the concrete, inducing fracture of the material.As early as 1929, Holtzmann began to document the development of degenerative arthritis in workers who used hand held demolition breaker.Despite the machine's noise, and ergonomic issues, the jackhammer has not seen substantial redesign or development over the past century.In 1969, Benjumea and Sikarskie developed a model of the crushing and chipping process that occurs after the impact of a rigid chisel on a brittle material such as concrete or granite.This model clearly showed a primary crushing and secondary chipping process following the impact of the chisel.Dutta, in 1972, modeled the geometric indentation of the crushing and chipping zones as being dependant on the geometry of the chisel tip and the material being impacted.A more in-depth understanding of the upper and lower limits of the crushing and chipping sequence as well as the effect of repeated impacts was developed by Pang, Goldsmith and Hood in 1989.These models took into consideration the material characteristics, chisel geometry, and force with which the chisel is struck.They made the assumption that the time delay between strikes will have little impact on the indentation geometry.The research in this thesis, developed and tested a high frequency hydraulic mechanical jackhammer capable of reaching impact frequencies of over 80 Hz, more than doubling the impact frequencies of a single hammer.This machine implemented a design using two hammer
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.003 |
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".