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Synopsis Jumping is an important form of locomotion, and animals employ a variety of mechanisms to increase jump performance. While jumping is common in insects generally, the ability to jump is rare among ants. An exception is the Neotropical ant Gigantiops destructor (Fabricius 1804) which is well known for jumping to capture prey or escape threats. Notably, this ant begins a jump by rotating its abdomen forward as it takes off from the ground. We tested the hypotheses that abdominal rotation is used to either provide thrust during takeoff or to stabilize rotational momentum during the initial airborne phase of the jump. We used high speed videography to characterize jumping performance of G. destructor workers jumping between two platforms. We then anesthetized the ants and used glue to prevent their abdomens from rotating during subsequent jumps, again characterizing jump performance after restraining the abdomen in this manner. Our results support the hypothesis that abdominal rotation provides additional thrust as the maximum distance, maximum height, and takeoff velocity of jumps were reduced by restricting the movement of the abdomen compared with the jumps of unmanipulated and control treatment ants. In contrast, the rotational stability of the ants while airborne did not appear to be affected. Changes in leg movements of restrained ants while airborne suggest that stability may be retained by using the legs to compensate for changes in the distribution of mass during jumps. This hypothesis warrants investigation in future studies on the jump kinematics of ants or other insects.
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Experimental Investigation of Stochastic Jumps during Crack Initiation and Growth in IN718
This study investigates the statistical significance of crack jump noise in Inconel 718 (IN718) for several different loading conditions. A direct current potential drop (DCPD) method is used to experimentally measure in-situ the crack length. Data is collected for six different peak loads at R=0.15 for a statistically significant number of trails. FEA-derived calibration curves relate measured potential to crack length. We determine that the mean crack length jumps, over subsequent cycles, increased with loading, the range of the crack length jump distributions decreases with increasing load, while the noise has a non-zero mean distribution. Findings from this study suggest that crack length jumps are not random events but contain statistical features that can potentially be used with machine learning approaches to better understand fatigue progression in Ni-based superalloys.
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- Award ID(s):
- 1709568
- PAR ID:
- 10097639
- Date Published:
- Journal Name:
- Physical review materials
- ISSN:
- 2475-9953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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