Stand for Biomimetic Swimming Fins Fatigue Testing

Abstract

TThe aim of the work is to present a newly developed stand and methodology of accelerated tests of fatigue strength of flexible propellers and fins. The paper presents the design and concepts of the measuring elements used in the research. Test methodology and water stressing were devel-oped. The mechanical properties of the following materials were presented: Arnitel EL-550 and QUEO 8230 with the addition of PP / EVA 50/50 (polypropylene / ethylene-vinyl acetate) - in the proportion of 70/30 (QUEO 8230 / additive). The constructed test stand and a new method of fa-tigue testing of biomimetic fins made it possible to determine the number of fin movement cy-cles under a given load, which may facilitate the determination of a warranty for a newly intro-duced product. The current consumption by the fin drive and video monitoring allowed for the selection of the range of the number of movement cycles and the determination of the moment of fatigue cracks until the fin structure loses its capacity. During the analysis, the test results showed that the fins made of Arnitel EL-550 did not show changes in the measured values of the current and the force generated by the fin. For a fin made of QUEO 8230, at 35,000 cycles, there is a decrease in the current and force consumed, which indicates the initiation of fatigue damage to the fin. The performed tests can be the basis for the development of standards for the fatigue strength of flexible propellers.

Strouhal Number Measurement for Novel Biomimetic Folding Fins Using an Image Processing Method

“…The thermoplastic elastomers from the Thermoplastic Copolyester group were used for the tests. The material parameters used for production as well as the fatigue strength [22] and the durability of the fins are presented in [23]. The following chapter includes a mathematical study of all tested fins.…”

“…K-the nondimensional parameter defining the shape of the fin; α-the fin angle of attack; k-the stiffness coefficient (2), which depends on the fin material parameters [23] defined with parameter E, the Young module, and the inertia of the fin I.…”

Propulsion System Analysis Based on Particle Image Velocimetry Method in Biomimetic Unmanned Underwater Vehicle

“…The thrust produced by the fin depends not only on the fin dimensions but also the frequency oscillation, angle of attack and on the fin flexibility [4,6]. This is a challenging task for analysis due to the lack of ready to use mathematical models.…”

“…One of the methods widely spread for fluid-structure interaction analysis is Particle Image Velocimetry (PIV) [6]. PIV is a non-invasive image processing method to measure fluid velocity in a specific region.…”