Snap-through of soft elliptical shells under volume-and pressure-control

Piri, Barnabás and Berezvai, Szabolcs (2026) Snap-through of soft elliptical shells under volume-and pressure-control. INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 326. No. 111883. ISSN 0020-7403

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Abstract

Soft materials are widely used in engineering applications due to their flexibility, energy absorption capability, and low prototyping cost. These characteristics make such materials an ideal basis for designing complex, compliant mechanical systems, addressed in soft robotics. Additionally, they often exhibit significant material and structural nonlinearities, which can be exploited through snap-through instability to achieve rapid and enhanced mechanical responses. While snap-through behavior has been extensively studied in the literature for soft spherical shells, this contribution extends shell geometries considering an axisymmetric elliptical generalization using fluidic actuation. A comprehensive framework is proposed for capturing the snap-through behavior of soft axisymmetric elliptical shells through numerical and experimental methods, utilizing volume- and pressure-controlled methods. A general geometric formulation is introduced to describe elliptical shells, and finite element models are developed to analyze their nonlinear snapping behavior. The numerical results are validated using a dedicated experimental setup capable of reproducing both control methods. The results show that axisymmetric simulations provide an efficient and reliable tool for parameter studies, while dynamic 3D simulations closely follow the stable branches of the quasi-static equilibrium paths. Equivalent energy-release geometries are identified, revealing a linear relation between key geometric parameters that enables the structural response to be tuned without changing the overall actuator size. The experiments confirm that volume control provides a more robust characterization of snap-through, whereas pressure control is more sensitive to control-loop limitations. Overall, the results demonstrate that elliptical shells offer additional geometric flexibility while preserving the performance of spherical snap-through actuators.

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