Soft Spots in Shell Buckling

The energy landscape of thin shells under quasistatic loading represents their potential energy as a function of their shape. It has recently been shown for a narrow plate [S. Lachmann and S. M. Rubinstein, Phil. Trans. R. Soc. A 381, 2244 (2023)10.1098/rsta.2022.0027PTRMAD1364-503X] that lateral probing can induce controlled trajectories in configuration space, providing an experimental method for measuring the energy landscape of a specific structure. In this Letter, we extend this method to explore the prebuckling behavior of poked cylindrical shells through the lens of the energy landscape. This approach offers an intuitive way to combine and synthesize the deformation responses from different probing locations into a cohesive description of the prebuckling dynamics, revealing the presence of local soft spots-regions where the structure is particularly susceptible to deformation. As the system is loaded, these soft spots appear as local minima in the energy barrier to buckling and are experimentally shown to act as attractors of nearby deformation. The energy landscape framework provides a general framework for understanding prebuckling dynamics, highlighting the role of spatially extended deformations and offering a new way of safely estimating shock sensitivity to buckling in real shells.