Buckling of an Elastic Ridge: Competition between Wrinkles and Creases.

Previous studies have explored how soft elastic materials deform under compression. These investigations often focus on planar surfaces and highlight the role of scale invariance in forming crease patterns. However, the behavior of elastic buckling in non-planar geometries, such as ridges, remains less understood. Established knowledge includes the observation of localized deformations like wrinkles and creases in soft solids. The role of geometry in influencing buckling modes has not been fully resolved. This uncertainty motivated researchers to examine how ridge angles affect buckling behavior. No prior work had resolved the transition between sinusoidal and crease-dominated buckling in ridge geometries. The lack of a clear threshold for this transition represents a knowledge gap. Understanding how ridge angles influence deformation modes could improve design in soft robotics and flexible electronics. This study aims to clarify the conditions under which different buckling patterns emerge.

This study aims to determine how ridge angles influence buckling modes in soft elastic prisms. The researchers sought to identify the critical angle at which buckling transitions from sinusoidal to crease-dominated. They also aimed to validate numerical predictions against experimental observations. The motivation stems from the need to understand how geometry affects localized deformations in soft materials. The study focuses on a triangular prism bonded to a rigid substrate under axial compression. The goal is to clarify the mechanical conditions leading to different buckling patterns. The researchers wanted to test whether scale invariance alone determines buckling behavior. This work contributes to the broader field of nonlinear elasticity and soft material mechanics.

The researchers used a triangular prism made of a soft elastomer bonded to a rigid slab. Axial compression was applied to induce buckling along the free ridge. Two buckling modes were observed: sinusoidal and crease-dominated. Experiments involved varying ridge angles and measuring deformation responses. A finite-element method was employed for numerical linear stability analysis. The simulations predicted the onset of sinusoidal buckling for angles below 90 degrees. Critical strain values were calculated for different ridge angles. The transition angle was determined by comparing experimental and numerical results.

The study found that buckling modes depend on ridge angles. For angles below 90 degrees, a sinusoidal buckling pattern was observed. Above 90 degrees, a series of creases formed along the ridge. The transition occurred at a critical angle of approximately 90 degrees. Numerical simulations matched experimental observations for angles below this threshold. The critical strain at the transition point was 0.44. This value corresponds to the onset of subcritical surface creasing instability. The results show that scale invariance is not sufficient for localization. The study reveals that geometry plays a key role in determining buckling patterns.

The authors conclude that ridge angles significantly influence buckling behavior in soft elastic prisms. The transition from sinusoidal to crease-dominated buckling occurs at a critical angle of about 90 degrees. Numerical simulations confirmed the experimental findings for angles below this threshold. The critical strain at the transition point was 0.44, matching the onset of subcritical instability. The study shows that scale invariance alone does not determine localization. Geometry plays a crucial role in shaping buckling patterns. The findings provide a new perspective on elastic ridge buckling. These results may inform the design of soft materials with controlled deformation behaviors.