postbucklingTests

Postbuckling tests are experimental investigations of structural elements after they have buckled under load, with the goal of characterizing postbuckling behavior, residual strength, and energy absorption. They complement traditional buckling tests by exploring how structures carry load beyond the initial critical buckling point.

Common test subjects include slender columns and struts under axial compression, plates and shells under biaxial or uniaxial loading, cylindrical shells under external pressure, and composite laminates. Tests can be monotonic, progressively loading until failure, or cyclic to assess fatigue and hysteresis in the postbuckling regime. Some studies apply combined loading—axial plus lateral—to reproduce realistic instabilities.

Instrumentation typically includes load cells, precise displacement transducers, strain gauges, and sometimes digital image correlation. Data collected encompass load–deflection curves, strain fields, and full-field deformations. Key outcomes include the postbuckling path, initial postcritical stiffness, peak load in the postbuckling regime, and energy absorption.

Analysis combines nonlinear finite element models and stability theory to compare with experimental results. Important considerations are sensitivity to geometric imperfections, boundary conditions, material nonlinearities, and scale effects. Applications span aerospace panels, automotive crash structures, civil engineering elements, and energy-absorbing devices.

Interpreting postbuckling behavior can be challenging because structures may sustain significant deformations with gradual loss of stiffness before collapse. Postbuckling tests thus provide essential data for designing against instability and for validating computational models.