Nonlinear Buckling and Post-buckling of Shape Memory Alloy Shallow Arches

In this work, the nonlinear buckling and post-buckling behavior of shallow arches made of Shape Memory Alloy (SMA) is investigated. Arches are susceptible to large deflections, due to their slenderness, especially when the external load exceeds the serviceability limit point. Beyond this, loss of stability may occur, the famous snap-through buckling. For this reason, curved beams can be used in passive vibration control devices for seismic response mitigation, and the geometrically nonlinear analysis is needed for the accurate prediction of their response. Thus, in this research effort, the assumptions of the Euler-Bernoulli beam theory are considered, and the Von Karman strain field is employed to account for large deflections. The formulation of the problem is displacement-based regarding the axial (tangential) and transverse (normal) displacements, while the two governing equations are coupled and nonlinear. In order to introduce the SMA constitutive law, the stress-strain experimental curves described in the literature are employed together with a fiber approach at specific control cross-sections along the beam. The numerical solution of the longitudinal problem is achieved using the Analog Equation Method (AEM), a Boundary Element Method (BEM) based technique, and the iterative procedure is based on a Newton-Raphson scheme by using a displacement control algorithm to trace the fully nonlinear equilibrium path and overcome the limit points. Several representative examples are studied, not only to validate the proposed model but also to investigate the nonlinear buckling and post-buckling of SMA shallow arches.