Flexure mechanisms are widely employed in precision engineering thanks to their intrinsic advantages over conventional articulated systems, including frictionless motion, high repeatability, absence of backlash, and possibility of monolithic fabrication. However, their performance is fundamentally constrained by inherent stiffness, limited stroke, and complex motions. To address the inherent stiffness limitation, stiffness tuning has emerged as a key design objective. In particular, axial precompression of flexible beams induces nonlinear load-deformation behavior associated with buckling phenomena, offering significant potential to expand the functional capabilities of flexure mechanisms. Nevertheless, despite this potential, existing approaches remain largely confined to isolated beam studies and lack general analytical models and systematic design methodologies for their integration into complete mechanisms.
This thesis addresses this gap by proposing a comprehensive analytical and design framework for buckling-based flexure mechanisms with enhanced mechanical functionalities. Within this framework, buckled beams are employed as functional elements to achieve targeted mechanical responses. By harnessing both pre- and post-buckling regimes, the approach enables stiffness reduction, negative stiffness, snap-through, constant-force behavior, and bistability within compact and monolithic structures.
A key aspect of the proposed framework is the distinction between guiding beams, which ensure motion guidance, and buckling beams, which provide additional mechanical functionalities through controlled preloading. A classification of preloading methods is introduced, including geometric, elastic, self, residual-stress, and gravity preloading, enabling informed selection based on scale, fabrication constraints, and targeted mechanical behavior.
A central contribution is the development of a generic analytical model for precompressed and buckled beams, applicable to a wide range of boundary conditions, preloading types, and actuation modes. Closed-form expressions and normalized graphs are derived to describe quasi-static load-deformation characteristics and snap-through behaviors. Five fundamental configurations are analyzed, including fixed-fixed, fixed-guided, pinned-pinned, fixed-pinned, and fixed-lever beams, actuated either in translation or rotation at one extremity. The model is validated by finite element simulations and experiments.
Building on these analytical results, the thesis introduces a catalog of elementary flexure mechanisms incorporating guiding and buckling beams. These simple mechanisms demonstrate how buckling effects can be exploited in flexure-based mechanisms to achieve reduced stiffness, adjustable stiffness, and constant-force behavior.
Finally, a design method for buckling-based flexure mechanisms is formulated. This method provides clear guidelines and practical considerations for selecting beam configurations, preloadi
