Effect of disk-to-disk variations on the nonlinear static characteristics and stability regimes of coned disk spring stacks: Experimental and computational studies of quasi-zero-stiffness isolators

Abstract

In this study, we introduce a novel approach to creating a Quasi-Zero Stiffness (QZS) isolator using off-the-shelf coned disk springs with a unique stack. These springs are affordable, compact, and can be adapted for a broad spectrum of force requirements, enabling the achievement of the QZS effect using a solitary component, thereby eliminating the need to balance the positive and negative stiffness elements. To address the issue of the limited displacement range offered by a single coned spring, the solution involves layering multiple disk springs with rigid spacers. Nonetheless, the nonlinear force–deflection behavior is significantly affected by manufacturing-driven geometric variability due to inherent differences from one disk spring to another. This aspect of variability has been overlooked by previous researchers, who have operated under the assumption that all disks in a stack are identical. This research delves into how variations in the disk springs’ geometry impact the nonlinear static behavior of the QZS stacks, employing both experimental and computational techniques. We illustrate the stability conditions and pinpoint the occurrences of buckling and snap-through events. Computational model for the multi-disk engineered stack is experimentally validated. Finally, we explore the QZS isolator design approaches that would take into account these geometric variations.