A generic design method of transforming linear elements into memory elements with the diamond-shaped structures

Abstract

The existing physical realization devices of mechanical memory elements including the fluid mem-inerter and tapered dashpot have totally different working mechanism. Inertance of the fluid mem-inerter is nonlinear and dependent on the fluid mass in the length-variable helical path of the device, however, while damping of the tapered dashpot is also nonlinear, it is dependent on varied area of circumferential seam. Obviously, it is impossible to design the fluid mem-inerter with the help of the working mechanism of the tapered dashpot and vice versa. In other words, the design method for the physical realization device of one memory element fails to offer guidance for the design of other memory elements in the current situation. This study proposes a new and generic methodology for designing memory elements. It utilizes a diamond-shaped structure’s geometric nonlinearity to transform linear inerter, spring, and dashpot into their corresponding memory elements (mem-inerter, mem-spring, and mem-dashpot). Mathematical models are created for these memory devices, and their memory properties are investigated. The theoretical analysis demonstrates that all of these devices are displacement-dependent memory elements. Furthermore, the diamond-shaped memory element devices are prototyped and the bench tests are conducted to verify the feasibility of the proposed design method with the diamond-shaped structure. Additionally, the load adaptivity and performance benefits are verified through the bench tests of each suspension system equipped with the memory element prototypes. This work provides a generic design method of transforming linear elements into memory elements, and the proposed diamond-shaped memory elements can be as candidates to improve adaptivity of passive vibration isolation systems, such as the seat suspension and the vehicle suspension with double diamond bionic structure.