The performance of mechanical systems is susceptible to unwanted vibrations. Structural vibrations can significantly degrade the manufacturing accuracy if not adequately controlled. For this reason, the development of effective vibration reduction methods to address the inherent challenges in precision mechanical systems is highly desirable. Currently, passive and active dampers are added to mechanical systems as conventional vibration reducers. These dampers, however, have several drawbacks that limit their applications. In most cases, the need to optimize their design to specific isolated objects requires additional dampers for each vibration mode, which makes their use complicated and costly.
To address the mentioned challenges, Professor Yasunori Sakai from Shibaura Institute of Technology and Professor Tomohisa Tanaka from Tokyo Institute of Technology developed a novel design of structural dampers for auto-damping mechanical systems. In the new method, the vibration in the mechanical systems is directly controlled by integrating a multimode damper, such as structural dampers and passive damper cells, into the mechanical systems. Their work is currently published in the research journal, Structures.
The passive damper with anisotropic composite structure (P-DACS), a composite of metal and polymer, was first integrated directly into the mechanical components, and its effectiveness in controlling the vibrations evaluated. The authors observed that the dynamic characteristics of P-DACS were controlled by the geometrical design parameters and materials properties. The number of lattices, lattice inclination angle, the shape of lattice, and the lattice ratio between tuned mass and lattice, were some of the design parameters that exhibited considerable influence on the stiffness, damping ratio, and frequency response function over a wide range. An increase in the inclination angle, for example, resulted in a corresponding increase in both the elastic deformation and damping ratio. Furthermore, it was worth noting that the controllable range of the static stiffness and damping ratio was more sensitive to the inclination angle when softer and harder materials were used, respectively.
The feasibility of the P-DACS design was validated by conducting numerical simulation analysis based on the assumption that the materials were linearly isotropic elastic and that there was no friction existing between the jointed parts. Results showed that the P-DACS could add auto-damping of static and dynamic vibrations to the structural elements. Furthermore, the damping could be simultaneously increased for multiple elastic vibration modes, thus enhancing the design performance. This was attributed to the fact that the damper that obtains the damping effects changes with respect to the changes in the vibration mode of the structure, and is common in smaller damper cells that get stacked in the structure with various orientations.
In a nutshell, the researchers developed a direct damping approach for controlling the vibrations of mechanical components by integrating P-DACS. Based on the results, P-DACS can effectively control the static and dynamic vibration characteristics based on design parameters and materials properties. Most importantly, it can add auto-damping of vibration in structural components. In a statement to Advances in Engineering, Professor Yasunori Sakai said he expect the study findings will help address the challenges of convention vibration reduction methods, thus improving the performance of precision mechanical systems. Its applications will also be expanded to flexible structures such as aerospace equipment and robots.
Sakai, Y., & Tanaka, T. (2020). Structural damper for auto-damping mechanical components. Structures,24, 864-868.