| Author: | Akbar, Muhammad Ayaz |
| Title: | Design and optimization of single-particle impact damper |
| Advisors: | Wong, Waion (ME) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Vibration Damping (Mechanics) Structural control (Engineering) Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Mechanical Engineering |
| Pages: | xv, 114 pages : color illustrations |
| Language: | English |
| Abstract: | Particle impact damper (PID) is a type of passive nonlinear vibration damper that offers easy installation, durability, and operation in harsh environments. They can be categorized as single-particle impact dampers (SPID) or multiple-particle impact dampers (MPID). SPID has a simpler design process and enhanced momentum transfer with the primary mass, while MPID exhibits complex nonlinear behaviour and generates more noise. Designing optimal PID is challenging due to nonlinear phenomena. MPID faces challenges in satisfying design parameters and suffers energy loss. SPID, on the other hand, has easier design parameters and simplified numerical modelling. Overall, PID shows promise in many vibration control applications. In light of these considerations, it becomes essential to analyse and compare the performance of SPID and MPID. The study reveals that MPID exhibits more complex nonlinear behaviour, making it challenging to develop an optimal design approach. The higher number of particles generating impacts in MPID also results in increased noise during operation. Additionally, the unpredictability of particle positioning makes it difficult to satisfy design parameters. In contrast, SPID with its single-particle mass offers enhanced momentum transfer with the primary mass and simpler design and analysis processes. To further enhance the design of SPID, an optimal design methodology is established using a numerical approach. This research study focuses on ensuring both non-chaotic responses and optimal damping performance of the system. A range of design parameters is identified through extensive numerical simulations, and a statistical approach is employed to identify the optimal solution with the minimum vibration amplitude. The influence of internal friction is also analysed, revealing that higher friction degrades damping performance. Experimental validation is conducted to confirm the optimal design combinations obtained from numerical simulations. Moreover, the impact force generated by the single-particle mass during impact raises concerns about potential risks to vulnerable structures or the induction of dangerous stresses over multiple impact cycles. To address this concern, an alternative design of the SPID is investigated, combining viscoelastic materials at the impact point between the particle and the primary mass. The study also compares the impact characteristics of soft and hard impacts on the damping performance of SPID. It is found that soft impacts contribute to slightly improved damping performance by enhancing energy dissipation. The clearance magnitude of the SPID design is identified as a significant parameter that plays a crucial role in the design process. Furthermore, a new hybrid damper design is proposed by combining the SPID with a friction damper (FD). Previous findings indicate that SPID alone cannot achieve vibration suppression comparable to the conventional tuned mass damper (TMD), while FD is ineffective at resonance but can generate significant damping forces. A mathematical model is developed for the hybrid damper, and optimal combinations of SPID and FD are estimated. The predicted results are validated through experimental tests on a prototype. A parametric analysis of the proposed hybrid damper demonstrates its ability to reduce the maximum vibration amplitude of a single-degree-of-freedom (SDOF) primary structure. The hybrid damper exhibits effectiveness over a wide range of excitation frequencies and achieves comparable vibration suppression performance to a TMD with a similar mass ratio. Unlike the TMD, the hybrid damper does not require optimally tuned natural frequency and damping, eliminating the detuning problem associated with TMD. Numerical simulations using random earthquake excitation data further confirm the performance of the hybrid damper as a passive vibration control solution. In summary, this research has focused on a single-particle impact damper (SPID) and has provided practical design strategies to optimize its damping performance. The study emphasizes the advantages of SPID, including its simplicity, ease of installation, and effectiveness over a wide frequency range. The findings of this research contribute valuable insights and open up new possibilities for the practical application of SPID in the field of structural vibration control. |
| Rights: | All rights reserved |
| Access: | open access |
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