Dynamic Absorber Experiment

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Department of Mechanical and Aerospace Engineering Hong Kong University of Science and Technology MECH 3840 LABORATORY II Spring 2014 Experiment A Dynamic Absorber Submitted to: CHEN Tongheng (Office NO. 4018) Submitted by: Group Tu8 TAM, Chung Tin TONG, Ka Chun Ronald CHENG, Hiu Yeung CHAN, Kwok Ching CHING, Chun Hung TANG, Cheuk Nam (20102957) (20104553) (20102294) (20108561) (20015893) (20107397) Experiment performed on: 4th March, 2014 Report submitted on: 11th March, 2014 1. Abstract In this experiment, the effect of fitting a dynamic absorber onto a vibrating structure was investigated. By forced vibration, the fundamental frequency of a simple mechanical structure was determined. Then, a dynamic absorber comprising a thin and flexible beam with two masses which can slide along the flexible beam was mounted onto the top of the concentrated mass. In order to optimize the use of the absorber and reduce the vibration to minimum, the specific position of the masses of the dynamic absorber was determined where minimum vibrating amplitude was detected. Lastly, the frequency response function of the structure with dynamic absorber was recorded and compared with that of the original one. 2. Introduction Machines usually operate at a fixed speed and exhibit vibration, so the machines will generally be excited at a fixed frequency which is sometimes the operating frequencies or other fixed frequencies which are proportional to the driving speed. When the machines have run over a long period or been installed in undesirable boundary conditions, the vibration amplitude of the machines may rise and reach some pre-defined vibration levels in accordance with the safety regulations or comfort criteria. In order to reduce the response amplitude in these cases, remedial work is applied. Many solutions are found to solve the vibration problems in the machines

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