Research On Frequency Adjustable Mass Dampers

In recent years,high strength lightweight material have been used.New structure forms and large space structure have been used in industrial buildings and other buildings.These structures have the characteristics of large span,light weight and low natural vibration frequency.Vibration of mechanical equipment may cause structural vibration.Such as central air conditioning mainframe,elevator,vibrating screen and so on.Moving equipment and vehicles,bridge cranes and factory workers also cause continuous vibration on the floor of the factory floor.In theory,the vibration can be suppressed by providing stiffness or changing the structural form.However,in most cases,it is not easy to achieve such an idea due to the confined space and the continuous working conditions in the factory environment.Although the dynamic response is not enough to cause structural safety problems,it will cause people’s discomfort.We recognize the use of TMD to control vibration and the deficiencies of existing TMD through the understanding of the research and application status of passive tuned mass dampers(TMD).A tunable tuned mass damper is proposed.The article first introduces the working principle of the original TMD.The influence of mass,damping ratio and frequency on vibration reduction effect is analyzed by MTALAB.Then,the frequency tuned mass damper is used to calculate the relationship between the span and its natural frequency.The modal analysis of ABAQUS is used to analyze the parameters to verify the accuracy of the formula.The relationship between natural frequency and span and the effect of vibration reduction are tested by experiments.Then,the single layer frequency tunable TMD is improved,and the MTMD structure and double layer frequency tunable TMD are proposed.MATLAB is used to analyze the damping effect of single TMD and MTMD,double layer frequency adjustable TMD,and the influence of damping ratio on vibration reduction effect.Using ABAQUS modal analysis to verify the relationship between span and double layer frequency tunable TMD.Using test to test the vibration reduction effect of double layer frequency adjustable TMD.The following conclusions are obtained:(1)In the theoretical analysis,the kinetic equations are established.The greater the mass ratio is,the more obvious the damping effect is.The larger the damping ratio is,the wider the damping band is,and the damping effect is weakened.For the frequency tunable TMD,when the vibration frequency is not consistent with the natural frequency of TMD,the TMD not only has no damping effect,but also increases the structural response.(2)In the experimental study of single layer frequency tunable TMD,the TMD is mounted on a cantilevered mass plate.Under constant frequency vibration condition,the vibration reduction effect reaches 80%.It not only solves the problem that the traditional TMD frequency can not be adjusted,but also solves the vibration of mechanical equipment.(3)The natural frequency of single layer TMD decreases with the increase of span.For double layer frequency adjustable TMD,when one layer is fixed,the natural frequency increases with the increase of the two layer span.When the span of the two layer is fixed,the natural frequency decreases with the increase of the span.(4)For MTMD,the damping effect of MTMD is better than that of a single TMD when the mass is constant.In the experimental study of double layer frequency adjustable TMD,it is found that the double-layer damping effect is better than that of single layer,and the vibration reduction effect reaches 90%.At the end of the paper,a brief summary of the above research results is given,and the theoretical basis and reference value for future practical projects are provided.