Vibration isolation of a symmetric and asymmetric rigid bar using struts subject to axial static and dynamic excitation

摘要

Many developed modern machineries such as compressors, engines, and presses represent a serious source of undesirable, uncomfortable, and uncontrollable vibrations leading to harmful failure and loss of machine availability. Therefore, research of mechanical engineers in maintenance sections in the industry has been devoted to the control, isolation, and minimization of harmful effects of such vibrations. The objective of the present paper is to study the influence of using a specific type of vibration isolator based on using post-buckled elastic clamped-clamped struts as an effective solution tool to relieve vibrating machines from these harmful effects. A model that consists of post-buckled struts acting as vibration isolators used to support symmetric and asymmetric rigid bars is introduced. The proposed clamped-clamped struts are subject to axial harmonic excitation at the base. The isolated bar is allowed to displace laterally. Displacement transmissibility is selected as the governing optimization variable of the isolator's effectiveness with the main objective to minimize vibrations transmitted from the base to the rigid bar. The transmissibility is calculated over a wide range of frequencies and plotted in the form of design charts to determine its effect on the vibration behaviour of struts. The lateral motion of the bar is considered. These plots are used to recognize the range of frequencies, for which full isolation is maintained. The frequencies at which resonance occurs in the system can then be depicted from the design graphs. The study reveals that at resonance frequencies, the most effective transmissibility is well below unity. Vibration characteristics are determined at specific frequencies, such that the physical performance of the vibrating system can be studied. All variables used in the analysis are normalized, such that the results are not dependent on any geometric of material property, such as the modulus of elasticity of the material, the section modulus of the profile used, or the length of the strut. In this way, the obtained results can be applied over a wide range of elastic materials, regardless of the type of material or section properties.