Study On The Design Of Spring-Sliding-Beam Isolator

Vibration isolation is a widely used method in engineering for controlling or cutting down harmful vibrations to protect machines or equipments. Simple in structure as a common linear isolator is, it cannot in principle bear simultaneously high static load capacity and low isolation start frequency. Thus it is of great practical meanings to design nonlinear isolation mounts with High-Static-Low-Dynamic-Stiffness (HSLDS).In this paper, a nonlinear isolation mount, called spring-sliding-beam isolator which has HSLDS property, is designed and studied. The spring-sliding-beam isolator is in structure a parallel combination of a linear spring and a sliding beam which allows large deformation. The static and dynamic analyses are firstly carried out, based on which the isolation performance of the isolator is then intensively explored. And lastly, an experimental rig of the isolator is established and tested to verify the theoretical outcomes. The main contents and conclusions are as follows:1. The static model and the equation of motion of the isolator are established. Through the stability analysis, the stiffness of the spring with which the isolator holds stable over the whole range of the possible displacement is obtained.2. The key principle behind this design is that the static working point of the isolator is creatively put at the unstable critical point of the sliding beam. The sliding beam supplies zero stiffness and max static load capacity at its unstable critical point where hence the dynamic stiffness is the stiffness of the linear spring whereas the static stiffness is the sum of that of the two components. Thus, in the vicinity of this point, the isolator has the HSLDS property and can be linearized to be a linear system which has the same dynamic stiffness of the linear spring.3. An approximate solution to the nonlinear equation of motion is finely found by applying the HB method rather than the multiple-scales method which can not deal with a nonlinear equation containing both a square term and a cubic term. The transmissibility of the isolator is derived and compared with that of its equivalent linear model. It is shown that the HSLDS isolator has a higher isolation capability.4. The isolation performance of the isolator during tiny motion is tested through a frequency response experiment. The experiment verifies the validity of linearation hypothesis and demonstrates the isolator has a wider isolation frequency bandwidth and lower transmissibility under tiny motion.