Vibration Isolation Rubber Characterization And Rubber Suspension Structural Optimization

Vibration isolation rubber can play an important role of reducing vibration and noise because of its unique mechanical properties,such as hyper-elasticity,viscoelasticity and volume incompressibility.However,these properties make it much more complex to depict the behavior of the vibration isolation rubber and to pursue optimization with rubber elements,than with metal materials.Aiming at better constitutive models for the static and dynamic characteristics of rubber materials and optimization design of rubber components.The conducted researches in this paper can mainly clarified as follows:As rubber hyper-elastic behavior is directly influenced by deformation mode,strain level,loading history and some other factors,it is still a challenge to effectively select a proper hyper-elastic model for an engineering application.Considering three typical deformation modes of the rubbers for vibration isolation,static mechanics tests were carried out under various strain levels.Six constitutive models for rubber hyper-elasticity were chosen and model parameters are respectively identified to fit the experimental data.Based on analysis on fitting errors and decision coefficients of each model,principles for model selection under different deformation levels are discussed,and a flowchart was defined for accurately selecting hyper-elastic constitutive model.A procedure was implemented to extend a chosen one-dimensional to its three-dimensional counterparts.The three-dimensional model can be readily used to predict the static properties of rubber components.The master curve of rubber materials for vibration isolation is mostly asymmetric,which is difficult to be accurately predicted using available viscoelastic constitutive models.A new 5-parameter fractional-derivative model was thus built by adding another Abel pot to the fractional-order Zener model.Theoretical analysis was performed to evaluate the influence of model parameters of the newly established model.Temperature scanning tests and frequency scanning tests were respectively conducted on a chosen rubber material for vibration isolation,according to the DMA techniques,from which curves of the dynamic modulus and loss factor curve were drawn in a chosen reference temperature.Model parameters were identified for the new viscoelastic model by means of nonlinear least square fitting.The one-dimensional constitutive model was then extended to the three-dimensional form,and a user material subroutine was developed,which is a proper model for more accurately predicting the viscoelastic property of the rubber material for vibration isolation.Due to material nonlinearity and optimization complexity,it is a bigger challenge to achieve optimization on rubber components than on metal materials.To satisfy design requirement of rubber components for vibration isolation,structure optimization was deduced into the topology optimization and size optimization,and corresponding optimization strategies were put forward for each stage.For the topology optimization,nonlinear interpolation was adopted for cell density and model parameters.By defining the static property as the cost function while the dynamic property and component volume as constraints,the optimization with multi objectives in static and dynamic performance was transformed into an equivalent single-objective topology optimization.For size optimization on the other hand,the niche genetic algorithm was combined with the design variables dynamic adjustment,so as to improve optimization efficiency.Optimization on a rubber engine mount was chosen as an example,which demonstrates that the suggested approach effectively reduces the difficulty and complexity with topology optimization on the rubber structure.As a response to the design demand on rubber suspension for commercial vehicles,comprehensive studies were carried out,where a systematic approach was explored for structure design on complex rubber components.In the first step,structure configuration and elastic characteristic curve of the component were determined according to the desired stiffness characteristics.The material topological distribution and the dimension parameters were then figured out by the aforementioned optimization strategies.Static and dynamic characteristics were calculated using the developed models for the rubber suspensions with or without optimization.The results clearly reveal that optimized rubber suspension has better performance related to vehicle comfort,which indicated that the proposed approach and developed software are applicable to the top down design of complex rubber components like the rubber suspensions.