Analytical design and optimization of an automotive rubber bushing

The ride comfort, driving safety, and handling of the vehicle should be designed and tuned to achieve the expectations defined in the company's design. The ideal method of tuning the characteristics of the vehicle is to modify the bushings and mounts used in the chassis system. To deal with the noise, vibration and harshness on automobiles, elastomeric materials in mounts and bushings are determinant in the automotive components design, particularly those related to the suspension system. For most designs, stiffness is a key design parameter. Determination of stiffness is often necessary in order to ensure that excessive forces or deflections do not occur. Many companies use trial and error method to meet the requirements of stiffness curves. Optimization algorithms are an effective solution to this type of design problems. This paper presents a simulation-based methodology to design an automotive bushing with specific characteristic curves. Using an optimum design formulation, a mathematical model is proposed to design and then optimize structural parameters using a genetic algorithm. To validate the resulting data, a finite element analysis (FEA) is carried out with the optimized values. At the end, results between optimization, FEA, and characteristic curves are compared and discussed to establish the correlation among them

Stiffness characteristic comparison between metal-rubber and rubber isolator under sonic vibration

Stiffness of rubber and metal rubber (MR) changes nonlinearly. Based on hysteretic damping theory and energy conservation equations, a unified stiffness model is developed. The ring type of isolators made from rubber and metal rubber are studied. The isolator samples are tested on the electro-hydraulic loading system, which is fixed by a clamping device. We aim to study the deformations under different loading rates, loading forces and other quasi-static loading states. The dynamic stiffness affected by the preload and vibration frequency is studied on the sonic drilling processing. It can be concluded that the metal rubber isolators deform larger plastic than the rubber. The damping, plastic deformation and elastic deformation of the metal rubber and rubber material are inversely proportional to the loading rate. The total deformation of the rubber is larger than the metal rubber, no matter when the load increases or decreases. The dynamic stiffness of the metal rubber isolator is proportional to the vibration frequency. However, the dynamic stiffness of the rubber remains the same under different preloads, while decreases when the preload increases

Modeling of Bearing Dynamics Using Combined EFEM-DEM Method

The objective of this investigation was to develop a 3D dynamic model to study the rotorbearing- housing system. To achieve the objective, an existing dynamic bearing model (DBM) was combined with a flexible bearing housing model and a flexible rotor model. The DBM is based on the discrete element method (DEM), in which all bearing components are assumed to be rigid and have six degrees of freedom. The 3D explicit finite element method (EFEM) was used to develop the flexible housing and rotor models. To couple the bearing outer race (OR) with housing, a novel algorithm was developed to detect contact conditions between the housing support and OR and then calculate contact forces based on the penalty method. A study of housing support geometry demonstrates that bearing support plays a large role on the dynamic performance of the bearing. Motion of bearing outer race is closely related to the geometry and deformation of the housing. The effect of elastomeric bushing support on bearing dynamics was also studied and then compared to the bearing housings made with linear-elastic material. The EFEM was used to model a cylindrical elastomeric bushing, which was then coupled with DBM. Constitutive relationship for the elastomeric material is based on the Arruda-Boyce model combined which uses a generalized Maxwell-element model to capture both hyperelastic and viscoelastic behaviors of the material. Comparison between the two types of housings illustrated that elastomeric materials as expected have large damping to reduce vibration and absorb energy which leads to a reduction in ball-race contact forces and friction. It was also shown that a desired bushing support performance can be achieved by varying bushing geometry. Simulations using the combined EFEM bushing and DBM model demonstrated that the elastomeric bushing provides better compliance to bearing misalignment as compared to a commonly used rigid support model. Modeling with a bearing surface dent showed that vibrations due to surface abnormalities can be significantly reduced using elastomeric bushing support. It has also been shown that choosing a proper bushing is an efficient way to tuning bushing vibration frequencies. The model was further developed to study the effects of rotor and support flexibilities on the performance of rotor-bearing-housing system. The system is composed of a flexible rotor and two supporting deep-groove ball bearings mounted in flexible bearing housings. In order to combine the dynamic bearing model with finite element rotor and support system, new contact algorithms were developed for the interactions between the various components in the system. The Total Lagrangian formulation approach was applied to decrease the computational effort needed for modeling the rotor-bearing-housing system. The combined model was then used to investigate the effects of bearing clearances and housing clearances. It was found that as the rotor is deformed due to external loading, the clearances have a significant impact on the bearing varying compliance motion and reaction moments. Results also show that the deformation of the flexible housing depends on the total force and moment generated within the bearing due to rotor deformation. The first critical speed of rotor was simulated to investigate the unbalance response of the rotor-bearing system. It was demonstrated that rotor critical speed has a significant effect on inner race displacement and reaction moment generated at bearing location. The dynamic behavior of the cage in a ball bearing was studied using experimental and analytical investigations. For the experimental investigation, a wireless sensor telemeter system was designed and developed to monitor the cage motions. The sensor, which was integrated on the bearing cage, is comprised of a commercially-available capacitor-inductor (LC) circuit. The LC circuit on the rotating cage was coupled to a transceiver which was stationary and positioned in close proximity to the cage. In order to achieve the objective of the analytical investigation, the explicit finite element method (EFEM) was used to simulate the bearing cage. The EFEM cage model was then combined with the dynamic bearing model to simulate the cage motion during operation. The results from the experimental measurement using the telemeter were then compared with the analytical modeling. The developed telemeter demonstrated the capability of the cage telemeter in detecting various bearing frequencies. These include: the cage frequency, shaft frequency, and ball pass frequency on outer race (BPFO) which was introduced by creating a spall on bearing outer race. Compared to standard accelerometers which are commonly used to measure vibrations on the bearing housing, the cage telemeter has shown advantage in sensing cage motions and detecting bearing defect regardless of the location of the damage. Analytical simulation using the EFEM cage model correlated well with the experimental results and provided more insight into the bearing cage dynamics

Elastomer bushing response: experiments and finite element modeling

 Elastomer bushings are essential components in tuning suspension systems since they isolate vibration, reduce noise transmission, accommodate oscillatory motions and accept misalignment of axes. This work presents an experimental study in which bushings are subjected to radial, torsional and coupled radial-torsional modes of deformation. The experimental results show that the relationship between the forces and moments and their corresponding displacements and rotations is nonlinear and viscoelastic due to the nature of the elastomeric material. An interesting feature of the coupling response is that radial force decreases and then increases with torsion. The experimental results were used to assess bushing behavior and to determine the strength of radial-torsional coupling. The experimental results were also compared to finite element simulations of a model bushing. While finite element analysis predicted small displacements at the relaxed state reasonably well, the response to larger radial deformations and coupled deformations was not well captured.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42461/1/31630025.pd

Lightweight design of a suspension arm by friction stir welding

The research seeks initially to investigate why a greater shift to lightweight technologies for suspension design has not occurred already over the mass market vehicle sector. It outlines the 'knock-on' benefits of lightweight design and identifies roadblocks which hinder progress. Recent annual metrics of vehicle performance related to mass are investigated. Focusing on individual areas of the suspension, benchmarking identifies the best practice amongst current designs. Manufacturing and process engineering strategies are proposed to support the development of lightweight products with considerably improved environmental acceptability.MIG (Metal Inert Gas) welding, universally accepted as the default joining technology in this field, was found to be restrictive to progress due primarily to detrimental effects on metallurgical, dimensional and process variation on both steel and aluminium products. The latest construction materials were reviewed for suspension application, but the focus remained on proposing light weighting solutions for material generically available in economic volumes today, but with new joining technologies to overcome current restrictions in using less of these materials for each component. Following a full review of the joining technologies available for automotive suspension construction, friction stir welding (FSW) was proposed as an alternative joining technology, with FSW replacing MIG in conjunction with extruded aluminium materials. This removed the barriers incumbent in the use of MIG, which demands a more conservative, heavier design to ensure adequate service lifetime. Design concepts were engineered to take maximum advantage of the strategy of aluminium, extrusions, assembled with friction stir welding. Several viable designs were conceived, from which two were developed and compared. The optimum design was then carried forward into a manufacturing feasibility stage. The extrusions were developed for ease of manufacture, and friction stir welding trials progressed on coupons (plain plates) to ensure that the process was viable. Aluminium in the soft and hardened conditions in different thicknesses and joint configurations were successfully friction stir welded during the trial. Future work would develop the extruded aluminium arm further, into the prototype phase, with sample extrusions being manufactured, FSW welded and assembled. Prototypes would then be rig tested to ensure mechanical and durability performance prior to vehicle trials. There are also possibilities in developing high strength thin wall multi-phase steel solutions, utilising Friction Stir Spot Welding (FSSW). This welding technology enhances the selection of high strength steels, as minimal strength is sacrificed during the joining operation

Experimental and numerical investigation of rubber damping ring and its application in multi-span shafting

A new approach for establishing the mechanical model of the rubber damping ring was studied numerically and experimentally. Firstly, parameters of Mooney–Rivlin and Prony series models of the rubber material were identified based on ISIGHT integrating with ANSYS and MATLAB, in which the rubber damping ring’s hysteresis loop was obtained by vibration experiment and ANSYS simulation, respectively; meanwhile, the dynamic stiffness and damping were calculated simultaneously by a parameter separation and identification method. Subsequently, the accuracy of the constitutive model parameters was verified experimentally. In the light of this, based on the experimental design and the approximate model method of the joint simulation platform, a mechanical model of dynamic stiffness and damping of the rubber damping ring was established. Finally, the rubber damping ring’s mathematical model was employed to perform a vibration reduction analysis in a multi-span shafting, where the numerical and experimental investigation was conducted, respectively. The results show that the theoretical and experimental error of vibration reduction rate is less than 17%, which verifies the accuracy of the mechanical model of the rubber damping ring

Updating Finite Element Model of a Wind Turbine Blade Section Using Experimental Modal Analysis Results

This paper presents selected results and aspects of the multidisciplinary and interdisciplinary research oriented for the experimental and numerical study of the structural dynamics of a bend-twist coupled full scale section of a wind turbine blade structure. The main goal of the conducted research is to validate finite element model of the modified wind turbine blade section mounted in the flexible support structure accordingly to the experimental results. Bend-twist coupling was implemented by adding angled unidirectional layers on the suction and pressure side of the blade. Dynamic test and simulations were performed on a section of a full scale wind turbine blade provided by Vestas Wind Systems A/S. The numerical results are compared to the experimental measurements and the discrepancies are assessed by natural frequency difference and modal assurance criterion. Based on sensitivity analysis, set of model parameters was selected for the model updating process. Design of experiment and response surface method was implemented to find values of model parameters yielding results closest to the experimental. The updated finite element model is producing results more consistent with the measurement outcomes