Rubber bushing is an engineering material with good elasticity, which can withstand large strains without permanent deformation and fracture. In the automobile industry, rubber materials are widely used in various shock and noise reduction devices. In the development of rubber products, durability is the key performance, because the fatigue failure of rubber bushings will greatly affect the stability and comfort of the entire vehicle, and even affect the normal safety performance, leading to accidents.
At present, the design and development of domestic rubber products mainly rely on tests for verification, resulting in long product design cycles and high development costs. If in the early stage of project development, through the method of virtual simulation analysis, the durability of the rubber bushing can be effectively predicted, and a lot of costs can be saved, and the development cycle can be shortened.
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1. The establishment of CAE mesh model of rubber bushing
Considering the large deformation of rubber, it is necessary to use hexahedral mesh elements for simulation calculation to obtain correct results. However, if the model structure is complex, hexahedral modeling is often very difficult. Rubber bushings need to consider the NVH performance of the vehicle, and the rigidity requirements in each direction are different, so the structural design is more complicated, making hexahedral mesh modeling very difficult. For different rubber bushings, we have formulated a variety of different bushing modeling methods. The following figure shows the modeling method of a certain swing arm comfort bushing.
2. Calculation of stress and strain of rubber bushing based on ABAQUS
Based on the ABAQUS software, select the appropriate rubber constitutive model to calculate the stress and strain of the rubber bushing. Because the rubber bushing must ensure the NVH performance of the whole vehicle, the general movement stroke is very large, so the strain of the bushing is extremely large. When the stress-strain nonlinear calculation is performed, it is easy to not converge, and the next fatigue calculation cannot be performed. By adjusting the finite element model, increasing the convergence control coefficient, and improving the stiffness of the hourglass, the convergence results can be obtained.
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3. Obtaining the fatigue parameters of rubber materials
The rubber crack growth method mainly studies the number of cycles that the initial micro cracks pre-existing in the structure expand to the critical size under various use environments. Most of the life of rubber parts depends on the growth of small cracks. Through a series of fatigue tests, the relationship between the rubber crack growth rate and the energy release rate can be obtained to form a crack growth parameter model. The Lake-Lindley model is used to study the fatigue life, and the material tests are performed to obtain the necessary parameters of the fatigue model, that is, the Lake-Lindley model of crack growth.
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4. Fatigue calculation of rubber bushing based on FE-SAFE RUBBER
The FE-SAFE RUBBER module is currently the only commercialized rubber fatigue analysis software. The calculation can be carried out after inputting the stress and strain results of the part and the load history. Support a variety of stress and strain calculation software interfaces, such as NASTRAN, ABAQUS, DYNA, etc. Comes with a variety of fatigue parameter curves for commonly used rubbers, and supports actual fatigue test parameters.
5. Typical case of fatigue simulation of rubber bushing
The following figure is the fatigue simulation calculation result of a
Suspension Bushing. It can be seen that the maximum damage position and the maximum stress and strain position are different, so it is necessary to perform fatigue simulation analysis.
There are still many problems to be solved in rubber fatigue simulation technology. The calculation of the large strain of rubber is still unstable: For example, there are many kinds of rubber materials, and the rubber formulas of different manufacturers are different. We only completed a few rubber material tests, and also spent a lot of money. Each type of rubber is tested. , It is definitely unrealistic. For example, the difference between simulation results and actual results requires further benchmarking. Therefore, the development of rubber fatigue simulation technology is a long way to go!
