Research On High Precision Modeling Technology Of Automotive Suspension Shock Absorber

Nowadays damper enterprise’s product design still mainly takes the traditional mode, i.e., combination experience with trial, which has low design accuracy, long development cycle and high cost. The mainly reasons of that can be summarized into two points. Firstly, because there have not been exact formula which can directly utilized for the deformation of the throttle valve and the theoretical calculation of its throttle characteristic, the solving precision of the established damper performance parameter model is very low and it is difficult to design a shock absorber to meet the engineering requirements. So, many experiments should be performed on the test sample to adjust the design parameters. Secondly, because of the unknown throttle valve’s opening law in the internal 3-dimensional finite element model of the shock absorber after the valve opened, the boundary conditions of coupling surface between the fluid and throttle are difficult to be defined accurately such that the accuracy of the established flow model is difficult to achieve the engineering requirements. Therefore, there exists a certain deviation of the conclusion from the flow model which the designed damper flow path and valve structure are unreasonable. Many experiments should be performed to make some adjustments on the test sample. However, the modern automobile companies have proposed an advocacy of ’Vehicle-Parts Synchronous Development’, and the damper enterprise cannot follow the pace of vehicle enterprise’s new product development in the traditional design pattern which seriously affects the shock absorber company’s product competitiveness. Based on those reasons, this paper focuses on the high-precision modeling techniques for dampers. The main contributions are shown as followings:First of all, through investigation and analysis of domestic scholars on the shock absorber performance simulation of high precision modeling method, the modeling method is proposed for the first time, which combines local 3D model, overall three-dimensional model and one-dimensional performance analysis model. Combined with the local three-dimensional finite element model and the characteristics of the product standardization and series of shock absorb, a local finite element calculation parameter management system is established. The stiffness of throttle valve combinations and throttle characteristics of orifices, that are existing in the enterprise, are solved by using the finite element software, then stored the results into the damper parameter management system, once the results are needed, enterprises can realize rapid call, to further shorten the damper development and debugging cycle.Secondly, a passenger car rear suspension with dual cylinder pneumatic hydraulic damper id selected as the research object. The mathematic model is established by analyzing the damper structure and working principle, then one-dimensional simulation model of shock absorb is constructed in AMESim.Third, verify the local three-dimensional model and one-dimensional performance analysis model to meet the requirements of high accuracy and high efficiency. The method is discussed, which to solve throttle valve stiffness and the throttle orifice characteristics quickly and accurately by establishing the local finite element model in ADINA. Drop-volumetric flow rate of orifice and stiffness of throttle valves which acquired by simulation are imported into AMESim simulation. Compared the results of simulation and experiment shows:shock absorber in 0.05m/s,0.3m/s,0.6m/s and 1.0m/s four conditions the maximum error of maximum damping force of the simulation results and test results are less than 7%, the maximum error of the damper acting (i.e. dynamometer enclosed area) does not exceed 3%, F-V curve substantially coincide. And compared the accuracy of solution and the efficiency with the existing modeling. Finally comes to the conclusion that the modeling method proposed in this paper is indeed feasible, which obtained from the modeling method, the accuracy of the model and the solving efficiency were higher than that of the existing modeling methods.Finally, verify the performance of the one-dimensional model with the overall three-dimensional flow model of combining modeling idea to meet the requirements of high accuracy and high efficiency. Established damper compression and restoration process flow model, based on the model of internal flow field, for fluid model after opening the valve, the fluid and the throttle valve coupled boundary conditions are defined by the throttle valve opening rules which extracted from the one dimensional simulation results. The damping characteristics of the 0.05m/s and 0.3m/s two working conditions of the open valve are calculated. By comparing the simulation and test results, the error before the open valve flow model maximum damping force is less than 8%, the error is less than 3% after the opening of the valve. And compared the accuracy of solution and the efficiency with the existing modeling. Finally comes to the conclusion that the modeling method proposed in this paper is indeed feasible, which obtained from the modeling method, the accuracy of the model and the solving efficiency were higher than that of the existing modeling methods. The distribution of the stress field and velocity field of the vibration absorber before and after the valve opening is analyzed.