The Design And Development Of Air Spring Fatigue Testing Machine

Fatigue failure is the major failure form of air-spring.In order to improve the quality of product,it is necessary to study the fatigue life of air-spring.The force of an air-spring in development phase predicted by the finite element method is used to design a fatigue testing machine.The main characteristic of this testing machine is the low energy consumption during working process,low manufacturing costs,and the ability to adjust the test amplitude and frequency.The experimental working condition is also close to the real working state of air-spring.To accurately estimate the maximum working load of the testing machine,the finite element method is used to simulate the maximum force of an air-spring in development phase in this paper.Based on theoretical deduction,the influence of model parameters and work parameters on stiffness is analyzed qualitatively.A finite element model of an air-spring with similar structure and type is built by using ABAQUS software,and the reliability of the modeling method is verified by the static stiffness test.Then using this method to build the finite element model of the air-spring in development phase and the stiffness test results are found similar to the simulation results.The influence of the initial pressure and the cord parameters on the mechanical properties of the spring is analyzed,and the maximum force is calculated in the influence of these parameters.Structural design and motor selection.By determine the exciting mode and whole structure of testing machine,the positions of cantilever beam support and fixture center are verified to meet enterprise requirements.Then calculate the length of crank connecting rod and eccentric distance under specific test amplitude requirements,and design a GUI interface for solving eccentricity.The LMS Virtual Lab is used to simulate the motion of machine and obtain the displacement and velocity curves of the testing machine.The rationality of the design of crank eccentric mechanism is verified and the test machine is proved to simulate the working state of air-spring,then calculating the angle between spring force and vertical direction in the movement process.The demand of driving force of test machine is analyzed under a variety of arrangement.Then the minimum energy consumption arrangement is selected and the motor power is calculated under this arrangement.Structural performance analysis.The finite element model of rack and beam is established to calculate the deformation of rack under the action of gravity and maximum air-spring force and to improve the rack structure to meet the test requirements.Then stress status of rack and beam in the extreme conditions is analyzed with the modal and fatigue analyses.Through the above analysis,the structural strength of the test machine is verified meeting the requirements.Testing machine manufacturing and testing capability verification.According to the design requirements,the testing machine manufacturing is completed outsourced.The actual structures of the testing machine are introduced,and the basic parameters of pressure sensor and Hall proximity switch are explained.The testing machine has been applied to the fatigue test of an air-spring and the test time up to 121.3 hours that fully proves the validity of the design method of the mechanical air-spring fatigue testing machine proposed in this paper,and the test results provide the basis for the further improvement of product quality.