Fatigue Life Simulation Analysis And Test Verification Of Leaf Spring Rubber Bearings For Heavy Trucks

The key load-bearing components of heavy vehicles are leaf spring rubber bearings,that can cushion and block the-impact force.However,their development are largely limited by the poor fatigue durability.Therefore,the study on fatigue mechanism of rubber bearings is a critical issue.Compared to traditional fatigue life tests,finite element analysis is employed to investigate fatigue mechanism,due to its short development cycle,high efficiency,and low cost.Based on the nonlinear viscoelastic theory and fatigue crack expansion theory,this thesis realizes the prediction of fatigue life of leaf spring rubber bearing,and optimizes the design of the leaf spring rubber bearing.The research and results are as follows:(1)With real structural parameters provided by China national heavy duty truck group as reference,the accurate construction of the geometric model of the plate spring rubber bearing was realized.Through the experimental testing of material mechanical properties,the hyperelastic constitutive equation of rubber and the elastoplastic mechanics of metal are obtained by fitting.Based on the study of mesh convergence,the mesh type of rubber is determined to be hexahedral cells.The global optimal mesh density is about 90,000 units.Combined with the specific assembly process of the support,the corresponding loading analysis step and interaction relationship are set.The forcedisplacement curves under the vertical and tangential loading conditions are investigated,and the static stiffness is calibrated with the test stiffness,and the error is only 4.4%.(2)Based on the fatigue crack expansion theory and rubber viscoelasticity theory,a joint Abaqus and Endurica simulation method was established to analyze the thermally coupled fatigue life of the leap spring rubber bearing.The simulation predicts the thermally coupled fatigue life of the leap spring rubber bearing under a vertical 260 k N compression load.The error of the hysteresis temperature is 5.2% compared with the experimental results.The error of the fatigue life under the consideration of thermally coupled heat generation is 4.1%,which is 58.3% lower than the result without considering the heat generation effect.(3)According to the phenomenon of permanent deformation of the leap spring rubber bearing after fatigue failure,the fatigue life of the leap spring rubber bearing under deformation failure mode is simulated and studied based on the thermal coupling fatigue life simulation analysis method established in(2).The results show that,when the compressive load increases,the longitudinal height difference between the two ends of the bearing plate gradually increases and remains stable after a certain degree.Under the same compression load,when the offset grows,the degree of permanent deformation of the rubber bearing gradually increases,the hysteresis temperature distribution becomes more uneven,and the fatigue life is greatly decreased.(4)The optimized design of the structure of the leaf spring rubber bearing was studied.It was found that the fatigue life could be significantly improved by adding a trapezoidal reinforcement structure with a thickness of 2 mm at 5mm from the edge of each inner steel plate and a bottom of 6 mm and 8 mm at the top and bottom respectively.The results showed that the fatigue life of the new structural support increased by 2.2 times under a vertical 260 k N compressive load and increased by 3.7 to 4.5 times under a vertical 170 k N compressive load(at 8 mm to 16 mm from the center point of offset),and the degree of permanent deformation decreased by 7.7% to 9.1% compared with the original support.The new structural support was experimentally verified by bench fatigue testing(260 k N compressive load).Compared to the test results,the error in static stiffness was 6.4% and the error in fatigue life was 5.3%.