| Torsion beam suspension is widely used in vehicle rear suspension systems due to its simple structure,low production cost,excellent lightweight and easy maintenance.However,the vehicle will be affected by various forces and moments on the ground when driving.The torsion beam absorbs the ground excitation through the torsion of the crossbeam member to ensure the smooth operation of the vehicle.Therefore,the crossbeam is more prone to fatigue failure under long-term load.In this paper,fatigue performance analysis of crossbeam in the torsion-beam rear suspension system under torsional condition was carried out based on the finite element simulation,and the fatigue life of the crossbeam was predicted.A new method for predicting the fatigue life of complex structural parts by using equivalent specimens in the fatigue danger area was proposed.The effect of annealing process on the fatigue performance of torsion-beam rear suspension crossbeam was investigated.The research work and its findings in this paper are as follows:(1)The finite element analysis model of the torsion-beam rear suspension was established,and the stress distribution law of the crossbeam under the torsion-beam torsion condition was analyzed.Based on the static analysis results,combined with the fatigue life curve of the crossbeam material duplex high strength steel FB590,the surface roughness and the surface residual stress of the formed crossbeam,the fatigue life of the crossbeam was calculated according to the nominal stress method and the Gerber average stress correction.Results show that the stress concentration area and fatigue danger area of the crossbeam are located at the corner of the transition section at both ends.The working amplitude-life curve of the crossbeam effectively covers all load conditions under service conditions,and the reference range of stress amplitude for the actual load spectrum was obtained by benchmarking the torsion beam bench test results.(2)Equivalent specimens with different bending radii(AR,R10 and R20)were designed based on the bending deformation degree of the crossbeam danger area,and the fatigue performance of the crossbeam danger area was characterized by the equivalent specimen tensile test and fatigue test.Results show that the pre-bending strain increases the strength of the material and improves the low-cycle fatigue properties of the bending specimens,while the reduction of elongation and the introduction of residual stress reduce the high-cycle fatigue properties of the bending specimens.The life of intersection between R10,AR,and R20 equivalent specimens is within the actual fracture life area of the crossbeam in the bench test,which effectively characterizes the fatigue performance of crossbeam dangerous area,and realized the effective prediction of the test results of torsion beam fatigue bench.In addition,a fatigue life prediction model of equivalent specimens was established based on the plastic strain energy method,which provided a basis for predicting the service life in the danger area of the crossbeam.(3)Tensile tests and fatigue tests were carried out under the annealing conditions of equivalent specimens,and the fatigue life numerical simulation of torsion beam annealed crossbeam was carried out based on the mechanical parameters and fatigue parameters of the annealed equivalent specimens.Studies have shown that the annealing treatment improves the high-cycle fatigue properties of pre-bent equivalent specimens.The fatigue simulation analysis shows that the annealing treatment improves the fatigue life of the crossbeam,especially the high-cycle fatigue performance improvement effect is remarkable,which realizes the effective verification of the bench test results of the annealed crossbeam.In addition,a fatigue life prediction model of annealed equivalent specimens was established based on the plastic strain energy method,which provided a basis for predicting the service life in the danger area of the annealed crossbeam. |
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