| Leaf spring is an important elastic component of vehicle suspension system,its strength and stiffness characteristics directly affect the vehicle's driving and handling stability.With the lightweight becoming the mainstream technical requirements,the taper leaf springs has been widely used because of its advantages of light-weight and long service life.The traditional design method of taper leaf springs is mostly based on the three-stage model.Although it is convenient for calculation,it is quite different from the shape of the variable section spring produced in practice,which makes it impossible to accurately calculate the spring stiffness and maximize the material utilization.In view of the above problems,this paper mainly carried out the following work:(1)The transfer matrix method for calculating the stiffness of taper leaf spring is established.Based on the theory of Euler-Bernoulli,the taper leaf spring is discretized into a series of trapezoidal beam elements.Based on the accurate analysis of the deformation characteristics of trapezoidal beam elements,the formulas for the Angle and deflection of trapezoidal variable section beam elements are derived.Combined with the force analysis of half leaf spring,the transfer matrix method for calculating the stiffness of a piecewise trapezoidal variable-section leaf spring is established.Considered the influence of section deformation on the calculation accuracy of stiffness,the correction coefficient of section deformation was obtained through the strength and stiffness test of springs.Finally,a numerical example is given to verify the validity of the proposed transfer matrix method.(2)A new optimization model of "five-stage standardization" taper leaf springs is proposedWith the aim of minimizing mass and considering the stiffness,strength and manufacturing process constraints of the suspension assembly,a new "five-stage standardization" optimization design model is proposed.The GUI optimization design program was developed by using Matlab as the development platform.The effectiveness of the optimization design model is verified by the case design of different forms of plate spring sheet and plate spring assembly.(3)The fatigue life analysis method of taper leaf spring was researchedBased on the nominal stress method for analyzing the fatigue life of leaf springs,the modified S-N curve of material was studied on the precondition of considering the influence factors such as surface roughness,heat treatment and shot-peening.Combined with the results of finite element simulation,the fatigue life cloud chart of taper leaf spring is obtained and the fatigue hazard area is determined.By controlling a single variable of residual compressive stress in the fatigue software to simulate the fatigue life of the taper leaf spring under different shot peening strength the influence law of residual compressive stress on the fatigue life was obtained.(4)The performance test of variable cross-section leaf spring was carried out.According to the standard test code,the strain electrical test,static load stiffness test and fatigue test under vertical load for the single and assembly structures of variable cross-section leaf spring studied in the previous paper are carried out.According to the error analysis of test data,the relative deviation is determined whether it meets the accuracy requirements of Engineering test.It provides effective data support for the transfer matrix method of stiffness calculation deduced in this paper and the five-stage optimal design model proposed. |
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