Stress Relaxation Characteristic Analysis And Service Life Evaluation Of Helical Compress Spring

Spring is an elastic element widely used in the field of aerospace and modern weapon equipment.Fatigue fracture and stress relaxation are the main failure modes of springs.In the process of long-term operation of aerospace vehicles or long-term storage of modern weapons and equipment,the spring in mechanism often appears stress relaxation phenomenon.The performance degradation or failure of elastic components due to stress relaxation will affect the normal operation of the whole system.Therefore,it has important engineering application value and significance to study the stress relaxation law of spring and predict its service life.In this paper,the spring in the upper lock of an aircraft cabin door is taken as the research object.The stress relaxation characteristics of the helical compression spring at high temperature are studied by stress relaxation test,theoretical derivation and numerical simulation,and the service life of the spring stress relaxation at room temperature is predicted.Firstly,aiming at the defects of traditional spring stress relaxation testing method,a continuous dynamic testing device for spring stress relaxation is built.The device can ensure that the loading displacement of stress relaxation test is constant,and the load change can be monitored in real time.The stress relaxation test of the helical compression spring in th,e door lock mechanism of an aircraft cabin was carried out under different temperatures and loads,and the relaxation dynamic curve was obtained.The stress relaxation service life prediction model of the spring at room temperature was established based on Arrhenius model.Secondly,based on the unification of stress relaxation and creep phenomena in mechanism,the creep constitutive equation describing the stress relaxation behavior of spring materials is derived by using the creep theory of metal materials and the stress characteristics of cylindrical helical springs.The material constants of the creep constitutive equation are obtained from the stress relaxation test results.Finally,according to the creep constitutive equation and material constants,the stress relaxation process of spring is simulated by ANSYS finite element software,and the stress relaxation curves of spring under different initial loads are predicted.The results show that the finite element simulation results are consistent with the stress relaxation test results,and the accuracy of creep constitutive equation based on spring relaxation test data is verified.