Research On Stress Field Characteristics And Life Prediction Of Surface Cracks Under Friction And Fatigue Composite Action

Crack problem is ubiquitous in practical engineering,and it is the main cause of engineering accidents.Tensile load is the main form of load which causes fatigue damage of cracked components.For structure with initial cracks,the propagation of cracks under tensile load plays a crucial role in the prediction of their useful life.In this paper,the sliding friction fatigue system is taken as the research object.Based on the theory of fracture mechanics,the effect of sliding friction effect on crack propagation is analyzed by finite element method.The main work is as follows:Firstly,the finite element model with 1/4 ellipse crack was constructed by using ABAQUS software.The singularity of stress field at crack tip was processed by ABAQUS finite element software,and the crack growth process was simulated.The stress intensity factor of crack tip was calculated by ABAQUS finite element method and compared with the theoretical value to prove the feasibility of finite element method for calculating stress intensity factor.Secondly,a typical sliding friction-fatigue finite element model was established.By using the finite element method to simulate the sliding friction process,the equivalent stress contour of the crack tip with time was obtained.The variation of stress field at the surface crack tip was analyzed under different normal loads,different friction coefficient and different sliding velocity.The stress and temperature values on the surface of friction fatigue system increase with the increasing of normal load,sliding velocity and friction coefficient.Thirdly,the finite element model of the sliding friction fatigue under the thermo-structure coupling action is established.The distribution of the stress field and temperature field is obtained on the basis of the heat conduction of the friction,the heat conduction and the thermal convection of the external environment.The results show that it the change of normal load P has the greatest influence on the thermal stress and temperature rise of the friction fatigue system.The friction factor fs has a great influence on the temperature variation of the friction fatigue system,but has less influence on the change law of the thermal stress.The greater the sliding velocity v is,the greater the thermal stress and temperature rise of the friction fatigue system,but it is nonlinear with the velocity of the sliding block.Finally,according to the Paris formula,the fatigue crack life prediction model is given.Based on this,the fatigue life of the crack in the friction pair is estimated,and the influence of the friction effect on the fatigue life of the crack is analyzed.