Study On Fatigue Life Prediction Of SiC Particle Reinforced Al-Si Alloy Composite Prepared By Spray Deposition For High Speed Train

With increasing the speed of high-speed train,higher performance of the braking technology and braking device of the train is required.Uniform thermal stress formed during braking results in heat spots on the brake disc,which promotes crack initiation and propagation,causing the fracture failure ofbrake disc and affecting the running safety terribly.Spray-deposited SiCp/Al-Si composites,as ideal substitute materials for brake disc steels of high-speed train,possess many advantages such as low density,high specific strength,high specific stiffness and low thermal expansion coefficient.Spray-deposited SiCp/Al-Si composites have been developed yet,however,researches on their fatigue behavior,especially fatigue life prediction,are few,restricting structure design and engineering application of the material Therefore,the fatigue life prediction of spray-deposited SiCp/Al-Si composites brake discs is studies in this paper.built.The main research results are as follows:(1)The effect of SiC particle size on the indirect strengthening yield strength is established based on the mixed strengthening model.Subsequently,the indirect strengthening is used as the yield strength value of the composite matrix,which is replaced by the modified shear lag model(direct strengthening).Finally,a mixed strength yield prediction model for spray deposited SiCp/Al-Si composites based on SiC particle size is established.Compared to the experimental data,theoretical calculation of the model can predict the yield strength of aluminum matrix composites with different SiC particle sizes.(2)The influence of SiC particle size on fatigue life predication is discussed.The particle strengthening mechanism is introduced into the plastic strain,the driving force of the fatigue crack tip is calculated,the fatigue crack propagation rate is calculated with the J integral,and the low cycle fatigue life prediction model of the spray deposited composite material based on the SiC enhanced particle size is obtained.The calculated value of the model was in good agreement with the experimental data.(3)The fatigue life prediction with different initial speeds considering conventional braking and emergency braking is studied.The temperature distribution is calculated by stimulation and internal stress state is analyzed,the fatigue life of spray deposited Al-Si composite brake discs in the braking temperature and load is predicted finally.The results show that the spray-deposition aluminum matrix composites have good fatigue resistance and better service life.It is further proved that the material is an ideal new-style brake disc material.