Research On Fatigue Characteristic Of Coupler Knuckle On Heavy-load Wagon

Coupler is one of the most important bearing weight parts of heavy haul train which is related with the safety and reliability of the train-running. With the further development of railway transportation of freight wagons running at higher speed and heavier load, the portrait wallop of freight wagon increases rapidly and damage of coupler knuckle is becoming more and more critical which has influenced the safety and benefit of railway transportation, so, it is necessary to study the fatigue reliability of coupler knuckle to improve its fatigue lifetime. The objects researched in this paper are the types of no.16 coupler knuckle, which is widely used on heavy load wagon in china.The contents of this paper can be summarized as follows:Firstly, the static strength of the coupler knuckle was analyzed with NX-IDEAS software and the stiffness and strength weakness point of coupler knuckle could be found through researching the regularity of deformation and stress region which could offer reference for the fatigue life estimation.then multi-body contact FEM was established based on NX-IDEAS software and was calculated for elasticity and plasticity analysis. From the calculation result we can obtain that the weakness point of this component is the part with the highest stress where crack used to happen.Secondly, based on the finite element results calculated by software NX-IDEAS and coupler load chart of freight wagons in AAR standard, germination life of coupler knuckle can be calculated with material's P-S-N curve by using the software FE-SAFE which is specially useful in analyzing fatigue lifetime for structure; Growth life can be calculated with the crack growth rate according to fracture mechanics theory. Fatigue lifetime of coupler knuckle was calculated by adding its germination life to growth life which showed great consistency with its actual serving time.Finally, apply the elasticity-plasticity fracture criterion in combination with software NX-IDEAS and fracture mechanics theory to study ultimate carrying capacity of coupler knuckle in which some crack appears. Results show that with the crack dimensions growing greater, the ultimate carrying capacity calculation of coupler knuckle reducing faster.