Fracture Failure Analysis Of Cooling Ribs Of Vermicular Graphite Cast Iron Brake Disc

Vermicular cast iron brake disc is a key part of the braking system of passenger train,along with the development of rail transportation,the crack appeared frequently in recent years,most lateral ribs of vermicular iron brake disc may appear crack within service life,or even fracture,this situation has seriously affected the running safety of train.The research on the crack and fracture failure of the cooling ribs of the vermicular iron brake disc is of great significance to ensure the safety of the speed increasing passenger train.The service conditions of passenger trains vermicular iron brake disc based on the method of material analysis and finite element simulation technology combined,reveals the cooling ribs of the vermicular iron brake disc fracture failure mechanism,put forward the improvement measures of production and quality of service process.The main contents and conclusions of this paper are as follows:(1)the failure of the brake disc and the brake disc performance without the use of foundation and organization in the study of fracture morphology and analysis of passenger train vermicular iron brake disc fracture ribs on the failure form of ribs is brittle cracking,put forward the existence of flake graphite and ribs weakens the mechanical properties is caused by the internal cause of crack initiation and propagation.(2)according to the cross section of the outer layer of cooling ribs found flake graphite,the solidification simulation analysis,to determine the cause of cooling rib surface layer appear flake graphite is the cooling speed causes the solidification process of the formation of B type of flake graphite,slow cooling ribs,put forward improvement measures to reduce or eliminate the flake graphite.(3)on the basis of testing the mechanical properties and thermal properties of the material,the thermal mechanical coupling finite element temperature field and the stress field simulation technology of the vermicular iron brake disc under the service condition of the passenger car are established by using ANSYS software.The temperature test of the 1:1 power brake platform shows that the error of the finite element simulation technique is less than 10%,and the simulation precision is very good.(4)the analysis of temperature field and stress field under different braking conditions.Finite element analysis shows that two consecutive emergency braking at 180km/h speed,the peak temperature of the braking process reaches 400 ℃ vermicular cast iron brake disc allowable temperature;if the locomotive brake and brake pads are not involved in eccentric wear,160km/h speed from the whole of the brake temperature can reach 397 ℃,and 180km/h speed for two consecutive times the maximum temperature of emergency braking and the maximum stress level is similar.Based on the simulation results,some effective measures are proposed to ensure that the brake is involved in the braking process and reduce the brake wear.(5)for radiating rib crack and fracture problems,simulation study on the force situation of different positions based on ribs,studies showed that the lateral ribs root during the braking process of the maximum stress and tension and compression under cyclic stress,which is the external reason of radiating rib crack initiation and propagation.The fracture appearance of ribs of vermicular cast iron brake disc analysis,microstructure and properties of the finite element simulation technology,reveals the cooling rib crack and cracking mechanism,the proposed improvement measures have important guiding significance to improve the vermicular iron brake disc product quality and operation safety.