Heavy Truck Brake Drum Failure Analysis And Countermeasures

Automotive Braking System is an important component of vehicles and directly impacts on the safety of automobile driving.In order to comprehensively carry through and implement the spirit of "the State Council on strengthening the work of the energy-saving",the ministry of communications encourages companies to development the high-speed and heavy-haul vehicles.Since 1999,the sales of the heavy truck have been a strong growth trend.At present,mechanical friction braking way is the main one of braking system for heavy lorry.Under the conditions,frequent or long-time braking has brought new challenges to the working life of the braking drum.The motor vehicles and parts industry are the development emphasis of machinery industry in Yunnan province,moreover,Jinning County in Kunming is the largest production base of the brake drum in China. Therefore,the thesis mainly does the researches on the failure mechanism and countermeasures to prolong the service life of braking drum for heavy truck.First,it analyzed the failure of braking drum by cheesing the typical failure parts,including the understanding of the background,the macro-examination,the chemical composition,Mechanical Properties microstructure and so on.The brake drum' s performance can not meet the heavy load vehicles brake drum performance requirement and the improper operation by users makes it early fail.Secondly,because the performance of the braking drum can not meet the brake drum performance requirement of the heavy load vehicles,we do some researches on it.Through the analysis of the quality requirements of the brake drum get the conclusion that the tensile strength must be greater than 160 MPa,the hardness must between 170HBS and 240 HBS,more pearlite, medium length A-type graphite,appropriate suitable alloying elements.In order to ensure its quality and consider the economic factors,the content of carbon is about 3.7%and can add a small amount or amount of Sn,Sb, Cr,Cu or other elements.22 programs had been designed,through the analysis of the chemical composition,the mechanical properties,the microstructure and the heat fatigue get the conclusion that three programs that Sn(0.04),Cu(0.2%)and homemade inoculant(0.6%)suit for the material of the heavy load vehicles brake drum.Also,we do research on the gray cast iron which is different from partite,the conclusion is that the gray cast iron that the content of pearlite between 5%and 15%has better heat fatigue properties.To do research on the gray cast iron having different tensile strength,the experiments show that the gray cast iron that the tensile strength is about 250MPa has better heat fatigue properties.To do research on the ferrite ductile iron,the conclusion is that the ferrite ductile iron have good heat fatigue properties.Compacted graphite cast iron is one of the ideal material of the heavy truck brake drum.Based on the above findings and the actual situation of the manufacturers,five programs had been poured to braking drum,through the analysis of the chemical composition,the mechanical properties,the microstructure and the heat fatigue,three programs that Sn(0.02%), Sn(0.02%)+Cr(0.1%),and SiCaBa bred have been test by loading,the failure rate was 0%,considering the economic factors,SiCaBa is the best program.Finally,other proposals for correctly operating the vehicle, correctly maintaining the brake drum and improving the structure are presented to extend the service life of the braking drum.The innovation of the thesis:the self-made thermal fatigue simulation device has some advantages of equipment simple,low production costs,the better reflect the actual brake drum conditions,convenient operation and small experimental error.