Experiment On Friction And Wear Of Rubber Material Of Aviation Tire And Molecular Dynamics Simulation

In the overall structure of aviation aircraft,tire is the most critical part,is an important factor affecting the safety of aircraft operation.Authorities have found that more than half of all plane crashes occur during takeoff and landing,80%of which are related to tires.The airplane tire always faces the extremely complex working condition in the use process:the high speed,the high load,the high inflatable pressure and the big deformation.The friction and wear of tires under such extreme conditions seriously affects the safety of aircraft.However the lack of research in this field in China has seriously restricted the development of aviation tire manufacturing of large aircraft.Therefore it is imperative to study the friction and wear of aviation tire under this condition.This paper based on the large aircraft aircraft tire characteristics of extreme conditions in practical application,the self-made friction wear testing machine simulation landing aircraft tire process,examines the friction and wear of tire under different conditions and the distribution of chip size and the wear quantity and particle size distribution of four kinds of softener rubber system.The experimental test results show that with the increasing of rotating speed and load,the wear amount of aviation tire increases continuously.Among them,the influence of rotating speed on the wear amount of aviation tire is the most obvious,followed by the load.In addition,the mass proportion of tread rubber abrasive chips in the range of particle size greater than 1mm and 0.1-0.4mm is large,while the mass proportion in the range of 0.4-1mm is relatively small.Among the four softener rubber systems,the rubber samples of TDAE had the largest wear,followed by styrene resin,which had poor wear resistance compared with DAE,while the petroleum resin of C9 had the smallest wear and the best wear resistance.Moreover,DAE,TDAE and styrene resin had similar distribution patterns of abrasive particles in the rubber system.In all cases,the mass proportion of abrasive particles in the range of 0.1-0.4mm was high,while the proportion in the range of greater than 0.4mm was low,indicating that the abrasive particles of the three rubber systems were relatively small.In the rubber system with softener C9 petroleum resin,the mass proportion of the particle size greater than 1mm is high,indicating that the particle size is relatively large in this rubber system.In order to simulate the friction and wear of tire under dry and wet conditions,an improved Akron grinding machine was used to test the relationship between different roll ratios and the friction and wear properties of rubber materials under dry and wet conditions.The results show that under dry wear condition,the volume wear of tire sample is proportional to the slip-roll ratio.While under wet wear condition,the volume wear is inversely proportional.And under high slip-roll ratio,the wear of dry wear is far greater than that of wet wear.By analyzing the morphology of the tire samples under dry wear condition,it is found that the wear strength increases with the increase of the sliding-roll ratio and the corresponding particle size also increases.The wear surface of the high sliding roll is large and many and has serious curling deformation.Moreover,the surface morphology of tire samples with different sliding and rolling ratios after wear can be divided into three regions:L,M and R.With the gradual increase of the slide-roll ratio,the degree of adhesive tearing in the M region became larger and larger,and the yarn Mach pattern in the L region and R region did not change significantly.However,under the condition of wet abrasion,the whole rubber strip has no obvious three zones and the overall morphology is uniform.When the sliding roll is relatively low,the wear surface is subjected to severe abrasive wear.With the increase of the sliding roll ratio,the abrasive wear degree gradually decreases,and the curling wear occurs at the same time.When the slip-roll ratio increases to a certain extent,adhesive fatigue appears on the worn surface.As the slip-roll ratio continues to increase,the degree of adhesive fatigue increases,and the abrasive debris gradually becomes less and almost disappears.Finally,the molecular dynamics method was used to simulate the cracking behavior of the polyisoprene rubber system at different temperatures.The results showed that the chain number of rubber molecules decreased gradually and the number of molecules and molecular types increased gradually during the heating process.At different temperatures,the higher the temperature of the polyisoprene rubber system,the more complete the pyrolysis will be,and the more the final small molecule products(C1,C2,C3 will be obtained,as well as the more types and number of molecules.Among the final products of pyrolysis,C4-C9 is the largest,C5H8 and C5H9 are the main ones.The results showed that the temperature change only affected the reaction rate and cracking degree,the reaction path and the final product were basically unchanged.Different chain length systems were selected to crack at the same temperature.It was found that with the increase of molecular chain length,natural rubber molecules began to crack faster and faster.In addition,the number of small molecules produced increased significantly after Nr=10.In all the systems of Nr>30,the number of rubber molecules was 0 at the beginning of cracking,indicating that the increase of chain length would accelerate cracking.However,the cracking situation generated after the increase to a certain value did not change much.