The Effect Of Local Contact On The Temperature Field And Friction Performance Of Brake Disc

Disc brake is one of the basic braking methods for trains.During the braking process,the surface of the brake disc cannot always maintain a high degree of contact with the brake pads.The brake disc will be affected by a variety of objective and subjective factors,which will cause the stress change of the contact surface,which will lead to the occurrence of local contact,and the occurrence of local contact will affect the heat distribution of the disc surface and influence each other,thereby causing the brake disc Defects such as thermal deformation seriously affect driving safety.Therefore,studying the effect of local contact on the temperature distribution of the brake disc and the brake pad surface is of great significance to the improvement of the braking performance of the train friction pair.In this paper,the brake pads are processed into four different local contact situations,the temperature change of the brake disc surface is obtained by a combination of test and simulation,and the difference between the results of the test and the simulation is compared and the reason is analyzed.The conclusions obtained are as follows:(1)The different contact positions of local contact have different effects on the peak temperature and temperature distribution of the brake disc surface.Under full contact,the uniformity of the temperature distribution on the disc surface is the highest,the peak temperature is the smallest,the radial temperature difference is the smallest,and the radial temperature curve is parabolic;under three-point local contact,the temperature distribution on the disc surface is similar to that of full contact,but the uniformity is reduced,and the peak temperature is equal to The radial temperature gradient becomes larger;when two points are locally contacted,the heat source is concentrated on the inner and outer sides of the disk surface,and the peak temperature is higher.The radial temperature curve is bimodal;when the two points are locally contacted in the circumferential direction,the heat source is concentrated in the middle area of the disk surface.,The radial temperature gradient of the disc surface is the largest,the radial temperature curve is a single peak shape,the peak temperature is the highest(2)The contact area corresponding to different local contact conditions and the contact position of the brake pad are different.The contact area has a greater influence on the peak temperature of the disk surface and the temperature distribution form of the disk surface.When the contact area is the same,the contact position has The influence of the temperature distribution pattern on the disk surface is the main influencing factor.Compared with full contact,the contact area of the three-point local contact is reduced by 50%,an average increase of 4%;the contact area of the two-point radial local contact and the two-point circumferential local contact are reduced by 65%,each increasing by an average of 17 % And37%;Compared with the three-point local contact,the contact area of the two-point radial local contact and the two-point circumferential local contact are reduced by 33%,and the peak temperature is increased by 12% and 22.1%,respectively.(3)As the initial braking speed increases,the peak temperature difference of the disc surface caused by local contact will increase.When the initial braking speed is 40km/h,the peak temperature of the disc surface under full contact and two-point circumferential partial contact are 44°C and 62°C respectively,a difference of 18°C.When the initial braking speed is increased to 200km/h,the peak temperature of the disc surface under full contact and twopoint circumferential partial contact is 315°C and 397°C respectively,a difference of 82°C,which is 3.5 times higher.(4)The effect of local contact on the average friction coefficient is also different.The average friction coefficient under full contact and three-point local contact is lower,the average friction coefficient of two-point radial local contact is higher,and the two-point circumferential local contact The average coefficient of friction is the highest.Under the same braking pressure,the average friction coefficient of full contact decreases with the increase of the initial braking speed,and the average friction coefficient of the other three types of local contacts first decreases and then increases.(5)There is a certain deviation between the results obtained from the test and the simulation.As the initial braking speed and brake pressure increase,the difference between the test and the simulation will increase.Compared with the simulation results,the peak temperature of the tested disk surface is higher,and the high-temperature area is also biased to the area inside the disk surface.The shape of the radial temperature distribution curve of the disk surface obtained by the two has a higher degree of similarity.At low speed and low pressure,the difference between the peak temperature of the test and the simulation is small.As the initial braking speed and brake pressure increase,the difference between the test and the simulation peak temperature becomes larger and larger.When the initial braking speed reaches 200km/ At h,there will be a small decrease in the peak temperature difference.