| In the process of using wet multi disc brake,the phenomenon of warping and cracking of the friction pair often occurs,which seriously affects the performance and safety of the wet multi disc brake.To solve this problem,the causes of warping and cracking are analyzed from the point of view of temperature field and stress field.But the influence of cooling system on the temperature field and stress field is not considered in the calculation of the temperature field and stress field.In order to calculate the temperature field and stress field more accurately,the cooling system of wet multi disc brake is considered in this paper.The temperature field and stress field of the wet multi disc brake was calculated in the thermal-liquid-solid coupled method by the finite element simulation software ANSYS Workbench.Then,The causes of warping and cracking phenomenon were analyzed according to the temperature field and the stress field distribution.First,by consulting the relevant literature,the theoretical basis of the thermal-liquid-solid coupled method and the realization method of the thermal-liquid-solid coupling of wet multi disc brake are mastered.The finite element model of the wet multi disc brake friction pair and the finite element model of flow field were established in ANSYS Workbench and the simulation parameters and flow field simulation parameters are calculated.Then the contact pressure on the surface of the friction pair was simulated and analyzed in the solid deformation field.The contact pressure distribution on the surface of friction pair was obtained by simulation.By changing the simulation parameters,the influence of the rotational angular velocity,brake pressure,friction coefficient,the elastic modulus of the static friction disc and the elastic modulus of the friction plate on the contact pressure were analyzed.Then,the flow field of the wet multi disc brake cooling system was simulated by Fluent software.The distribution characteristics of velocity and pressure in the flow field and the effect of rotational angular velocity on the maximum velocity and maximum pressure in the internal flow field are obtained through the flow simulation.Then,the fluid solid coupling simulation of the wet multi disc brake was carried out by using ANSYS Workbench software.Through the fluid solid coupling simulation,it was found that the effect of the flow field pressure on the contact pressure was very small,and the effect was smaller and smaller with the process of braking.Finally,the thermal-liquid-solid coupling analysis process of the wet multi disc brake was established by ANSYS Workbench software and the simulation of the temperature field and stress field was carried out.The simulation results showed that in the process of braking,the temperature of the static friction disc and the friction lining increased first and then decreased,while the chip temperature increased all the time.There were large temperature gradients in the surface of the friction pair and temperature gradients of the static friction disc and the friction lining mainly occurred in the friction lining about 3/4 along the radial direction and the contact region with the cooling oil,while the temperature gradient of chip mainly occurred in the contact region with the cooling oil.The main cause of the temperature gradients were the uneven distribution of the contact pressure and the temperature difference in the contact region with the cooling oil.The temperature gradient was the main cause of the thermal stress,and the high temperature stress mainly occurs in the regions which had large temperature gradients.High temperature and high thermal stress are the reasons for the occurrence of warping and cracking.High temperature led to the formation of thermal deformation which resulted in the phenomenon of warping and High temperature stress caused the production of fatigue cracks after after long-time serve. |
