【作者】 李峰；

【导师】 赵健；

【作者基本信息】 吉林大学 ， 工程硕士（专业学位）， 2018， 硕士

【摘要】 进入新世纪以来,随着我国经济存量和增量的快速增长,汽车的保有量正在高速增加,这也反映了中国城市化水平的提高。然而,汽车数量的急剧增加也给城市道路交通带来了巨大的安全隐患。客车液压盘式制动器是保障驾驶员和乘客生命安全操作率最高的功能部件,直接关系到客车正常行驶时的安全性和舒适性。客车制动时,车辆的动能通过制动系统的摩擦转化为热能耗散到空气中。由于盘式制动器的散热性能和抗衰退性能更好,因而在各型车辆上得到越来越广泛地应用。制动器工作时会产生大量的热。当制动器摩擦面的温度未达到树脂摩擦材料受热分解温度,此时的摩擦是干摩擦。摩擦面的摩擦因数会略微上升后保存不变。如果温度过高,树脂摩擦材料受热分解,此时的摩擦是混合摩擦,呈现磨粒磨损并被流体润滑的特点,摩擦因数显著降低。在这种情况下,摩擦面能够产生的制动扭矩迅速降低,即产生热衰退现象。本文采用理论分析与仿真相结合的方法,对某型中小客车的前轮液压通风盘式制动器的温度场和制动系数开展研究,基于ABAQUS有限元分析软件在考虑对流换热系数随车速变化的情况中构建制动器的热力耦合模型。根据相关的试验方法,确定了仿真的循环工况。并对制动器在该循环制动工况下的温度变化采用热力耦合的方法开展计算分析,得出了每一个制动循环温度场的变化规律。在得到温度场的基础上,对盘式制动器摩擦因数随温度的变化展开研究,根据已有文献中的试验结果,拟合在制动过程中制动盘摩擦因数随温度场的变化关系。并对影响盘式制动器摩擦因数的结构因素进行了简要的分析,比较了不同散热翅片数目对制动盘温度场和摩擦因数的影响,通过合理设置参数避免了温度过高导致的客车通风盘式制动器表面的摩擦因数降低及制动失效。结果表明,不同散热翅片的制动器,制动开始时,摩擦因数均呈现出短暂的上升,然而增长的幅度有限。随着制动次数的增加,摩擦因数呈现出了下降甚至是急剧下降的趋势。对于散热翅片较少的制动盘,摩擦因数减小斜率的绝对值较大,摩擦因数的最小值可减少至0.233。通过分析循环制动工况,散热翅片数目是90条时,制动盘表面的最高温度最低,摩擦因数减少较慢,在制动盘结构概念设计阶段,应尽量选定散热翅片数目多的制动盘为宜。通过对制动盘制动系数热衰退的研究,最终降低液压制动盘的热衰退性,并增加制动时的可靠性。更多还原

【Abstract】 Since the beginning of the new century,with the rapid growth of China’s economic stock,the number of vehicles has been increasing at a rapid rate.The annual increase in car ownership reflects the increase in urbanization in China.However,after the rapid increase in the number of cars,it also brought huge security risks to urban road traffic.Hydraulic disc brake is the functional component with the highest operating rate to protect the safety of the driver and passengers.When the car brakes,the kinetic energy of the vehicle is transferred to friction energy and dissipated into the air by the braking system.According to the structure,vehicle brakes can be divided into drum brakes and disc brakes.The former has better heat dissipation performance and anti-water decay performance,and thus is more and more widely used in various types of vehicles.If the temperature of the friction surface for the hydraulic disc brakes of passenger vehicles does not reach the thermal decomposition temperature of the resin friction material,the friction at this time is dry friction.The friction coefficient of the friction surface will slightly increase and then remain unchanged.If the temperature is too high,the friction material of the resin is decomposed by heat,and the friction at this time is mixed friction,which shows the characteristics of abrasive wear and fluid lubrication.The friction factor is significantly reduced.While braking,the braking torque that can be transmitted is rapidly reduced,that is,a thermal decay phenomenon occurs.The disc brakes for vehicles are the functional components with the highest operating rates of the drivers.Directly related to the safety and comfort of the vehicle when vehicle is running normally.While the vehicle is braking,the kinetic energy of the vehicle is dissipated into the air through the frictional process of the braking system.According to the structure,vehicle brakes can be classified into drum brakes and disc brakes.The former has better heat dissipation performance and water repellency,and thus it is more and more widely used in various types of vehicles.In this thesis,the temperature field and braking coefficient of front wheel hydraulically ventilated disc brakes of a passenger vehicle is studied by theoreticalanalysis and numerical simulation.A thermo-mechanical coupling model of the brake is constructed based on ABAQUS finite element analysis software in consideration of convective heat transfer coefficient variation with vehicle speed.The temperature change of the brake is calculated and analyzed under a cyclic braking condition.The change of braking coefficient with temperature is studied according to the test results in the existing literature.It is fitted for the relationship between the braking coefficient and the temperature field of the brake disc.A brief analysis of the factors that affect the brake coefficient of disc brakes is conducted to avoid the phenomenon that the friction coefficient of the brake is reduced due to the high temperature.The brakes of different heat-dissipating fins showed a brief increase in the friction factor at the start of braking,but the growth rate was limited.With the increase in the times of brakes,the friction factor has shown a decline or even a sharp decline in the trend.For brake discs with more fins,the friction factor reduces,and the minimum friction factor can be reduced to 0.233.By analyzing the cyclic braking conditions,when the number of radiating fins is 90,the temperature on the surface of the brake disc is the lowest,and the friction factor decreases slowly.In the conceptual design phase of the brake disc structure,it is advisable to select the brake disc with a large number of radiating fins as much as possible.Finally,the thermal decay of the brake discs is reduced and thereby the reliability of the brake system is increased.更多还原