全文总字数：12650字

1. 研究目的与意义（文献综述）

the braking system is an important part of the car. it is used to forcibly slow down or stop the car while driving, to keep the speed of the car driving downhill stable, and to keep the parked car in the same place (including on the slope).according to relevant information, in traffic accidents caused by the problem of the vehicle itself, the accident caused by the failure of the braking system is 45% of the total.

double-decker buses are buses with upper and lower levels of passenger space. they have the advantages of large passenger capacity and saving parking space. although their length and width are almost the same as ordinary buses, but because of an additional layer, the height of the vehicle is higher than other vehicles, and this makes this type of vehicle carry more than other models, however , because the vehicle body is huge and the center of gravity of the vehicle is higher than that of ordinary buses, the front and rear axle load transfers are larger during braking, and the braking efficiency on the road with the same adhesion coefficient is relatively low. with the rapid development of the highway industry and the increasing traffic density, people have higher and higher requirements for safety and reliability. in order to ensure the safety of people and vehicles, it is necessary to equip double-decker buses with very reliable brakes. therefore, this graduation design will design and study the braking system of double-decker buses, which has certain reference value for the design and optimization of the braking system of double-decker buses in the future.

in foreign countries, drum brakes have occupied the automotive brake field for a long time, but since the introduction of actro s trucks equipped with disc brakes manufactured by sehmit z in 1996, disc brakes have gradually replaced drum brakes. in view of various advantages, by 2000, the proportion of foreign buses equipped with disc brakes accounted for more than 50%^[1].many foreign scholars have contributed to the research of the braking system, and have great guiding significance and reference value for the design and optimization of the braking system.

2. 研究的基本内容与方案

using the library and network resources, by consulting relevant literature, under the guidance of the teacher, a safe, efficient and stable braking system that can be successfully matched to the vehicle model will be designed according to the relevant data and characteristics of double-decker buses.first, the basic performance and characteristics of various brakes (friction brakes, hydraulic brakes, electromagnetic brakes) should be understanded ,and determine the preliminary design of the braking system based on the actual conditions of the double-decker bus. then, calculate the data which determines the required braking force of the car for the given vehicle model ,and the braking force of the brake can be determined, after that, the type, construction and parameters of the brake will be determined, and the last step is designing the brake drive mechanism. the basic content is as follows：

（1）investigate the composition and classification of braking systems, understand the current status of automotive braking systems at home and abroad, and clarify the design requirements of braking systems.

（2）the disc brake is initially selected as the disc brake, then draw the ideal braking force distribution i curve according to the vehicle parameters of a given double-decker bus, so that the braking force distribution coefficient of the brake can be calculated, and then draw the β line; analyze and compare the i and β curves, and initially select the appropriate braking force distribution coefficient, then began to design and calculate the main components of the brake (brake caliper, brake disc, brake pad, friction material, brake clearance) and parameters (synchronous adhesion coefficient, braking efficiency factor, friction characteristics of the friction pad).

3. 研究计划与安排

1-2 (18-19^thweeks of 7^thsemester): determination of graduation design topics, perfect the graduation design task book (relevant parameters), collection of materials on campus and off campus.

3 (1^st-2^nd weeks of 8^thsemester): scheme idea, literature search, and complete the thesis proposal.

4. 参考文献（12篇以上）

[1] liu luxiu.foreign heavy-duty trailer axle——trailer axle with disc brake and structural features [j] .automobile parts, 2004 (25): 31-33.

[2] balaji r,mukesh nadarajan,ashish selokar,sreenu s kumar,sivakumar s. modelling and analysis of disk brake under tribological behaviour of al-al2o3 ceramic matrix composites/kevlar 119 composite/c/sic-carbon matrix composite/cr-ni-mo-v steel[j]. materials today: proceedings,2019,18(pt 7).

[3] m tirovic,n sergent,j campbell ,p roberts , r vignjevic . structural analysis of a commercial vehicle disc brake caliper[j]. proceedings of the institution of mechanical engineers,2012,226(5).