| Vehicle brake is not only a part of vehicle brake system, but an important component in the vehicle; it converts directly pressure of brake system into brake power, as executive element of brake system, brake influences vehicle's running safety. Brake performance is one of important characters for vehicle and brake is an important component to show vehicle's brake performance, so how well brake is designed affects how well unit brake performance is, as the result of it, studying brake is an essential part in vehicle field.The object of this project lies in a sliding pin floating brake caliper. Compared with drum brake, caliper braker features better brake performance, simple structure and easy maintenance, so caliper braker is used wider and winder. Caliper braker can be divided into fixed and floating, floating brake boasts brake fluid uneasy gasification, simple structure, easy manufacture and cost low over drum brake.The main propose for this project is to use computer finite element to analyze critical parts and components of brake caliper in finite element statics and nonlinear contact finite element. Generally, theory calculation, test and practical check are the main ways to study feasibility and reliability, but finite element which features cost low, getting a result quickly is becoming a normal way to study with computer development, and it can get high reliability analysis result, connected with traditional theory calculation. In order to improve the reliability of finite element analysis result, the object compares finite element analysis result with traditional statics analysis result.Because practical brake power is changeable, I study three working conditions in the project, they are max brake power, brake cylinder pressured 32MPa and permissive long pin brake power.1. Analyzing critical parts and components of brake caliper in statics, the result is:Among three work conditions, max compression stress of brake disc should further less than permissive stress between lining and brake disc, so lining and brake disc have big safe factor. Evaluating the safety of lining and brake disc in the compression stress, they are safe. If cylinder utmost stress is in the static 36.5MPa, lining owes safe factor enough.Under work condition of max brake power, long pin has enough safefactor, max bend direct stress of long pin is less than material strength limitation and yield limitation, safe factor is more than 1.5. In work condition of 32MPa cylinder stress, max bend stress of long pin is closed to material yield limitation, safe factor is 1.38 which is the lower limit value, but this condition only can occur in the lab, it can't happen in reality, pin strength is enough in analysis of statics. If cylinder utmost internal pressure is less than 23.57MPa, it is sure that long pin has enough safe factor. In practice, max air pressure is 0.8MPa, pressure ratio for air-over-oil cylinder is 23, max hydraulic value is 18.4MPa, so safe factor for long pin is big enough.2. The result for brake caliper in finite element static analysis and in contact nonlinear finite element analysis.Compared with traditional static, the analysis result of finite element static for long pin is that max stress value is a little low, but inaccuracy is acceptable, two results are consistent and can be checked each other.The analysis result for long pin in contact nonlinear finite element is closed to the one in traditional statics. Under three work conditions, max stress in traditional statics is 527,723 and 533MPa, the one in contact nonlinear finite element is 562,721 and 531MPa. This means that two groups of number are reliable, and the analysis result in contact nonlinear finite element is closer to the practical condition.The analysis result for lining and caliper disc in contact nonlinear finite element shows that cylinder max pressure is 18.5MPa in work condition of permissive brake power. Safe factor is a little low in max brake power and 32MPa cylinder pressure. As the above said, cylinder max pressure is 18.4MPa in practice, so it is safe. It should be emphasized that practical permissive stress for lining is not as accurate as steel, permissive stress of linings from different factories is different, neither are different material linings. The parameter and result in the article are only consulted, test result is more important in special use. In addition, lining is a consumable part, which has a short fatigue life, it should be considered when analyzing its fatigue.Compared with calculation result of drum brake, safe factor of utmost stress for disc brake lining is higher, especially safe factor is much higher. The reason for this phenomenon is that the shape of disc brake lining is simple, easy manufacture, so some material with high permissive stress can be used,requirement for safe factor of drum brake is higher in the same utmost stress.3. Based on modal analysis theory, critical components are analyzed in finite element modal analysis, and structure free frequency and mode are made out in finite element. Based on model analysis result, structure is analyzed in dynamics response by software ANSYS. |
PDF Full Text Request