First, the theoretical basis of automotive reliability Automotive reliability refers to the ability of automotive products to maintain specified functions within the specified time under the specified conditions of use. The reliability (R) refers to the probability that an automobile product will maintain the prescribed function within the specified time under the specified conditions of use. The usage conditions for the set include: mileage, operating conditions, load size, and maintenance conditions; the specified time refers to a specific use time, such as reliability test mileage, warranty period, first overhaul mileage, and end-of-life Period, etc.; The prescribed functions refer to the international and national standards, technical regulations, as well as the functional and performance requirements specified in the operating instructions and contracts for automotive products. Probability refers to the probability of random failures occurring in r experiments in n experiments. The reliability of the vehicle must be assessed within a specified time. The reliability of a repairable product can be considered from the perspective of reliability and maintenance. A car is a typical repairable product, and it is necessary to improve reliability as well as maintenance. Second, the concept of reliability distribution The so-called reliability allocation is to assign the reliability indicators of the system to each unit that makes up this system. When the reliability of the system is assigned, the system's reliability index must be clarified first, and the reliability function relationship between the system and the unit must be clearly defined. Secondly, due to the requirement of reasonable distribution, it is necessary to know the importance of each unit in the system. , the degree of influence on the system work when the unit fails; the technological status of each unit and the potential for product improvement; the cost of the unit. Also consider the effect of maintenance and repair on the function. Third, the significance and application of vehicle reliability distribution The significance of vehicle reliability distribution lies in the rational or optimal determination of the reliability of each unit in the system under the specified conditions to meet the reliability requirements of the automotive system. Make designers at all levels clarify their reliability design requirements, estimate the required manpower, time, and resources based on requirements, and study the possibilities and methods for achieving this requirement. Specifically, (1) The reliability index of each unit in the system is reasonably determined so as to ensure the unit design, manufacture, test, and acceptance. In turn, it will promote the improvement and improvement of design, manufacturing, testing and acceptance methods and technologies. (2) Through the distribution of reliability, the designer is helped to understand the relationship between the reliability of parts, units (subsystems), and systems (overall), so that they can be aware of each other, reduce blindness, and clarify basic design issues. (3) Through the distribution of reliability, designers can more fully balance the performance, function, weight, cost and effectiveness of the system with time, in order to obtain a more reasonable system design and to capture the high product design quality. (4) Through the reliability allocation, the reliability value obtained by the system is more realistic than before distribution, and the time and cost of manufacturing can be saved. Implement the system's reliability indicators; define the reasonable reliability requirements for each system or unit; expose system weaknesses and provide data for improved design. If reliability prediction is based on parts → subsystems → systems from bottom to top, reliability distribution is implemented by systems → subsystems → parts from top to bottom. Therefore, forecasting is the basis for allocation. Reliability prediction is always performed first, and then reliability is assigned. In the process of distribution, if weak links are found, the design or exchange of parts should be improved, and then re-estimated and redistributed. The combination of the two constitutes a bottom-up, top-down, repeated process until the subjective requirements are unified with the objective reality. In order to ensure that the automotive system has the required level of reliability, the reliability of the system must be calculated or predicted during the design phase. In general, the functional block diagram or reliability block diagram should be drawn based on the functional relationship of each unit in the automotive system as a reliability model of the automotive system, and the reliability calculation or distribution is performed according to the model. The reliability allocation is mainly applicable to the program demonstration and preliminary design stage, and it should be carried out as early as possible and iteratively iteratively. Fourth, the principle of car reliability distribution Usually the reliability allocation should consider the following principles: (1) Technical level. For mature technology units, higher reliability can be ensured, or the reliability can be assuredly increased to a higher level when it is expected to be put into use, and higher reliability can be assigned. (2) Complexity. For simpler units, the number of components that make up the unit is small, the assembly is easy to guarantee quality, or it is easy to repair after a failure, then it can be assigned to a higher degree of reliability. (3) The degree of importance. For an important unit, the failure of the unit will have serious consequences, or failure of the unit will often lead to failure of the whole system, and it should be assigned a higher degree of reliability. (4) The task situation. Considering the work cycle of the unit and its working environment, etc., if it is necessary to work continuously and the working conditions are severe throughout the entire mission time, and it is difficult to guarantee a unit of high reliability, it should be assigned to a lower reliability. (5) Consider the constraints of cost, weight, size, and other conditions. In short, the ultimate goal is to meet system reliability requirements at the lowest cost. Fifth, the method of car reliability distribution The reliability allocation can assign the reliability of the system to each unit according to the situation, and can also assign the unreliability to each unit or allocate the failure rate of the system to each unit. There are many methods for assigning reliability, which vary with the amount of reliability data, the design period, and the goals and restrictions. Such as: equal distribution method, redistribution method, proportional distribution method, comprehensive scoring allocation method and dynamic programming allocation method. Different system reliability assignments: (1) The reliability of the simple system is allocated for the initial stage of design. Since there is little grasp of the reliability data of each unit, it is assumed that the conditions of the units are the same and the equal distribution method is adopted. If the units or subsystems of the tandem system are all subject to an exponential distribution, the system is also subject to an exponential distribution. Thus, the reliability allocation is distributed in proportion to the failure rate and can be approximately distributed in proportion to the predicted value of the unreliability. When assigning the reliability of the series system, it is not always to directly assign the reliability, but rather to assign the unallowable degree (failure rate) of the system to each unit or sub-system. This is because the reliability of the series system is the product of unit reliability, and the failure rate of the system is the sum of the failure rates of each unit, which can be calculated using probability addition. Therefore, it is more convenient to allocate according to the ratio of relative failure rate. The basic starting point of this allocation method is that the failure rate assigned to each unit is proportional to the expected failure rate of the unit, and its advantage is that the unit's existing reliability level can be considered. The reliability of the parallel system is proportional to the distribution valve calculation. It is necessary to optimize the process from expected to distribution and then to redistribution. The specific steps are as follows: a: Simplify the redundant part of the system into a single unit, so that the redundant part becomes a unit in the series system; b: The distribution method of the series system, the reliability of this simplified series system is assigned; c : Using these assigned values, the reliability of the original redundant part is estimated, and compared with the required reliability index to obtain the difference; d: corrective redistribution of these differences, and then repeat c), d) Two steps until the requirements are met. For a hybrid system, when the distribution of reliability is performed using the equal distribution method, it is generally first converted into an equivalent unit, and equivalent units of the same level are assigned to the same reliability. (2) Complex systems can be seen as consisting of several subsystems. The distribution method varies. Subsystem importance distribution method - for the various subsystems that make up the system, the degree of importance in the system is different, then it should be assigned to different reliability. The index reflecting its importance is the degree of importance. Sub-systems with high importance should be assigned to high reliability, and subsystems with low importance should be assigned lower reliability. Subsystem Complexity Allocation Method - For each subsystem that makes up the system, the complexity in the system is different, then it should be assigned to different reliability. The complexity of the subsystem is expressed as the ratio of the number of components in the subsystem to the total number of system components. Comprehensive Score Allocation Method—According to the experience, each unit considers the major factors to be comprehensively scored, and is assigned to the corresponding reliability index according to how many units are scored. Regarding the factors considered, the scoring method can also be determined according to the specific circumstances. Weighted factor allocation method - factors such as importance, complexity, mission time of environmental conditions, and quality of parts are used as factors. In the distribution process, the weighting factor of typical subsystems in the system is set to 1; other subsystems refer to For typical subsystems, determine their respective weighting factors and then calculate the factorial product of each subsystem. Relative failure rate distribution method - based on the ratio of subsystem failure rate and system failure rate. This method is applicable to a serial system with a constant failure rate, and the system task time is the same as the subsystem task time. Redistribution method - further improving the original design to improve its reliability, that is, to redistribute the reliability indicators of each subsystem. The basic idea is to increase the reliability of the original sub-system with lower reliability to a certain value, while the degree of retentivity of the original sub-system with higher reliability remains unchanged. After reliability redistribution, the new system can meet the specified reliability index. Sixth, the end For automotive products, reliability is closely related to personal safety and economic benefits. The automobile is composed of a lot of assemblies, components, and parts. To improve the reliability of the product, we must reasonably distribute the reliability. The competition of automotive product quality is to a large extent the competition of product reliability. The reliability level of China's auto products is still relatively low, which has become the bottleneck of the rapid development of China's auto industry. In order to steadily improve the quality of our automotive products, it is necessary to build reliability engineering for automotive products. At the beginning of the redesign, the reliability of the product must be reasonably distributed. It is very important to master the basic principles and methods of reliability distribution. Rectangle Trampoline,Top Rated Trampolines,Gymnastics Rectangle Trampoline,17Ft Gymnastics Rectangle Trampoline Jiangsu Baoxiang Sports Equipment Co., Ltd , https://www.skyboundup.com