Design Method Of Safety Factor Based On Reliability And Software Development

This stage is the transition phase from the traditional design to the reliability design, and it introduces the safety factor concept. This paper uses the safety factor which corresponds with reliability index to replace the empirical formula selected allowable safety factor in traditional design, and then applies to conventional mechanical design. Using this method to design products can not only meet the requirements of reliability, but also save a lot of cumbersome and complex reliability calculation, and easily apply to the majority of designers in practical engineering.Stress-strength interference model is the foundation of Mechanical Component Reliability Analysis (MCRA). With the basic idea of stress-strength random variables interference analysis, this paper establishes safety factor model subject to different types of static strength distribution. This model not only characterizes the requirements of structural reliability, but also reflects the discrete nature of the stress and intensity. The value of the safety factor varies according to stress and structural reliability parameters. It is calculated for each specific condition, rather than a general experience fixed value.The traditional interference model is only applicable to the case of one-time loading. But the most practical engineering parts will be under random multiple loading in its service time. Therefore, this paper studies the effect of random loading times on the reliability of the safety factor, and then uses order statistic theory to deduce the equivalent load of random repeatedly load cumulative distribution function and probability density function. Besides that, this paper further improves the static strength reliability safety coefficient model which can scientifically reflect the designated loading number or working time.Secondly, for mechanical parts with multiple danger point, every dangerous point is sometimes possible to fail. In this paper, the whole machine is regarded as a system, and each dangerous point of the parts is as a unit in the system. Then we use system-level reliability analysis and modeling methods, combine the system reliability treatment of multi-hazard point failure risk with independent and dependent failure, then research and improve the reliability safety factor design method of multi-hazard point system.Thirdly, applying the safety factor of reliability design method, this paper regards the multi-gear system as the research object and applies the theoretical calculations to meet the system reliability requirements of different failure modes of gear teeth on multi-hazard point safety factor in order to verify rationality and feasibility of this method.Finally, considering the practical engineering requirements and increase the research value of the theory application, this paper applies MATLAB platform GUI module to develop "gear system safety factor" software. This software is mainly composed of five modules which are the main interface design, design information registration, design input requirements, structure and material selection, distribution system reliability and safety factor calculations. In order to verify the practicality, we use a secondary level straight tooth cylindrical gear reducer of low speed gear transmission design as an example, and choose two aspects respectively from the application software calculation and traditional safety factor method to get different safety factors, and then substitute it into the conventional mechanical design to obtain main geometric parameters of components and make a comparison to verify the correctness and the superiority of this theoretical method. This method provides a theoretical basis for improving the reliability of parts and saving the manufacturing cost.