Reliability Modeling For Competing Failure With Dependent Functional Failure Mode

From the perspective of the function loss, failures of mechanical products can be divided into degradation failure and sudden failure, and competition exists between these two kinds of failure modes during their life periods, which eventually results in the competing failure for mechanical products. Most of the traditional reliability models assume that these two failure modes are independent each other, and there will be a large deviation in the reliability evaluation. In practical engineering, there exists interaction between the two failure modes, but the reliability researches that focused on correlated failure modes are not perfect enough. According to the influence of the degradation failure process on the sudden failure process, as well as the attenuation characteristic of the shock load, so the correlation between the failure modes is studied and a competing failure model is established, which is used to evaluate the reliability of products. The main research results are as follows:(1) In view of the load condition, the fatigue load will make the product performance degradation, and degradation will lead to degradation failure, shock load will lead to sudden failure. The random load in practical engineering is simplified as fatigue load and shock load, the alternate load condition of fatigue load and shock load is analyzed, and a traditional reliability evaluation model is established,which is used to explain the traditional modeling method of reliability evaluation.(2) The influence of degradation process on shock process is considered, two dependent failure processes are analyzed: on the one hand.it is shown that the degradation failure and sudden failure are affected by the same shock process; on the other hand, the total degradation affects not only the intensity of the shock process but also the magnitude of the shock load.Taking advantage of Poisson process, a reliability model of the dependent competing failure of product is proposed.(3) There exists a kind of degradation phenomenon in process of sudden failure,the continuous degradation and the sudden increase in the degradation process are described, and a sudden failure process model is established. Then the correlation between degradation failure process and sudden failure process is analyzed: firstly,degradation failure and sudden failure are affected by the same shock process;secondly, considering the influence of the degradation failure process on the sudden failure process, that means degradation characteristic in the sudden failure process.Based on the theory of stochastic process, a reliability model for dependent competing failure of product is derived.(4) Considering the attenuation phenomenon of shock load for mechanical product during its sudden failure process, the reliability assessment for competing failure analysis of product based on shock attenuation model is studied. Two kinds of attenuating shock processes with periodic and stochastic characteristics are introduced, then the exponential function is used to describe the attenuation law and the impulse generated by the shock is investigated, a quantitative model between the damage and impulse caused by the shock load is developed. Then the Wiener process is used to describe the continuous degradation process, a reliability model based on dependent competing failure analysis is proposed. Finally, a numerical example is given to account for the computational efficiency of the re liability assessment whether considering the shock attenuation or not.