非概率响应面法在起落架结构安全性评估中的应用

Safety analysis for the landing gear structure on the basis of the non-probabilistic reliability theory

由于起落架结构的安全性分析参数多为区间变量,随机分布较难获得,采用传统的概率分析方法受到一定的制约。基于此,针对起落架运营事件的严重度分析,提出了基于区间理论的起落架结构非概率可靠性方法,在只知道不确定参量的界限而不知其分布情况的条件下,即可求得结构的可靠度。以非概率可靠性理论为基础,结合响应面法建立结构的非概率模型,并通过改进的解析方法求解非概率可靠性指标。以某型飞机起落架结构为研究对象,对起落架结构进行数值分析获取建立非概率模型所需的数据样本,进而进行结构的安全性评估。算例分析表明,非概率可靠性方法能够有效评估起落架结构的安全状态,可为飞机结构的运营安全性分析提供参考。

The present paper is inclined to clarify the performance function of the landing gear structure via the non-probabilistic reliability theory so as to overcome the parametric uncertainty due to the structural uncertain parameters as interval variables.As is well known,the non-probabilistic reliability theory has been built up on the safety assessment of the structure reliability to overcome the boundary obstacle of the uncertain parameters given,which is hard to gain. In such a case,the reliability of the structure can be gained through the analysis of its advantages. And,therefore,first of all,it would be necessary to establish a non-probabilistic model of the structure in combination with the response surface method by taking the structural uncertain parameters as the interval variables. It is just on such a basis that the improved analytic method of the non-probabilistic reliability index can be gained and the advantage of the improved one-dimensional optimization algorithm can be given from the interval variables. And,then,in comparison with the analytic index algorithm,it would be possible to improve the computational efficiency by reducing the number of solutions. Last of all,we have also presented a case study for the specific landing gear structure. And,meanwhile,we have also managed to build up a non-probabilistic model with the analysis of the concerned data samples from the finite element analysis. Moreover,the acquired data samples can also be processed to work out the performance functions and solve the non-probabilistic reliability indexes based on the improved analytic method. And,in so doing,the result we have gained via the improved analytic method can be made equal to η,which should be greater than 1 (η = 1. 3801 > 1). It can also have been taken as the non-probabilistic reliability index of the structure. And,next,0 < η < 1 should be taken as unsafe,whereas η = 1 tends to mean that the structure remains in a"critical"state between being safe and unsafe,in which η > 1 can be taken as being safe. Thus,consequently,it turns out that the landing gear structure ought to be reliable. To sum up,the above example shows that the non-probabilistic reliability method can help to evaluate the state of landing gear structure effectively and efficiently so as to provide for a reference to the aircraft structure safety assessment. Hence,the non-probabilistic model we have worked out can be regarded qualified enough as an important supplement to the probabilistic reliability theory in case there is no enough data available for analyzing the distribution of the parameters.