The method of synthesis of finite-element model of strengthened fuselage frames
Authors: В. В. Борисов  , В. В. Сухов  
Published: December 2021

One of the main problems, which solved during the design of transport category aircraft, is problem of analysis of the stress distribution in the strengthened fuselage frames structure. Existing integral methods of stress analysis does not allow for the mutual influence of the deformation of a large number of elements. The most effective method of solving the problem of analysis of deformations influence on the stress distribution of structure is finite element method, which is a universal method for analyzing stress distribution arbitrary constructions.This article describes the features of the finite element model synthesis of the strengthened fuselage frames structure of the aircraft fuselage transport category. It is shown that the finite element model of strengthened frames can be synthesized by attaching additional finite element models of the reinforcing elements to the base finite element model which is built by algorithm which is developed for normal frame. For each reinforcing element developed a separate class of finite element model synthesis algorithm. The method of synthesis of finite element model of strengthened frame, which are described in this article, developed for object-oriented information technology implemented in an object-oriented data management system "SPACE".Finite-element models of the reinforcing elements are included in the finite element model of the fuselage box after the formation of a regular finite element model of the fuselage box. As the source data for the synthesis of finite element models of the reinforcing elements used the coordinates of the boundary sections nodes of existing finite element models of conventional frames.Reinforcing elements belong to the group of irregular structural elements that connect regular elements of the cross set with different elements that are not intended for the perception and transmission of loads. The only exceptions are the vertical amplification increasing the stiffness of  frames in a direction parallel to the axis OY.Source data input for the synthesis of finite element models of the reinforcing elements can occur only through the individual user interfaces that supported by objects of the corresponding classes. Structure of user interfaces depends on the number and type of additional data that required for the synthesis of finite element models of the reinforcing elements. For example, for the synthesis of structures of finite element models of horizontal beams that support the floor of cargo cabin, you must specify the distance between the upper surface of the beam and the horizontal axis of the fuselage, as well as the height of the beam section. For the synthesis of the structure of the finite element model of vertical reinforcing element is enough to specify the distance between the its inner belt and the a vertical axis of symmetry of the fuselage.And in both cases you must to specify a reference to the basic finite element model, by selecting from a list of frame designations. List of frames, as well as links to objects containing the appropriate finite-element models, must be transmitted from an object which references to the level of decomposition, in which the general model of the fuselage box is created.Finite-element models of the reinforcing elements include two groups of nodes. The first group is taken from an array of nodes, which is transmitted from the base finite element model. The second group is formed by the synthesis algorithm of finite element model of the selected class reinforcing element. Therefore, the synthesis of finite element models of the reinforcing elements starts with the formation of their local model versions. On the basis of these models are formed temporary copies, which are transmitted to the general finite element model of the box. This should be considered when developing of data conversion algorithm of data copying from a local finite element model to the temporary copy.Based on this analysis, we can conclude that this method improves the quality of the design of the aircraft fuselage, increasing the amount of structure variant number and reduce the likelihood of errors.