Method for predicting fatigue life of multi-nail connecting pieces under spectrum loading

Abstract

A method for predicting fatigue life of multi-nail connecting pieces under spectrum loading comprises the following five steps: 1, a fatigue S-N curve of a simple small single-nail connecting-piece sample is measured through a fatigue test; 2, a relation between bypass stress of a joint of multi-nail connecting pieces dangerous fasteners and dimension parameters of the connecting pieces is established according to an equilibrium equation of a single fastener aperture; 3, a computational formula of fatigue life of the multi-nail connecting pieces under cyclic stress is established; 4, a computational formula of fatigue life of the multi-nail connecting pieces under spectrum loading is established; and 5, known basic fatigue properties of the small single-nail connecting-piece sample and structural properties of the multi-nail connecting pieces are plugged into the computational formula of fatigue life. Then, the total periodic number of the multi-nail connecting pieces under the action of spectrum loading, namely fatigue life of the multi-nail connecting pieces, can be determined. The method provided by the invention is simple and practical. Only by plugging fatigue performance of the small single-nail connecting-piece sample and stress state and dimension parameters of the multi-nail connecting pieces into a model, fatigue life of the multi-nail connecting pieces in any arrangement forms can be obtained.

Description

technical field [0001] The invention provides a method for predicting the spectrum load fatigue life of a multi-nail connector, which belongs to the technical field of metal structure fatigue reliability. Background technique [0002] The main structure of the aircraft - the fuselage, wings and empennage are all thin-walled structural parts connected by a large number of fasteners, and the fatigue crack initiation in the actual use of aircraft structures often occurs in the details of such multi-nail connected structural parts. place. For a long time, the aviation sector has been paying attention to and working on the fatigue design of aircraft structures, and formulating airworthiness standards to prevent catastrophic fatigue failure accidents. In order to ensure the safety of aircraft flight, it is very important to accurately predict the spectral load fatigue life of multi-nail connectors. Today's multi-nail connector spectral load fatigue life prediction methods are ma...

AI Technical Summary

Problems solved by technology

Today's multi-nail connector spectral load fatigue life prediction methods are mainly based on fatigue tests and theoretical calculations. The test method requires multiple connector components, the cost of samples and tests is high, and it is inconvenient to design and use; while the theoretical calculation method is mainly through finite element simulation. The influence of the number of bolts, radius, friction coefficient, stiffness, position, etc. on the transmitted load and stress-strain distribution, there are many influencing factors to be considered, the calculation is complex, the error is large, and the calculation accuracy and efficiency are low; there is still a lack of prediction of the multi-nail joint spectrum. Therefore, a simple and practical method for predicting the spectrum load fatigue life of multi-nail connectors is invented. This method only needs the fatigue performance of small samples of simple single-nail connectors and the geometric size parameters, the fatigue life of multi-nail connectors under spectral loading can be calculated, and the invention has important academic significance and engineering application value

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