Method for monitoring fatigue life of airplane structure key part online under spectrum loading on the basis of indirect strain measurement

Abstract

The invention discloses a method for monitoring the fatigue life of an airplane structure key part online under spectrum loading on the basis of indirect strain measurement and relates to the technical field of airplane structure fatigue crack initiation and propagation. The method for monitoring the fatigue life of the airplane structure key part online under spectrum loading on the basis of indirect strain measurement comprises the following steps of (1) calculating a dangerous point of a structural part by using a finite element analysis method and calibrating a sensor position and a stressconcentration factor; (2) mounting a sensor to carry out online strain monitoring; (3) using a rain-flow counting method to carry out cycle counting on the monitored strain and calculating local stress strain of the dangerous point; (4) calculating damage accumulation of the cycle and judging whether crack initiation monitoring needs to be started or not; (5) calculating a crack initiation evaluation parameter and comparing the crack initiation evaluation parameter with a judging parameter and selecting whether the crack initiation monitoring needs to be continued or not after judging the initiation situation of a fatigue crack; and (6) selecting the crack initiation monitoring needs to be continued or not after inspecting a damage accumulation result. The monitoring result shows that themethod for monitoring the fatigue life of the airplane structure key part online under spectrum loading on the basis of indirect strain measurement can preferably monitor the life situation of the fatigue crack of the airplane structure key part.

Description

technical field [0001] The application field of the invention is the direction of fatigue life monitoring, in particular an online monitoring method for fatigue life of key parts of an aircraft structure based on indirect measurement of strain under spectral loading. Background technique [0002] Aircraft occupy an important position in the country's economic, transportation, and military fields. Structural fractures caused by aircraft fatigue will cause serious accidents. Aircraft structural fracture accidents often start with the initiation of a fatigue crack. When the fatigue crack expands to a certain length, it will directly cause structural damage and lead to accidents. Therefore, the present invention proposes an online fatigue life monitoring method for key parts of the aircraft structure to ensure safe and reliable service of the aircraft, which has important practical significance. [0003] The current life on-line monitoring method usually installs strain sensors...

AI Technical Summary

Problems solved by technology

[0003] The current life on-line monitoring method usually installs strain sensors around the stress concentration parts of the key parts of the aircraft to estimate the stress and strain at the dangerous point to calculate the life, but the life obtained by this traditional calculation method is generally twice the actual life. Left or right, even larger errors, and crack monitoring often requires more complex sensors and is too sensitive to cause false alarms. Therefore, on the basis of traditional methods, a fatigue crack that is also based on online measurement of strain around stress concentration parts is superimposed The emergence monitoring method can be closer to the actual online monitoring life

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