Method for determining fatigue life index of hydraulic conduit

Abstract

The invention, which belongs to the hydraulic system of the airplane, discloses a method for determining a fatigue life index of a hydraulic conduit. The method comprises: (1), a monitoring point easily causing a fatigue fracture is found out; (2), a tested piece the same as that of an airplane is employed; (3), a rated working pressure of a system is applied into the tested piece; (4), a foil gauge and an acceleration sensor are loaded at the monitoring point; (5), an output frequency of a vibrating table is controlled to be an inherent frequency of the tested piece; (6), output amplitudes of the vibrating table are controlled to be set successively in a range from 0,75 sigma b to sigma -1 in a descending order according to stress values generated on the conduit, a stress value and an acceleration value at the monitoring point are measured, and the number of times of cycling of the tested piece in a fracture mode is recorded; (7), according to the stress value and the number of times of cycling or the acceleration value and the number of times of cycling, a fatigue life curve of the tested piece is fitted; and (8), a stress value or acceleration value of a position close to a horizontal line on the fatigue life curve is a fatigue life index control value of a hydraulic conduit. With the method, reasonability, reliability, and durability of the airplane hydraulic system pipeline design can be evaluated effectively.

Description

technical field [0001] The invention belongs to an aircraft hydraulic system, in particular to a method for determining a fatigue life index of a hydraulic conduit. Background technique [0002] The fatigue life (stress level) control of hydraulic conduit is the key to ensure the long-term safe and reliable operation of the hydraulic system. GJB1396-1992 "Aircraft Hydraulic Emergency Pneumatic System Test Requirements and Methods" clearly requires that the hydraulic system should be subjected to vibration measurement to verify that there is no harmful resonance state caused by the operation of the hydraulic system under various operating conditions of the aircraft. This requirement is only a qualitative requirement, not a quantitative one. [0003] In the American standard and European standard systems, there are vibration test requirements for hydraulic systems. For example, SAEAS5440 "Military Aircraft Hydraulic System Design and Installation Requirements" requires that ...

AI Technical Summary

Problems solved by technology

[0006] At present, the determination of the fatigue life curve of the material is all measured on the standard test piece (solid metal material, 200mm straight pipe section), and the given material fatigue life curve cannot truly reflect the actual use environment of the thin-walled hydraulic metal conduit (high vibration, High pressure pulsation) in the fatigue life, engineering can not be directly used

Moreover, the measurement method and related information of the fatigue life curve of thin-walled hydraulic metal conduits have not been found in the public material manual.

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