Composite material connection structure pre-tightening force online monitoring method

Abstract

The invention discloses a composite material connection structure pre-tightening force online monitoring method. The composite material connection structure pre-tightening force online monitoring method comprises the steps of firstly embedding a strain sensor into a metal bolt, embedding a strain sensor for temperature compensation into a metal bolt for temperature compensation, wherein the strain sensor is connected with a measurement channel of a strain gage, and the strain sensor for temperature compensation is connected with a temperature compensation channel of the strain gage; then exerting drawing force to perform a tensile test at two ends of the meta bolt to measure elasticity modulus of the metal bolt; finally applying the metal bolt of the strain sensor into a composite material connection structure, and calculating change relation of pre-tightening force borne by the bolt and the time according to bolt strain measured by the strain gage under the pre-tightening force effect and the elasticity modulus of a bolt material tested by the tensile test. The composite material connection structure pre-tightening force online monitoring method is especially suitable for measurement of composite material connection structure pre-tightening force and provides a basis for evaluation of the healthy condition of the composite material connection structure at present and within a time period.

Description

technical field [0001] The invention relates to an online monitoring method for the pre-tightening force of a composite material connection structure, in particular to a measurement method suitable for the relaxation of the pre-tightening force of a composite material connection structure. Background technique [0002] Composite materials are widely used in aviation, aerospace and construction fields because of their good specific stiffness, specific strength and corrosion resistance. Restricted by the technical level and the need for easy disassembly and assembly, bolted connections are widely used in composite material structures. However, the mechanical properties of the composite material in the thickness direction are poor. Under the action of long-term preload, the matrix material undergoes plastic deformation under the action of its own viscoelasticity, which leads to the continuous decrease of preload and the instability of the structure. At the same time, the degra...

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Problems solved by technology

Moreover, there are many failure modes and the failure mechanism is complex, so it is impossible to determine the health status of the current composite material structure and predict its future service life

From the perspective of safety, abandoning the composite material structure that has shown progressive damage but can still serve normally will inevitably result in a waste of resources

[0003] 201310378100.3 provides a method for measuring the pre-tightening force of a bolt group, which overcomes the deficiency that the existing ordinary axial force meter bolt pre-tightening force measurement device can only be used for a single threaded fastener, and can measure the pre-tightening force of multiple bolts , but cannot monitor the pre-tightening force of the bolts online in real time

201310235117.3 discloses a new method capable of real-time on-line monitoring of bolt pre-tightening force, by installing a threaded fastener pre-tightening force measuring device between the fastener and the fastened object to monitor the change of bolt pre-tightening force, But this method is not conducive to the measurement of small bolt preload

The principle of 200720087776.7 is similar to that of 201310235117.3, except that the change of preload is monitored by the gasket sensor, but because the size of the bolt is not fixed, the preload measuring device needs to be customized to meet the measurement needs

According to the measurement objects of the above-mentioned inventions and utility models, there are currently few methods for real-time online monitoring of the pretension force of composite material connection structures.

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