Flexible circumferential intersected array eddy current sensing film and method for monitoring crack

Abstract

The invention provides a flexible circumferential intersected array eddy current sensing film and a method for monitoring a crack, wherein the film and the method are used for monitoring a bolt connecting structure hole edge crack. The film comprises an intersected sensing array which is composed of at least exciting coil and at least three induction coils. According to the intersected sensing array which is composed of the exciting coil and the induction coils, a lead is printed on a flexible film through flexible printed circuit board technology for manufacturing an integral member. The exciting coil covers the hole wall of the whole connecting structure. The induction coils form an induction coil intersected sensing array which is distributed in the circumferential direction of the boltand has an intersected sensing area. The induction coils of the induction coil intersected sensing array are distributed on the upper side and the lower side of two film layers. When the two film layers are stacked, the induction coils are successively distributed in a staggered manner in one direction for forming the intersected array. The intersected array according to the invention can realizethe same crack identification capability at a random circumferential position and has no crack identification blind area.

Description

technical field [0001] The invention relates to an eddy current sensing film in the field of structural health monitoring, in particular to a flexible circumferential crossing array eddy current sensing film (Circumference-crossing EddyCurrent Array Sensing Film, CECAS) for quantitatively monitoring cracks at the edge of a bolted connection structure, and The invention discloses a method for monitoring cracks in a bolted connection structure through the flexible circumferential cross-array eddy current sensing film. Background technique [0002] The connecting structure is an important load-bearing structure of the aircraft, and the bolt connection is a typical form of the connecting structure of the aircraft. The bolted connection structure has the advantages of strong bearing capacity, high reliability, and convenient disassembly and maintenance. It is usually designed to bear large and complex loads, and there is a phenomenon of stress concentration. Structural load bear...

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Problems solved by technology

See the literature "Rakow A, Chang F K. Astructural health monitoring faster for tracking fatigue crack growth inbolted metallic joints. Structural Health Monitoring, 2012, 11 (3): 253-267." Rakow and Chang of Stanford University proposed a The eddy current sensor pasted on the outer surface of the bolt screw can be used to monitor the expansion of the crack at the edge of the hole, but it cannot quantitatively identify the expansion of the crack along the thickness direction or the radial direction of the bolt

[0004] See the literature "Sun H, Shao J, Wang Y, Qing X. Quantitative monitoring of hole-edge damage growth using eddy current array sensor-based intelligent bolt. Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 1060005 (27March 2018) ,doi:10.1117 / 12.2299272.", and application number CN201710866543.5, a Chinese invention patent titled "Flexible eddy current array sensor and method for monitoring cracks at the edge of holes in bolted joint structures", in order to realize quantitative monitoring of cracks, Sun Hu from Xiamen University, etc. People designed a flexible eddy current array sensor pasted on the screw. The sensor has multiple induction coils to form an array and covers the entire thickness of the connection structure sequentially along the depth direction. It can quantitatively monitor the expansion of cracks around the hole along the depth direction. However, cracks adjacent to the coils cannot be identified

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