JP2021060356A - Method for detecting defects of honeycomb structure - Google Patents

Abstract

To easily detect defects of a honeycomb core with high accuracy.SOLUTION: Disclosed is a method for detecting defects of a honeycomb structure which is formed by sandwiching a honeycomb core between a pair of skins. This method includes: an installation step of installing an ultrasound probe in the outer surface of only one skin of the pair of skins; and a flaw detection step of performing the ultrasonic flaw detection by transmitting an ultrasonic wave from the ultrasonic probe into the honeycomb structure. In the flaw detection step, the ultrasonic wave of a predetermined frequency is transmitted from the ultrasonic probe so as to reach the other skin and a bottom reflected wave reflected from the other skin is received by the ultrasonic probe.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a method for detecting defects in a honeycomb structure.

In recent years, a technique for forming the wings and fuselage of an aircraft by a honeycomb structure has been widely used. As an example, the honeycomb structure has a honeycomb core having a hexagonal cross-sectional shape and being formed by arranging a plurality of hollow bodies extending in the thickness direction, and a skin covering the honeycomb core from both sides in the thickness direction. ing.
When a honeycomb structure is used as an aircraft member, defects may occur at the interface (adhesive layer) between the honeycomb core and the skin or inside the skin due to stress or the like that is repeatedly applied during operation.

As a technique for detecting such defects by non-destructive inspection, Patent Document 1 below discloses a device using an ultrasonic converter as a 1 MHz input type converter. This device has a drive probe arranged on one surface of the inspection object and a tracking probe arranged on the other surface on the opposite side of the one surface, and detects defects in the inspection object by a so-called transmission method. Therefore, in the case of an inspection object in which a closed space is formed inside, such as a flap of an aircraft member, the tracking probe cannot be placed in the internal space. Further, since the tracking probe is held only by the magnet with respect to the driving probe, the scanning speed is limited to the extent that the tracking probe follows, and the degree of freedom of scanning is low.

Further, Patent Document 2 discloses an apparatus for inspecting using ultrasonic waves after removing the skin on the surface of the honeycomb structure. The purpose of the device is not to inspect the honeycomb structure but to inspect the solid plate to which the honeycomb core is attached. When using this device, a polymer gel is inserted into the gap between the honeycomb cores to propagate ultrasonic waves into the polymer gel. That is, the solid plate is inspected via the polymer gel.

Further, Non-Patent Document 1 discloses a technique for non-destructively testing a joint portion of an aircraft composite material. It is said that this technique can detect peeling between the skin and the honeycomb core. That is, this technique employs a wideband 1 MHz probe that resonates within the structure to be inspected when excited by a strong square wave pulse. The receiver filter of the measuring device is adjusted to the thickness of the honeycomb structure and operates at the corresponding half wavelength. If there is peeling between the skin and the honeycomb core, the rigidity of the structure is reduced, the wavelength of resonance is lengthened, and the resonance frequency is lowered. For example, the bottom surface signal is attenuated by 6 to 12 dB due to the peeling of 25 mm × 25 mm on the internal structure. Therefore, the energy that can be incident is significantly reduced.

Here, if the technique of Non-Patent Document 1 is to be adopted, a strong rectangular wave pulse is required, so that special equipment is required. Also, the receiver filter must be adjusted to the thickness of the honeycomb structure. That is. Every time the thickness of the honeycomb structure changes, it is necessary to scan the frequency band that seems to be appropriate, find the appropriate frequency, and then perform the inspection, which complicates the work.

In addition, a method of detecting defects by a so-called NON-CONTACT type ultrasonic probe is also known, but it has a drawback that the energy that can be incident is significantly reduced. Therefore, the ultrasonic waves reflected from the back surface of the honeycomb structure cannot be detected.

Japanese Unexamined Patent Publication No. 2005-337395 International Publication No. 2017/1687995

Non-destructive joint testing of aircraft composites, [online], [Searched September 13, 1991], Internet <https://www.olympus-ims.com/en/applications/non-destructive-bond -testing-aircraft-composites />

The present disclosure has been made to solve the above problems, and is capable of easily and accurately detecting defects in the entire honeycomb structure having a pair of skins and a honeycomb core. The purpose is to provide a method.

In order to solve the above problems, the defect detection method for the honeycomb structure according to the present disclosure is a defect detection method for the honeycomb structure in which the honeycomb core is sandwiched between a pair of skins, and is one of the pair of skins. It is provided with an installation step of installing an ultrasonic probe on the outer surface of only the skin of the above, and a flaw detection step of transmitting ultrasonic waves from the ultrasonic probe to the inside of the honeycomb structure to perform ultrasonic flaw detection. In the flaw detection step, ultrasonic waves having a predetermined frequency are transmitted from the ultrasonic probe so as to reach the other skin, and the bottom surface reflected wave reflected from the other skin is transmitted by the ultrasonic probe. Receive.

According to the defect detection method of the honeycomb structure of the present disclosure, it is possible to easily and accurately detect the entire defect of the honeycomb structure including the honeycomb core.

It is sectional drawing which shows an example of the honeycomb structure to which the detection apparatus which concerns on embodiment of this disclosure is applied. FIG. 5 is an enlarged cross-sectional view of a main part showing an enlarged area Z in FIG. It is sectional drawing which looked at the honeycomb core which concerns on embodiment of this disclosure from the thickness direction. It is a flowchart which shows each step of the defect detection method of the honeycomb structure which concerns on embodiment of this disclosure.

(Structure of wing body)
Hereinafter, the defect detection method for the honeycomb structure and the detection device 90 according to the embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. The detection device 90 is a device used for detecting defects in the blade body 100. As shown in FIG. 1, the airfoil 100 has an airfoil cross-sectional shape extending from the front edge L toward the trailing edge T. Of the pair of surfaces connecting the front edge L and the trailing edge T, one surface is a negative pressure surface Sn that bulges outward in a curved shape, and the other surface is a positive pressure surface Sp that dents inward. Has been done.

Specific examples of the wing body 100 include aircraft flaps, slats, ailerons, elevators, ladders, and the like. Although not shown in detail, these members are attached to the main wing, tail wing, and vertical stabilizer as auxiliary wings of an aircraft. The wing body 100 has a hollow structure.

(Structure of honeycomb structure)
As shown enlarged in FIG. 2, the wall surface of the blade body 100 is formed by the honeycomb structure 80. The honeycomb structure 80 has a laminated structure including a pair of skins 1, a honeycomb core 2 sandwiched between the skins 1, and an adhesive layer g for connecting the skins 1 and the honeycomb core 2. ..

The skin 1 is formed of a composite material containing, for example, CFRP (Carbon Fiber Reinforced Plastic) or GFRP (Glass Fiber Reinforced Plastic). As an example, the honeycomb core 2 is formed by arranging a plurality of hollow bodies 21 having a hexagonal cross-sectional shape when viewed from the thickness direction so as to be adjacent to each other without a gap, as shown in FIG. The honeycomb core 2 is arranged so that the extending direction of the hollow body 21 is along the blade height direction of the blade body 100.

A pair of skins 1 are attached to both sides of the honeycomb core 2 in the thickness direction via an adhesive layer g. Of these pair of skins 1, the skin 1 forming the outer surface of the wing body 100 is referred to as the surface side skin 1a. The skin 1 forming the inner surface of the wing body 100 is the back surface side skin 1b.

The surface of the surface side skin 1a facing the outside of the blade body 100 (that is, the opposite side of the honeycomb core 2) is the outer surface A1, and a detection device 90 described later is installed on the outer surface A1. The inward facing surface of the surface side skin 1a is the inner surface A2. The inner surface A2 is bonded to one side surface (core outer surface B1) of the honeycomb core 2 via the first adhesive layer g1.

The surface of the back surface side skin 1b facing the outside (that is, the honeycomb core 2 side) of the blade body 100 is the outer surface A3. The outer surface A3 is bonded to the other surface (core inner surface B2) of the honeycomb core 2 via the second adhesive layer g2. The inward facing surface of the back surface side skin 1b is the inner surface A4. A space is formed inside the inner surface A4.

(Configuration of detection device)
The detection device 90 is arranged on the surface (outer surface A1) of the surface side skin 1a to inspect the entire honeycomb structure 80 for defects by ultrasonic waves (ultrasonic flaw detection is performed). That is, the detection device 90 is an ultrasonic probe. The detection device 90 allows ultrasonic waves to reach from the outer surface A1 to the second adhesive layer g2. More specifically, the frequency of the ultrasonic wave emitted from the detection device 90 is 500 kHz or more and 1 MHz or less.

Further, the standard of the honeycomb structure 80 capable of detecting flaws by ultrasonic waves of the above frequency is determined by the shape and dimensions of the honeycomb core 2 and the material of the skin 1. Specifically, a hexagonal (Hex type) honeycomb shape, a honeycomb size of 3.2 mm, a honeycomb core 2 having a thickness of 5.0 mm, 9.5 mm or 23 mm, and a rectangular (Ox type) honeycomb shape. A honeycomb core 2 having a honeycomb size of 4.8 mm and a thickness of 19.5 mm is suitable.

(Defect detection method)
Next, a defect detection method for the honeycomb structure 80 according to the present embodiment will be described with reference to FIG. This method includes an installation step S1 and a flaw detection step S2. In the installation step S1, the detection device 90 is installed only on the outer surface A1 of only one skin 1 (front surface side skin 1a). In the flaw detection step S2, ultrasonic flaw detection is performed by the reflection method. That is, in the flaw detection step S2, while moving the detection device 90 along the surface of the surface side skin 1a, ultrasonic waves are transmitted from the detection device 90 to the inside of the honeycomb structure 80 to perform ultrasonic flaw detection. In the flaw detection step S2, the ultrasonic waves having the predetermined frequency described above are transmitted from the detection device 90 so as to reach the other skin 1 (back surface side skin 1b).

When there is no defect in any part of the honeycomb structure 80, the ultrasonic wave transmitted from the detection device 90 passes through the surface side skin 1a, the first adhesive layer g1, the honeycomb core 2, and the second adhesive layer g2. It propagates to the back skin 1b. Then, as a result of the ultrasonic waves being reflected by the inward facing surface A4 on the back surface side skin 1b, the reverse path, that is, the second adhesive layer g2, the honeycomb core 2, the first adhesive layer g1, and the front surface is used as the bottom surface reflected wave. It reaches the detection device 90 via the side skin 1a. That is, the ultrasonic waves transmitted from the detection device 90 are the front surface side skin 1a, the first adhesive layer g1, the honeycomb core 2, the second adhesive layer g2, the back surface side skin 1b, the second adhesive layer g2, the honeycomb core 2, and the second. It proceeds along a path R that sequentially passes through one adhesive layer g1 and the surface side skin 1a. When there is no defect in the honeycomb structure as described above, the bottom reflected wave is normally received by the detection device 90.

On the other hand, for example, when a defect is present in the surface side skin 1a or the first adhesive layer g1, the ultrasonic wave transmitted from the detection device 90 is reflected by the defect portion. As a result, the ultrasonic waves do not reach the inward facing surface A4 of the back surface side skin 1b, so that the bottom surface reflected wave is not received by the detection device 90. If the bottom surface reflected wave is not received by the detection device 90, it is determined that there is a defect in any part of the honeycomb structure 80. Specific examples of the defect in the first adhesive layer g1 include peeling between the surface side skin 1a and the honeycomb core 2.

Further, for example, when a defect exists in the honeycomb core 2, the ultrasonic wave transmitted from the detection device 90 is reflected at the defect portion. As a result, similarly to the above, the bottom reflected wave travels in a direction deviating from the initial path R, is not received by the detection device 90, and it is determined that there is a defect in any part of the honeycomb structure 80. Since the honeycomb core 2 has a hollow structure as described above, it has been considered extremely difficult to detect flaws from one side by ultrasonic waves. However, by setting the ultrasonic frequency to 500 kHz or more and 1 MHz or less as described above, it is possible to detect the defect of the honeycomb core 2.

Further, for example, when a defect is present in the back surface side skin 1b or the second adhesive layer g2, the ultrasonic wave transmitted from the detection device 90 is reflected by the defect portion deviating from the path R. As a result, the bottom reflected wave is not received by the detection device 90 as described above. If the bottom surface reflected wave is not received by the detection device 90, it is determined that there is a defect in any part of the honeycomb structure 80. Specific examples of the defect in the second adhesive layer g2 include peeling between the back surface side skin 1b and the honeycomb core 2.

(Action effect)
According to the above method, defects in the honeycomb structure 80 can be detected only by installing the detection device 90 on the outer surface A1 of one of the skins 1. That is, not only defects at the boundary between the front surface side skin 1a and the back surface side skin 1b but also internal defects at the back surface side skin 1b and the honeycomb core 2 can be detected. That is, even for the honeycomb structure 80 in which probes and the like cannot be arranged on both sides of the honeycomb structure 80 in the thickness direction as in the conventional case, ultrasonic flaw detection of the entire honeycomb structure 80 can be easily performed from the outside. it can.

Therefore, for example, the defect inspection can be performed without disassembling the bag structure of the flap of the aircraft formed from the honeycomb structure 80. That is, since the reflection method is used in the flaw detection step S2, it is not necessary to provide an ultrasonic probe on the front surface of the back surface side skin 1b, so that the work can be performed efficiently and smoothly. If it is necessary to provide a pair of ultrasonic probes so as to sandwich the honeycomb structure 80, it is necessary to hold these ultrasonic probes with magnets or the like. Therefore, there is a risk of dropping, which is not preferable in terms of safety. In the defect detection method of the present embodiment, such a demerit can be avoided.

Further, in the present embodiment, by setting the frequency of the ultrasonic wave to a predetermined value, it is possible to inspect by the reflection method from one side. Therefore, for example, a special device that emits a strong rectangular wave pulse is not required, and the inspection can be performed by a normal ultrasonic flaw detection device.
Further, the inspection device 90 may be installed on the surface side skin 1a and moved along the surface thereof, and it is not necessary to adjust the frequency corresponding to the thickness of the honeycomb structure 80, for example.
Further, since the presence or absence of a defect can be determined by whether or not the bottom reflected wave can be received, it is possible to perform highly accurate defect detection with less noise.

Although the embodiments of the present disclosure have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within a range not deviating from the gist of the present disclosure are also included.

<Additional notes>
The defect detection method of the honeycomb structure 80 described in each embodiment is grasped as follows, for example.

(1) The defect detection method for the honeycomb structure 80 according to the first aspect is a defect detection method for the honeycomb structure 80 in which the honeycomb core 2 is sandwiched between the pair of skins 1, and is among the pair of skins 1. The installation step S1 in which the ultrasonic probe 90 is installed on the outer surface A1 of only one skin 1, and the ultrasonic probe 90 transmits ultrasonic waves into the honeycomb structure 80 to perform ultrasonic flaw detection. In the flaw detection step S2, ultrasonic waves having a predetermined frequency are transmitted from the ultrasonic probe 90 so as to reach the other skin 1b, and are reflected from the other skin 1b. The bottom reflected wave is received by the ultrasonic probe 90.

According to the above method, the defect of the honeycomb structure 80 can be detected only by installing the ultrasonic probe on the outer surface A1 of one of the skins 1. That is, even for the honeycomb structure 80 in which probes and the like cannot be arranged on both sides of the honeycomb structure 80 in the thickness direction as in the conventional case, ultrasonic flaw detection can be easily performed from the outside. Further, not only defects at the boundary between one skin 1a and the other skin 1b but also defects at the honeycomb core 2 can be detected.

(2) In the defect detection method of the honeycomb structure 80 according to the second aspect, in the flaw detection step S2, when the ultrasonic wave is transmitted and the bottom surface reflected wave is received, it is determined that there is no defect. If the bottom surface reflected wave is not received, it is determined that any part of the honeycomb structure 80 including the honeycomb core 2 has a defect.

According to the above configuration, defects in the entire honeycomb structure 80 can be detected with high accuracy.

(3) In the defect detection method of the honeycomb structure 80 according to the third aspect, the predetermined frequency is 500 kHz to 1 MHz.

According to the above configuration, the interface between the honeycomb core 2 and the skin 1 and the defects of the honeycomb core 2 itself can be detected with high accuracy.

100 Wing body 90 Detection device 80 Honeycomb structure 1 Skin 1a Front side skin 1b Back side skin 2 Honeycomb core 21 Hollow body A1, A3 Outer surface A2, A4 Inner surface B1 Core outer surface B2 Core inner surface g1 First adhesive layer g2 Second adhesive layer L Front edge R Path Sn Negative pressure surface Sp Positive pressure surface T Trailing edge

Claims (3)

A defect detection method for a honeycomb structure in which a honeycomb core is sandwiched between a pair of skins.
The installation process of installing the ultrasonic probe on the outer surface of only one of the pair of skins, and
A flaw detection process in which ultrasonic waves are transmitted from the ultrasonic probe to the inside of the honeycomb structure to perform ultrasonic flaw detection, and
With
In the flaw detection process,
A honeycomb structure in which an ultrasonic wave having a predetermined frequency is transmitted from the ultrasonic probe so as to reach the other skin, and a bottom reflected wave reflected from the other skin is received by the ultrasonic probe. Defect detection method. In the flaw detection process,
When the ultrasonic wave is transmitted,
When the bottom reflected wave is received, it is judged that there is no defect, and it is judged that there is no defect.
A method for detecting a defect in a honeycomb structure, which determines that any part of the honeycomb structure including the honeycomb core has a defect when the bottom reflected wave is not received. The method for detecting defects in a honeycomb structure according to claim 1 or 2, wherein the predetermined frequency is 500 kHz to 1 MHz.

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