Layered damage repair method for aircraft panel

Abstract

The invention provides an aircraft panel layered damage repair method, which comprises the following steps: taking a crack as a reference, if the crack is close to the inner side of an opening frame, completely removing the opening frame flange crack on the inner side of the opening frame along the direction parallel to the crack; if the crack is close to the outer side of the mouth frame, completely removing the mouth frame flange crack on the outer side of the mouth frame in the direction parallel to the crack; carrying out nondestructive testing on the mouth frame part; the mouth frame part is coated with oxidation liquid; if the milled part is located on the inner side of the opening frame, a base plate part is manufactured, and after the base plate part is subjected to yellow anodizing, polyurethane primer is sprayed; if the milling part is located on the outer side of the mouth frame, a mouth cover pressing ring part is manufactured, and the mouth cover pressing ring part is milled to replace an original mouth cover pressing ring part; if the milling part is located on the inner side of the opening frame, the milling part of the opening frame is coated with sealant; and the contact surface of the base plate part and the milling part of the mouth frame is coated with sealant, and then the base plate part is installed on the milling part of the mouth frame. Outfield quick repair response time can be reduced, and aircraft safety and reliability are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft wing structure repair, and in particular relates to a layered damage repair method for aircraft wall panels. Background Art

[0002] With the rapid development of digital design and manufacturing technology in the aviation industry, aircraft structural design has adopted a large number of integral structural designs. The integral fuel tank of an aircraft is an important structural component of the aircraft. If it is damaged or leaked during use, it will easily lead to serious consequences. The integral fuel tank has extremely high sealing performance. At the same time, it needs to maintain the good appearance of the aircraft and participate in the overall force of the aircraft. How to better solve the maintenance and repair problems of the integral fuel tank of the aircraft and shorten the maintenance and repair time is of great significance to improving the utilization rate of the aircraft, reducing flight hazards, and reducing maintenance and repair costs. The wall panel of the integral fuel tank integrates the wing skin with the long stringer, vertical ribs, docking and other structural parts that can be attached (such as the oil filling port frame, inspection port frame, etc.) into an integral processing. This type of wall panel has a complex structure, the surface of the part is a curved surface, and the required material blank is relatively thick. Therefore, the process method of first flat plate machining and then integral press bending is adopted; but press bending is a very complex elastic-plastic deformation process, and the residual stress of the wall panel during the rebound process is still large at the top and root of the rib. As the service environment of aircraft becomes increasingly harsh (humid marine atmosphere, heavy salt fog, strong sea waves, large temperature differences, etc.), materials are more sensitive to stress corrosion cracking under harsh corrosion conditions, resulting in stress corrosion cracks in the wall panel inspection frame.

[0003] The integral wall panels of aircraft wings have the same lifespan as the aircraft. The wall panels are usually equipped with elliptical maintenance covers. When cracks appear in the cover frame, the traditional repair method is to cut off the cracked wall panel, or make special seals, or replace the entire wall panel with a new one. However, cutting off the wall panel will interrupt the main force transmission path of the entire wall panel; special seals need to be re-molded, which is costly; replacing new wall panels has great safety risks: the sealant at the sealing ribs is difficult to debond; removing the cracked wall panels may cause the wing box to deform, requiring new assembly tooling to ensure; after replacing the new wall panels, the two end surfaces of the wing box section need to be re-finished, which may cause the hole diameter of the connection part to exceed the tolerance, etc., posing a flight safety hazard. Summary of the invention

[0004] In order to solve the problems in the prior art that when cracks appear in the aircraft mouth frame, the main force transmission route is interrupted due to the cutting of the wall panel, the cost of special seals is high, and the replacement of the whole wall panel brings great risks, the present invention provides a method for repairing cracks in the aircraft wall panel mouth frame, which does not change the structural force transmission route and meets the strength design requirements, solves the problems of cutting off the wall panel to interrupt the force transmission path, the high cost of special seals, and the safety risks caused by replacing the whole wall panel. In addition, the method is simple, convenient, and fast, which reduces the response time of rapid repairs in the field and improves the safety and reliability of the aircraft. The technical scheme is as follows:

[0005] In a first aspect, a method for repairing layered damage of an aircraft panel is provided, the method comprising:

[0006] Step 1: Taking the crack as a reference, if the crack is close to the inner side of the mouth frame, the crack of the mouth frame flange is completely removed on the inner side of the mouth frame in a direction parallel to the crack by milling, and the two ends of the mouth frame are chamfered after removal; if the crack is close to the outer side of the mouth frame, the crack of the mouth frame flange is completely removed on the outer side of the mouth frame in a direction parallel to the crack by milling, and the two ends of the mouth frame are chamfered after removal;

[0007] Step 2: Perform nondestructive testing on the removed mouth frame. If the test result is good and there is no internal damage or surface damage, proceed to step 3.

[0008] Step 3, coating the removed mouth frame with an oxidizing liquid, and then spraying multiple layers of polyurethane primer;

[0009] Step 4, if the milling part is located on the inner side of the mouth frame, a backing plate part is manufactured, the shape of which matches the milling shape of the inner side of the mouth frame, and the backing plate part is yellow anodized and then sprayed with a layer of polyurethane primer; if the milling part is located on the outer side of the mouth frame, a mouth cover pressure ring part is manufactured, and the mouth cover pressure ring part is milled to make the inner side of the mouth cover pressure ring part partially thickened and match the milling shape of the outer side of the mouth frame, and the original mouth cover pressure ring part is replaced with the milled mouth cover pressure ring part, and the repair work in this case is completed;

[0010] Step 5: If the milling part is located inside the mouth frame, apply a layer of sealant on the milling part of the mouth frame; proceed to step 6;

[0011] Step 6: Apply a layer of sealant on the contact surface between the backing plate part and the milled part of the frame to ensure the sealing of the fuel tank, and then install the backing plate part on the milled part of the frame.

[0012] Furthermore, the method further comprises:

[0013] Step 7: Perform strength assessment on the repaired siding frame structure to determine whether it meets the strength requirements; if it does, it is determined that the siding frame structure has been repaired successfully.

[0014] Optionally, in step 7,

[0015] When evaluating the strength of the repaired wall panel frame structure, the frame is simplified into a beam element and the maximum axial force F = σA at the frame is calculated first. eq , and then according to the axial tension and compression equivalent cross-sectional area A of the repaired mouth frame eq ', calculate the maximum axial stress at the repaired mouth frame σ2=F / A eq ', thus calculating the safety margin MS = σ based on the maximum axial stress at the mouth frame 0.2 / σ2-1, if the safety margin MS is greater than 0, it is determined that the wall panel frame structure is repaired successfully;

[0016] Where σ represents the tensile stress at the mouth frame, A eq represents the equivalent cross-sectional area of ​​the original frame in axial tension and compression, σ 0.2 Indicates the yield limit of the mouth frame material.

[0017] Optionally, in step 1, the chamfered corners at both ends of the rear opening frame are removed to R10.

[0018] Optionally, in step 2, the non-destructive testing methods are eddy current and ultrasonic testing.

[0019] Optionally, the polyurethane primer in step 3 and step 4 is S06-1010H polyurethane primer.

[0020] Optionally, the sealant in step 5 and step 6 is XM-22 sealant.

[0021] Optionally, in step 6, the backing plate part is installed on the milling portion of the mouth frame by means of double-sided countersunk ring groove sealing rivets.

[0022] Optionally, in step 4, the material of the backing plate part is the same as the material of the wall plate, and the material of the mouth cover pressure ring part is the same as the material of the original mouth cover pressure ring part.

[0023] The beneficial effects of the present invention are at least:

[0024] The repair method of the present invention specially manufactures a backing plate part of the same material as the wall panel or a cover pressure ring part similar to the original cover pressure ring. The structural force transmission route is not changed, and the strength design requirements are met, which solves the problems of interrupting the force transmission path by cutting off the wall panel, high cost of special seals, and safety risks caused by replacing the entire wall panel. In addition, the method is simple, convenient and fast, which reduces the response time of rapid repair in the field and improves the safety and reliability of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a partial schematic diagram of the inspection opening frame of the wing upper wall panel;

[0026] Figure 2This is a typical schematic diagram of the wing upper panel frame and cover coordination;

[0027] Figure 3 To strengthen the minimum cross-sectional dimensions of the mouth frame;

[0028] Figure 4 is the crack length and depth;

[0029] Figure 5 For crack location and grinding condition;

[0030] Figure 6 This is the mouth frame milling area;

[0031] Figure 7 It is a schematic diagram of the pad parts;

[0032] Figure 8 It is a schematic diagram of the connection between the wall plate and the backing plate parts;

[0033] Fig. 9 It is a schematic diagram of the cover pressure ring parts;

[0034] Fig.10 The present invention is a flow chart of the aircraft wall panel layered damage repair method. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below through specific implementation modes and drawings.

[0036] See also Fig.10 An embodiment of the present invention provides a layered damage repair method for aircraft wall panels, the method comprising the following steps:

[0037] Step 1: Taking the crack as a reference, if the crack is close to the inner side of the mouth frame, the crack of the mouth frame flange is completely removed on the inner side of the mouth frame in a direction parallel to the crack by milling, and the two ends of the mouth frame are chamfered after removal; if the crack is close to the outer side of the mouth frame, the crack of the mouth frame flange is completely removed on the outer side of the mouth frame in a direction parallel to the crack by milling, and the two ends of the mouth frame are chamfered after removal;

[0038] Step 2: Perform nondestructive testing on the removed mouth frame. If the test result is good and there is no internal damage or surface damage, proceed to step 3.

[0039] Step 3, coating the removed mouth frame with an oxidizing liquid, and then spraying multiple layers of polyurethane primer;

[0040] Step 4, if the milling part is located on the inner side of the mouth frame, a backing plate part is manufactured, the shape of which matches the milling shape of the inner side of the mouth frame, and the backing plate part is yellow anodized and then sprayed with a layer of polyurethane primer; if the milling part is located on the outer side of the mouth frame, a mouth cover pressure ring part is manufactured, and the mouth cover pressure ring part is milled to make the inner side of the mouth cover pressure ring part partially thickened and match the milling shape of the outer side of the mouth frame, and the original mouth cover pressure ring part is replaced with the milled mouth cover pressure ring part, and the repair work in this case is completed;

[0041] Step 5: If the milling part is located inside the mouth frame, apply a layer of sealant on the milling part of the mouth frame; proceed to step 6;

[0042] Step 6: Apply a layer of sealant on the contact surface between the backing plate part and the milled part of the frame to ensure the sealing of the fuel tank, and then install the backing plate part on the milled part of the frame.

[0043] Embodiment 1:

[0044] Crack description: Right wing upper panel rib 4 to rib 5 fuel tank inspection frame (material: 1973T2), see Figure 1 , Figure 2 , its typical circumferential cross section is shown in Figure 3 Obvious circumferential cracks were found on the side surface. After eddy current and ultrasonic flaw detection, the crack fault was initially determined as follows: (1) The crack length was about 100 mm. Figure 4 The maximum depth is about 15 mm. Except for the two ends, the depth of the rest parts is uniform. The minimum distance between the crack and the end face of the long stringer is 18 mm. (2) The distance between the crack and the upper surface of the mouth frame is about 9 mm, and the distance from the lower surface of the mouth frame is about 6 mm. The height of the side end face of the mouth frame from the upper and lower surfaces remains basically unchanged along the circumference of the mouth frame. Figure 5 .

[0045] Taking the above crack as an example, a layered damage repair method for aircraft wall panels provided by the present invention may specifically include the following steps:

[0046] 1) According to the crack position, take the crack as the reference, completely mill out the crack of the mouth frame flange parallel to the crack direction on the inner side of the mouth frame, mill the crack depth direction according to 19mm, and make the sharp corner R4 smooth transition; ensure that the crack is completely removed along the crack length direction, and the two ends R10 are smooth transition, see Figure 6 ;

[0047] 2) After the mouth frame flange is milled, non-destructive testing is performed on the milled parts. If there is no internal damage or surface damage, continue to execute according to this plan; if there is damage, it is necessary to repeat 1);

[0048] 3) After inspection, apply oxidation liquid to the milled parts, and then spray multiple layers of S06-1010H polyurethane primer;

[0049] 4) Press Figure 7 A special pad part is made of 1973T2 material, and its shape is determined by the span-wise milling size; the pad is anodized yellow and then coated with S06-1010H polyurethane primer;

[0050] 5) Apply a layer of XM-22 sealant on the milled part of the mouth frame;

[0051] 6) Before installing the pad and the wall panel frame, a layer of XM-22 sealant is applied on the contact surface according to relevant technical conditions (technical conditions for manufacturing the integral fuel tank of the central wing and the middle and outer wings, etc.) to ensure the sealing of the fuel tank.

[0052] 7) Special pad parts Figure 8 As shown, it is connected to the mouth frame with a gasket, and connected with 5 double-sided countersunk ring groove sealing rivets. The margin of the rivets at both ends along the length of the crack is 9mm, and the 4 in the middle are equally spaced; the margin of the 5 rivets along the depth of the crack is 7mm; after the gasket is connected, the excess sealant at the mouth frame is removed; when the rivet is countersunk at the connection surface between the mouth frame and the metal sealing ring, it is made at an angle of 90°, with a countersunk diameter of D=5mm and a depth of less than 1.7mm. To ensure the installation of the sealing ring, the double-buried rivet should be smooth and flat after connection, without burrs, and flush with the original mouth frame. When the countersunk is φ5, the part entering the R area of ​​the mouth frame has a smooth transition.

[0053] 8) Strength analysis

[0054] When evaluating the strength of the repaired wall panel frame structure, the frame is simplified into a beam element and the maximum axial force F = σA at the frame is calculated first. eq , and then according to the axial tension and compression equivalent cross-sectional area A of the repaired mouth frame eq ', calculate the maximum axial stress at the repaired mouth frame σ2=F / A eq ', thus calculating the safety margin MS = σ based on the maximum axial stress at the mouth frame 0.2 / σ2-1, if the safety margin MS is greater than 0, it is determined that the wall panel frame structure is repaired successfully;

[0055] Where σ represents the tensile stress at the mouth frame, A eq represents the equivalent cross-sectional area of ​​the original frame in axial tension and compression, σ 0.2 Indicates the yield limit of the mouth frame material.

[0056] a) Qualitative analysis:

[0057] The No. 2 upper wall plate of the outer wing in the impact analysis is an integral machined part, made of 1973T2.

[0058] (σ 0.2 =441MPa), the specific structure is as follows Figure 1 shown.

[0059] Depend on Figure 1It can be seen that the two long girders of the wing are disconnected on both sides of the mouth frame. In order to transfer the load of the long girders and the load of the wall panel, the inspection mouth frame is partially strengthened. The minimum cross-sectional size of the inspection mouth frame reinforcement is as follows: Figure 3 As shown, the strengthened inspection port frame mainly bears axial tensile pressure.

[0060] Depend on Figure 5 It can be seen that the milling area is located near the center line of the mouth frame, which mainly plays the role of fixing the inspection cover and mainly bears the axial tensile and compressive stress of the mouth frame.

[0061] After the crack area is milled out, the cross-sectional area of ​​the mouth frame decreases and the axial tensile and compressive stresses of the mouth frame increase.

[0062] b) Strength assessment:

[0063] Specifically, the strength assessment includes the following steps:

[0064] 1. Calculate the maximum axial force at the mouth frame:

[0065] After checking the document "Finite element model and stress analysis of the outer and middle wings of a certain type of aircraft", the maximum axial tensile stress σ of the finite element solution of the whole machine at the mouth frame is 137.93MPa, and the maximum axial compressive stress σ is 254.72MPa.

[0066] Depend on Figure 3 It can be seen that the minimum cross-sectional area of ​​the reinforcement frame is:

[0067] A=A1+A2+A3=(33-4.3-15)×21+15×(19+21)+4.3×(19-14+21)=999.5mm 2 .

[0068] Section centroid:

[0069]

[0070] The distance between the bottom of the section and the chord line is h0 = 74.37 mm, so the equivalent cross-sectional area is:

[0071] A eq =A×((18.15+74.37) / (33+74.37)) 2 =731.6mm 2 .

[0072] Maximum axial force at the mouth frame F = σA eq =254.72×731.6=186353.15N.

[0073] 2. Calculate the equivalent cross-sectional area after repair:

[0074] Depend on Figure 5 It can be known that the minimum cross-sectional area of ​​the mouth frame after milling is:

[0075] A'=A1'+A2'+A3'=21×(33-4.3-15+6)+(19+21)×(15-6)+(21+19-14)

[0076] ×4.3=885.50mm 2 .

[0077] Section centroid:

[0078]

[0079] Equivalent cross-sectional area:

[0080] A eq '=A'×((18.34+74.37) / (33+74.37)) 2 =660.20mm 2 .

[0081] The calculation shows that the minimum cross-sectional area of ​​the mouth frame is reduced by 11.41%, and the minimum equivalent cross-sectional area of ​​the mouth frame is reduced by 9.76%.

[0082] 3. Calculate the maximum axial force and safety margin MS after repair

[0083] σ2=F / A eq '=186353.15 / 660.20=282.27MPa.

[0084] MS=σ 0.2 / σ2-1=441 / 282.27-1=0.56.

[0085] The strength design requirements were met and the siding frame structure was repaired successfully.

[0086] If the crack is close to the outside of the mouth frame, Fig. 9 Special cover pressure ring parts are used for repair.

[0087] The above only expresses the implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. In addition, the parts not detailed in the present invention are all conventional technologies.

Claims

1. A method for repairing layered damage of aircraft panels, characterized in that: The method comprises: Step 1: Taking the crack as a reference, if the crack is close to the inner side of the mouth frame, the crack of the mouth frame flange is completely removed on the inner side of the mouth frame in a direction parallel to the crack by milling, and the two ends of the mouth frame are chamfered after removal; if the crack is close to the outer side of the mouth frame, the crack of the mouth frame flange is completely removed on the outer side of the mouth frame in a direction parallel to the crack by milling, and the two ends of the mouth frame are chamfered after removal; Step 2: Perform nondestructive testing on the removed mouth frame. If the test result is good and there is no internal damage or surface damage, proceed to step 3. Step 3, coating the removed mouth frame with an oxidizing liquid, and then spraying multiple layers of polyurethane primer; Step 4, if the milling part is located on the inner side of the mouth frame, a backing plate part is manufactured, the shape of which matches the milling shape of the inner side of the mouth frame, and the backing plate part is yellow anodized and then sprayed with a layer of polyurethane primer; if the milling part is located on the outer side of the mouth frame, a mouth cover pressure ring part is manufactured, and the mouth cover pressure ring part is milled to make the inner side of the mouth cover pressure ring part partially thickened and match the milling shape of the outer side of the mouth frame, and the original mouth cover pressure ring part is replaced with the milled mouth cover pressure ring part, and the repair work in this case is completed; Step 5: If the milling part is located inside the mouth frame, apply a layer of sealant on the milling part of the mouth frame; proceed to step 6; Step 6: Apply a layer of sealant on the contact surface between the backing plate part and the milled part of the frame to ensure the sealing of the fuel tank, and then install the backing plate part on the milled part of the frame.

2. The method according to claim 1, characterized in that The method further comprises: Step 7: Perform strength assessment on the repaired siding frame structure to determine whether it meets the strength requirements; if it does, it is determined that the siding frame structure has been repaired successfully.

3. The method according to claim 2, characterized in that In step 7, When evaluating the strength of the repaired wall panel frame structure, the frame is simplified into a beam element and the maximum axial force F = σA at the frame is calculated first. eq , and then according to the axial tension and compression equivalent cross-sectional area A of the repaired mouth frame eq ', calculate the maximum axial stress at the repaired mouth frame σ2=F / A eq ', thus calculating the safety margin MS = σ based on the maximum axial stress at the mouth frame 0.2 / σ2-1, if the safety margin MS is greater than 0, it is determined that the wall panel frame structure is repaired successfully; Where σ represents the tensile stress at the mouth frame, A eq represents the equivalent cross-sectional area of ​​the original frame in axial tension and compression, σ 0.2 Indicates the yield limit of the mouth frame material.

4. The method according to claim 1, characterized in that: In step 1, remove the rounded corners of both ends of the rear frame to R10.

5. The method according to claim 1, characterized in that In step 2, the non-destructive testing methods are eddy current and ultrasonic testing.

6. The method according to claim 1, characterized in that The polyurethane primer in step 3 and step 4 is S06-1010H polyurethane primer.

7. The method according to claim 1, characterized in that The sealant used in step 5 and step 6 is XM-22 sealant.

8. The method according to claim 1, characterized in that In step 6, the backing plate part is installed on the milling part of the mouth frame through double-sided countersunk ring groove sealing rivets.

9. The method according to claim 1, characterized in that: In step 4, the material of the backing plate part is the same as the wall plate material, and the material of the mouth cover pressure ring part is the same as the original mouth cover pressure ring part material.

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