Method for making comparative test blocks for ultrasonic testing of rivets

Abstract

This invention discloses a method for fabricating a rivet ultrasonic testing comparison block, belonging to the technical field of aviation testing specimens. The method pre-embeds a simulated defect at the connection between the pier head and the polished rod. The comparison block produced by the invention features stable simulated defect dimensions, free from factors affecting the stability of the simulated defect during the fabrication process. The invention also cleverly displays the internal structural state of the rivet, skin, and structural component after riveting, assisting later technicians in waveform assessment research and improving the accuracy of rivet testing.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation detection samples and relates to a method for manufacturing a rivet ultrasonic detection comparison test block. Background Art

[0002] The connection between the aircraft air inlet skin and the structural parts adopts riveting technology, which cuts grooves on the skin surface and rivets the skin and structural parts together (such as Figure 1 、 2 As shown in the figure, when the aircraft is repaired, it is necessary to perform ultrasonic testing on the rivet polished rod part in the air inlet (the area from the connection between the rivet head and the polished rod to the connection between the pier head and the polished rod).

[0003] According to the provisions of GJB 1580A "Ultrasonic Testing Methods for Deformed Metals", in order to achieve the purpose of testing the entire rivet polished rod, it is necessary to use the longitudinal wave contact pulse reflection method. Since ultrasonic waves will attenuate when propagating in materials, the simulated defect embedded in the comparison test block used to calibrate the detection sensitivity should be at the connection between the pier head and the polished rod (the maximum position of the sound path). The size of the simulated defect is 0.8mm (chord height) × 0.12mm (slot width). Currently, there are two main methods for making comparison test blocks:

[0004] Method 1: In Figure 1 The possible location of the connection between the pier head and the polished rod is estimated on the rivet polished rod, and then a simulated defect is embedded at this location. The rivet with the simulated defect is then riveted to the skin and structural parts as a comparison test block for testing;

[0005] The second method is to embed the simulated defect on the rivet first, and then rivet the rivet with the simulated defect to the skin and structural parts. The difference is that the location of the simulated defect is selected at Figure 1 The easily identified connection between the rivet head and the polished rod on the rivet polished rod.

[0006] Because simulated defects are embedded in the polished rod during riveting, the simulated defects are affected by the extrusion of the rivets, and their size and direction are easily changed, which directly affects the sensitivity and accuracy of the detection. In addition, the position estimated by the first method has a large deviation, and it may take multiple repetitions to meet the requirements; the second method may miss areas with a large sound path. Therefore, the existing comparison test block production method has a low success rate and cannot guarantee the accuracy of the embedded position of the simulated defects and the sensitivity calibration, which poses a hidden danger to product quality. Therefore, a new method for producing comparison test blocks for rivet ultrasonic testing is needed to ensure that simulated defects can be accurately embedded in the connection between the rivet head, pier head and polished rod, ensure the accuracy of sensitivity calibration, and improve the success rate of making comparison test blocks. Summary of the Invention

[0007] In order to solve the problems in the prior art, the present invention proposes a method for manufacturing a rivet ultrasonic testing comparison test block.

[0008] The technical solution of the present invention is:

[0009] A method for preparing a rivet ultrasonic testing comparison test block comprises the following steps:

[0010] Step 1: Select metal plates with the same material and specifications as the rivet assembly part to be inspected, and cut them into regular shapes. The number of metal plates cut for each material and specification is 2;

[0011] Step 2: Use general milling equipment to mill the cut metal sheets into rectangles or squares of the same size and remove burrs. Metal sheets of the same material and specifications are used in pairs;

[0012] Step 3: Select a steel plate with a thickness greater than the thickness of the rivet assembly to be inspected, and machine a groove on its surface. The groove should be larger than the assembled metal plates, but not too large. The corners of the groove should be machined into an arc shape to facilitate the removal of the metal plates from the groove. The radius of the arc should not be too large, and the center of the arc should be the intersection of the two adjacent sides. Machine a bolt hole at a certain distance on the left and right sides of the groove;

[0013] Step 4: Place the assembled metal sheets into the groove according to the structural form of the rivet assembly part to be inspected, and stack the metal sheets in a cross pattern;

[0014] Step 5: Install screws into the bolt holes on the left and right sides of the groove, place a gasket in the middle, and rotate the screws to make the gasket fit tightly against the upper metal plate to ensure that the metal plate is fixed in the groove;

[0015] Step 6: Use a CNC milling machine to mill a through hole at the joints between the fixed metal plates. The center of the through hole is offset by 1mm from the joints between the two metal plates. The diameter of the through hole is D = d + 0.1mm, where d is the diameter of the polished rod of the rivet being inspected. Then, mill four through holes of the same diameter around it, and then score the five through holes at 90°.

[0016] Step 7: Use the riveting method to rivet rivets into the five through holes. The rivet materials and specifications of the through holes where the metal plates meet are the same as those of the rivets being inspected.

[0017] Step 8: Remove all rivets except those at the joints between the metal sheets.

[0018] Step 9: Separate the metal plates, but do not separate the rivet side of the metal plates where they meet, thus obtaining the riveted rivets. At this point, the rivet status is consistent with the original state, and the connection between the rivet head and the polished rod, as well as the connection between the pier head and the polished rod, are clearly visible.

[0019] Step 10: Use techniques such as electric spark and chemical etching to machine simulated defects of the required size at the connection between the rivet head and the polished rod, and at the connection between the pier head and the polished rod;

[0020] Step 11: Reassemble the rivets with simulated defects and the split metal sheet together, and then re-rivet the through holes after the rivets were removed in step 8. At this point, the comparison test block that meets the requirements is completed.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention realizes the pre-embedding of simulated defects at the connection between the pier head and the polished rod;

[0023] (2) The simulated defect size of the comparison test block produced by the present invention is stable, and there are no factors that affect the stability of the simulated defect during the production process;

[0024] (3) The present invention cleverly presents the internal structural status of the rivets, skin and structural parts after riveting, which can provide assistance to later technicians in their research work on waveform evaluation and improve the accuracy of rivet detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the state of the rivet before riveting.

[0026] Figure 2 Schematic diagram of the rivet structure and assembly status after riveting.

[0027] Figure 3 Schematic diagram of the mold prepared in step 3.

[0028] Figure 4 Schematic diagram of milling 5 through holes in step 6.

[0029] Figure 5 This is a schematic diagram of the riveted metal sheet after being disassembled.

[0030] Figure 6 It is a schematic diagram of the processing flow. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] A structure was simulated: the interior of the air inlet consists of a skin (made of aluminum, δ1.8) and a structural member (made of titanium, δ2.0). The skin and the structural member were riveted together using 90° countersunk rivets (made of aluminum, with a polished rod diameter of 5mm). For this rivet, a corresponding rivet ultrasonic testing comparison test block was prepared, which specifically includes the following steps:

[0033] Step 1: Select aluminum and titanium plates of the same specifications and cut them into 15mm x 30mm rectangles, 2 each;

[0034] Step 2: Use general milling equipment to mill the four rectangular plates to a size of 14mm × 28mm and remove burrs;

[0035] Step 3: Select a 30mm thick steel plate and machine a groove on its surface. The groove dimensions are 30mm (length) × 30mm (width) × 3.8mm (depth). The four corners of the groove are machined into arcs with a radius of 1mm. The center of the arc is the intersection of the two adjacent sides. A bolt hole with a diameter of 5mm is machined on the left and right sides of the groove, 3mm from the edge of the groove.

[0036] Step 4: Combine two 14mm×28mm aluminum plates into a 28mm×28mm aluminum plate and place it in the groove; then combine two 14mm×28mm titanium plates into a 28mm×28mm titanium plate, cross it with the aluminum plate, and stack it on top of the aluminum plate;

[0037] Step 5: Install a screw in the bolt hole with a diameter of 5mm, place a gasket in the middle, and rotate the screw to make the gasket fit tightly with the titanium plate to ensure that the aluminum plate and titanium plate are fixed in the groove;

[0038] Step 6: Use a CNC milling machine to mill out five through holes with a diameter of 5.1mm on the fixed aluminum and titanium plates. Then, make a 90° groove on one side of the titanium plate. Offset the center of the middle through hole by 1mm.

[0039] Step 7: Use the riveting method to rivet rivets into the five through holes. The rivet riveted into the middle through hole is the rivet required for making the comparison test block.

[0040] Step 8: Remove the remaining four rivets except the one in the middle.

[0041] Step 9: Separate the aluminum plate, titanium plate and rivet to obtain the riveted rivet. At this point, the rivet is in the same state as the original one, and the connection between the rivet head and the polished rod, as well as the connection between the pier head and the polished rod, are clearly visible.

[0042] Step 10: Use the electric spark technology to process the simulated defect of the required size at the connection between the pier head and the polished rod;

[0043] Step 11: Reassemble the rivets with simulated defects with the aluminum plate and titanium plate and rivet them together. At this point, the comparison test block that meets the requirements is completed.

Claims

1. A method for making a comparative test block for ultrasonic testing of rivets, characterized in that: The method comprises the following steps: Step 1: Select metal plates with the same material and specifications as the rivet assembly part to be inspected, and cut them into regular shapes. The number of metal plates cut for each material and specification is 2; Step 2: Mill the cut metal sheets into rectangles or squares of the same size and remove burrs. Use metal sheets of the same material and specifications in pairs. Step 3: Select a steel plate with a thickness greater than that of the rivet assembly part to be inspected, and machine a groove on its surface. The groove size is larger than the assembled metal plate; machine a bolt hole on the left and right sides of the groove respectively; Step 4: Place the assembled metal sheets into the groove according to the structural form of the rivet assembly part to be inspected, and stack the metal sheets in a cross pattern; Step 5: Install screws into the bolt holes on the left and right sides of the groove, place a gasket in the middle, and rotate the screws to make the gasket fit tightly against the upper metal plate to ensure that the metal plate is fixed in the groove; Step 6: Mill a through hole at the joints between the fixed metal plates. The center of the through hole is offset by 1mm from the joints between the two metal plates. Then mill four through holes of the same diameter around it, and then score the five through holes at 90°. Step 7: Use the riveting method to rivet rivets into the five through holes. The rivet materials and specifications used in the through holes where two metal plates meet are the same as those of the rivets being inspected. Step 8: Remove all rivets except those at the joints between the metal sheets. Step 9: Separate the metal plates, but do not separate the rivet side of the metal plates where they meet, thus obtaining the riveted rivets. At this point, the rivet status is consistent with the original state, and the connection between the rivet head and the polished rod, as well as the connection between the pier head and the polished rod, are clearly visible. Step 10: Process simulated defects of the required size at the connection between the rivet head and the polished rod, and at the connection between the pier head and the polished rod; Step 11: Reassemble the rivets with simulated defects and the split metal sheet together, and then re-rivet the through holes after the rivets were removed in step 8. At this point, the comparison test block that meets the requirements is completed.

2. The method for making a rivet ultrasonic testing comparison test block according to claim 1, characterized in that: In step 3, the corners of the groove are processed into arc shapes to facilitate taking the metal sheet out of the groove, and the center of the arc is the intersection of the two adjacent sides.

3. The method for making a rivet ultrasonic testing comparison test block according to claim 1 or 2, characterized in that: In step 6, the diameter of the through hole where two metal plates are connected is D=d+0.1 mm, where d is the diameter of the polished rod of the rivet to be inspected.

Images