A processing method for emergency disconnection safety pin of aircraft main landing gear

Abstract

The present invention discloses a processing method for an emergency breakaway pin for an aircraft main landing gear. The pin is hollow and cylindrical, with two breakaway slots provided in the inner bore corresponding to two locations bearing shear force. A thickened section is provided between the two breakaway slots, and the inner bore diameter corresponding to the thickened section is smaller than that at other locations. The bottom of the breakaway slot is connected to the straight stepped surfaces on both sides by a rounded transition. The emergency breakaway pin of this solution has a breakaway slot design that not only controls precise breakaway but also limits the breakaway area. The rounded transition between the bottom of the breakaway slot and the straight stepped surfaces on both sides improves fatigue strength, and the thickened section between the two breakaway slots improves static strength. The measured breakaway value can be controlled within a range of ±4% of the set threshold, achieving precise breakaway.

Description

Technical Field

[0001] The present invention relates to the field of aviation equipment, and in particular to a method for processing an emergency disconnect pin of an aircraft main landing gear. Background Art

[0002] In addition to using aerodynamics to provide lift for the aircraft, the wings of civil airliners also serve as the aircraft's fuel tanks. The aircraft's main landing gear is located on both sides of the wings close to the fuselage, so it is actually located below the aircraft's fuel tanks. Various extreme situations need to be considered when designing the aircraft. During landing, if the load is too heavy, the landing gear may puncture the fuel tank, causing an explosion and leading to a devastating aviation disaster.

[0003] Emergency breakaway technology is a structural design method designed solely for the safety of the aircraft and its occupants. A more mature implementation of this technology, employed by Boeing and Airbus, involves attaching emergency breakaway pins to the main intersection of the landing gear. These two companies maintain strong confidentiality and exclusivity regarding the use of this technology, making their breakaway designs currently unavailable in my country. The basic principle is that when the landing gear pin experiences pressure exceeding a designed threshold, the emergency breakaway pins disengage, allowing the landing gear to jettison, preventing it from puncturing the fuel tank and potentially rupturing it.

[0004] The difficulty in manufacturing emergency breakaway pins lies in ensuring they precisely break away near the designed breakaway threshold—that is, "break when they shouldn't, but break when they should." This ensures the pins can withstand the loads of normal takeoff and landing, while also enabling timely abandonment of the landing gear in the event of an overloaded landing. To achieve this, the precision of each manufacturing step must be precisely controlled during the production process, and the acceptable product characteristics must be narrowed to a very narrow range. In actual production, each pin must be inspected, starting with the raw materials, and the range of various product characteristics must be strictly controlled at every processing step. These stringent requirements and extremely narrow tolerances result in a very low final yield rate and very high production costs.

[0005] Therefore, how to improve the yield and reduce production costs while ensuring that the final product characteristics meet the standards is a technical problem that technical personnel in this field urgently need to overcome. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an emergency disconnection safety pin for an aircraft main landing gear and a processing method thereof.

[0007] The specific technical solution of the present invention to solve the above technical problems is:

[0008] An emergency disconnect pin for an aircraft main landing gear is hollow cylindrical in shape, with disconnection weak grooves provided at two positions in the inner hole corresponding to the shear force bearing positions. A thickened section is provided between the two disconnection weak grooves, and the inner hole diameter corresponding to the thickened section is smaller than the inner hole diameter at other positions. The bottom of the disconnection weak groove is connected to the straight step surfaces on both sides by a rounded transition.

[0009] Furthermore, it includes a front end flange area, which is processed with a stop-rotation square edge structure boss to prevent the landing gear from rotating safely;

[0010] Furthermore, it includes a tail thread / spline connection area: the tail section of the landing gear safety pin is provided with a thread, and a spline is processed at the rear section of the thread to prevent the nut from loosening.

[0011] This solution has the following beneficial technical effects:

[0012] The safety pin is designed with a breakaway weak groove, which can not only control the precise breakaway, but also limit the breakaway area. At the same time, the R zone design with a rounded transition connection between the bottom of the breakaway weak groove and the straight step surfaces on both sides can improve fatigue strength. The setting of the thickened section between the two breakaway weak grooves can improve static strength.

[0013] The main landing gear safety pin assembly designed in this scheme is installed between the rear joint of the main landing gear and the wing structure. It can simultaneously meet the load-bearing function within the normal load design envelope of the landing gear and the emergency disconnection function under overload conditions. Under normal operating conditions, the safety pin has sufficient strength and rigidity to ensure the transmission of ground loads and maintain the integrity of the aircraft structure. Under vertical load overload conditions, the safety pin can accurately and promptly disconnect when the load reaches the designed disconnection load, ensuring that the overload load is not transmitted to the wing and protecting the wing fuel tank structure.

[0014] The processing method of the emergency disconnection safety pin of the above-mentioned aircraft main landing gear is as follows:

[0015] S1. Select stainless steel bar as the original bar. The length of the original bar, L, is greater than or equal to (the length of the safety pin, l + 60 mm).

[0016] S2, rough processing, the original bar material is rough turned and roughly punched to obtain the safety pin raw material, the single side allowance of the safety pin raw material is ≥0.5mm;

[0017] S3, performing aging treatment under vacuum state to obtain aged raw material;

[0018] S4, blanking process, obtain the safety pin blank and the furnace part blank from the same aged blank, and the length of the furnace part blank is greater than or equal to 60mm;

[0019] S5. Take at least three shear test bars and three tensile test bars along the axial direction of the blank with the furnace, with the centers of the shear test bars and the tensile test bars evenly distributed on a designated circle, and the shear test bars and the tensile test bars are closely adjacent to each other. The designated circle has the center of the blank with the furnace as its center, and its diameter is equal to (blank outer diameter + blank inner hole diameter) / 2;

[0020] S6. Perform a tensile test on the tensile test bar to select the safety pin blanks with a tensile strength within the set threshold value P1±a% as the coarse screening blanks;

[0021] Perform a shear test on the shear test bar corresponding to the coarse screened blank to verify whether the shear strength of the shear test bar corresponding to the coarse screened blank is within the set threshold value P2±a%. The safety pin blank corresponding to the test bar that meets the standards in both the tensile test and the shear test is used as the screened blank. The value of a is based on the allowable fluctuation range of the break value of the final product, such as 0<a<5. The smaller the value of a, the smaller the difference between the actual break value of the final product and the designed break value. The shear strength of the shear test bar is represented by the average shear strength of all qualified samples; the tensile strength of the tensile test bar is represented by the average tensile strength of all qualified samples.

[0022] S6. Process a safety pin with the screened blank, and process a breakaway groove in the inner cavity of the safety pin at the position corresponding to the shear force. Under the premise that the outer diameter of the safety pin and the material properties are fixed, the size of the breakaway groove changes according to the change of the designed breakaway load. Specifically, the greater the designed breakaway load, the thicker the safety pin wall at the position corresponding to the breakaway groove.

[0023] This solution has the following beneficial effects:

[0024] During the material selection step, screening is performed to ensure that the raw materials have better consistency. The safety pin blank and the accompanying blank are obtained from the same aged raw material. Shear test bars and tensile test bars are taken from the accompanying blank to ensure that the materials for the shear test and the tensile test are as consistent as possible with the materials used to make the safety pin. Tensile tests are performed on the tensile test bars to screen out tensile test bars with tensile strengths within ±a% of the set breakage threshold P1. Shear tests are performed on the shear test bars to screen out shear test bars with shear strengths within ±a% of the set breakage threshold P2. The safety pin blanks corresponding to the test bars that meet both the shear test and the tensile test are processed into the final safety pins, and a breakaway groove is machined into the inner hole of the safety pin. When the outer diameter and material properties of the safety pin are fixed, the size of the breakaway groove changes according to the change in the designed breakaway load. Specifically, the greater the designed breakaway load, the greater the wall thickness at the corresponding position of the safety pin breakaway groove. As for the relationship between the load change and the wall thickness change, the corresponding relationship can be obtained through mathematical analysis software, experimental measurement, etc. This solution ensures that the emergency disconnect pin will disconnect promptly within a ±a% range around the set threshold P0, and will not disconnect under forces below the set threshold. This ensures precise disconnection, ensuring it disconnects when it should and never disconnects when it shouldn't.

[0025] Furthermore, in step S1, a 15-5PH precipitation hardened stainless steel bar with a Brinell hardness between H1 and H2 is selected as the original bar, wherein (H2-H1)<30.

[0026] Furthermore, the vacuum state in step S3 specifically refers to 0.133 Pa to 13.3 Pa; the uniformity of the heat treatment furnace temperature is ±6°C.

[0027] The beneficial effect of adopting the above further technical solution is to ensure the stability of heat treatment performance. The core technology of this solution is to ensure the stability of the performance of the final product.

[0028] Furthermore, the aging treatment in step S3:

[0029] The furnace temperature is slowly raised to 587°C to 599°C within 180 to 240 minutes, which is close to the target temperature. The slower the heating curve, the more likely it is to exceed the set upper temperature limit. The furnace temperature is strictly controlled between 587°C and 599°C for 360 to 375 minutes. By slowly raising the temperature, temperature overshoot is prevented and the high temperature point in the furnace is prevented from exceeding the upper temperature limit of 599°C. Secondly, by slowly raising the temperature, the temperature difference between the raw material and the temperature inside the furnace is reduced, and the internal structure of the raw material is fully improved.

[0030] The beneficial effect of adopting the above-mentioned further technical solution is to ensure the stability of the aging treatment, especially the requirement to maintain the furnace temperature fluctuation within ±6°C in the later stage, which was difficult to ensure with previous processes. This solution slows down the heating curve when the furnace temperature approaches the target temperature, avoids the furnace temperature from being too high, and prevents the terminal furnace temperature from exceeding the set threshold, thereby improving the stability of the aging treatment and further ensuring the consistency of the product.

[0031] Furthermore, the 15-5PH precipitation hardened stainless steel bar material is made from the same manufacturer. Since the products from the same manufacturer use the same process, the same formula, the same technology, etc., the consistency of various properties of the raw materials can be further improved.

[0032] Furthermore, for example, when used on a model A aircraft (the load range of model A aircraft is fixed), and 15-5PH-solid solution-H1100 is used, (that is, the raw material is 15-5PH, solid solution precipitation hardened stainless steel bar, and aged according to the H1100 standard, the industry is accustomed to using the form of "15-5PH-solid solution-H1100" to simplify the expression, H1100 is the industry's description of the heat treatment requirements, "H" means age hardening treatment, and "1100" means 1100°F, that is, at 1 100 ° environment for age hardening treatment), the diameter of the tensile test bar is 6.25 ± 0.1mm, and the diameter of the shear test bar is 12.69-12.70mm. According to the traditional testing method, only raw materials with a tensile strength P1 between 1027.0Mpa and 1057.0Mpa can be made into products. However, based on this solution, the breakaway value of the final product is adjusted by adjusting the size of the breakaway weak groove, so that materials with a tensile strength P1 between 1021.0-1089.2Mpa can be processed into qualified products. Of course, if the subsequent raw material properties change, the weight of the applicable aircraft, the size of the safety pin, the relevant fracture value requirements, and other external factors change, the corresponding tensile strength range also needs to be adaptively adjusted. Tensile strength and shear strength are both used to test material properties. In theory, the results of the two tests are interchangeable. Therefore, in theory, only one test method needs to be used for implementation. Of course, both methods can be used for testing separately to verify the accuracy of the test results.

[0033] Furthermore, in step S1, the hardness H1 is 325 HB and the hardness H2 is 345 HB. Further limiting the hardness range of the raw materials and combining these materials with products from the same manufacturer, the same process, and the same formula is to improve the consistency of the various properties of the raw materials and thus ensure the consistency of the performance of the final product.

[0034] Furthermore, in step S2, the heat treatment process is controlled in accordance with the requirements of the Commercial Aircraft Corporation of China (COMAC) specification CPS5002 "Heat Treatment of Precipitation Hardening Stainless Steel", and the equipment temperature control is carried out in accordance with the requirements of the Commercial Aircraft Corporation of China (COMAC) specification CPS8100 "High Temperature Measurement".

[0035] Management based on NADCAP (National Aerospace and Defense Contractor's Accreditation Program) requirements and temperature measurement based on CPS8100 are both aimed at improving the consistency of various influencing factors in the entire processing process and improving the consistency of the final product.

[0036] Furthermore, the outer circle precision of the processed safety pin is within 0.02mm, and the inner hole precision is within 0.05mm.

[0037] Furthermore, even if the original rods are selected from products of the same specification and model from the same manufacturer, there will inevitably be some differences in properties between each rod. This inherent difference in properties will cause the tensile strength in the tensile test to be distributed within a total strength range. This total strength range is divided into several sub-strength ranges, and each sub-strength range spans 10Mpa. An adaptive breakaway groove size is set for each sub-strength range. This operation can further improve the accuracy of the breakaway load. At the same time, by adjusting the size of the breakaway groove, the difference in final tensile strength caused by the difference in the properties of the raw materials themselves can be adapted, thereby reducing the requirements for consistency of raw material properties and improving the utilization rate of raw materials. Under the condition that the basic properties of the raw materials meet the standards, any range of the tensile strength of the raw materials after heat treatment can be processed into breakaway safety pin products. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of the emergency disconnect pin at the rear intersection point of the aircraft main landing gear of the present invention;

[0039] Figure 2 This is a schematic diagram of the raw material of the aircraft main landing gear rear intersection emergency disconnect pin after rough processing of the present invention;

[0040] Figure 3 This is a schematic diagram of blanking of the aircraft main landing gear rear intersection emergency disconnect pin of the present invention;

[0041] Figure 4 This is a schematic diagram of the sampling positions of the shear test bar and the tensile test bar for the aircraft main landing gear rear intersection emergency disconnect pin of the present invention;

[0042] Figure 5 This is a comparison table of tensile strength sub-strength ranges and fracture weak zone size classifications.

[0043] In the accompanying drawings, the component names represented by the reference numerals are listed as follows:

[0044] 1. Straight section; 2. Cut-off weak groove section; 3. Thickened section; 4. Diameter of groove bottom area; 5. Radius of first R zone; 6. Radius of second R zone; 7. Front flange area; 8. Boss; 9. Tail section; 11. Safety pin blank; 12. Furnace part blank; 13. Tensile specimen; 14. Shear specimen. DETAILED DESCRIPTION

[0045] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0046] Example 1:

[0047] This embodiment takes Model A aircraft as an example, that is, produces the emergency disconnection safety pin of the rear intersection point of the main landing gear of Model A aircraft.

[0048] like Figure 1 As shown, an emergency disconnect safety pin for the rear intersection of the main landing gear of an aircraft is hollow cylindrical and includes an equal straight section 1, a disconnect weak groove section 2, a thickened section 3 and a tail section 9. The disconnect weak groove section 2 is the position that bears shear force, and disconnect weak grooves are respectively provided at two positions in the inner hole corresponding to the shear force; the thickened section 3 is located between the two disconnect weak grooves, and the inner hole diameter corresponding to the thickened section is smaller than the inner hole diameter at other positions; the bottom of the disconnect weak groove and the equal straight section step surfaces on both sides are connected by a rounded transition.

[0049] The breakaway groove consists of the groove bottom, a first R-zone connecting the groove bottom to the outer straight step surface, and a second R-zone connecting the groove bottom to the thickened section. For a fixed outer diameter of the breakaway pin, the groove bottom diameter (4), the first R-zone radius (5), and the second R-zone radius (6) are determined by the designed breakaway load and the tensile strength of the raw material used to make the breakaway pin.

[0050] The front flange area 7 is processed with a stop-rotation square edge structure boss 8 to prevent the landing gear from rotating;

[0051] The tail section 9 of the landing gear safety pin is provided with a thread, and a spline is processed at the rear section of the thread to prevent the nut from loosening.

[0052] Example 2:

[0053] Example 2 is the processing method of Example 1:

[0054] First, the raw material selected is 15-5PH precipitation hardening stainless steel produced by Company B, and the material state is solid solution state.

[0055] In order to know the shear strength of the final product in advance, it is necessary to reserve a certain length of the raw material bar so that a section can be taken from the same bar for tensile testing and shear testing. The tested part and the part used for the emergency disconnect pin must be subjected to various heat treatments, aging treatments, etc. at the same time to ensure that the shear strength of the material used to make the emergency disconnect pin is consistent with the shear strength of the furnace-mounted parts used for the test.

[0056] Figure 2 It is the rough material for processing safety pins. The outer diameter of the original bar is 140mm, the outer diameter of the main body after rough processing is 90mm, the inner hole diameter is 48mm, and the outer diameter of the end is 140mm. The length of the safety pin blank 11 used for processing the safety pin is 340mm. The total length of the bar is reserved for 80mm more, so that there is a long enough size to cut the furnace blank 12 test block. Therefore, the total length of the original bar in this example is 420mm.

[0057] The 420mm-long slab was heat treated using vacuum equipment with a controlled vacuum level of 0.133 Pa to 13.3 Pa. Because the slab's end had a step, a support was installed to maintain a level surface within the furnace and prevent rolling. The furnace temperature uniformity was ±6°C. Vacuum heat treatment equipment management was conducted in accordance with NADCAP requirements, and high-temperature measurements were performed in accordance with CPS8100.

[0058] S21, raising the furnace temperature to 300°C within 10-20 minutes;

[0059] S22, raising the furnace temperature to 510°C within 20-40 minutes;

[0060] S23, raising the furnace temperature to 587°C within 150-180 minutes;

[0061] S24. When the furnace temperature reaches 587°C, maintain the furnace temperature within the range of 593±6°C and maintain it for 360min-375min; at this stage, the smaller the furnace temperature fluctuation, the better the effect.

[0062] S25. Introduce high-purity argon gas at room temperature into the furnace for cooling for at least half an hour, so that the temperature of the raw material in the furnace drops to 427°C within 30-60 minutes, and then open the furnace door for air cooling.

[0063] The material after aging treatment is called aged raw material;

[0064] Cut the aged raw material into pieces and obtain Figure 3 As shown, a safety pin blank 11 and a furnace component blank 12 test block with a length of 80 mm are obtained.

[0065] With the center of the blank 12 test piece as the center, draw a circle with a diameter of 69 mm. 69 mm is half of the (blank outer diameter 90 mm + blank inner hole diameter 48 mm). Three test bars with a diameter of 11 mm are evenly distributed on this circle for tensile testing, and three test bars with a diameter of 13 mm are evenly distributed on this circle for shear testing. The outer diameter of the 11 mm diameter test bar is finely ground to a diameter of 6.25 ± 0.1 mm to obtain tensile test bar 13. The outer diameter of the 13 mm diameter test bar is finely ground to a diameter of 12.69-12.70 mm to obtain shear test bar 14.

[0066] In the traditional judgment standard for conducting a tensile test on a tensile test bar, only materials with a tensile strength P1 between 1027.0 MPa and 1057.0 MPa can be further processed into products, and materials exceeding this range are judged as unqualified. However, based on this solution, by adjusting the size of the breakaway weak groove to adjust the breakaway value of the final product, materials with a tensile strength P1 between 1021.0 and 1089.2 MPa can be processed into qualified products and meet the relevant breakaway value requirements. Specifically, by Figure 5 Use the table shown to determine which sub-strength range the tensile test results fall into. Based on the corresponding breakaway slot dimensions within this sub-strength range, process the breakaway slots. In the table, breakaway dimension A corresponds to a slot bottom diameter of 4, breakaway dimension B corresponds to a first R-zone radius of 5, and breakaway dimension C corresponds to a second R-zone radius of 6. By adjusting the breakaway slot dimensions based on the material's tensile strength range, and thereby adjusting the final product's strength, the breakaway value falls within the designed range. This allows materials that would otherwise be considered substandard to be processed into qualified products, thereby improving the yield rate of the raw materials.

[0067] Moreover, compared with the traditional method of using only a span of 30Mpa to determine whether the material meets the standard, this solution divides the tensile strength into several small intervals with 10Mpa as one level, and calculates and tests the matching weak groove size for each small interval separately, making the processing process control more refined and the final product's break value more accurate.

[0068] The classification in the table is based only on tensile strength. There is a positive correlation between tensile strength and shear strength. Therefore, in practice, tensile strength is mainly used. The results of the shear test are used to verify the tensile strength test data to ensure the accuracy of the experimental data.

[0069] The inner and outer circles of the safety pin must be concentric, and the coaxiality must be controlled within 0.05mm. The coaxiality is measured with a dial indicator.

[0070] The wall thickness of the safety pin should be uniform, with an accuracy of less than 0.02mm. Prevent the appearance of a tapered surface, especially the inner hole, and avoid turning into a tapered hole. Use an inside micrometer and an outside micrometer to measure at the left, middle, and right points.

[0071] The surface roughness of the outer circle and inner hole of the safety pin is controlled to be above Ra1.6;

[0072] The thread of the safety pin is threaded with a UNJ special thread cutter to ensure that the thread bottom is an arc thread bottom, and is tested with a 3A ring gauge.

[0073] The outer diameter precision of the safety pin is within 0.02, and the inner hole precision is within 0.1, ensuring that the fluctuation range of the cross-sectional area is within the allowable error. This ensures that when the aircraft landing gear collides with the ground under overload, the main landing gear can be completely separated from the aircraft body, and that the separation of the landing gear will not cause damage to the fuel tank and leakage. The test process of the above emergency separation safety pin is as follows:

[0074] In actual installation applications, the safety pin is mainly subjected to shear force, so the test project designed in this stage based on the actual situation of the safety pin is a shear test.

[0075] To simulate the actual disconnection of the safety pin, the shearing fixture was designed based on the actual installation conditions. This meant that the connection between the fixture and the safety pin was consistent with the actual installation. However, due to the complex structure of the safety pin connection, this was difficult to achieve. Therefore, the joint was simplified to a single- and double-ear joint. The joint and safety pin connection was used as the basic dimensions for the fixture design, ensuring that the thickness of the single and double ears, the gap between the single and double ears, and the assembly relationship between the various parts were consistent with the installation.

[0076] By simulating the actual aircraft configuration to conduct safety pin limit load, ultimate load static strength test and separation test, it was found that the actual measured values ​​of emergency separation load produced by the above method all met the design separation load range requirements and could be controlled within the range of ±4% of the set value, achieving precise separation.

[0077] This solution solves the problem of foreign countries' technical monopoly on emergency disconnection safety pins for civil aircraft and enables the localization of safety pins.

[0078] 15-5PH precipitation-hardened stainless steel produced by Company B was used in a solid solution state, with a Brinell hardness between 325HB and 345HB. This material was heat treated to H1100 in a vacuum heat treatment furnace using an adjusted heat treatment heating curve. Specimens and tensile bars cut from the same raw material were then subjected to tensile testing, and material with a tensile strength range of 1021.0 MPa to 1089.2 MPa was selected for use in manufacturing safety pins. Traditional processing methods only allow for materials with a tensile strength between 1027.0 MPa and 1057.0 MPa to be manufactured. Therefore, this solution significantly improves the yield rate of the raw material.

[0079] By controlling the characteristics of raw materials, strictly controlling the heat treatment process of raw materials, selecting and determining the matching of raw material properties and heat treatment processes, and taking samples of the same raw material for shear tests, we can ultimately ensure that the shear strength fluctuation range of the final finished safety pin is controlled within the set threshold of ±4%, achieving precise separation.

[0080] The safety pin is designed with reasonable outer circle and inner hole dimensions and tolerances, simulates the actual aircraft configuration, designs the separation tooling, and conducts the safety pin separation test. The measured separation load values ​​all meet the design separation value ±5% range.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for processing an emergency disconnect pin of an aircraft main landing gear, characterized in that: The hollow cylindrical structure has two shear-bearing positions in the inner hole, each provided with a breakaway groove. A thickened section is provided between the two breakaway grooves, and the inner hole diameter corresponding to the thickened section is smaller than the inner hole diameter at other positions. The bottom of the breakaway groove and the straight step surfaces on both sides are connected by a rounded transition. The processing method of the aircraft main landing gear emergency breakaway safety pin is as follows: comprising the following steps: S1. Select stainless steel bar as the original bar. The length of the original bar, L, is greater than or equal to (the length of the safety pin, l + 60 mm). S2, rough processing, the original bar material is rough turned and roughly punched to obtain the safety pin raw material, the single side allowance of the safety pin raw material is ≥0.5mm; S3, performing aging treatment under vacuum state to obtain aged raw material; S4, blanking process, obtain the safety pin blank and the furnace part blank from the same aged blank, and the length of the furnace part blank is greater than or equal to 60mm; S5. Take at least three shear test bars and three tensile test bars along the axial direction of the blank with the furnace, with the centers of the shear test bars and the tensile test bars evenly distributed on a designated circle, and the shear test bars and the tensile test bars are closely adjacent to each other. The designated circle has the center of the blank with the furnace as its center, and its diameter is equal to (blank outer diameter + blank inner hole diameter) / 2; S6. Perform a tensile test on the tensile test bar to select the safety pin blanks with a tensile strength within the set threshold value P1±a% as the coarse screening blanks; Perform a shear test on the shear test bars corresponding to the coarse screened blanks to verify whether the shear strength of the shear test bars corresponding to the coarse screened blanks is within the set threshold value P2±a%. The safety pin blanks corresponding to the test bars that meet the tensile test and / or shear test standards are used as the screened blanks; the shear strength of the shear test bars is represented by the average shear strength of all qualified samples; the tensile strength of the tensile test bars is represented by the average tensile strength of all qualified samples; S7. Process the safety pin with the screened blank, and process the breakaway groove in the inner cavity of the safety pin at the position corresponding to the shear force. Under the premise that the outer diameter of the safety pin and the material properties are fixed, the size of the breakaway groove changes according to the change of the designed breakaway load. The greater the designed breakaway load, the thicker the safety pin wall at the position corresponding to the breakaway groove.

2. The method for processing the emergency disconnect pin of the aircraft main landing gear according to claim 1, characterized in that: It includes the front end flange area, which is processed with a anti-rotation square edge structure boss to prevent the landing gear from rotating.

3. The method for processing the emergency disconnect pin of the aircraft main landing gear according to claim 1 or 2, characterized in that: Including the tail thread / spline connection area: the tail section of the landing gear safety pin is provided with threads, and the rear section of the thread is processed with splines to prevent the nut from loosening.

4. The method for processing the emergency disconnect pin of the aircraft main landing gear according to claim 3, characterized in that: The vacuum state in step S3 specifically refers to 0.133 Pa to 13.3 Pa; the uniformity of the heat treatment furnace temperature is ±6°C.

5. The method for processing the emergency disconnect pin of the aircraft main landing gear according to claim 4, characterized in that: In the aging treatment in step S3, the furnace temperature is raised to 587° C. to 599° C. within 180 to 240 minutes, and the furnace temperature is maintained between 587° C. and 599° C. for 360 to 375 minutes.

6. The method for processing the emergency disconnect pin of the aircraft main landing gear according to any one of claims 3 to 5, characterized in that: In step S1, a 15-5PH precipitation hardened stainless steel bar with a Brinell hardness between H1 and H2 is selected as the original bar, where (H2-H1) is less than 30.

7. The method for processing the emergency disconnect pin of the aircraft main landing gear according to claim 6, characterized in that: In step S1, the hardness H1 is 325HB, and the hardness H2 is 345HB.

8. The method for processing the emergency disconnect pin of the aircraft main landing gear according to any one of claims 3 to 5, characterized in that: The tensile strength in the tensile test is distributed within a total strength range due to the inherent characteristic differences of the original bar material. This total strength range is divided into several sub-strength ranges, and an adaptive breakaway weak groove size is set for each sub-strength range.

9. The method for processing the emergency disconnect pin of the aircraft main landing gear according to claim 8, characterized in that: Each sub-intensity interval spans 10Mpa.

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