Evaluation Method for the Service Reliability of Additively Manufactured Titanium Alloy Reinforced Angle Boxes Installed in Aircraft

Abstract

The present invention relates to the technical field of aircraft structure maintenance, specifically an evaluation method for the in-service reliability of additively manufactured titanium alloy reinforced angle boxes. The specific steps are as follows: S1. Through coupon-level tests, master the basic mechanical property data of TA15 titanium alloy additively manufactured structures and compare the fracture behavior differences with titanium alloy plates through fracture analysis means; S2. Conduct mechanical tests on typical parts of TA15 titanium alloy additively manufactured structures, specifically including static and fatigue tests on T-shaped connection structures and beam structures; S3. Conduct mechanical tests on in-service parts of TA15 titanium alloy additively manufactured structures, specifically including static and fatigue tests on L-shaped angle box repair parts, airframe structures, cracked airframe structures, steel angle box reinforced cracked airframe structures, and additively manufactured titanium alloy angle box reinforced cracked airframe structures; Considering the three main factors affecting the reliability of the reinforced angle box, namely structure, material, and processing method, the reliability level of the additively manufactured reinforced angle box made of TA15 titanium alloy material for in-service use can be effectively evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft structure maintenance, and specifically to an evaluation method for the service reliability of additively manufactured titanium alloy reinforced angle boxes installed on aircraft. Background Art

[0002] With the large-scale repair of the new generation of aircraft, the demand for high-strength steel reinforced angle boxes used in aircraft structure repair has increased sharply. The traditional processing method is to first process forgings and then carry out machining. The manufacturing process is relatively cumbersome, with a long cycle and low efficiency, which greatly restricts the aircraft repair cycle. In addition, the material utilization coefficient is low and the repair cost is high. This traditional machining method is increasingly difficult to meet the development requirements of the flexible repair of the new generation of aircraft. In recent years, with the continuous maturity of additive manufacturing technology, high-strength and high-performance materials can be quickly manufactured into aircraft structure repair parts that meet the requirements of structural repair through additive manufacturing technology, which has important engineering application value for improving the repair efficiency of aircraft structures and reducing the repair cycle. Research and analysis show that for titanium alloy reinforced angle boxes processed by additive manufacturing, the single-piece processing cycle can be saved by 30%, the material utilization rate can be increased by 40%, the manufacturing cost can be saved by 10%, and the single-piece weight can be reduced by 25%.

[0003] Although the additive manufacturing method is very advanced, there is currently no national or industry process standard for additive manufacturing. It is currently difficult to effectively confirm the mechanical properties of the reinforced angle boxes manufactured by additive manufacturing, and the safety of the additively manufactured reinforced angle boxes installed on aircraft is difficult to guarantee. This uncertainty seriously hinders the popularization and application of additively manufactured reinforced angle boxes in the field of aircraft maintenance. How to comprehensively and accurately evaluate the mechanical properties of TA15 titanium alloy additively manufactured reinforced angle boxes to meet the requirements of installation on aircraft has become the main problem to be solved by the present invention. Summary of the Invention

[0004] To solve the above problems, the present invention proposes an evaluation method for the service reliability of additively manufactured titanium alloy reinforced angle boxes installed on aircraft.

[0005] The evaluation method for the service reliability of additively manufactured titanium alloy reinforced angle boxes installed on aircraft comprises the following specific steps:

[0006] S1. Master the basic mechanical property data of the TA15 titanium alloy additively manufactured structure through coupon-level tests and compare the fracture behavior differences with titanium alloy plates through fracture analysis means. The specific test procedures are as follows:

[0007] 1.1. Conduct tests on tensile (i.e., static) test pieces and record the test results;

[0008] 1.2. Conduct tests on shear test pieces and record the test results;

[0009] 1.3. Conduct tests on impact test pieces and record the test results;

[0010] 1.4. Conduct tensile and fatigue tests on test specimens and record the test results;

[0011] S2. Mechanical tests on typical parts of TA15 titanium alloy by additive manufacturing, specifically including static and fatigue tests on T-shaped connection structures and beam structures;

[0012] 2.1. The specific procedures for the static test at the typical part level are as follows:

[0013] 2.1.1. Test loading and restraint for the T-shaped connection structure, with a 100% limit load P = 31000N;

[0014] 2.1.2. Test loading and restraint for the beam structure, with a 100% limit load P = 28800N;

[0015] 2.1.3. Pretest: For each test, take 5% of the limit load as one level, and gradually load up to 60% of the limit load to eliminate the initial clearance of the test specimen and check whether the entire test system is in good condition;

[0016] 2.1.4. Formal test:

[0017] a) 100% limit load test. For each test, take 5% of the limit load as one level, gradually load up to 100% of the limit load, hold for 30S, and then gradually unload to 0;

[0018] b) For the 150% limit load test, between 100% - 120% of the limit load, take 5% of the limit load as one level and gradually load up to 120% of the limit load; between 120% - 140% of the limit load, take 2% of the limit load as one level and gradually load up to 140% of the limit load; after 140% of the limit load, take 1% of the limit load as one level and gradually load up to 150% of the limit load, hold for 3S, and then take 2% of the limit load as one level and gradually load until failure;

[0019] 2.2. The typical part level fatigue test is carried out on an MTS testing machine or a testing machine of the same grade: The design, processing, test procedures, determination and representation of test results of the testing machine and fixtures shall comply with the relevant regulations of the corresponding national standards or aviation standards;

[0020] 2.2.1. The T-shaped part fatigue test adopts constant amplitude spectrum loading, Pmax = 36500N, R = 0.06, f = 5 - 10Hz;

[0021] 2.2.2. The short beam bending fatigue test adopts constant amplitude spectrum loading, Pmax = 58752N, R = 0.06, f = 5 - 10Hz;

[0022] S3. Mechanical tests at the installed component level for TA15 titanium alloy additive manufacturing, specifically including static and fatigue tests on L-shaped corner box repair parts, airframe structures, airframe structures with cracks, steel corner box reinforced airframe structures with cracks, and additive manufacturing titanium alloy corner box reinforced airframe structures with cracks;

[0023] 3.1. The specific procedures for the static test at the installed component level are as follows:

[0024] 3.1.1. Tensile test loading and restraint for the L-shaped corner box repair structure, 100% limit load P = 121147 N;

[0025] 3.1.2. Test loading and restraint for the airframe structure, 100% limit load P = 220000 N;

[0026] 3.1.3. Test loading and restraint for the airframe structure with cracks, 100% limit load P = 110000 N;

[0027] 3.1.4. Test loading and restraint for the 30CrMnSiA material corner box reinforced airframe structure with cracks, 100% limit load P = 250000 N;

[0028] 3.1.5. Test loading and restraint for the additive manufacturing titanium alloy corner box reinforced airframe structure with cracks, 100% limit load P = 250000 N;

[0029] 3.1.6. Preliminary test: For each test, with 5% of the limit load as one level, gradually load up to 60% of the limit load to eliminate the initial clearance of the test piece and check whether the entire test system is in good condition;

[0030] 3.1.7. Formal test:

[0031] a) 100% limit load test. For each test, with 5% of the limit load as one level, gradually load up to 100% of the limit load, hold for 30 s, then gradually unload to 0. After the test is completed, analyze the test data and check the deformation of the test piece;

[0032] b) For the 150% limit load test, between 100% - 120% of the limit load, with 5% of the limit load as one level, gradually load up to 120% of the limit load. Between 120% - 140% of the limit load, with 2% of the limit load as one level, gradually load up to 140% of the limit load. After 140% of the limit load, with 1% of the limit load as one level, gradually load up to 150% of the limit load, hold for 3 s, then with 2% of the limit load as one level, gradually load until failure;

[0033] 3.2. Fatigue tests at the installed component level shall be carried out on an MTS testing machine or a testing machine of the same grade. The design and processing of the testing machine and fixtures, the test procedures, the determination and representation of test results shall all comply with the relevant provisions of the corresponding national standards or aviation standards;

[0034] 3.2.1. The fatigue test of the L-shaped angle box repair structure shall adopt constant amplitude spectrum loading, Pmax = 40000 N, R = 0.06, f = 5 - 10 Hz;

[0035] 3.2.2. The fatigue test of the airframe structure shall adopt constant amplitude spectrum loading, Pmax = 100000 N, R = 0.06, f = 5 - 10 Hz;

[0036] 3.2.3. The fatigue test of the cracked airframe structure shall adopt constant amplitude spectrum loading, Pmax = 70000 N, R = 0.06, f = 5 - 10 Hz;

[0037] 3.2.4. The fatigue test of the steel angle box reinforced cracked airframe structure shall adopt constant amplitude spectrum loading, Pmax = 100000 N, R = 0.06, f = 5 - 10 Hz;

[0038] 3.2.5. The fatigue test of the additively manufactured titanium alloy angle box reinforced cracked airframe structure shall adopt constant amplitude spectrum loading, Pmax = 100000 N, R = 0.06, f = 5 - 10 Hz.

[0039] The test piece level test in step S1 is used to demonstrate whether the additively manufactured titanium alloy material can meet the mechanical properties for aviation structure applications.

[0040] Each test in step S2.1.1 and step S2.1.2 includes a pre-test and a formal test. During the formal test, one 100% limit load test and one 150% limit load test are carried out. If the test piece does not fail under the 150% limit load condition, a failure load test is carried out. Each test adopts a step-by-step loading method.

[0041] The T-shaped structure test piece in step S2.1.1 mainly examines the ability of the additively manufactured TA15 titanium alloy structural part to transfer load at the structural chamfer under tensile load.

[0042] The short beam structure test piece in step S2.1.2 mainly examines the deformation coordination and load-bearing capacity of the additively manufactured TA15 titanium alloy structural part under bending load.

[0043] After the a test in step S2.1.4 is completed, the test data is analyzed and the test piece is inspected for deformation.

[0044] The connection test piece of the L-shaped corner box repair structure in step S3.2.1 mainly examines the reinforcement effect of the TA15 titanium alloy additive manufacturing structure on the opening-mode crack.

[0045] The test piece of the steel corner box reinforced belt crack body in step S3.2.4 mainly examines the reinforcement effect of the TA15 titanium alloy additive manufacturing structure on the slip-mode crack.

[0046] The beneficial effects of the present invention are as follows: In the process of carrying out the three-level assessment and verification of "specimen level - typical part level - installed part level", the typical parts and installed parts are combined with the typical structural characteristics of the body strengthening corner box to design the test pieces, and the tests are carried out by simulating the actual loading method, which can comprehensively and accurately reflect the actual use situation of the structure, and timely discover defects and weak parts; among them, the T-shaped connection structure and the beam structure are prepared by two methods of additive manufacturing and traditional machining using TA15 material; the L-shaped connection repair structure and the reinforcement corner box repair structure are compared with the high-strength steel corner box repair structure parts widely used in aircraft maintenance under the same conditions. Through the comparison between different preparation methods and different preparation materials, the various performances of the TA15 titanium alloy material additive manufacturing reinforcement corner box can be more fully examined, and the risk items can be excluded; the present invention considers the three main factors affecting the reliability of the reinforcement corner box, namely structure, material, and processing method, and can effectively evaluate the reliability level of the TA15 titanium alloy material additive manufacturing reinforcement corner box for installed use. Brief Description of the Drawings

[0047] The present invention will be further described below with reference to the drawings and embodiments.

[0048] Figure 1 It is the front view schematic diagram of the specimen-level tensile and static test piece of the present invention;

[0049] Figure 2 It is the top view schematic diagram of the specimen-level tensile and static test piece of the present invention;

[0050] Figure 3 It is the front view schematic diagram of the specimen-level shear test piece of the present invention;

[0051] Figure 4 It is the side view schematic diagram of the specimen-level shear test piece of the present invention;

[0052] Figure 5 It is the front view schematic diagram of the specimen-level impact test piece of the present invention;

[0053] Figure 6 It is the A-A structural schematic diagram of the specimen-level impact test piece of the present invention;

[0054] Figure 7 It is the front view schematic diagram of the specimen-level tensile and fatigue test piece of the present invention;

[0055] Figure 8 Top view schematic diagram of the specimen-level tensile and fatigue test piece of the present invention;

[0056] Figure 9 Front view schematic diagram of the T-shaped test piece of the present invention;

[0057] Figure 10 Schematic diagram of the B-B structure of the T-shaped test piece of the present invention;

[0058] Figure 11 Front view schematic diagram of the beam-type test piece of the present invention;

[0059] Figure 12 Side view schematic diagram of the beam-type test piece of the present invention;

[0060] Figure 13 Front view schematic diagram of the L-shaped connection test piece of the present invention;

[0061] Figure 14 Schematic diagram of the D-D of the L-shaped connection test piece of the present invention;

[0062] Figure 15 Schematic diagram of the E-E of the L-shaped connection test piece of the present invention;

[0063] Figure 16 Top view schematic diagram of the L-shaped connection test piece of the present invention;

[0064] Figure 17 Schematic diagram of the airframe structure of the present invention;

[0065] Figure 18 Schematic diagram of the F-F structure of the airframe structure of the present invention;

[0066] Figure 19 Schematic diagram of the airframe with crack at the installed part level of the present invention;

[0067] Figure 20 Schematic diagram of the G-G structure of the airframe with crack at the installed part level of the present invention;

[0068] Figure 21 Schematic diagram of the steel angle box reinforced airframe with crack of the present invention;

[0069] Figure 22 Schematic diagram of the H-H structure of the steel angle box reinforced airframe with crack of the present invention;

[0070] Figure 23 Of the present invention Figure 22 Cross-sectional structure schematic diagram;

[0071] Figure 24 Schematic diagram of the structure of the additively manufactured titanium angle box reinforced airframe with crack of the present invention;

[0072] Figure 25 Schematic diagram of the I-I structure of the additively manufactured titanium angle box reinforced cracked airframe of the present invention;

[0073] Figure 26 Of the present invention Figure 25 Cross-sectional structure schematic diagram;

[0074] Figure 27 Schematic diagram of the T-shaped structure test loading and restraint of the present invention;

[0075] Figure 28 Schematic diagram of the beam structure test loading and restraint of the present invention;

[0076] Figure 29 Schematic diagram of the L-shaped angle box repair structure test loading and restraint of the present invention;

[0077] Figure 30 Schematic diagram of the test loading and restraint of the installed parts of the present invention. Detailed implementation manners

[0078] In order to make the technical means, creative features, achieved purposes and effects realized by the present invention easy to understand, the present invention will be further described below.

[0079] As Figures 1 to 30 shown, based on the evaluation method for the reliability of additively manufactured titanium alloy reinforced angle boxes in service, the specific steps are as follows:

[0080] S1. Master the basic mechanical property data of the TA15 titanium alloy additively manufactured structure through coupon-level tests and compare its fracture behavior differences with titanium alloy plates through fracture analysis means. The specific test procedures are as follows:

[0081] 1.1. Tensile or static test specimens such as Figure One , Figure Two shown, conduct tests according to the provisions of HB5143-96 and record the test results;

[0082] 1.2. Shear test specimens such as Figure Three , Figure Four shown, conduct tests according to the provisions of HB6736-93 and record the test results;

[0083] 1.3. Impact test specimens such as Figure Five , Figure Six shown, conduct tests according to the provisions of HB5144-96 and record the test results;

[0084] 1.4. Tensile or fatigue test specimens such as Figure Seven , Figure Eight shown, conduct tests according to the provisions of HB5287-96 and record the test results;

[0085] S2. Mechanical tests at the typical part level of TA15 titanium alloy additive manufacturing, specifically including static and fatigue tests on T-shaped connection structures and beam structures;

[0086] 2.1. The specific procedures for the static test at the typical part level are as follows:

[0087] 2.1.1. The loading and restraint of the T-shaped connection structure test are as Figure Two shown in Figure 17, and the 100% limit load P = 31000N;

[0088] 2.1.2. The loading and restraint of the beam structure test are as Figure Two shown in Figure 18, and the 100% limit load P = 28800N;

[0089] 2.1.3. Pretest: For each test, with a 5% limit load as one level, gradually load up to 60% of the limit load to eliminate the initial clearance of the test piece and check whether the entire test system is in good condition;

[0090] 2.1.4. Formal test:

[0091] a) 100% limit load test. For each test, with a 5% limit load as one level, gradually load up to 100% of the limit load, hold for 30S, and then gradually unload to 0;

[0092] b) For the 150% limit load test, between 100% - 120% of the limit load, with a 5% limit load as one level, gradually load up to 120% of the limit load; between 120% - 140% of the limit load, with a 2% limit load as one level, gradually load up to 140% of the limit load. After 140% of the limit load, with a 1% limit load as one level, gradually load up to 150% of the limit load, hold for 3S, and then with a 2% limit load as one level, gradually load until failure;

[0093] 2.2. The fatigue test at the typical part level is carried out on an MTS testing machine or a testing machine of the same grade: The design and processing of the testing machine and fixture, the test procedure, the determination and representation of the test results shall comply with the relevant regulations of the corresponding national standards or aviation standards;

[0094] 2.2.1. The T-shaped part fatigue test adopts constant amplitude spectrum loading, Pmax = 36500N, R = 0.06, f = 5 - 10Hz;

[0095] 2.2.2. The short beam bending fatigue test adopts constant amplitude spectrum loading, Pmax = 58752N, R = 0.06, f = 5 - 10Hz;

[0096] S3. Mechanical tests at the installed component level for TA15 titanium alloy additive manufacturing, specifically including static and fatigue tests on L-shaped angle box repair parts, airframe structures, airframe structures with cracks, steel angle box reinforced airframe structures with cracks, and additive manufacturing titanium alloy angle box reinforced airframe structures with cracks;

[0097] 3.1. The specific procedures for the static test at the installed component level are as follows:

[0098] 3.1.1. The loading and restraint of the tensile test on the L-shaped angle box repair structure are as Figure Two shown in Figure 19, and the 100% limit load P = 121147 N;

[0099] 3.1.2. The loading and restraint of the airframe structure test are as Figure Three shown in Figure 10, and the 100% limit load P = 220000 N;

[0100] 3.1.3. The loading and restraint of the airframe structure with cracks test are as Figure Three shown in Figure 10, and the 100% limit load P = 110000 N;

[0101] 3.1.4. The loading and restraint of the airframe structure with cracks reinforced by a 30CrMnSiA material angle box are as Figure Three shown in Figure 10, and the 100% limit load P = 250000 N;

[0102] 3.1.5. The loading and restraint of the airframe structure with cracks reinforced by an additive manufacturing titanium alloy angle box are as Figure Three shown in Figure 10, and the 100% limit load P = 250000 N;

[0103] 3.1.6. Pretest: For each test, with a 5% limit load as one level, gradually load up to 60% limit load to eliminate the initial clearance of the test piece and check whether the entire test system is in good condition;

[0104] 3.1.7. Formal test:

[0105] a) 100% limit load test. For each test, with a 5% limit load as one level, gradually load up to 100% limit load, hold for 30 s, then gradually unload to 0. After the test is completed, analyze the test data and check the deformation of the test piece;

[0106] b) For the 150% limit load test, between 100% - 120% limit load, with a 5% limit load as one level, gradually load up to 120% limit load. Between 120% - 140% limit load, with a 2% limit load as one level, gradually load up to 140% limit load. After 140% limit load, with a 1% limit load as one level, gradually load up to 150% limit load, hold for 3 s, then with a 2% limit load as one level, gradually load until failure;

[0107] 3.2. The fatigue test at the installed component level is carried out on an MTS testing machine or a testing machine of the same grade. The design and processing of the testing machine and fixture, the test procedure, and the determination and representation of the test results shall comply with the relevant provisions of the corresponding national standards or aviation standards;

[0108] 3.2.1. The fatigue test of the L-shaped angle box repair structure adopts constant amplitude spectrum loading, Pmax = 40000N, R = 0.06, f = 5 - 10Hz;

[0109] 3.2.2. The fatigue test of the airframe structure adopts constant amplitude spectrum loading, Pmax = 100000N, R = 0.06, f = 5 - 10Hz;

[0110] 3.2.3. The fatigue test of the cracked airframe structure with steel angle box reinforcement adopts constant amplitude spectrum loading, Pmax = 70000N, R = 0.06, f = 5 - 10Hz;

[0111] 3.2.4. The fatigue test of the cracked airframe structure with steel angle box reinforcement of the steel angle box adopts constant amplitude spectrum loading, Pmax = 100000N, R = 0.06, f = 5 - 10Hz;

[0112] 3.2.5. The fatigue test of the cracked airframe structure with reinforcement of the additively manufactured titanium alloy angle box adopts constant amplitude spectrum loading, Pmax = 100000N, R = 0.06, f = 5 - 10Hz.

[0113] In the process of carrying out the three-level assessment and verification of "specimen level - typical component level - installed component level" of the present invention, the test pieces are designed in combination with the typical structural characteristics of the reinforced angle box of the typical component and the installed component, and the test is carried out by simulating the actual loading method, which can comprehensively and accurately reflect the actual use situation of the structure and timely discover defects and weak parts; among them, the T-shaped connection structure and the beam structure are prepared by two methods of additive manufacturing and traditional machining using TA15 material; the L-shaped connection repair structure and the reinforced angle box repair structure are compared with the high-strength steel angle box repair structure parts widely used in aircraft maintenance under the same conditions. Through the comparison between different preparation methods and different preparation materials, the various performances of the additively manufactured reinforced angle box of TA15 titanium alloy material can be more fully evaluated, and risk items can be excluded; the present invention considers the three main factors affecting the reliability of the reinforced angle box, namely structure, material, and processing method, and can effectively evaluate the reliability level of the additively manufactured reinforced angle box of TA15 titanium alloy material.

[0114] The specimen-level test in step S1 is used to demonstrate whether the additively manufactured titanium alloy material can achieve the mechanical properties required for aviation structure applications.

[0115] In the coupon-level assessment, the experimental contents include the main contents of basic mechanical experiments, which are tensile, shear, impact, and fatigue performance tests respectively. The experimental contents are carried out in accordance with the standards of HB5143-96, HB6736-93, HB5144-96, and HB5287-96. The content of the demonstration is that the titanium alloy material manufactured by additive manufacturing can achieve the mechanical properties for aerospace structural applications.

[0116] Through the coupon-level test, master the basic mechanical property data of the additive manufacturing structure of TA15 titanium alloy, and compare the fracture behavior differences with titanium alloy plates through fracture analysis methods, conduct the performance evaluation of the additive manufacturing coupon level and record the evaluation results.

[0117] As Figure Two Eleven. Figure Two Twelve. Figure Two As shown in Figure 14, in the figure, the reference numeral a is arranged at equal intervals and staggered, and the reference numeral b is the typical edge distance.

[0118] As Figure Three As shown in Figure 10, in the figure, the reference numeral e restricts the degrees of freedom of 2, 3, 4, and 5, the reference numeral f restricts the degrees of freedom of 1, 2, 3, 4, and 5. For the airframe structure test piece and the cracked airframe structure test piece with angle box strengthening strips, both have 4 degrees of freedom restricted at the left fixed end and 5 degrees of freedom restricted at the right fixed end, and two normal compression loads are applied to the upper flange.

[0119] Each test in the steps S2.1.1 and S2.1.2 includes a pre-test and a formal test. During the formal test, one 100% limit load test and one 150% limit load test are carried out. If the test piece does not fail under the 150% limit load condition, a failure load test is carried out. Each test adopts a step-by-step loading method.

[0120] As Figure Two As shown in Figure 17, in the figure, the reference numeral c is the loading end and the reference numeral d is the fixed end.

[0121] The T-shaped structure test piece in the step S2.1.1 mainly assesses the ability of the TA15 titanium alloy additive manufacturing structural part to transfer load at the structural chamfer under tensile load.

[0122] The short beam structure test piece in the step S2.1.2 mainly assesses the deformation coordination and load-bearing capacity of the TA15 titanium alloy additive manufacturing structural part under bending load.

[0123] After the test a in the step S2.1.4 is completed, analyze the test data and check the deformation of the test piece.

[0124] The process of the typical parts of TA15 titanium alloy additive manufacturing is tested through typical part-level tests. Through comparative tests with typical parts prepared by traditional machining methods, the differences in mechanical properties and fracture behaviors of the two types of typical parts are studied. Finally, the performance evaluation of the additive manufacturing typical parts is carried out and the evaluation results are recorded.

[0125] The connecting test piece of the L-shaped corner box repair structure in step S3.2.1 mainly examines the reinforcement effect of the TA15 titanium alloy additive manufacturing structural part on the opening-mode crack.

[0126] The test piece of the steel corner box reinforced belt crack airframe in step S3.2.4 mainly examines the reinforcement effect of the TA15 titanium alloy additive manufacturing structural part on the slip-mode crack.

[0127] The connection process between the TA15 titanium alloy additive manufacturing installation-level test piece and the airframe structure is tested through installation-level tests. Through comparative tests with high-strength steel installation-level test pieces prepared by traditional machining methods, the differences in mechanical properties and fracture behaviors of the two types of typical parts are studied. Finally, the performance evaluation of the additive manufacturing installation level is carried out and the evaluation results are recorded.

[0128] On the basis of understanding the material properties, the mechanical properties of the TA15 titanium alloy additive manufacturing aerospace structure are further evaluated through experimental verification methods. In the arrangement of typical part-level experiments, by extracting the typical structural features of the reinforced corner box on the aerospace structure, two types of typical structural test pieces are developed. One is the T-shaped structural test piece, Figure Nine 、 Figure Ten as shown, and the other is the beam-type structural test piece, Figure Ten One、 Figure Ten Two shown; the T-shaped structural test piece mainly examines the load transfer ability of the TA15 titanium alloy additive manufacturing structural part at the structural chamfer under tensile load. The beam-type structural test piece mainly examines the deformation coordination and load-bearing ability of the TA15 titanium alloy additive manufacturing structural part under bending load. Comparative experiments are arranged for both types of structural test pieces with machined parts of the same material. The experimental results show that the titanium alloy structures manufactured by additive manufacturing can also achieve the strength performance for aerospace structure applications.

[0129] As Figure Nine 、 Figure Ten shown, the T-shaped structural test piece extracts the typical structural features of the on-board reinforced corner box and simulates the tensile of the rib along the normal direction of the panel.

[0130] As Figure Ten One、 Figure Ten Two shown, the beam-type structural test piece is a typical I-beam stiffened structure, and 4 stiffening ribs are evenly arranged at the web of the I-beam.

[0131] Finally, the installation part-level assessment was designed. Combining the crack and fracture characteristics encountered in aircraft structure repair, two types of structural test pieces with two reinforcement methods were designed: the first is the L-shaped connection test piece for verifying the reinforcement effect of opening-mode cracks. Figure Ten III. Figure Ten IV. Figure Ten V. Figure Ten As shown in Figure VI, the L-shaped connection test piece mainly assesses the reinforcement effect of the additive manufacturing structural part of TA15 titanium alloy on opening-mode cracks; the second is the reinforced angle box test piece for verifying the reinforcement effect of slip-mode cracks. As Figures 24 to 26 shown, the reinforced angle box test piece mainly assesses the reinforcement effect of the additive manufacturing structural part of TA15 titanium alloy on slip-mode cracks. Since the simulation of slip-mode cracks is relatively complex, the present invention supplements the comparative experiment between the intact structural part and the cracked structural part in the verification experiment of slip-mode cracks. The comparative experiment of the above two installation-level verification test pieces refers to the high-strength steel repair parts widely used in aircraft structure repair. Through the comparative experiment, it is verified that the structural repair parts made of TA15 titanium alloy by additive manufacturing can achieve the same or higher structural reinforcement effect.

[0132] As Figure Ten III. Figure Ten IV. Figure Ten V. Figure Ten As shown in Figure VI, the L-shaped connection test piece is composed of two sections of L-shaped aluminum alloy profiles and the middle L-shaped repair structure connected by bolts.

[0133] As Figure Nineteen 、 Twenty shown, simulating the situation where cracks appear in the airframe structure at typical repair positions in the aircraft structure, the crack position is marked at the middle symmetry line.

[0134] In this way, through the above three-level comparative reference experiments, it can be shown that the additive manufacturing structural parts of TA15 titanium alloy have the performance basis for installation application and reach the application state for installation use.

[0135] Through the tensile, shear, fatigue, and impact performance tests at the coupon level, the basic mechanical property data of the additive manufacturing material are obtained, and it is verified that the material properties obtained by additive manufacturing have the same properties as those obtained by forging processing of the same material;

[0136] In the typical part-level assessment and verification, by extracting the typical structural characteristics of the on-board reinforced angle box, typical structural test pieces are designed, including T-shaped connection structures and beam structures, to verify that the additive manufacturing process can also achieve the strength performance of machining.

[0137] During the installation component level assessment stage, considering the typical repair characteristics in aircraft structure repair, two types of test pieces were designed under two repair conditions. They include the L-shaped angle box repair structure and the angle box reinforced airframe structure, verifying that the additive manufactured titanium angle box can replace the traditional high-strength steel angle box and achieve the application state for installation use.

[0138] The three-level comparative reference experiment can show that the additive manufactured structural parts of TA15 titanium alloy have the performance basis for installation application and reach the application state for installation use.

[0139] The T-shaped structural test piece and the beam-type structural test piece in the typical component level stage have typical structural characteristics and can effectively simulate the typical structure of the aircraft.

[0140] The L-shaped connection structure and the angle box reinforced airframe structure in the installation component level stage can truly and accurately simulate the actual repair state.

[0141] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An evaluation method for the service reliability of an additively manufactured titanium alloy reinforced angle box installed in a machine, characterized in that: The specific steps are as follows: S1. Master the basic mechanical property data of the additive manufacturing structure of TA15 titanium alloy through coupon-level tests, and compare the fracture behavior differences with titanium alloy plates through fracture analysis methods; S2. Conduct mechanical tests on typical parts of TA15 titanium alloy additive manufacturing, specifically including static and fatigue tests on T-shaped connection structures and beam structures; S3. Conduct mechanical tests on installed parts of TA15 titanium alloy additive manufacturing, specifically including static and fatigue tests on L-shaped angle box repair parts, airframe structures, cracked airframe structures, steel angle box reinforced cracked airframe structures, and additive manufacturing titanium alloy angle box reinforced cracked airframe structures; In the step S2, the specific process is as follows: 2.

1. The specific procedure for the static test at the typical part level is as follows: 2.1.

1. Loading and restraint for the T-shaped connection structure test, 100% limit load P = 31000N; 2.1.

2. Loading and restraint for the beam structure test, 100% limit load P = 28800N; 2.1.

3. Pre-test: Each test takes 5% of the limit load as one level, and is gradually loaded to 60% of the limit load to eliminate the initial clearance of the test piece and check whether the entire test system is in good condition; 2.1.

4. Formal test: a) 100% limit load test: Each test takes 5% of the limit load as one level, and is gradually loaded to 100% of the limit load and then held for 30S, and then gradually unloaded to 0; b) For the 150% limit load test, between 100% - 120% of the limit load, it is gradually loaded to 120% of the limit load with 5% of the limit load as one level; between 120% - 140% of the limit load, it is gradually loaded to 140% of the limit load with 2% of the limit load as one level; after 140% of the limit load, it is gradually loaded to 150% of the limit load with 1% of the limit load as one level, held for 3S, and then gradually loaded to failure with 2% of the limit load as one level; 2.

2. The typical part-level fatigue test is carried out on an MTS testing machine or a testing machine of the same grade: The design and processing of the testing machine and fixture, the test procedure, the measurement and representation of the test results shall comply with the relevant provisions of the corresponding national standards or aviation standards.

2. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box installed machine according to claim 1, characterized in that: The step 2.2 is specifically as follows: 2.2.

1. The T-shaped part fatigue test adopts constant amplitude spectrum loading, Pmax = 36500N, R = 0.06, f = 5 - 10Hz; 2.2.

2. The short beam bending fatigue test adopts constant amplitude spectrum loading, Pmax = 58752N, R = 0.06, f = 5 - 10Hz.

3. According to the evaluation method for the service reliability of the additive manufacturing titanium alloy reinforced angle box installed on the aircraft as claimed in claim 1, it is characterized in that: In the step S3, the specific process is as follows: 3.

1. The specific procedure for the static test at the installed part level is as follows: 3.1.

1. Loading and restraint for the tensile test of the L-shaped angle box repair structure, 100% limit load P = 121147N; 3.1.

2. Loading and restraint for the airframe structure test, 100% limit load P = 220000N; 3.1.

3. Loading and restraint for the cracked airframe structure test, 100% limit load P = 110000N; 3.1.4、Test loading and restraint of the cracked airframe structure with angle box reinforcement belt made of 30CrMnSiA material, 100% limit load P = 250000N; 3.1.5、Test loading and restraint of the cracked airframe structure with angle box reinforcement belt made of additive manufacturing titanium alloy, 100% limit load P = 250000N; 3.1.6、Preliminary test: Each test takes 5% of the limit load as one level, and is gradually loaded to 60% of the limit load to eliminate the initial clearance of the test piece and check whether the entire test system is in good condition; 3.1.7、Formal test: a) 100% limit load test, each test takes 5% of the limit load as one level, and is gradually loaded to 100% of the limit load and then holds the load for 30S, and then is gradually unloaded to 0. After the test is completed, the test data is analyzed and the deformation of the test piece is checked; b) For the 150% limit load test, between 100% - 120% of the limit load, take 5% of the limit load as one level and gradually load to 120% of the limit load. Between 120% - 140% of the limit load, take 2% of the limit load as one level and gradually load to 140% of the limit load. After 140% of the limit load, take 1% of the limit load as one level and gradually load to 150% of the limit load, hold the load for 3S, and then take 2% of the limit load as one level and gradually load to failure; 3.2、The fatigue test of the installed parts level is carried out on an MTS testing machine or a testing machine of the same grade. The design and processing of the testing machine and fixture, the test procedure, the measurement and representation of the test results shall comply with the relevant regulations of the corresponding national standards or aviation standards; 3.2.1、The fatigue test of the L-shaped angle box repair structure adopts constant amplitude spectrum loading, Pmax = 40000N, R = 0.06, f = 5 - 10Hz; 3.2.2、The fatigue test of the airframe structure adopts constant amplitude spectrum loading, Pmax = 100000N, R = 0.06, f = 5 - 10Hz; 3.2.3、The fatigue test of the cracked airframe structure with reinforcement belt adopts constant amplitude spectrum loading, Pmax = 70000N, R = 0.06, f = 5 - 10Hz; 3.2.4、The fatigue test of the cracked airframe structure with steel angle box reinforcement belt adopts constant amplitude spectrum loading, Pmax = 100000N, R = 0.06, f = 5 - 10Hz; 3.2.5、The fatigue test of the cracked airframe structure with angle box reinforcement belt made of additive manufacturing titanium alloy adopts constant amplitude spectrum loading, Pmax = 100000N, R = 0.06, f = 5 - 10Hz.

4. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box installation machine according to claim 1, characterized in that: The test piece level test in step S1 is used to demonstrate whether the additive manufacturing titanium alloy material can achieve the mechanical properties for aviation structure applications.

5. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box according to claim 2, characterized in that: Each test in step S2.1.1 and step S2.1.2 includes a preliminary test and a formal test. During the formal test, one 100% limit load test and one 150% limit load test are carried out.

6. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box according to claim 2, characterized in that: The T-shaped structure test piece in step S2.1.1 mainly examines the ability of the TA15 titanium alloy additive manufacturing structural part to transfer load at the structural chamfer under tensile load.

7. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box installation machine according to claim 2, characterized in that: The short beam - type structural test piece in step S2.1.2 mainly assesses the deformation - coordinated load - bearing capacity of the TA15 titanium alloy additive - manufactured structural part under bending load.

8. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box installed machine according to claim 2, characterized in that: After the test in step S2.1.4 is completed, the test data is analyzed and the test piece is inspected for deformation.

9. The evaluation method for the service reliability of the additive manufacturing titanium alloy reinforced angle box installed machine according to claim 3, characterized in that: The connecting test piece of the L - shaped corner box repair structure in step S3.2.1 mainly assesses the reinforcement effect of the TA15 titanium alloy additive - manufactured structural part on the opening - type crack.

10. The evaluation method for the service reliability of the additively manufactured titanium alloy reinforced angle box installed machine according to claim 3, characterized in that: The test piece of the steel corner box - strengthened belt cracked airframe in step S3.2.4 mainly assesses the reinforcement effect of the TA15 titanium alloy additive - manufactured structural part on the slip - type crack.

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