Method and system for obtaining fracture performance of aerospace thin-walled metal welded joints

Abstract

The present invention provides a method and system for obtaining the fracture performance of aerospace thin-walled metal welded joints, including: preparing small-sized thin-sheet specimens at typical positions; measuring the test load-displacement curve through a micro-tensile test, and calculating the true stress-true strain curve of the corresponding material; performing micro-tensile simulation based on the finite element method of the damage mechanics model, and outputting the simulated load-displacement curve, and automatically adjusting the material damage parameters by an intelligent algorithm until the objective function is satisfied; performing bending / tensile test simulation according to the standard SENB / CT specimens specified in the current fracture toughness test related standards according to the true stress-true strain curve and the optimal material damage parameters, and calculating the crack extension resistance curve cluster and fracture toughness distribution corresponding to each typical position of the welded joint. The method and system of the present invention can effectively solve the problem that the fracture performance of aerospace thin-walled metal welded joints cannot be measured according to existing standards and specifications, and the acquisition process is simple, convenient, reliable, and low-cost.

Description

Technical Field

[0001] The present invention relates to the field of structural integrity of spacecraft metal components, and in particular to a method and system for obtaining fracture performance of aerospace thin-walled metal welded joints. Background Art

[0002] The structural integrity of spacecraft metal components is directly related to the successful launch and safe operation of spacecraft in orbit. With the development of low cost, high carrying capacity and long service life of spacecraft, higher performance and lighter weight requirements are put forward for metal components. To meet this requirement, thin-walled metal welded structures are widely used. The welded joint area becomes a weak link of reverse fracture failure due to the uneven microstructure and mechanical properties of the material and its sensitivity to crack defects. Therefore, it is of great significance to conduct integrity assessment and damage tolerance design of this area.

[0003] In order to achieve accurate assessment and reasonable design, it is necessary to obtain the fracture properties (crack extension resistance curve and fracture toughness) of this area. According to current specifications and standards, the specimens used for the determination of fracture performance parameters are all SENB / CT specimens with a certain thickness. However, aerospace thin-walled metal components are usually obtained by machining thin plates, which do not meet the thickness requirements of standard SENB / CT specimens. The material organization of each area of ​​the thin-walled welded structure is not completely consistent with the material organization of each area of ​​the thick-walled welded structure. Therefore, the fracture performance measured by the specimen prepared by the plate with the required thickness cannot truly reflect the fracture performance of the actual thin-walled welded structure. Therefore, it is necessary to provide a method for obtaining the fracture performance of aerospace thin-walled metal welded joints.

[0004] Patent document CN104062188B (application number: 201410293802.6) discloses a method for measuring the fracture toughness JIC of each micro-region in the heat affected zone of a welded joint. The invention effectively controls the direction of crack propagation by opening a V-shaped groove in the coarse grain area or fine grain area of ​​the heat affected zone on a three-point bending specimen, ensuring that the crack propagates in the coarse grain area or fine grain area of ​​the heat affected zone, thereby measuring the fracture toughness of each micro-region in the heat affected zone of the welded joint. This method is still based on a standard large-size SENB specimen and cannot be applied to thin-walled welded joints. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a method and system for obtaining the fracture performance of aerospace thin-walled metal welded joints.

[0006] A method for obtaining fracture performance of aerospace thin-walled metal welded joints provided by the present invention comprises:

[0007] Step S1: For the typical positions x1, x2, ..., x2 of the aerospace thin-walled metal welding joint to be obtained n, prepare small size thin slice sample S f1 , S f2 ,...,S fn ;

[0008] Step S2: Prepare a small-size thin-film sample S f1 , S f2 ,...,S fn Micro tensile tests TE1, TE2, ..., TE n , the test load-displacement curve was measured According to the test load-displacement curve and the thin-film specimen, the true stress-true strain curve C of the local material at each position is calculated. σε1 , C σε2 , ..., C σεn ;

[0009] Step S3: According to the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn , the finite element method based on the damage mechanics model was used to analyze the micro-tensile tests TE1, TE2, ..., TE n Perform simulation and output simulated load-displacement curve

[0010] Step S4: Establish the objective function F(DP) and use the intelligent algorithm to evaluate the simulated load-displacement curve and the measured test load-displacement curve The error is automatically adjusted by adjusting the material GTN damage parameters until the objective function is met, and the optimal material damage parameters DP1, DP2, ..., DP n ;

[0011] Step S5: According to the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn and material damage parameters DP1, DP2, ..., DP n , for different positions of thin-walled metal welded joints, the standard SENB / CT specimen S specified in the current fracture toughness test standards is used. SENB1 , S SENB2 ,...,S SENBn Perform bending / tensile test simulation and output the load, displacement and crack extension length (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(Pni ,V ni ,a ni );

[0012] Step S6: According to the obtained (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ), calculate the typical positions of the welding joints x1, x2, ..., x n The corresponding crack extension resistance curve C R1 , C R2 , ..., C Rn and fracture toughness J IC1 , J IC2 , ..., J ICn ;

[0013] Step S7: For n data pairs (x1, J IC1 )、(x2,J IC2 ),...,(x n ,J ICn ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints; for n groups of crack growth resistance curves C R1 , C R2 , ..., C Rn By plotting, we can obtain a cluster of crack growth resistance curves for aerospace thin-walled metal welded joints.

[0014] Preferably, the typical positions of the aerospace thin-walled metal weld joint include: welding fusion zone FZ, heat affected zone HAZ, near interface zone NIZ and base metal zone BMZ.

[0015] Preferably, the thickness B1 of the small-size thin sheet sample is 0.3 mm to 2 mm; the width W1 of the stretching section is 2 mm to 5 mm, and the length L1 is 8 mm to 12 mm.

[0016] Preferably, the step S2 adopts:

[0017] Step S2.1: Test load-displacement curve Select multiple sets of load displacement data pairs (p1, v1), (p2, v2), ..., (p n ,v n ), where p n represents the load, v n Indicates displacement;

[0018] Step S2.2: Based on each set of load-displacement data pairs (p i ,v i ) to calculate the corresponding engineering stress and engineering strain

[0019]

[0020]

[0021] Step S2.3: Convert engineering stress and engineering strain Convert to true stress Hezhen Adaptability

[0022]

[0023]

[0024] Step S2.4: All true stress and true strain data are Plot the material true stress-true strain curve C σε .

[0025] Preferably, the objective function F(DP) in step S4 is:

[0026]

[0027] Where N represents the number of simulated loads output in the displacement interval; and are the simulated load and test load at displacement point j, respectively.

[0028] Preferably, the selection of the damage mechanics model is determined by the fracture mechanism of the weld joint material, including: Beremin damage mechanics model, Rousselier damage mechanics model or Gurson-Tvergaard-Needleman damage mechanics model; the number and type of specific material damage parameters are determined by the adopted damage mechanics model.

[0029] Preferably, the S4 adopts:

[0030] Step S4.1: Determine the number of comparative evaluation groups m and the number of data in each group k based on the optimization capability of the intelligent algorithm;

[0031] Step S4.2: Setting the first set of displacements Enter the initial material damage parameters for finite element simulation and use Python script to identify the corresponding load , and output to Matlab analysis software;

[0032] Step S4.3: Determine whether the objective function F(DP) meets the requirements. If not, the intelligent algorithm automatically adjusts the material damage parameters through the python script until the objective function F(DP) meets the requirements; repeatedly trigger steps S4.2 to S4.3 to identify and evaluate the remaining m-1 groups in turn until all load-displacement curves are identified.

[0033] Step S4.4: Output the final optimal material damage parameters.

[0034] Preferably, the step S5 adopts:

[0035] The crack extension length a at each load step i is the projection extension length of the crack on the initial crack plane measured from the pore volume fraction cloud map iVVF The sum of the crack tip blunting effect correction value CTOD / 2 before crack initiation:

[0036] a i =a iVVF +CTOD / 2

[0037] Where CTOD represents the crack opening displacement.

[0038] Preferably, the step S6 adopts:

[0039] Step S6.1: Calculate the stress field intensity factor K corresponding to each loading point i i ;

[0040]

[0041] Where S represents the span; W2 is the width of the SENB specimen, B2 is the thickness of the SENB specimen, and B N is the effective thickness of SENB sample, a i is the crack length;

[0042] Step S6.2: Calculate the elastic J integral J corresponding to this incremental step ei and plasticity J integral J pi :

[0043]

[0044]

[0045] Among them, K i represents the stress field intensity factor; b i-1 is the remaining ligament length corresponding to displacement point i-1; A pIt represents the area of ​​the plastic deformation part under the curve corresponding to each loading point on the load-displacement curve, that is, the energy absorbed by the plastic deformation of the specimen; A pi -A p(i-1) It represents the difference in the plastic area between point i and point i-1 on the load-displacement curve;

[0046] Step S6.3: Calculate the J integral J corresponding to the current loading point i :

[0047] J i =J ei +J pi

[0048] Step S6.4: Integrate the J corresponding to each loading point i and crack extension length a i Plot and obtain the crack extension resistance curve C R ;

[0049] Step S6.5: Determine the fracture toughness J of the material using the passivation line IC :

[0050]

[0051] Among them, σ s Indicates the yield strength of the material; σ b represents the yield strength of the material; M represents the constraint coefficient.

[0052] A system for acquiring fracture performance of aerospace thin-walled metal welded joints provided by the present invention comprises:

[0053] Module M1: Typical positions x1, x2, ..., x of aerospace thin-walled metal welded joints to be acquired n , prepare small size thin slice sample S f1 , S f2 ,...,S fn ;

[0054] Module M2: Prepare small-size thin-film samples S f1 , S f2 ,...,S fn Micro tensile tests TE1, TE2, ..., TE n , the test load-displacement curve was measured According to the test load-displacement curve and the thin-film specimen, the true stress-true strain curve C of the local material at each position is calculated. σε1 , C σε2 , ..., C σεn ;

[0055] Module M3: Based on the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn , the finite element method based on the damage mechanics model was used to analyze the micro-tensile tests TE1, TE2, ..., TE n Perform simulation and output simulated load-displacement curve

[0056] Module M4: Establishing the objective function F(DP) and using intelligent algorithms to evaluate the simulated load-displacement curve and the measured test load-displacement curve The error is automatically adjusted by adjusting the material damage parameters until the objective function is met, and the optimal material damage parameters DP1, DP2, ..., DP n ;

[0057] Module M5: Based on the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn and material damage parameters DP1, DP2, ..., DP n , for different positions of thin-walled metal welded joints, the standard SENB / CT specimen S specified in the current fracture toughness test standards is used. SENB / CT1 , S SENB / CT2 ,...,S SENB / CTn Perform bending / tensile test simulation and output the load, displacement and crack extension length (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni );

[0058] Module M6: According to the obtained (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ), calculate the typical positions of the welding joints x1, x2, ..., x n The corresponding crack extension resistance curve C R1 , C R2 , ..., C Rnand fracture toughness J IC1 , J IC2 , ..., J ICn ;

[0059] Module M7: For n data pairs (x1, J IC1 )、(x2,J IC2 ),...,(x n ,J ICn ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints; for n groups of crack growth resistance curves C R1 , C R2 , ..., C Rn By plotting, we can obtain a cluster of crack growth resistance curves for aerospace thin-walled metal welded joints.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] 1. The method provided by the present invention effectively solves the problem that the fracture performance of aerospace thin-walled welded joints cannot be directly measured based on standard size specimens in existing standards;

[0062] 2. The present invention achieves the acquisition of material mechanical properties and fracture properties at typical positions or continuous areas of thin-walled welded joints only through small-sized thin-sheet specimens, and adopts the acquisition method of intelligent algorithm + finite element simulation to replace the existing test method, which is simple, convenient, reliable and low-cost;

[0063] 3. The method provided by the present invention has a wide range of applications and is not only applicable to all thin-walled metal welding structures in aerospace, but can also be extended to thick-walled metal welding structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0065] Figure 1 Flow chart of the method for obtaining fracture properties of aerospace thin-walled metal welded joints.

[0066] Figure 2 A schematic diagram of an aerospace thin-wall 316L stainless steel argon arc welding joint according to an embodiment of the present invention.

[0067] Figure 3 Schematic diagram of a small-sized thin-sheet sample according to an embodiment of the present invention.

[0068] Figure 4 1 is a load-displacement curve of each position test according to an embodiment of the present invention.

[0069] Figure 51 is a true stress-true strain curve of local material at each position according to an embodiment of the present invention.

[0070] Figure 6 This is a micro-stretching simulation model according to an embodiment of the present invention.

[0071] Figure 7 Detailed description of the experimental and simulated load-displacement curve evaluation process according to one embodiment of the present invention.

[0072] Figure 8 This is a complete simulation model of a standard SENB specimen according to an embodiment of the present invention.

[0073] Fig. 9 is a cluster of crack extension resistance curves according to an embodiment of the present invention.

[0074] Fig.10 is the fracture toughness distribution according to one embodiment of the present invention. DETAILED DESCRIPTION

[0075] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0076] Example 1

[0077] According to a method for obtaining fracture performance of a thin-walled metal welded joint provided by the present invention, Figure 1 As shown, including:

[0078] Step 1: For the typical positions x1, x2, …, x2 of the aerospace thin-walled metal weld joint to be obtained n , prepare small size thin slice sample S f1 , S f2 ,…,S fn ;

[0079] Among them, the typical positions of aerospace thin-walled metal welding joints include welding fusion zone (FZ), heat affected zone (HAZ), near interface zone (NIZ) and parent metal zone (BMZ); the thickness B1 of small-size thin-film specimens is 0.3mm~2mm; the width W1 of the tensile section is 2mm~5mm, and the length L1 is 8mm~12mm;

[0080] Step 2: The small-sized thin-film samples S1, S2, ..., S prepared in step 1 are n Micro tensile tests TE1, TE2, ..., TE n, the test load-displacement curve was measured According to the test load-displacement curve and the thin-film sample geometry, the true stress-true strain curve C of the local material at each position is calculated. σε1 , C σε2 ,…,C σεn ;

[0081] The calculation process of true stress-true strain curve of local materials at each position of the weld joint includes:

[0082] Step 2.1: Test load-displacement curve Select several groups of load displacement data pairs (p1, v1), (p2, v2), ..., (p n , v n );

[0083] Step 2.2: For each set of load displacement data (p i , v i ), the corresponding engineering stress is calculated by equation (1) and equation (2): and engineering strain

[0084]

[0085]

[0086] Step 2.3: According to equations (3) and (4), the engineering stress and engineering strain Convert to true stress Hezhen Adaptability

[0087]

[0088]

[0089] Step 2.4: Combine all true stress and true strain data Plot the material true stress-true strain curve C σε ;

[0090] Step 3: According to the true stress-true strain curve C obtained in step 2 σε1 , C σε2 ,…,C σεn The finite element method based on the damage mechanics model was used to analyze the micro-tensile tests TE1, TE2, ..., TE n Perform simulation and output simulated load-displacement curve

[0091] Establish the objective function F(DP) and use intelligent algorithm to evaluate the simulated load-displacement curve And the test load-displacement curve measured in step 2 The error is automatically adjusted by adjusting the material damage parameters until the objective function is met, and the optimal material damage parameters DP1, DP2, ..., DP n ;

[0092] The objective function F(DP) is specifically as shown in formula (5):

[0093]

[0094] in, and are the simulated load and test load at displacement point j, respectively, and N is the number of simulated loads output in the displacement interval;

[0095] The selection of damage mechanics model is determined by the fracture mechanism of the weld joint material, and usually includes Beremin damage mechanics model, Rousselier damage mechanics model, Gurson-Tvergaard-Needleman damage mechanics model, etc. The number and type of specific material damage parameters are determined by the adopted damage mechanics model.

[0096] Wherein, step 3 comprises:

[0097] Step 3.1: Determine the number of comparative evaluation groups m and the number of data in each group k based on the optimization capability of the intelligent algorithm;

[0098] Step 3.2: Set the first set of displacements Input the initial material damage parameter set [q1, q2, f0, f c , f F , f N , ε N , S N ] Perform finite element simulation and use Matlab to identify the corresponding loads

[0099] Step 3.3: Determine whether the objective function F(DP) meets the requirements. If not, the intelligent algorithm automatically adjusts the material damage parameter group through the python script until the objective function F(DP) meets the requirements.

[0100] Step 3.4: Repeat steps 3.2 and 3.3 to identify and evaluate the remaining m-1 groups in turn until all load-displacement curves are identified.

[0101] Step 3.5: Input the final optimal material damage parameter set [q1, q2, f0, f c , f F , f N , ε N , SN ];

[0102] Specifically, the crack length a of each load step in step 4 is i is the projection extension length of the crack on the initial crack plane measured from the pore volume fraction cloud map iVVF The sum of the crack tip blunting effect correction value CTOD / 2 before crack initiation, that is:

[0103] a i =a iVVF +CTOD / 2 (6)

[0104] Where CTOD is the crack opening displacement.

[0105] Step 4: According to the true stress-true strain curve C obtained in step 2 σε1 , C σε2 ,…,C σεn And the material damage parameters DP1, DP2, ..., DP obtained in step 3 n , for different positions of thin-walled metal welded joints, the standard SENB / CT specimen S specified in the current fracture toughness test standards is used. SENB / CT1 , S SENB / CT2 ,…,S SENB / CTn Perform bending / tensile test simulation and output the load, displacement and crack extension length (P 1i , V 1i , a 1i )、(P 2i , V 2i , a 2i ),…,(P ni , V ni , a ni );

[0106] Step 5: According to the (P 1i , V 1i , a 1i )、(P 2i , V 2i , a 2i ),…,(P ni , V ni , a ni ), calculate the typical positions of the welding joints x1, x2, ..., x n The corresponding crack extension resistance curve C R1 , C R2 ,…,C Rn and fracture toughness J IC1 , J IC2 , …, J ICn ;

[0107] For n sets of data pairs (x1, J IC1 )、(x2,J IC2 ),…,(x n , J Icn ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints; for n groups of crack growth resistance curves C R1 , C R2 ,…,C Rn By drawing a graph, we can obtain the crack growth resistance curve cluster of aerospace thin-walled metal welded joints;

[0108] Among them, the crack extension resistance curve C in step 5 R and fracture toughness J IC The calculation process includes:

[0109] Step 5.1: First, calculate the stress field intensity factor K corresponding to each loading point i according to formula (7): i :

[0110]

[0111] Where S is the span, W2 is the width of the SENB specimen, B2 is the thickness of the SENB specimen, and B N is the effective thickness of SENB sample, a i is the crack length;

[0112] Step 5.2: Calculate the elastic J integral J corresponding to this incremental step according to equations (8) and (9) respectively: ei and plasticity J integral J pi :

[0113]

[0114]

[0115] Among them, K i Calculated by formula (7); b i-1 is the remaining ligament length corresponding to displacement point i-1, equal to Wa i ; A p A is the area of ​​the plastic deformation part under the curve corresponding to each loading point on the load-displacement curve, that is, the energy absorbed by the plastic deformation of the specimen; pi -A pi-1 It refers to the difference in the plastic area corresponding to point i and point i-1 on the load-displacement curve.

[0116] Step 5.3: Calculate the J integral J corresponding to this loading point according to formula (10): i :

[0117] J i =Jei +J pi (10)

[0118] Step 5.4: Integrate the J corresponding to each loading point i and crack extension length a i Plot and obtain the crack extension resistance curve C R ;

[0119] Step 5.5: Determine the fracture toughness J of the material using the passivation line IC , the formula is as follows:

[0120]

[0121] Among them, σ s is the yield strength of the material; σ b is the yield strength of the material; M is the constraint coefficient.

[0122] A system for acquiring fracture performance of a thin-walled metal welded joint provided by the present invention comprises:

[0123] Module M1: Typical positions x1, x2, ..., x of aerospace thin-walled metal welded joints to be acquired n , prepare small size thin slice sample S f1 , S f2 ,...,S fn ;

[0124] Module M2: Prepare small-size thin-film samples S f1 , S f2 ,...,S fn Micro tensile tests TE1, TE2, ..., TE n , the test load-displacement curve was measured According to the test load-displacement curve and the thin-film specimen, the true stress-true strain curve C of the local material at each position is calculated. σε1 , C σε2 , ..., C σεn ;

[0125] Module M3: Based on the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn , the finite element method based on the damage mechanics model was used to analyze the micro-tensile tests TE1, TE2, ..., TE n Perform simulation and output simulated load-displacement curve

[0126] Module M4: Establishing the objective function F(DP) and using intelligent algorithms to evaluate the simulated load-displacement curve and the measured test load-displacement curve The error is automatically adjusted by adjusting the material damage parameters until the objective function is met, and the optimal material damage parameters DP1, DP2, ..., DP n ;

[0127] Module M5: Based on the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn and material damage parameters DP1, DP2, ..., DP n , for different positions of thin-walled metal welded joints, the standard SENB / CT specimen S specified in the current fracture toughness test standards is used. SENB / CT1 , S SENB / CT2 ,...,S SENB / CTn Perform bending / tensile test simulation and output the load, displacement and crack extension length (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni );

[0128] Module M6: According to the obtained (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ), calculate the typical positions of the welding joints x1, x2, ..., x n The corresponding crack extension resistance curve C R1 , C R2 , ..., C Rn and fracture toughness J IC1 , J IC2 , ..., J ICn ;

[0129] Module M7: For n data pairs (x1, J IC1 )、(x2,J IC2 ),...,(x n ,J ICn ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints; for n groups of crack growth resistance curves C R1 , CR2 , ..., C Rn By plotting, we can obtain a cluster of crack growth resistance curves for aerospace thin-walled metal welded joints.

[0130] Example 2

[0131] Embodiment 2 is a preferred embodiment of Embodiment 1

[0132] A specific embodiment of the present invention is given below by taking a stainless steel 316L argon arc welding joint as an example, and a method and result for obtaining fracture performance of an aerospace thin-walled metal welding joint of the present invention are specifically described.

[0133] Step 1: Target Figure 2 The typical positions of the aerospace thin-walled 316L stainless steel electron beam welding joint are the fusion zone (x3 = 0mm), heat affected zone (x2 = -2mm), near interface zone (x4 = 2mm), and parent material zone (x1 = -5mm, x5 = 5mm). Small-size thin-section specimens S f1 , S f2 , S f3 , S f4 , S f5 ; Sample thickness B1 = 0.5mm, stretching section width W1 = 2mm, stretching section length L1 = 9mm, specific geometry as follows Figure 3 As shown;

[0134] Step 2: Perform micro-tensile tests TE1, TE2, TE3, TE4, TE5 on the small-sized thin-film samples S1, S2, S3, S4, and S5 prepared in step 1, and measure the test load-displacement curves like Figure 4 As shown;

[0135] Step 2.1: In the above test load-displacement curve C EPV Select 100 sets of load displacement data pairs (p1, v1), (p2, v2), ..., (p 100 , v 100 );

[0136] Step 2.2: For each set of load displacement data (p i , v i ), the corresponding engineering stress is calculated by equation (1) and equation (2): and engineering strain

[0137]

[0138]

[0139] Step 2.3: According to formula (3) and formula (4), the engineering stress and engineering strain Convert to true stress Hezhen Adaptability

[0140]

[0141]

[0142] Step 2.4: Combine all true stress and true strain data Plot the local material true stress-true strain curve C of 5 typical positions of thin-walled 316L stainless steel argon arc welding joints σε1 , C σε2 , C σε3 , C σε4 , C σε5 ,like Figure 5 As shown;

[0143] Step 3: Use ABAQUS commercial finite element analysis software to perform full-scale modeling of small-size thin-walled specimens S1, S2, S3, S4, and S5. The material properties are obtained from the true stress-true strain curve C obtained in step 2. σε1 , C σε2 , C σε3 , C σε4 , C σε5 Determine; select the Gurson-Tvergaard-Needleman damage mechanics model, whose material damage parameters include 8: material monomer cell pore growth coefficients q1 and q2, initial pore volume fraction f0, critical pore volume fraction f0 when pores aggregate c , critical void volume fraction f when the material fails F , the volume fraction of nucleable inclusions or nucleation second phases f N , the average equivalent plastic strain ε when 50% of the nucleated particles rupture N and the standard deviation of nucleation strain S N ; Input the initial material damage parameter group [q1 = 1.5, q2 = 1, f0 = 0.0001, f c =0.01, f F =0.05, f N =0.1,ε N =0.3, S N=0.1]; set boundary conditions on the left end of the specimen (U1=U2=U3=UR1=UR2=UR3=0), and set boundary conditions on the right end (U2=U3=UR1=UR2=UR3=0); apply a horizontal rightward displacement load U1=20mm on the right end; select 8-node reduced integration element (C3D8R) as the mesh type, and perform finite element simulation on the stretching process. The finite element model is as follows Figure 6 As shown;

[0144] This embodiment is based on the hybrid ion group algorithm, and determines the number of comparative evaluation groups m=10 and the number of data in each group k=6 according to its optimization capability;

[0145] Establish the objective function F(DP), as shown in formula (5):

[0146]

[0147] Identify the first set of displacements through Python script The corresponding load And output to Matlab, the material damage parameter group is automatically adjusted through the python script until the objective function F(DP) meets the requirements. The identification process is as follows Figure 7 shown.

[0148] Repeat steps 3B and 3C for the remaining 9 groups of displacement V 2 、V 3 、V 4 、V 5 、V 6 、V 7 、V 8 、V 9 The corresponding load P 2 , P 3 , P 4 , P 5 , P 6 , P 7 , P 8 , P 9 The identification evaluation is performed until all load-displacement curves are identified.

[0149] Finally, the optimal GTN damage parameters of local materials at 5 typical locations are output, as shown in the following table.

[0150] <![CDATA[q1]]> <![CDATA[q2]]> <![CDATA[f0]]> <![CDATA[f c ]]> <![CDATA[f F ]]> <![CDATA[f N ]]> <![CDATA[ε N ]]> <![CDATA[S N ]]> <![CDATA[DP1]]> 1.5 1 0.000001 0.04 0.25 0.002 0.3 0.1 <![CDATA[DP2]]> 1.5 1 0.00005 0.02 0.21 0.002 0.3 0.1 <![CDATA[DP3]]> 1.5 1 0.0002 0.01 0.18 0.002 0.3 0.1 <![CDATA[DP4]]> 1.5 1 0.00001 0.015 0.2 0.002 0.3 0.1 <![CDATA[DP5]]> 1.5 1 0.000001 0.035 0.23 0.002 0.3 0.1

[0151] Step 4: According to the true stress-true strain curve C obtained in step 2 σε1 , C σε2 , C σε3 , C σε4 , C σε5The material damage parameters DP1, DP2, DP3, DP4, and DP5 obtained in step 3 are used to obtain the standard SENB specimen S specified in the current fracture toughness test standards at different positions of the thin-walled metal welded joint. SENB1 , S SENB2 , S SENB3 , S SENB4 , S SENB5 The bending test simulation was carried out, and the specimen geometry was as follows Figure 8 As shown;

[0152] Output the load, displacement and crack extension length (P) corresponding to each loading point i in each test group. 1i , V 1i , a 1i )、(P 2i , V 2i , a 2i ),…,(P ni , V ni , a ni );

[0153] Step 5: First, calculate the stress field intensity factor K corresponding to each loading point i according to formula (7): i :

[0154]

[0155] Among them, span S = 57.6mm, SENB sample width W2 = 14.4mm, SENB sample thickness B2 = 7.2mm, SENB sample effective thickness B N =7.2mm, a i is the crack length;

[0156] According to equations (8) and (9), the elastic J integral J corresponding to this incremental step is calculated respectively: ei and plasticity J integral J pi :

[0157]

[0158]

[0159] Among them, K i Calculated by formula (7); b i-1 is the remaining ligament length corresponding to displacement point i-1, equal to Wa i ; A p A is the area of ​​the plastic deformation part under the curve corresponding to each loading point on the load-displacement curve, that is, the energy absorbed by the plastic deformation of the specimen; pi -A pi-1It refers to the difference in the plastic area corresponding to point i and point i-1 on the load-displacement curve.

[0160] According to formula (10), the J integral J corresponding to this loading point is calculated i :

[0161] J i =J ei +J pi (10)

[0162] The J integral J corresponding to each loading point i and crack extension length a i Plot the crack propagation resistance curve C at each typical position of the weld joint. R1 , C R2 , C R3 , C R4 , C R5 ,like Fig. 9 As shown;

[0163] Determining the fracture toughness J of a material using the passivation line IC1 , J IC2 , J IC3 , J IC4 , J IC5 , the formula is as follows:

[0164]

[0165] Among them, σ s is the yield strength of the material; σ b is the yield strength of the material; M is the constraint coefficient.

[0166] <![CDATA[J IC1 ]]> <![CDATA[J IC2 ]]> <![CDATA[J IC3 ]]> <![CDATA[J IC4 ]]> <![CDATA[J IC5 ]]> 1602 1356 1123 1244 1590

[0167] For 5 data pairs (x1, J IC1 )、(x2,J IC2 )、(x3,J IC3 )、(x4,J IC4 )、(x5,J IC5 ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints, such as Fig.10 As shown; for 5 groups of crack extension resistance curves C R1 , C R2 , C R3 , C R4 , C R5 By plotting, we can obtain the crack growth resistance curve cluster of aerospace thin-walled metal welded joints, such as Figure 8 shown.

[0168] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0169] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for obtaining fracture performance of aerospace thin-walled metal welded joints, characterized in that: include: Step S1: For the typical positions x1, x2, ..., x2 of the aerospace thin-walled metal welding joint to be obtained n , prepare small size thin slice sample S f1 , S f2 ,...,S fn ; Step S2: Prepare a small-size thin-film sample S f1 , S f2 ,...,S fn Micro tensile tests TE1, TE2, ..., TE n , the test load-displacement curve was measured According to the test load-displacement curve and the thin-film specimen, the true stress-true strain curve C of the local material at each position is calculated. σε1 , C σε2 , ..., C σεn ; Step S3: According to the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn , the finite element method based on the damage mechanics model was used to analyze the micro-tensile tests TE1, TE2, ..., TE n Perform simulation and output simulated load-displacement curve Step S4: Establish the objective function F(DP) and use the intelligent algorithm to evaluate the simulated load-displacement curve and the measured test load-displacement curve The error is automatically adjusted by adjusting the material damage parameters until the objective function is met, and the optimal material damage parameters DP1, DP2, ..., DP n ; Step S5: According to the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn and material damage parameters DP1, DP2, ..., DP n , for different positions of thin-walled metal welded joints, the standard SENB / CT specimen S specified in the current fracture toughness test standards is used. SENB / CT1 , S SENB / CT2 ,...,S SENB / CTn Perform bending / tensile test simulation and output the load, displacement and crack extension length (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ); Step S6: According to the obtained (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ), calculate the typical positions of the welding joints x1, x2, ..., x n The corresponding crack extension resistance curve C R1 , C R2 , ..., C Rn and fracture toughness J IC1 , J IC2 , ..., J ICn ; Step S7: For n data pairs (x1, J IC1 )、(x2,J IC2 ),...,(x n ,J ICn ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints; for n groups of crack growth resistance curves C R1 , C R2 , ..., C Rn By drawing a graph, we can obtain the crack growth resistance curve cluster of aerospace thin-walled metal welded joints; In step S4, the objective function F(DP) is: Where N represents the number of simulated loads output in the displacement interval; and are the simulated load and test load at displacement point j, respectively; The step S4 adopts: Step S4.1: Determine the number of comparative evaluation groups m and the number of data in each group k based on the optimization capability of the intelligent algorithm; Step S4.2: Setting the first set of displacements Enter the initial material damage parameters for finite element simulation and use Python script to identify the corresponding load And output to Matlab analysis software; Step S4.3: Determine whether the objective function F(DP) meets the requirements. If not, the intelligent algorithm automatically adjusts the material damage parameters through the python script until the objective function F(DP) meets the requirements; repeatedly trigger steps S4.2 to S4.3 to identify and evaluate the remaining m-1 groups in turn until all load-displacement curves are identified; Step S4.4: Output the final optimal material damage parameters.

2. The method for obtaining fracture performance of aerospace thin-walled metal welded joints according to claim 1, characterized in that: The typical positions of the aerospace thin-walled metal weld joints include: welding fusion zone FZ, heat affected zone HAZ, near interface zone NIZ and base metal zone BMZ.

3. The method for obtaining fracture performance of aerospace thin-walled metal welded joints according to claim 1, characterized in that: The thickness B1 of the small-size thin sheet sample is 0.3 mm to 2 mm; the width W1 of the stretching section is 2 mm to 5 mm, and the length L1 is 8 mm to 12 mm.

4. The method for obtaining fracture performance of aerospace thin-walled metal welded joints according to claim 1, characterized in that: The step S2 adopts: Step S2.1: Test load-displacement curve Select multiple sets of load displacement data pairs (p1, v1), (p2, v2), ..., (p n ,v n ), where p n represents the load, v n Indicates displacement; Step S2.2: Based on each set of load-displacement data pairs (p i ,v i ) to calculate the corresponding engineering stress and engineering strain Step S2.3: Convert engineering stress and engineering strain Convert to true stress Hezhen Adaptability Step S2.4: All true stress and true strain data are Plot the material true stress-true strain curve C σε .

5. The method for obtaining fracture performance of aerospace thin-walled metal welded joints according to claim 1, characterized in that: The selection of the damage mechanics model is determined by the fracture mechanism of the weld joint material, including: Beremin damage mechanics model, Rousselier damage mechanics model or Gurson-Tvergaard-Needleman damage mechanics model; the number and type of specific material damage parameters are determined by the adopted damage mechanics model.

6. The method for obtaining fracture performance of aerospace thin-walled metal welded joints according to claim 1, characterized in that: The step S5 adopts: The crack extension length a at each load step i is the projection extension length of the crack on the initial crack plane measured from the pore volume fraction cloud map iVVF The sum of the crack tip blunting effect correction value CTOD / 2 before crack initiation: a i =a iVVF +CTOD / 2 Where CTOD represents the crack opening displacement.

7. The method for obtaining fracture performance of aerospace thin-walled metal welded joints according to claim 1, characterized in that: The step S6 adopts: Step S6.1: Calculate the stress field intensity factor K corresponding to each loading point i i ; Where S represents the span; W2 is the width of the SENB specimen, B2 is the thickness of the SENB specimen, and B N is the effective thickness of SENB sample, a i is the crack length; Step S6.2: Calculate the elastic J integral J corresponding to this incremental step ei and plasticity J integral J pi : Among them, K i represents the stress field intensity factor; b i-1 is the remaining ligament length corresponding to displacement point i-1; A p It represents the area of ​​the plastic deformation part under the curve corresponding to each loading point on the load-displacement curve, that is, the energy absorbed by the plastic deformation of the specimen; A pi -A p(i-1) It represents the difference in the plastic area between point i and point i-1 on the load-displacement curve; Step S6.3: Calculate the J integral J corresponding to the current loading point i : I i =J ei +J pi Step S6.4: Integrate the J corresponding to each loading point i and crack extension length a i Plot and obtain the crack extension resistance curve C R ; Step S6.5: Determine the fracture toughness J of the material using the passivation line IC : Among them, σ s Indicates the yield strength of the material; σ b represents the yield strength of the material; M represents the constraint coefficient.

8. A system for acquiring fracture performance of aerospace thin-walled metal welded joints, characterized in that: include: Module M1: Typical positions x1, x2, ..., x of aerospace thin-walled metal welded joints to be acquired n , prepare small size thin slice sample S f1 , S f2 ,...,S fn ; Module M2: Prepare small-size thin-film samples S f1 , S f2 ,...,S fn Micro tensile tests TE1, TE2, ..., TE n , the test load-displacement curve was measured According to the test load-displacement curve and the thin-film specimen, the true stress-true strain curve C of the local material at each position is calculated. σε1 , C σε2 , ..., C σεn ; Module M3: Based on the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn , the finite element method based on the damage mechanics model was used to analyze the micro-tensile tests TE1, TE2, ..., TE n Perform simulation and output simulated load-displacement curve Module M4: Establishing the objective function F(DP) and using intelligent algorithms to evaluate the simulated load-displacement curve and the measured test load-displacement curve The error is automatically adjusted by adjusting the material GTN damage parameters until the objective function is met, and the optimal material damage parameters DP1, DP2, ..., DP n ; Module M5: Based on the obtained true stress-true strain curve C σε1 , C σε2 , ..., C σεn and material damage parameters DP1, DP2, ..., DP n , for different positions of thin-walled metal welded joints, the standard SENB / CT specimen S specified in the current fracture toughness test standards is used. SENB / CT1 , S SENB / CT2 ,...,S SENB / CTn Perform bending / tensile test simulation and output the load, displacement and crack extension length (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ); Module M6: According to the obtained (P 1i ,V 1i ,a 1i )、(P 2i ,V 2i ,a 2i ),...,(P ni ,V ni ,a ni ), calculate the typical positions of the welding joints x1, x2, ..., x n The corresponding crack extension resistance curve C R1 , C R2 , ..., C Rn and fracture toughness J IC1 , J IC2 , ..., J ICn ; Module M7: For n data pairs (x1, J IC1 )、(x2,J IC2 ),...,(x n ,J ICn ) to obtain the fracture toughness distribution of aerospace thin-walled metal welded joints; for n groups of crack growth resistance curves C R1 , C R2 , ..., C Rn By drawing a graph, we can obtain the crack growth resistance curve cluster of aerospace thin-walled metal welded joints; The objective function F(DP) in the module M4 is: Where N represents the number of simulated loads output in the displacement interval; and are the simulated load and test load at displacement point j, respectively; The module M4 adopts: Module M4.1: Determine the number of comparative evaluation groups m and the number of data in each group k based on the optimization capability of the intelligent algorithm; Module M4.2: Setting the first set of displacements Enter the initial material damage parameters for finite element simulation and use Python script to identify the corresponding load And output to Matlab analysis software; Module M4.3: Determine whether the objective function F(DP) meets the requirements. If not, the intelligent algorithm automatically adjusts the material damage parameters through the python script until the objective function F(DP) meets the requirements; repeatedly trigger modules M4.2 to M4.3 to identify and evaluate the remaining m-1 groups in turn until all load-displacement curves are identified; Module M4.4: Output the final optimal material damage parameters.

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