A method for predicting creep life of linear friction welded blisks

Abstract

The present invention proposes a method for predicting the creep life of an integral blade after linear friction welding. Based on the ABAQUS commercial finite element software, the method can intuitively analyze the life prediction and crack initiation location of the integral blade during service, and can give full play to the advantages of finite element simulation calculations to achieve complex boundary loading conditions and various visualization post-processing operations; by assigning the stress field of the overall model as the initial residual stress, the deformed finite element model is used as the geometric model for creep life prediction, which can avoid the interference of the original model on the experiment, greatly approach the actual working state of complex geometric structural parts, and have high prediction accuracy; the present invention assigns material parameters of different materials to the linear friction welded integral blade model and the creep model, thereby obtaining an integral blade suitable for different materials, and obtaining its creep performance respectively, which is suitable for other complex geometric structural parts and has the advantage of extremely strong adaptability.

Description

Technical Field

[0001] The invention belongs to the field of solid phase welding and creep numerical simulation, and in particular relates to a method for predicting the creep life of an integral blade disk after linear friction welding. Background Art

[0002] With the increasing thrust-to-weight ratio of aircraft engines, blisk structures are increasingly being used in fans and compressors. The blisk structure is primarily based on the hub surface, with blades of complex profiles distributed circumferentially. The thinnest part is less than 2mm, and the openness is poor, making it a multi-island, complex, thin-walled structural component. Traditional blisk components are directly machined from forgings, resulting in a material removal rate exceeding 80%, low machining efficiency, and unqualified machining of a single blade will result in the scrapping of the entire blisk component, resulting in high production costs. To address the problems of low blisk machining efficiency, difficulty in blade repair, and increased costs caused by blade scrapping, several domestic research institutes have conducted research on linear friction welding technology for blisk components. This welding method connects the blades to the disc body, providing a new direction for the machining and repair of blisks.

[0003] In recent years, integral blades have been serving in high-temperature (above 1000°C) and high-pressure (above 100MPa) working environments. Ensuring their inherent safety during long-term operation has become a very prominent issue in the development of aerospace. Under high-temperature conditions, creep deformation and fracture become important failure modes that limit the service life of high-temperature equipment. However, due to the high requirements of high-temperature creep performance testing (taking high-temperature creep uniaxial tensile testing as an example) on experimental equipment, the time required is hundreds or thousands of hours, and the cost is high, resulting in an extreme lack of high-temperature creep performance data for integral blades. The development of finite element software can well meet people's understanding of complex stress-strain behavior and numerical simulation of extreme working environments (high temperature, high load).

[0004] Linear friction welding technology is a solid-phase connection technology. After welding the integral blade disk, complex residual stress exists in the integral blade disk. In the study of the influence of residual stress on creep life by Liu Dezheng et al., it was found that different levels of residual stress will affect the creep process (Dezheng Liu et al. Estimating the Influences of Prior Residual Stress on the Creep Rupture Mechanism for P92 Steel[J]. Metals, 2019, 9(6): 639-639.). However, the existing finite element simulation of aerospace parts based on ABAQUS software, such as "A Creep-Fatigue Life Design Method for Complex Geometric Components (11460583A)" applied by Guo Sujuan, Chen Keming, Wang Runzi, Zhang Xiancheng, Wang Yining, Tu Shandong, and Ye Youjun, uses the ABAQUS user subroutine UVARM to put the temperature of the integration point into the state variable, reflecting the creep-fatigue life of the turbine disk under the actual service temperature field. However, this application only predicts the life of the turbine disk, without considering the connection method between the turbine disk and the blades, the impact of the blades on the life of the components under actual working conditions, and the impact of residual stress on the life of the turbine disk and blades after linear friction welding. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: in order to solve the defect that the existing technology cannot predict the creep life of the integral blade in complex situations, the present invention provides a method for predicting the creep life of the integral blade after linear friction welding, so as to realize visual processing operation and improve the accuracy and practicality of the life prediction of the integral blade.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a method for predicting the creep life of an integral blade after linear friction welding, comprising the following steps:

[0007] Step 1: Based on the actual blisk structure, a geometric model of the blisk linear friction welding process is established using ABAQUS commercial finite element software, and the linear friction welding stress field of the blisk is obtained by analysis and calculation;

[0008] Step 2: Import the ODB file obtained by the analysis and calculation of the commercial finite element software ABAQUS in step 1 into the Hypermesh software, and regenerate the deformed geometric model through the mesh;

[0009] Step 3: Open the deformed geometric model generated in step 2 in ABAQUS commercial finite element software, and assign the stress field in step 1 to the new geometric model through the ODB file using data transmission technology;

[0010] Step 4: Assign material properties to the new geometric model formed in step 3, set boundary conditions and temperature fields according to the actual service conditions of the blisk, and form an ABAQUS finite element model of the blisk with linear friction welding residual stress creep;

[0011] Step 5: Create a creep damage subroutine using Fortran language, embed it into ABAQUS commercial finite element software to build a creep model, and simulate creep damage and creep life;

[0012] Use FORTRAN language to write the calculation formula in the creep model and create a FOR file;

[0013] Step 6. Select the FOR file created in step 5 in the ABAQUS commercial finite element software for simulation.

[0014] Preferably, the step 1 specifically includes the following sub-steps:

[0015] Create the geometric model of each component in the integral blade in the part module;

[0016] Assign material properties in the material module, including material density, elastic and plastic performance parameters, thermal conductivity and specific heat capacity;

[0017] Assemble the model in the assembly module and determine the positional relationship between each component;

[0018] Create a dynamic display analysis step of temperature-displacement coupling in the step module and set the welding time;

[0019] Set the contact properties in the interaction module:

[0020] Set welding parameters in the load module, including displacement boundary conditions and amplitude conditions;

[0021] Set mesh parameters and divide the mesh in the mesh module;

[0022] Submit the job and perform analysis in the job module.

[0023] Preferably, the creep model in step 5 adopts the Sinh hyperbolic sinusoidal creep constitutive model, and the model calculation equations include the creep strain rate equation and the damage evolution equation;

[0024] The creep strain rate equation is

[0025] The damage evolution equation is: Where, is the creep strain rate, ω is the creep damage; is the creep damage rate, A is the second stage creep coefficient, σs is the creep mechanism transition stress; the parameters can be determined using Mcvetty's minimum creep rate law; λ, M(hr-1), σ t (MPa), χ, and φ are material constants.

[0026] Effects of the Invention

[0027] The present invention provides a creep life prediction method for linear friction welded blisks with residual stress after linear friction welding. Based on the commercial finite element software ABAQUS, the method can intuitively analyze the life prediction and crack initiation location of the blisks during service. It can also give full play to the advantages of finite element simulation calculations, realize complex boundary loading conditions and various visual post-processing operations.

[0028] The present invention assigns the stress field of the overall model as the initial residual stress and uses the deformed finite element model as the geometric model for creep life prediction, thereby avoiding the interference of the original model on the experiment, greatly approaching the actual working state of complex geometric structural parts, and having the advantage of high precision.

[0029] The present invention assigns material parameters of different materials to the linear friction welded integral blade disc model and creep model, thereby obtaining integral blade discs suitable for different materials and respectively obtaining their creep properties. It is a universal thermal engine life prediction method that is applicable to other complex geometric structural parts and has the advantage of extremely strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flowchart of the method of the present invention

[0031] Figure 2 This is the flow chart of the creep damage simulation of the integral blade in the present invention

[0032] Figure 3 The finite element results of the linear friction welding of the integral blade are established

[0033] Figure 4 The finite element simulation results of creep damage of the integral blade DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific implementation cases. It should be understood that the following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0035] A method for predicting creep life of an integral blade after linear friction welding, comprising the following steps:

[0036] Step 1: Based on the actual blisk structure, a geometric model of the blisk linear friction welding process is established using ABAQUS commercial finite element software, and the linear friction welding stress field of the blisk is obtained by analysis and calculation;

[0037] Step 2: Import the ODB file obtained by the analysis and calculation of the commercial finite element software ABAQUS in step 1 into the Hypermesh software, and regenerate the deformed geometric model through the mesh;

[0038] Step 3: Open the deformed geometric model generated in step 2 in ABAQUS commercial finite element software, and assign the stress field in step 1 to the new geometric model through the ODB file using data transmission technology;

[0039] Step 4: Assign material properties to the new geometric model formed in step 3, set boundary conditions and temperature fields according to the actual service conditions of the blisk, and form an ABAQUS finite element model of the blisk with linear friction welding residual stress creep;

[0040] Step 5: Use the Fortran language to establish a creep damage subroutine, embed it into the ABAQUS commercial finite element software to establish a creep model, and simulate creep damage and creep life; use the FORTRAN language to write the calculation formula in the creep model and create a FOR file;

[0041] Step 6. Select the FOR file created in step 5 in the ABAQUS commercial finite element software for simulation.

[0042] Under actual operating conditions, complex geometric components exhibit significant residual stress, making creep effects highly pronounced under cyclic loading. Therefore, the present invention proposes a creep life prediction method for blisks after linear friction welding. This method is based on ABAQUS and simulates creep life prediction. This method considers the interaction between thermal and mechanical loads, assigns actual operating temperature and load spectra to structural components, and assigns constitutive parameters to materials at different temperatures. Based on a non-unified cyclic constitutive equation for steady-state stress-strain response, this method is applied to blisks, thereby determining creep damage under steady-state cycles and the creep life of the component.

[0043] Reference Figures 1-4 Taking a simplified aviation turbine disk as an example, the blisk is a geometric model of the turbine disk, blades, and upsetting shaft. According to one embodiment of the present invention, a creep life prediction method for a blisk with residual stress after linear friction welding includes the following steps:

[0044] Step 1: Use ABAQUS commercial finite element simulation software to model the linear friction welding process of the integral blade, set the boundary conditions according to the actual welding situation, complete the simulation of the linear friction welding of the integral blade, and obtain the linear friction welding stress field of the integral blade.

[0045] Using the 3D turbine disk, blades, fixture, and upset shaft as the integral blisk, a geometric model of the linear friction welding process was created using ABAQUS commercial finite element software. Titanium alloy TB9 was selected as the material. Material properties were assigned to the turbine disk, blades, fixture, and upset shaft. Meshing properties were assigned to each of the 3D turbine disk, blades, fixture, and upset shaft, and meshing was performed. A temperature-displacement coupled display analysis step was established, suitable for analyzing large deformation processes with thermomechanical coupling. Contact properties and loading conditions were set for each component, including welding parameters such as displacement, vibration frequency, and vibration amplitude. The specific setup steps are as follows:

[0046] In the part module, create geometric models of each component: the model used in this example is a three-dimensional model. Based on the actual shape and loading conditions of the blisk, the models that need to be built include the turbine disk, blades, blade fixture, and upset shaft. The contact area between the turbine disk and blades is partitioned.

[0047] Set material properties in the material module: Set material parameters, including density, elastic and plastic performance parameters, thermal conductivity, and specific heat capacity. The performance parameters are all set to be temperature-dependent. Material properties are assigned to the three-dimensional turbine disk, blades, fixture, and upset shaft. This example uses titanium alloy TB9, a commonly used material for turbine disks, as an example. The material's static yield stress A = 436.14 MPa, strain hardening coefficient B = 90 MPa, strain hardening exponent n = 0.48, thermal softening coefficient m = 1.05, strain rate hardening coefficient C = 0.552, material melting point Tm = 1220°C, and room temperature Tr = 25°C.

[0048] Assemble the model in the assembly module and determine the positional relationship between each component;

[0049] Create an analysis step in the step module: Use the temperature-displacement coupled dynamic display analysis step to simulate the friction welding process, and set the welding time to 8 seconds. Set the ALE adaptive mesh attribute in the other function column, and assign ALE attributes to the large deformation area near the contact surface of the turbine disk and blade.

[0050] Set the contact properties in the interaction module: set the friction coefficient of the turbine disk and blade contact surface, which changes with temperature, and set the heat transfer coefficient for the two components, both set to 30W / (m 2K); simplify the contact between the fixture and the blade, and between the upsetting shaft and the turbine disk, and set them to hard contact;

[0051] Set the welding parameters in the load module: Set the displacement boundary condition for the upsetting shaft in the boundary condition function column to determine its feed rate; set the displacement boundary condition for the fixture and set the amplitude condition to a periodic function, where the parameters include vibration amplitude and vibration frequency; limit the boundary conditions for the turbine disk and blades to ensure the smooth progress of the welding process;

[0052] In the mesh module, set mesh parameters and divide the mesh: set mesh parameters for several components and select C3D4T four-node linear displacement-temperature coupled tetrahedron element as the element type; add mesh to each component and refine the mesh near the contact surface;

[0053] Submit the job and perform analysis in the job module.

[0054] Step 2: Import the ODB file calculated by ABAQUS into Hypermesh software and regenerate the deformed geometric model through meshing. The specific steps include:

[0055] Create a new model in Hypermesh, select import-Part from the File drop-down menu, select the ODB file analyzed in step 1, and select the deformation result of 8s.

[0056] Importing the deformed model, the imported model loses the material, boundary, load, and analysis step;

[0057] In the model-1 settings, select Do not use parts and assemblies in input files,

[0058] In assembly, create an assembly to put the model back together;

[0059] In the Job module, recreate a task and export the inp file through write input;

[0060] In Tool>faces, select all solid meshes through elems and create surface meshes on the solid meshes;

[0061] In Gemo>surfaces, select Form FE and create solid faces by Create, and create solid faces on the surface mesh on the solid mesh;

[0062] Create several new components in Component>Create for subsequent model segmentation;

[0063] In the Organize module on the toolbar, select the dest component created before, and use elem to separate the turbine disc, blades, and top shaft into different modules by selecting Move.

[0064] In File>export>Geometry, Export the deformed geometric model.

[0065] Step 3: Based on the deformed geometric model formed in step 2, use data transmission technology to assign the stress field to the new model through the ODB file as the initial residual stress of the material to form a new geometric model; open the deformed geometric model restored by Hypermesh through ABAQUS, and in the Load module, use the Predefined Field Manager function to directly assign the stress values ​​of each area obtained in step 1 to the new model through the ODB file to form an ABAQUS finite element model of the integral blade with linear friction welding residual stress creep.

[0066] Step 4: Assign material properties to the new geometric model formed in step 3. According to the actual service conditions of the integral blade, set the boundary conditions and temperature field of the new model formed in step 3 to form an ABAQUS finite element model of the integral blade with linear friction welding residual stress creep.

[0067] Define the material property parameters in the property module, select elastic properties, Young's modulus to 215GPa, Poisson's ratio to 0.29; select creep properties, and select user-defined law;

[0068] Set the heat exchange properties of the blisk in the interaction module and select heat conduction and convection;

[0069] In the Load module, set the load and boundary conditions. Apply the rotational speed to account for the centrifugal force of the blisk. Apply the centrifugal load based on the actual load conditions of the blisk. Limit the displacement and rotation of the central axis. Use the Predefined Field Manager to set the material temperature field.

[0070] Step 5: Create a creep damage subroutine using Fortran language, embed it into ABAQUS commercial finite element software to build a creep model, and simulate creep damage and creep life.

[0071] The creep model adopts the Sinh hyperbolic sinusoidal creep constitutive model, which consists of two parts: the creep strain rate equation (1) and the damage evolution equation (2):

[0072]

[0073]

[0074] Where, is the creep strain rate, ω is the creep damage; is the creep damage rate, A (% 1 / hr) is the second stage creep coefficient, σ s (MPa) is the creep mechanism transition stress, using McVetty's minimum creep rate law ε min =Asinh(σ / σ s ) can determine the parameters; λ, M(hr-1), σ t (MPa), χ, and φ are material constants.

[0075] By transforming formulas (1) and (2), the strain rate damage analysis formula (3) is obtained as follows:

[0076]

[0077] Taking the initial time t0 = 0, assuming the initial damage D0 = 0 (assuming that the material has no internal damage when creep begins), integrating formula (4) to obtain the fracture life equation

[0078]

[0079] d c =∫ω(t)dt (5)

[0080] When d c is the creep damage value, when d c =0 means the material is not damaged; 0 <d c <1 indicates material damage but not failure; d c =1 indicates that the material has failed.

[0081] The calculation formula mentioned above is written in FORTRAN language and drawn into a FOR file.

[0082] The programming content is as follows:

[0083]

[0084]

[0085]

[0086] Step 6: In ABAQUS, go to the JOB module and select the task. In the subroutine, select the FOR file created in Step 5 and run the simulation. The simulation results show that damage occurs at the root of the blisk at 10362.8 hours, and the component fails. Therefore, the creep life of the component is 10362.8 hours.

[0087] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for predicting creep life of an integral blade after linear friction welding, characterized in that: The following steps are involved: Step 1: Based on the actual blisk structure, a geometric model of the blisk linear friction welding process is established using ABAQUS commercial finite element software, and the linear friction welding stress field of the blisk is obtained by analysis and calculation; Step 2: Import the ODB file obtained by the analysis and calculation of the commercial finite element software ABAQUS in step 1 into the Hypermesh software, and regenerate the deformed geometric model through the mesh; Step 3: Open the deformed geometric model generated in step 2 in ABAQUS commercial finite element software, and assign the stress field in step 1 to the new geometric model through the ODB file using data transmission technology; Step 4: Assign material properties to the new geometric model formed in step 3, set boundary conditions and temperature fields according to the actual service conditions of the blisk, and form an ABAQUS finite element model of the blisk with linear friction welding residual stress creep; Step 5: Create a creep damage subroutine using Fortran language, embed it into ABAQUS commercial finite element software to build a creep model, and simulate creep damage and creep life; Use FORTRAN language to write the calculation formula in the creep model and create a FOR file; Step 6. Select the FOR file created in step 5 in the ABAQUS commercial finite element software for simulation.

2. The method for predicting creep life of a blisk after linear friction welding according to claim 1, characterized in that: The step 1 specifically includes the following sub-steps: Create the geometric model of each component in the integral blade in the part module; Assign material properties in the material module, including material density, elastic and plastic performance parameters, thermal conductivity and specific heat capacity; Assemble the model in the assembly module and determine the positional relationship between each component; Create a dynamic display analysis step of temperature-displacement coupling in the step module and set the welding time; Set the contact properties in the interaction module: Set welding parameters in the load module, including displacement boundary conditions and amplitude conditions; Set mesh parameters and divide the mesh in the mesh module; Submit the job and perform analysis in the job module.

3. The method for predicting creep life of a blisk after linear friction welding according to claim 1, characterized in that: The creep model in step 5 adopts the Sinh hyperbolic sinusoidal creep constitutive model, and the model calculation equation includes the creep strain rate equation and the damage evolution equation; the creep strain rate equation is , the damage evolution equation is , where is the creep strain rate, ω is the creep damage; is the creep damage rate, A is the second stage creep coefficient, Transform stress for creep mechanism; The parameters can be determined using Mcvetty's minimum creep rate law; λ, M, 、 、 is the material constant.

Images