A method for predicting the fatigue limit of a surface-strengthened aeroengine blade

Abstract

This invention belongs to the field of aero-engine blade technology, specifically disclosing a method for predicting the fatigue limit of surface-strengthened aero-engine blades. By analyzing the surface state evolution test results of titanium alloy material samples after surface strengthening, a finite element model of a simulated titanium alloy blade is constructed for first-order modal simulation analysis. Furthermore, the first-order bending vibration fatigue test results of the simulated titanium alloy blade are analyzed to obtain the corresponding structural stress parameters for prediction, thereby obtaining the predicted fatigue limit value of the surface-strengthened aero-engine blade. This invention, by employing a blade high-cycle fatigue strength assessment method that considers the surface state and its evolution after surface strengthening, can accurately assess the fatigue performance of surface-strengthened blades, solving the problem of predicting the high-cycle fatigue strength of complex blade structures after surface strengthening. This has significant scientific and engineering value for the manufacturing and application of aero-engine blades.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine blade technology, specifically relating to a method for predicting the fatigue limit of surface-strengthened aero-engine blades. Background Technology

[0002] Fan and compressor blades are core components of aero-engines, mostly made of titanium alloys. Titanium alloy blades generate high-frequency vibrations under high-speed airflow, making them highly susceptible to fatigue failure. High-cycle fatigue failure of blades is a significant factor limiting the service life of aero-engines. Surface strengthening techniques such as shot peening and laser shock peening can introduce residual compressive stress and gradient microstructure on the blade surface, improving fatigue performance, and are therefore widely used in blade manufacturing. However, due to the irregular geometry of blades, the surface conditions after surface strengthening, such as residual stress and microstructure, are complex, and the surface state parameters evolve under high-cycle fatigue loads, posing challenges to the evaluation of the fatigue performance of surface-strengthened blades.

[0003] The internationally accepted models for assessing blade fatigue strength are mainly designed for material-level tests on plate-shaped components. However, accurately assessing the fatigue performance of surface-strengthened blades, given their complex structures, remains a challenging problem. Summary of the Invention

[0004] The purpose of this invention is to provide a method for predicting the fatigue limit of surface-strengthened aero-engine blades, in order to solve the above-mentioned problems existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] Firstly, a method for predicting the fatigue limit of surface-strengthened aero-engine blades is provided, including:

[0007] The surface state evolution test results of fatigue specimens of surface-strengthened titanium alloy were obtained, and the fatigue strength test results of titanium alloy before and after surface strengthening were obtained.

[0008] The fatigue risk points of the simulated titanium alloy blade after surface strengthening were determined based on the surface condition evolution test results, and the strengthening factor was determined based on the fatigue strength test results of the titanium alloy material.

[0009] A finite element model of a titanium alloy simulated blade is constructed. The simulated blade finite element model contains several mesh elements. First-order modal simulation is performed using the simulated blade finite element model to determine the simulation critical point and far-field point, as well as the stress ratio between the simulation critical point and the far-field point.

[0010] The results of the first-order bending vibration fatigue test of the titanium alloy simulated blade were obtained, and the test stress corresponding to the simulated critical point when the titanium alloy simulated blade reached the fatigue limit was determined based on the results of the first-order bending vibration fatigue test.

[0011] The unstrengthened stress at the far field point is calculated using the test stress corresponding to the simulated critical point and the stress ratio between the simulated critical point and the far field point. The strengthened stress at the far field point is calculated using the unstrengthened stress at the far field point and the strengthening factor.

[0012] The simulation stress parameters of the first-order modal simulation of the simulated blade finite element model are extracted, and the average stress corresponding to the fatigue critical point is calculated based on the simulation stress parameters using the critical distance method.

[0013] The fatigue limit of the titanium alloy blade after surface strengthening is estimated based on the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point.

[0014] In one possible design, determining the fatigue risk points of the simulated titanium alloy blade after surface strengthening based on surface state evolution test results includes:

[0015] Based on the surface condition evolution test results, the calibration stress σ' and interpolated residual stress σ' at each point of the fatigue specimen of the surface-strengthened titanium alloy were determined. res and interpolation fatigue limit σ' -1 ;

[0016] Based on the calibration stress σ' and interpolated residual stress σ' at each point res and interpolation fatigue limit σ' -1 Calculate the evolutionary parameters corresponding to each point, where the evolutionary parameters = σ' -1 / (σ'+σ' res );

[0017] A two-dimensional scatter plot is constructed using the evolutionary parameters corresponding to each point, the two-dimensional scatter plot is displayed, and the point where the evolutionary parameters in the two-dimensional scatter plot appear is selected in response to the user's first operation command.

[0018] The selected points were designated as fatigue risk points after surface strengthening of the titanium alloy simulated blade.

[0019] In one possible design, determining the strengthening factor based on the fatigue strength test results of the titanium alloy material includes:

[0020] Based on the fatigue strength test results of titanium alloy materials, the fatigue limit of titanium alloy materials before and after strengthening is determined under a set stress ratio. The strengthening factor is obtained by dividing the fatigue limit of titanium alloy materials after strengthening by its fatigue limit before strengthening.

[0021] In one possible design, the first-order modal simulation using a simulated blade finite element model is performed to determine the simulated critical point and far-field point, as well as the stress ratio between the simulated critical point and the far-field point, including:

[0022] First-order modal simulation was performed using a simulated blade finite element model, and the simulation results were presented.

[0023] In response to the user's second operation command, the far-field point and simulation danger point are selected in the simulation result model, and the simulation stress σ of the far-field point in the simulation result model is determined. A_sim And the simulated stress σ of the simulated danger point in the simulation result model. B_sim ;

[0024] Simulated stress σ at far-field points A_sim Simulated stress σ at the simulated hazardous point B_sim Calculate the stress ratio γ between the simulated critical point and the far-field point, where γ = σ B_sim / σ A_sim .

[0025] In one possible design, the calculation of the unreinforced stress at the far-field point using the test stress corresponding to the simulated critical point and the stress ratio between the simulated critical point and the far-field point includes:

[0026] The unreinforced stress at the far-field point is obtained by dividing the test stress corresponding to the simulated hazardous point by the stress ratio between the simulated hazardous point and the far-field point.

[0027] In one possible design, the calculation of the strengthening stress at the far-field point using the unstrengthened stress and strengthening factor at the far-field point includes:

[0028] The strengthening stress corresponding to the far-field point is obtained by multiplying the unstrengthened stress corresponding to the far-field point by the strengthening factor.

[0029] In one possible design, the extraction of simulation stress parameters from the first-order modal simulation of the simulated blade finite element model, and the calculation of the average stress corresponding to the fatigue hazard point using the critical distance method based on the simulation stress parameters, includes:

[0030] Determine the residual stress σ after surface strengthening of the simulated titanium alloy blade res Determine the distance r between all center points and the critical fatigue hazard point. c The grid cells are within the range, and the center point is at a critical distance r from the fatigue hazard point. c The grid cells within the range are used as the target cells, where:

[0031] r c =1.54l0

[0032]

[0033] M is the set geometric correction coefficient, σ -1 For a given titanium alloy simulated blade, ΔK th The fatigue threshold stress intensity factor is set.

[0034] Determine the absolute value of the maximum principal stress for each target element, and then determine the average stress σ of all target elements based on the absolute value of the maximum principal stress for each target element. C And utilize the strengthening factor and mean stress σ C and residual stress σ res Calculate the superimposed stress σ of each target element. i ,in:

[0035] σ i =ασ C +σ res

[0036] α is the enhancement factor, and i represents the index of the target unit;

[0037] Utilizing the superimposed stress σ of each target element i Calculate the average stress σ corresponding to the fatigue critical point aver ,in:

[0038]

[0039] η is the set bending effect correction coefficient, N is the number of target elements, and V i Let i be the cell volume of the target cell i.

[0040] In one possible design, estimating the fatigue limit of the titanium alloy blade after surface strengthening based on the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point includes:

[0041] Substituting the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point into the preset fatigue limit prediction formula for surface-strengthened blades, the fatigue limit of the aero-engine blade after surface strengthening with titanium alloy material is obtained. The fatigue limit prediction formula for surface-strengthened blades is as follows:

[0042]

[0043] Where, σ A'_sim The stress corresponding to the far-field point is characterized by γ, and the stress ratio between the simulated critical point and the far-field point is characterized by γ.

[0044] Secondly, a fatigue limit prediction system for surface-strengthened aero-engine blades is provided, comprising a first acquisition unit, a result determination unit, a modal simulation unit, a second acquisition unit, a first calculation unit, a second calculation unit, and a limit estimation unit, wherein:

[0045] The first acquisition unit is used to acquire the surface state evolution test results of the fatigue specimen of the surface-strengthened titanium alloy material, and to acquire the fatigue strength test results of the titanium alloy material before and after surface strengthening.

[0046] The result determination unit is used to determine the fatigue risk points after surface strengthening of the titanium alloy simulated blade based on the surface state evolution test results, and to determine the strengthening factor based on the fatigue strength test results of the titanium alloy material.

[0047] The modal simulation unit is used to construct a simulated blade finite element model of a titanium alloy simulated blade. The simulated blade finite element model contains several mesh elements, and first-order modal simulation is performed using the simulated blade finite element model to determine the simulation critical point and far-field point, as well as the stress ratio between the simulation critical point and the far-field point.

[0048] The second acquisition unit is used to acquire the first-order bending vibration fatigue test results of the titanium alloy simulated blade, and determine the test stress corresponding to the simulated danger point when the titanium alloy simulated blade reaches the fatigue limit based on the first-order bending vibration fatigue test results.

[0049] The first calculation unit is used to calculate the unstrengthened stress corresponding to the far field point using the test stress corresponding to the simulated danger point and the stress ratio between the simulated danger point and the far field point, and to calculate the strengthened stress corresponding to the far field point using the unstrengthened stress corresponding to the far field point and the strengthening factor.

[0050] The second calculation unit is used to extract the simulation stress parameters of the first-order modal simulation of the simulated blade finite element model, and to calculate the average stress corresponding to the fatigue hazard point based on the simulation stress parameters using the critical distance method.

[0051] The limit estimation unit is used to estimate the fatigue limit of titanium alloy blades after surface strengthening based on the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point.

[0052] Thirdly, a fatigue limit prediction system for surface-strengthened aero-engine blades is provided, comprising:

[0053] Memory, used to store instructions;

[0054] A processor is configured to read instructions stored in the memory and execute the method described in any one of the first aspects above, according to the instructions.

[0055] Fourthly, a computer-readable storage medium is provided, on which instructions are stored, which, when executed on a computer, cause the computer to perform any of the methods described in the first aspect. A computer program product is also provided, which, when executed on a computer, performs any of the methods described in the first aspect.

[0056] Beneficial effects: This invention adopts a blade high-cycle fatigue strength evaluation method that considers the surface state and evolution law of aero-engine blades after surface strengthening. It can accurately evaluate the fatigue performance of surface-strengthened blades, solve the problem of predicting the high-cycle fatigue strength of blades with complex surface strengthening, and has important scientific significance and engineering value for the manufacturing and application of aero-engine blades. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of the steps in the method of Embodiment 1 of the present invention;

[0059] Figure 2 This is a two-dimensional scatter plot in Embodiment 1 of the present invention;

[0060] Figure 3 This is a schematic diagram of the simulation result model in Embodiment 1 of the present invention;

[0061] Figure 4 This is a schematic diagram of the system configuration in Embodiment 3 of the present invention. Detailed Implementation

[0062] It should be noted that the descriptions of these embodiments are intended to aid in understanding the invention and do not constitute a limitation thereof. The specific structural and functional details disclosed herein are merely for describing exemplary embodiments of the invention. However, the invention may be embodied in many alternative forms and should not be construed as being limited to the embodiments described herein.

[0063] It should be understood that, unless otherwise explicitly specified and limited, the corresponding terms should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments according to the specific circumstances.

[0064] Specific details are provided in the following description to provide a complete understanding of the exemplary embodiments. However, those skilled in the art will understand that the exemplary embodiments can be implemented without these specific details. For example, apparatus may be shown in block diagrams to avoid obscuring the examples with unnecessary details. In other embodiments, well-known processes, structures, and techniques may be omitted with non-essential details to avoid obscuring the embodiments.

[0065] Example 1:

[0066] This embodiment provides a method for predicting the fatigue limit of surface-strengthened aero-engine blades, which can be applied to corresponding evaluation systems, such as... Figure 1 As shown, the method includes the following steps:

[0067] S1. Obtain the surface state evolution test results of the fatigue specimen of the surface-strengthened titanium alloy material, and obtain the fatigue strength test results of the titanium alloy material before and after surface strengthening.

[0068] In practice, surface state evolution tests can be conducted on fatigue specimens of surface-strengthened titanium alloy materials (using the same titanium alloy material as aero-engine blades, such as TC17 titanium alloy) to obtain the corresponding surface state evolution test results. Fatigue strength tests can also be conducted on the surface of aero-engine blade titanium alloy materials before and after laser shock strengthening to obtain the corresponding fatigue strength test results.

[0069] S2. Based on the surface condition evolution test results, determine the fatigue risk points after surface strengthening of the titanium alloy simulated blade, and determine the strengthening factor based on the fatigue strength test results of the titanium alloy material.

[0070] In practice, the surface condition evolution test results contain the evolution laws of surface conditions such as residual stress and microhardness under fatigue load, which can be used to determine the fatigue risk points of the simulated titanium alloy blade after surface strengthening. For example, the interpolated surface condition evolution test results of the surface-strengthened TC17 titanium alloy sample are shown in Table 1 below:

[0071] Table 1

[0072]

[0073]

[0074] The calibration stress σ' and interpolated residual stress σ' at each point can be determined based on the surface state evolution test results. res and interpolation fatigue limit σ' -1 Then, based on the calibrated stress σ' and interpolated residual stress σ' at each point... res and interpolation fatigue limit σ'-1 Calculate the evolutionary parameters corresponding to each point, where the evolutionary parameters = σ' -1 / (σ'+σ' res Then, using the evolutionary parameters corresponding to each point, construct as follows: Figure 2 The two-dimensional scatter plot shown illustrates that the evolution law parameter values ​​initially decrease rapidly with increasing depth, then slow down after reaching an inflection point. Although there is no obvious minimum value, since cracks always initiate near the surface, fatigue cracks are more likely to initiate at the inflection point than at deeper interior areas. This point can be considered a critical point for the surface-strengthened TC17 titanium alloy simulated blade. At this point, the depth is 80mm. The user can mark this point using the first operation command. The system responds to the user's first operation command by selecting the point where the evolution law parameter in the two-dimensional scatter plot reaches an inflection point, and designates the selected point as the fatigue critical point after surface strengthening of the titanium alloy simulated blade.

[0075] The fatigue limit of titanium alloy before and after laser shock strengthening can be determined based on the fatigue strength test results of the titanium alloy under a set stress ratio. The strengthening factor α is obtained by dividing the fatigue limit of the titanium alloy after laser shock strengthening by its fatigue limit before laser shock strengthening. For example, when the stress ratio is 0.1, the fatigue limits of TC17 titanium alloy before and after laser shock strengthening are 510 MPa and 565.71 MPa, respectively. After conversion using the Goodman formula, when the stress ratio is -1, the fatigue limits of TC17 titanium alloy before and after strengthening are 707.73 MPa and 802.65 MPa, respectively. By dividing the fatigue limit after strengthening (802.65 MPa) by the fatigue limit before strengthening (707.73 MPa), the strengthening factor α can be calculated to be 1.13.

[0076] S3. Construct a finite element model of a titanium alloy simulated blade. The finite element model of the simulated blade contains several mesh elements. First-order modal simulation is performed using the finite element model of the simulated blade to determine the simulation critical point and far-field point, as well as the stress ratio between the simulation critical point and the far-field point.

[0077] In practice, a finite element model of the simulated titanium alloy blade can be constructed based on its design dimensions. This finite element model contains several mesh elements. Then, a first-order modal simulation is performed using the simulated blade finite element model, and the simulation results are displayed. For example, the simulation results model is shown below. Figure 3 As shown, the user can determine the far-field point A and the simulated danger point B based on the displayed simulation result model. In response to the user's second operation command, the system selects the far-field point A and the simulated danger point B in the simulation result model and determines the simulated stress σ at the far-field point A in the simulation result model.A_sim And the simulated stress σ of the simulated hazardous point B in the simulation result model. B_sim Finally, the simulated stress σ at far-field point A is used. A_sim And the simulated stress σ at the simulated hazardous point B B_sim Calculate the stress ratio γ between the simulated critical point and the far-field point, where γ = σ B_sim / σ A_s i m .

[0078] S4. Obtain the first-order bending vibration fatigue test results of the titanium alloy simulated blade, and determine the test stress corresponding to the simulated critical point when the titanium alloy simulated blade reaches the fatigue limit based on the first-order bending vibration fatigue test results.

[0079] In practice, a first-order bending vibration fatigue test of a titanium alloy simulated blade can be carried out to obtain the first-order bending vibration fatigue test results of the unreinforced blade. Based on the first-order bending vibration fatigue test results, the system determines the test stress corresponding to the simulated critical point when the titanium alloy simulated blade reaches the fatigue limit.

[0080] S5. Calculate the unstrengthened stress corresponding to the far-field point using the test stress corresponding to the simulated danger point and the stress ratio between the simulated danger point and the far-field point, and calculate the strengthened stress corresponding to the far-field point using the unstrengthened stress corresponding to the far-field point and the strengthening factor.

[0081] In practice, the system divides the test stress corresponding to the simulated hazardous point by the stress ratio γ between the simulated hazardous point and the far-field point to obtain the unreinforced stress corresponding to the far-field point. Then, it multiplies the unreinforced stress corresponding to the far-field point by the reinforcement factor α to obtain the reinforced stress σ corresponding to the far-field point. A'_sim .

[0082] S6. Extract the simulation stress parameters from the first-order modal simulation of the simulated blade finite element model, and calculate the average stress corresponding to the fatigue hazard point based on the simulation stress parameters using the critical distance method.

[0083] In practice, after conducting numerical simulations of the first-order vibration mode of the blade, all principal stress data and Mises stress data for each mesh element are output and imported into MATLAB. MATLAB is then used to extract the simulation stress parameters from the first-order modal simulation of the finite element model of the blade, including the absolute value of the maximum principal stress and residual stress. Based on the simulation stress parameters, the average stress corresponding to the fatigue hazard point is calculated using the critical distance method. The entire process includes:

[0084] Determine the residual stress σ after surface strengthening of the simulated titanium alloy blade res Determine the distance r between all center points and the critical fatigue hazard point. cThe grid cells are within the range, and the center point is at a critical distance r from the fatigue hazard point. c The grid cells within the range are used as the target cells, where:

[0085] r c =1.54l0

[0086]

[0087] M is the set geometric correction coefficient, typically taken as 1, σ -1 For a given titanium alloy simulated blade, ΔK th The fatigue threshold stress intensity factor, for TC17 titanium alloy, can be set to [value missing].

[0088] Determine the absolute value of the maximum principal stress for each target element, and then determine the average stress σ of all target elements based on the absolute value of the maximum principal stress for each target element. C For example, the average absolute value of the maximum principal stress of each target element is calculated based on the absolute value of the maximum principal stress of the target element. This average absolute value of the maximum principal stress is then multiplied by the proportionality coefficient β between the actual measured stress of the reinforced blade and the numerical simulation stress of the first-order mode (e.g., the simulated stress σ at far-field point A). A_sim Its actual stress measurement value is σ A'_test Then β=σ A'_test / σ A_sim The average stress σ of all target elements is obtained. C Then, using the strengthening factor and the mean stress σ C and residual stress σ res Calculate the superimposed stress σ of each target element. i ,in:

[0089] σ i =ασ C +σ res

[0090] α is the enhancement factor, and i represents the index of the target unit;

[0091] Utilizing the superimposed stress σ of each target element i Calculate the average stress σ corresponding to the fatigue critical point aver ,in:

[0092]

[0093] η is the set bending effect correction coefficient, N is the number of target elements, and V i Let i be the cell volume of the target cell i.

[0094] S7. Estimate the fatigue limit of the titanium alloy blade surface after strengthening based on the strengthening stress corresponding to the far field point, the stress ratio between the simulated critical point and the far field point, and the average stress corresponding to the fatigue critical point.

[0095] In practice, the system substitutes the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point into the preset fatigue limit prediction formula for surface-strengthened blades to calculate the fatigue limit of the aero-engine titanium alloy blade after surface strengthening. The fatigue limit prediction formula for surface-strengthened blades is as follows:

[0096]

[0097] Where, σ A'_sim The stress corresponding to the far-field point is characterized by γ, and the stress ratio between the simulated critical point and the far-field point is characterized by γ.

[0098] To verify the prediction accuracy of the method in this embodiment, bending vibration fatigue tests were conducted on six laser-shock-strengthened TC17 titanium alloy simulated blades to measure their actual fatigue limits. The measurement results are shown in Table 2 below:

[0099] Table 2

[0100]

[0101] The results show that the fatigue limit test value σ of the six laser-shock-strengthened titanium alloy blades is... e Compared with the predicted values, the prediction errors of the six laser-shock-strengthened titanium alloy blades were all within 10%, demonstrating good prediction accuracy.

[0102] Example 2:

[0103] This embodiment provides a fatigue limit prediction system for surface-strengthened aero-engine blades, including a first acquisition unit, a result determination unit, a modal simulation unit, a second acquisition unit, a first calculation unit, a second calculation unit, and a limit estimation unit, wherein:

[0104] The first acquisition unit is used to acquire the surface state evolution test results of the fatigue specimen of the surface-strengthened titanium alloy material, and to acquire the fatigue strength test results of the titanium alloy material before and after surface strengthening.

[0105] The result determination unit is used to determine the fatigue risk points after surface strengthening of the titanium alloy simulated blade based on the surface state evolution test results, and to determine the strengthening factor based on the fatigue strength test results of the titanium alloy material.

[0106] The modal simulation unit is used to construct a simulated blade finite element model of a titanium alloy simulated blade. The simulated blade finite element model contains several mesh elements, and first-order modal simulation is performed using the simulated blade finite element model to determine the simulation critical point and far-field point, as well as the stress ratio between the simulation critical point and the far-field point.

[0107] The second acquisition unit is used to acquire the first-order bending vibration fatigue test results of the titanium alloy simulated blade, and determine the test stress corresponding to the simulated danger point when the titanium alloy simulated blade reaches the fatigue limit based on the first-order bending vibration fatigue test results.

[0108] The first calculation unit is used to calculate the unstrengthened stress corresponding to the far field point using the test stress corresponding to the simulated danger point and the stress ratio between the simulated danger point and the far field point, and to calculate the strengthened stress corresponding to the far field point using the unstrengthened stress corresponding to the far field point and the strengthening factor.

[0109] The second calculation unit is used to extract the simulation stress parameters of the first-order modal simulation of the simulated blade finite element model, and to calculate the average stress corresponding to the fatigue hazard point based on the simulation stress parameters using the critical distance method.

[0110] The limit estimation unit is used to estimate the fatigue limit of titanium alloy blades after surface strengthening based on the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point.

[0111] Example 3:

[0112] This embodiment provides a fatigue limit prediction system for surface-strengthened aero-engine blades, such as... Figure 4 As shown, at the hardware level, it includes:

[0113] The data interface is used to establish data communication between the processor and external data terminals;

[0114] Memory, used to store instructions;

[0115] The processor is used to read the instructions stored in the memory and execute the surface-strengthened aero-engine blade fatigue limit prediction method in Embodiment 1 according to the instructions.

[0116] Optionally, the system also includes an internal bus, through which the processor, memory, and data interface can be interconnected. This internal bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc.

[0117] The memory may include, but is not limited to, random access memory (RAM), read-only memory (ROM), flash memory, first-in-first-out (FIFO) memory, and / or first-in-last-out (FILO) memory. The processor may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0118] Example 4:

[0119] This embodiment provides a computer-readable storage medium storing instructions. When these instructions are executed on a computer, the computer performs the fatigue limit prediction method for surface-strengthened aero-engine blades described in Embodiment 1. The computer-readable storage medium refers to a data storage medium, which may include, but is not limited to, floppy disks, optical disks, hard disks, flash memory, USB flash drives, and / or Memory Sticks. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.

[0120] This embodiment also provides a computer program product that, when run on a computer, executes the surface-strengthened aero-engine blade fatigue limit prediction method of Embodiment 1. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device.

[0121] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting the fatigue limit of surface-strengthened aero-engine blades, characterized in that, include: The surface state evolution test results of fatigue specimens of surface-strengthened titanium alloy were obtained, and the fatigue strength test results of titanium alloy before and after surface strengthening were obtained. The fatigue risk points of the simulated titanium alloy blade after surface strengthening were determined based on the surface condition evolution test results, and the strengthening factor was determined based on the fatigue strength test results of the titanium alloy material. A finite element model of a titanium alloy simulated blade is constructed. The simulated blade finite element model contains several mesh elements. First-order modal simulation is performed using the simulated blade finite element model to determine the simulation critical point and far-field point, as well as the stress ratio between the simulation critical point and the far-field point. The results of the first-order bending vibration fatigue test of the titanium alloy simulated blade were obtained, and the test stress corresponding to the simulated critical point when the titanium alloy simulated blade reached the fatigue limit was determined based on the results of the first-order bending vibration fatigue test. The unstrengthened stress at the far field point is calculated using the test stress corresponding to the simulated critical point and the stress ratio between the simulated critical point and the far field point. The strengthened stress at the far field point is calculated using the unstrengthened stress at the far field point and the strengthening factor. The simulation stress parameters of the first-order modal simulation of the simulated blade finite element model are extracted, and the average stress corresponding to the fatigue critical point is calculated based on the simulation stress parameters using the critical distance method. The fatigue limit of the titanium alloy blade after surface strengthening is estimated based on the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point.

2. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 1, characterized in that, The determination of fatigue risk points after surface strengthening of titanium alloy simulated blades based on surface condition evolution test results includes: Based on the surface condition evolution test results, the calibration stress σ' and interpolated residual stress σ' at each point of the fatigue specimen of the surface-strengthened titanium alloy were determined. res and interpolation fatigue limit σ' -1 ; Based on the calibration stress σ' and interpolated residual stress σ' at each point res and interpolation fatigue limit σ' -1 Calculate the evolutionary parameters corresponding to each point, where the evolutionary parameters = σ' -1 / (σ'+σ' res ); A two-dimensional scatter plot is constructed using the evolutionary parameters corresponding to each point, the two-dimensional scatter plot is displayed, and the point where the evolutionary parameters in the two-dimensional scatter plot appear is selected in response to the user's first operation command. The selected points were designated as fatigue risk points after surface strengthening of the titanium alloy simulated blade.

3. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 1, characterized in that, The determination of the strengthening factor based on the fatigue strength test results of titanium alloy materials includes: Based on the fatigue strength test results of titanium alloy materials, the fatigue limit of titanium alloy materials before and after strengthening is determined under a set stress ratio. The strengthening factor is obtained by dividing the fatigue limit of titanium alloy materials after strengthening by its fatigue limit before strengthening.

4. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 1, characterized in that, The method of using a simulated blade finite element model to perform first-order modal simulation to determine the simulated critical point and far-field point, as well as the stress ratio between the simulated critical point and far-field point, includes: First-order modal simulation was performed using a simulated blade finite element model, and the simulation results were presented. In response to the user's second operation command, the far-field point and simulation danger point are selected in the simulation result model, and the simulation stress σ of the far-field point in the simulation result model is determined. A_sim And the simulated stress σ of the simulated danger point in the simulation result model. B_sim ; Simulated stress σ at far-field points A_sim Simulated stress σ at the simulated hazardous point B_sim Calculate the stress ratio γ between the simulated critical point and the far-field point, where γ = σ B_sim / σ A_sim .

5. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 1, characterized in that, The calculation of the unreinforced stress corresponding to the far-field point using the test stress corresponding to the simulated critical point and the stress ratio between the simulated critical point and the far-field point includes: The unreinforced stress at the far-field point is obtained by dividing the test stress corresponding to the simulated hazardous point by the stress ratio between the simulated hazardous point and the far-field point.

6. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 1, characterized in that, The calculation of the strengthening stress corresponding to the far-field point using the unstrengthened stress and strengthening factor at the far-field point includes: The strengthening stress corresponding to the far-field point is obtained by multiplying the unstrengthened stress corresponding to the far-field point by the strengthening factor.

7. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 1, characterized in that, The extraction of simulation stress parameters from the first-order modal simulation of the simulated blade finite element model, and the calculation of the average stress corresponding to the fatigue critical point using the critical distance method based on the simulation stress parameters, includes: Determine the residual stress σ after surface strengthening of the simulated titanium alloy blade res Determine the distance r between all center points and the critical fatigue hazard point. c The grid cells are within the range, and the center point is at a critical distance r from the fatigue hazard point. c The grid cells within the range are used as the target cells, where: r c ＝1.54l0 M is the set geometric correction coefficient, σ -1 For a given titanium alloy simulated blade, ΔK th The fatigue threshold stress intensity factor is set. Determine the absolute value of the maximum principal stress for each target element, and then determine the average stress σ of all target elements based on the absolute value of the maximum principal stress for each target element. C And utilize the strengthening factor and mean stress σ C and residual stress σ res Calculate the superimposed stress σ of each target element. i ,in: s i =as C +s res α is the enhancement factor, and i represents the index of the target unit; Utilizing the superimposed stress σ of each target element i Calculate the average stress σ corresponding to the fatigue critical point aver ,in: η is the set bending effect correction coefficient, N is the number of target elements, and V i Let i be the cell volume of the target cell i.

8. The method for predicting the fatigue limit of surface-strengthened aero-engine blades according to claim 7, characterized in that, The estimation of the fatigue limit of the titanium alloy blade surface after strengthening, based on the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point, includes: Substituting the strengthening stress corresponding to the far-field point, the stress ratio between the simulated critical point and the far-field point, and the average stress corresponding to the fatigue critical point into the preset fatigue limit prediction formula for surface-strengthened blades, the fatigue limit of the aero-engine blade after surface strengthening with titanium alloy material is obtained. The fatigue limit prediction formula for surface-strengthened blades is as follows: Where, σ A'_sim The stress corresponding to the far-field point is characterized by γ, and the stress ratio between the simulated critical point and the far-field point is characterized by γ.

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