A fatigue test simulation design method for simulating the multi-axial stress state of the dangerous part of the wheel with compressive stress components

Abstract

The present invention relates to a fatigue test simulation part design method for simulating a multi-axial stress state containing a compressive stress component at a dangerous part of a wheel disc, and the steps are as follows: (1) obtaining a geometric model and material parameters of the wheel disc and determining the load conditions; (2) establishing a finite element model and calculating and obtaining the stress distribution of the wheel disc under actual working conditions; (3) optimizing the stress distribution at the notch by changing the notch shape; (4) further optimizing the stress distribution at the notch by changing the radius of the arc boss, the thickness of the plate and other geometric dimensions; (5) on the basis of step (4), adopting a multi-segment arc transition for the part where the geometric configuration of the three-dimensional plate changes more drastically; (6) repeatedly changing the initial value of the optimization parameter for multiple times to carry out repeated optimization to avoid falling into a local optimum. (7) after the geometric configuration of the three-dimensional plate is determined, clamping sections are designed at both ends. The simulation part designed by the present invention can generate compressive stress under tensile load, has lower requirements for the test, and is more applicable.

Description

Technical Field

[0001] The present invention is a fatigue test simulation part design method for simulating the multi-axial stress state of the dangerous part of the wheel disk containing compressive stress components. The present invention can simulate the multi-axial stress state of the dangerous part of the wheel disk center of an aerospace engine, and belongs to the field of aerospace engine technology. Background Art

[0002] As a key component in an aero-engine, the wheel must not only withstand the huge centrifugal stress caused by high-speed rotation under actual service conditions, but also withstand the vibration stress caused by gas impact, the thermal stress caused by uneven temperature field, and the additional stress caused by the deformation of related parts. Once failure occurs, serious consequences will inevitably occur. Therefore, the strength and life of the wheel are crucial to the structural design of the aero-engine. Due to the rotation of the wheel during the operation of the aero-engine, the load it is subjected to has a certain periodicity, so the main failure form of the wheel is low-cycle fatigue failure. Accurately predicting the low-cycle fatigue life of the wheel is not only the key to the wheel life problem, but also an urgent problem to be solved in engineering. However, given that the actual aero-engine wheel is large in size, complex in structure, expensive, and has a long fatigue life, it takes a lot of manpower and material resources to conduct component-level tests, so simulated parts are often used for fatigue tests.

[0003] Existing patents CN114756972A "A design method for micro-motion fatigue simulation parts of aircraft engine turbine disk mortise and tenon joint structure" and CN114840944A "A design method for crack initiation simulation parts based on consistent damage control parameters" have designed fatigue simulation parts for key parts of aircraft engines. The simulation parts design can only ensure that the equivalent stress or damage control parameters are consistent with the real structure within the critical distance range; the existing patent CN114756973A "A design method for multi-axis creep-fatigue simulation parts of rounded parts of turbine disks" can ensure that the stress of the simulation parts in both radial and circumferential directions is consistent with the real structure within the critical distance range, but the simulation parts need to be bidirectionally loaded during the test, which requires high test capabilities. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of existing simulation part design methods. On the basis of finite element calculation, a fatigue test simulation part design method is provided to simulate the multi-axial stress state containing compressive stress components in the dangerous parts of the wheel. Through structural optimization, the simulation part produces compressive stress in the thickness direction under the tensile load, thereby ensuring that the multi-axial stress state of the simulation part within a certain length path is consistent with the real structure under the condition of unidirectional loading, while eliminating the influence of secondary dangerous points, thereby simulating the fatigue failure behavior of the real structure under laboratory conditions.

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

[0006] A method for designing a fatigue test simulation component for simulating a multiaxial stress state containing a compressive stress component at a dangerous part of a wheel disc comprises the following steps:

[0007] Step (1), obtaining a real geometric model of the wheel disc, and determining the material parameters of the simulation part and the test conditions according to the wheel disc material and the actual service conditions;

[0008] Step (2), based on the known conditions obtained in step (1), establish a finite element model of the wheel disc, and calculate the stress distribution of the wheel disc under actual service conditions, focusing on the stress distribution of dangerous parts, determining the dangerous point as the point with the largest equivalent stress, and taking this point as the starting point, defining a path along the direction of the maximum equivalent stress gradient of the wheel disc, and obtaining the multi-axial stress distribution on the path;

[0009] Step (3), taking a two-dimensional double-sided elliptical notch plate as the basic shape, taking the center position of the ellipse, the radius of the major and minor axes, and the magnitude of the applied load as optimization parameters, and optimizing the stress distribution at the notch by changing the notch shape, so that the change gradient of the principal stress parallel to the loading direction and perpendicular to the loading direction at the notch root along the notch bisector is consistent with the change gradient of the first principal stress and the second principal stress on the path obtained in step (2) within a range of 1 mm;

[0010] Step (4), based on the two-dimensional double-sided elliptical notch plate optimized in step (3), design the geometric configuration in the thickness direction, set arc bosses on the upper and lower surfaces of the plate along the thickness direction, so that the plate can generate compressive stress in the thickness direction under a tensile load, and further optimize the stress distribution at the notch by changing the radius of the arc boss and the thickness of the plate, so that the principal stress gradients in all directions along the bisector of the notch root are consistent with the principal stress gradients in all directions on the path obtained in step (2) within a range of 1 mm;

[0011] Step (5), based on step (4), using multiple arcs to transition the places where the geometric configuration of the simulation part changes more dramatically;

[0012] Step (6), changing the initial values ​​of the optimization parameters multiple times to repeat the optimization to avoid the optimization results falling into the local optimum;

[0013] Step (7), after the geometric configuration of the three-dimensional plate is determined, clamping sections are designed at both ends of the test section.

[0014] In the step (1), the material performance parameters include material density, elastic modulus, Poisson's ratio, tensile strength and yield strength. These parameters are obtained through material performance testing and material data manuals. For material parameters that change with temperature, material parameters at multiple sets of temperatures should be given, and the temperature range taken should include the maximum and minimum values ​​in the working temperature field of the wheel. The test conditions include load conditions such as the temperature field and rotation speed under the actual service conditions of the wheel.

[0015] In the step (2), the path length is not less than 1 mm.

[0016] In the steps (3) and (4), in order to ensure that the simulation component can accurately reflect the fatigue failure law of the dangerous part of the wheel under the actual service conditions, the design goal of the simulation component is: starting from the maximum equivalent stress point of the dangerous part of the wheel, a path with a length of not less than 1 mm is defined along the direction of the maximum equivalent stress gradient, to ensure that the multi-axial stress gradient of the simulation component within the same length range along the notch bisector is consistent with the multi-axial stress gradient of the actual wheel along the direction of the maximum equivalent stress gradient, so as to better reflect the initiation and propagation process of fatigue cracks.

[0017] In the steps (3) and (4), the process of optimizing the configuration of the simulated component is as follows: by continuously adjusting the two-dimensional geometric configuration of the test section of the simulated component, the principal stress gradients along the notch bisector parallel to and perpendicular to the loading direction at the notch root of the simulated component are respectively consistent with the first principal stress and the second principal stress on the path obtained in step (2) within a range of 1 mm, thereby completing the two-dimensional design of the simulated component; on the basis of the two-dimensional design, the three-dimensional geometric configuration of the test section of the simulated component is further adjusted, so that the stress gradients in all directions along the notch bisector at the notch root of the simulated component are consistent with the corresponding stress gradients on the path obtained in step (2) within a range of 1 mm.

[0018] In the step (3), the number of points taken by the simulation and the actual wheel on the same length path should be equal.

[0019] In the step (3), if the maximum equivalent stress of the dangerous part of the wheel is less than the yield strength of the material, that is, the dangerous part of the wheel is always in the elastic stage under the actual service condition, then the stress of the dangerous part is proportional to the load size, and the principal stresses in each direction should be normalized based on the maximum value of the first principal stress to reduce the optimization parameters. At this time, the load size does not need to be used as an optimization parameter; if the maximum equivalent stress of the dangerous part of the wheel exceeds the yield strength of the material, normalization cannot be performed, and the load size still needs to be optimized as an optimization parameter until the two-dimensional design of the simulation part is completed.

[0020] In the step (4), in order to enable the simulation part to generate compressive stress in the thickness direction under a tensile load, arc boss configurations are set on the upper and lower surfaces of the three-dimensional plate along the thickness direction, and the magnitude of the compressive stress is changed by adjusting the radius, center position and thickness of the arc boss.

[0021] In step (5), in order to ensure that the simulated component can fail at the designed position, the secondary dangerous points other than the dangerous position at the root of the notch of the simulated component should be further optimized to reduce the stress level of the secondary dangerous points, so as to avoid competition with the designed dangerous positions in the formal test and affect the test results.

[0022] In the step (6), modern optimization algorithms such as adaptive simulated annealing algorithm are used to carry out optimization design.

[0023] The beneficial effects of the present invention are:

[0024] Existing patents CN114756972A "A design method for a micro-motion fatigue simulation part of a turbine disc mortise structure of an aircraft engine" and CN114840944A "A design method for a crack initiation simulation part based on consistent damage control parameters" only consider the influence of equivalent stress or damage control parameters within a certain range, and cannot accurately reflect the stress state of the actual disc structure. The present invention designs a double-sided notched flat plate as a test section, optimizes the configuration in the thickness direction to achieve that the three-dimensional principal stress of the simulation part on a certain length path is consistent with the actual disc structure, and can more accurately describe the failure law of fatigue crack initiation and propagation process of the actual disc structure; although the existing patent CN114756973A "A design method for a multi-axial creep-fatigue simulation part of a rounded part of a turbine disc" can also simulate the circumferential and radial stresses of the actual disc structure, its simulation part needs to be tested under bidirectional loading conditions. The simulation part designed by the present invention can generate compressive stress under tensile load, so only unidirectional loading is required to ensure that the multi-axial stress of the simulation part is consistent with the actual disc structure within a certain range, and the requirements for the test are lower and the applicability is stronger. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a flow chart of a method for designing a fatigue test simulation component for a compressor disk core under multi-axial stress;

[0026] Figure 2 shows the configuration and stress distribution of the simulated part after two-dimensional design;

[0027] Figure 3 is a comparison of the optimization effects of the two-dimensional design of the simulation parts;

[0028] FIG4 shows the configuration and stress distribution of the simulated part after three-dimensional design;

[0029] Figure 5 is a comparison of the optimization effects of the three-dimensional design of the simulation parts;

[0030] Figure 6 is a comparison of the simulation component configurations before and after the optimization of the secondary dangerous point;

[0031] Figure 7 is a comparison of stress distribution of the simulation parts before and after optimization of the secondary dangerous point;

[0032] FIG8 is a processing drawing of a simulation part;

[0033] FIG9 is a physical picture of the simulation part;

[0034] Figure 10 shows the fatigue fracture position of the simulated part;

[0035] Figure 11 shows the fatigue fracture characteristics of the simulated component. Implementation

[0036] The present invention is further described in detail below through specific examples in conjunction with the accompanying drawings.

[0037] like Figure 1 As shown, the present invention relates to a fatigue test simulation component design method for simulating the multi-axial stress state of the dangerous part of the wheel disk containing compressive stress components, and the steps are: (1) obtaining the geometric model and material parameters of the wheel disk, and determining the load conditions according to the actual working conditions; (2) establishing a finite element model, calculating and obtaining the stress distribution of the wheel disk under the actual working conditions, focusing on the stress distribution of the dangerous part, determining the dangerous point position as the point with the maximum equivalent stress, taking the point as the starting point, defining a path along the direction of the maximum equivalent stress gradient, and the path length is not less than 1mm, and obtaining the multi-axial stress state on the path; (3) taking a two-dimensional double-sided elliptical notched flat plate as the basic shape, taking the center position of the ellipse, the radius of the major and minor axes, the size of the applied load, etc. as optimization parameters, and optimizing the stress distribution at the notch by changing the notch shape, so that the change gradient of the principal stress parallel to the loading direction and perpendicular to the loading direction at the notch root along the notch bisector is consistent with that at the notch root. The gradients of the first principal stress and the second principal stress on the path obtained in step (2) tend to be consistent within 1 mm; (4) Based on the two-dimensional double-sided elliptical notch plate optimized in step (3), the geometric configuration in the thickness direction is designed, and arc bosses are set on the upper and lower surfaces of the plate along the thickness direction, so that the plate can generate compressive stress in the thickness direction under tensile load. By changing the radius of the arc boss, the thickness of the plate and other geometric dimensions, the stress distribution at the notch is further optimized, so that the principal stress gradients in all directions along the bisector of the notch root are consistent with the principal stress gradients in all directions on the path obtained in step (2) within 1 mm; (5) Based on step (4), multi-segment arc transition is used for the part where the geometric configuration of the three-dimensional plate changes more drastically to reduce the stress of the secondary dangerous point; (6) The initial values ​​of the optimization parameters are changed multiple times to carry out repeated optimization to avoid falling into the local optimum. (7) After the geometric configuration of the three-dimensional plate is determined, clamping sections are designed at both ends, and the size parameters of the clamping section and the transition connection section should be within a reasonable range.

[0038] The present invention will be further described below in conjunction with the embodiments. Example

[0039] The first step is to obtain the real geometric model of the wheel, and determine the material parameters and test conditions of the simulation parts according to the material and actual service conditions of the wheel. Material performance parameters include density, elastic modulus, Poisson's ratio, tensile strength and yield strength, etc. These parameters are obtained through material performance tests and material data manuals. For material parameters that change with temperature, material parameters at multiple sets of temperatures should be given, and the temperature range taken must include the maximum and minimum values ​​in the wheel's operating temperature field; the test conditions include the temperature field, speed and other load conditions of the wheel under actual service conditions.

[0040] In the second step, based on the known conditions obtained in the first step, a finite element model of the wheel is established to calculate the stress distribution of the wheel under actual service conditions, focusing on the stress distribution of dangerous parts. The dangerous point is determined as the point with the largest equivalent stress. Taking this point as the starting point, a path is defined along the direction of the maximum equivalent stress gradient of the wheel. The path length should be no less than 1 mm, and the multi-axial stress distribution on the path is obtained.

[0041] In the third step, the two-dimensional double-sided elliptical notch plate is used as the basic shape (circular notch when the major and minor axis radii are equal), the position of the geometric center of the elliptical notch, the major and minor axis radii, the applied load size, etc. are used as optimization parameters, and the constraints such as the blank size used for the simulation part processing and the specifications of the testing machine are considered to perform two-dimensional optimization design of the simulation part. By changing the notch geometry, the stress distribution at the notch is optimized. The optimization goal is that the change gradient of the principal stress parallel to the loading direction and perpendicular to the loading direction at the notch root along the notch bisector is consistent with the change gradient of the first principal stress and the second principal stress on the path obtained in the second step within the range of 1mm, and the number of points taken on the same length path of the simulation part and the actual wheel should be equal. If the maximum equivalent stress of the dangerous part of the wheel is less than the yield strength of the material, that is, the dangerous part of the wheel is always in the elastic stage under the actual service conditions, then the stress of the dangerous part is proportional to the load size, and the principal stresses in each direction should be normalized based on the maximum value of the first principal stress to reduce the optimization parameters. At this time, the load size does not need to be used as an optimization parameter; if the maximum equivalent stress of the dangerous part of the wheel exceeds the yield strength of the material, it cannot be normalized, and the load size still needs to be used as an optimization parameter for optimization. The geometric configuration and stress distribution of the simulated part after two-dimensional optimization are shown in Figure 2. Figure 3 compares the stress distribution of the simulated part and the actual wheel structure. It can be seen that the normalized stress gradients of the two on the same length path are basically consistent, and the two-dimensional preliminary design of the simulated part is completed.

[0042] The fourth step is to design the configuration of the simulation part in the thickness direction based on the two-dimensional double-sided elliptical notch plate optimized in the third step. In order to simulate the compressive stress component of the dangerous part of the wheel disc, arc bosses are set on the upper and lower surfaces of the three-dimensional notch plate along the thickness direction (as shown in Figure 4), so that the simulation part can generate compressive stress in the thickness direction under unidirectional tensile load. The center position of the arc boss, the arc radius, the thickness of the plate and other geometric dimensions are used as optimization parameters to further optimize the stress distribution at the notch, so that the principal stress gradients in all directions along the notch bisector of the notch root are consistent with the principal stress gradients in all directions on the path obtained in the second step within 1mm. The geometric configuration and stress distribution of the simulation part after three-dimensional optimization are shown in Figure 4. Figure 5 compares the stress distribution of the simulation part and the actual wheel disc structure. It can be seen that the normalized stress gradients in all directions of the two on the same length path are basically consistent, completing the three-dimensional preliminary design of the simulation part.

[0043] The fifth step is to ensure that the simulated part can break and fail at the designed position, the secondary dangerous points other than the dangerous position at the root of the notch of the simulated part should be further optimized to reduce the stress level of the secondary dangerous points, so as to avoid competition with the designed dangerous positions in the formal test and affect the test results. Based on the fourth step, multiple arcs are used for transition in places where the geometric configuration of the simulated part changes more drastically (as shown in Figure 6), which increases the cross-sectional area at the secondary dangerous point and significantly reduces the stress size of the secondary dangerous point. As can be seen from Figure 7, this configuration can effectively reduce the stress of the secondary dangerous point and ensure that the simulated part is destroyed at the designed position in the test.

[0044] The sixth step is to change the initial values ​​of the optimization parameters several times to repeat the optimization to avoid falling into the local optimum. Modern optimization algorithms such as adaptive simulated annealing algorithm can be used to carry out optimization design.

[0045] Step 7: After the geometric configuration of the three-dimensional plate is determined, it is also necessary to design clamping sections at both ends of the test section. The size parameters of the clamping section and the transition connection section should be within a reasonable range, considering the specifications of the fatigue testing machine used in the test and avoiding the occurrence of broken threads during the test. The final simulation part processing drawing is shown in Figure 8, and the actual simulation part processed according to the drawing is shown in Figure 9. After verification, the simulation part can indeed be fatigue-damaged at the designed position, as shown in Figure 10. The low-cycle fatigue fracture characteristics of the simulation part are shown in Figure 11. It can be seen that the crack initiates at the designed dangerous point, and the fatigue extension zone expands inward in a semicircular shape. The extension zone accounts for about 3 / 4 of the fracture area. The fatigue source extension zone is relatively gentle, the radial morphology is relatively clear, and the crack extension direction is along the design stress gradient direction, indicating that the simulation part can indeed simulate the failure law of the fatigue crack initiation and extension process of the actual dangerous part of the wheel well.

[0046] The above examples are provided only for the purpose of describing the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principles of the present invention should all be included within the scope of the present invention.

Claims

1. A method for designing a fatigue test simulation component for simulating a multiaxial stress state containing a compressive stress component at a dangerous part of a wheel disc, characterized in that: The following steps are involved: Step (1), obtaining a real geometric model of the wheel disc, and determining the material parameters of the simulation part and the test conditions according to the wheel disc material and the actual service conditions; Step (2), based on the known conditions obtained in step (1), establish a finite element model of the wheel disc, and calculate the stress distribution of the wheel disc under actual service conditions, focusing on the stress distribution of dangerous parts, determining the dangerous point as the point with the largest equivalent stress, and taking this point as the starting point, defining a path along the direction of the maximum equivalent stress gradient of the wheel disc, and obtaining the multi-axial stress distribution on the path; Step (3), taking a two-dimensional double-sided elliptical notch plate as the basic shape, taking the ellipse center position, the major and minor axis radii, and the applied load size as optimization parameters, and optimizing the stress distribution at the notch by changing the notch shape; In step (3), the number of points taken by the simulation and the actual wheel on the same length path should be equal; In the step (3), if the maximum equivalent stress of the dangerous part of the wheel is less than the yield strength of the material, that is, the dangerous part of the wheel is always in the elastic stage under the actual service condition, then the stress of the dangerous part is proportional to the load size, and the principal stresses in each direction should be normalized based on the maximum value of the first principal stress to reduce the optimization parameters. At this time, the load size does not need to be used as an optimization parameter; if the maximum equivalent stress of the dangerous part of the wheel exceeds the yield strength of the material, normalization cannot be performed, and the load size still needs to be optimized as an optimization parameter until the two-dimensional design of the simulation part is completed; Step (4), based on the two-dimensional double-sided elliptical notch plate optimized in step (3), designing the geometric configuration in the thickness direction, setting arc bosses on the upper and lower surfaces of the plate along the thickness direction, so that the plate can generate compressive stress in the thickness direction under a tensile load, and further optimizing the stress distribution at the notch by changing the radius of the arc boss and the thickness of the plate; In the steps (3) and (4), in order to ensure that the simulation component can accurately reflect the fatigue failure law of the dangerous part of the wheel under the actual service conditions, the design goal of the simulation component is: starting from the maximum equivalent stress point of the dangerous part of the wheel, a path with a length of not less than 1 mm is defined along the direction of the maximum equivalent stress gradient, ensuring that the multi-axial stress gradient of the simulation component within the same length range along the notch bisector is consistent with the multi-axial stress gradient of the actual wheel along the direction of the maximum equivalent stress gradient, so as to better reflect the initiation and propagation process of fatigue cracks; In the steps (3) and (4), the process of optimizing the configuration of the simulated component is as follows: by continuously adjusting the two-dimensional geometric configuration of the test section of the simulated component, the principal stress gradients along the notch bisector parallel to and perpendicular to the loading direction at the notch root of the simulated component are respectively consistent with the first principal stress and the second principal stress on the path obtained in step (2) within a range of 1 mm, thereby completing the two-dimensional design of the simulated component; on the basis of the two-dimensional design, further adjusting the three-dimensional geometric configuration of the test section of the simulated component, so that the stress gradients in all directions along the notch bisector at the notch root of the simulated component are consistent with the corresponding stress gradients on the path obtained in step (2) within a range of 1 mm; Step (5), based on step (4), using arcs to transition the places where the geometric configuration of the simulation part changes more dramatically; Step (6), changing the initial values ​​of the optimization parameters multiple times to repeat the optimization to avoid the optimization results falling into the local optimum; Step (7), after the geometric configuration of the three-dimensional plate is determined, clamping sections are designed at both ends of the test section.

2. The method for designing a fatigue test simulation component for simulating a multi-axial stress state containing a compressive stress component at a dangerous part of a wheel according to claim 1, characterized in that: In the step (1), the material performance parameters include material density, elastic modulus, Poisson's ratio, tensile strength and yield strength. These parameters are obtained through material performance testing and material data manuals. For material parameters that change with temperature, material parameters at multiple sets of temperatures should be given, and the temperature range taken should include the maximum and minimum values ​​in the working temperature field of the wheel. The test conditions include load conditions such as the temperature field and rotation speed under the actual service conditions of the wheel.

3. The method for designing a fatigue test simulation component for simulating a multi-axial stress state containing a compressive stress component at a dangerous part of a wheel according to claim 1, characterized in that: In the step (2), the path length is not less than 1 mm.

4. The method for designing a fatigue test simulation component for simulating a multi-axial stress state containing a compressive stress component at a dangerous part of a wheel according to claim 1, characterized in that: In the step (4), in order to enable the simulation part to generate compressive stress in the thickness direction under a tensile load, arc boss configurations are set on the upper and lower surfaces of the three-dimensional plate along the thickness direction, and the magnitude of the compressive stress is changed by adjusting the radius, center position and thickness of the arc boss.

5. The method for designing a fatigue test simulation component for simulating a multi-axial stress state containing a compressive stress component at a dangerous part of a wheel according to claim 1, characterized in that: In the step (5), multiple arcs are used to transition the portion where the geometric configuration of the simulation part changes more dramatically.

6. The method for designing a fatigue test simulation component for simulating a multi-axial stress state containing a compressive stress component at a dangerous part of a wheel according to claim 1, characterized in that: In the step (6), an adaptive simulated annealing algorithm is used to carry out optimization design.

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