Quantitative controllable impact pre-damage test device and method

Abstract

The invention provides a quantitative and controllable impact pre-damage device and a quantitative and controllable impact pre-damage method. The device is used for impacting a plate impact test piece (7) and comprises an emergent rod (1), a clamp (2), an incident rod (3), an impact rod (4), an energy absorption device (5) and a data acquisition device (6). Wherein the clamp (2) is used for fixing a plate impact test piece (7) between the emergent rod (1) and the incident rod (3) to ensure the stability of the plate impact test piece (7) in the stretching process; one end of the ejection rod (1) is in threaded connection with one end of the clamp (2), and the other end is rigidly fixed. According to the method, a new technical means can be provided for blade damage mechanism research and development of a damage repair technology by accurately simulating evolution of a microstructure in blade foreign object impact damage, and the residual life and residual strength of the blade under different damage conditions can be systematically evaluated through the method; and a scientific basis is provided for damage tolerance analysis and formulation of a repair strategy.

Description

Technical Field

[0001] This invention relates to the field of materials testing and measurement technology, and in particular to an impact damage pre-fabrication device and method. Background Technology

[0002] In the field of aero-engines, compressor blades are a critical component, and their performance directly affects the efficiency and reliability of the entire engine. During service, compressor blades may develop defects such as cracks and chipping due to foreign object impacts. These damages can seriously threaten flight safety and increase maintenance costs. Currently, simulation and pre-construction technologies for compressor blade damage have become an important research direction in aero-engine health management and maintenance strategies.

[0003] Impact damage at high strain rates can significantly affect the macroscopic mechanical properties and microstructure of metallic materials. For example, high strain rates can lead to localized plastic deformation, the formation of adiabatic shear bands, and even phase transformations. These changes not only reduce the strength and toughness of the material but may also cause premature failure of engine structures.

[0004] Despite some progress in existing research, there remains a technological gap in the development of quantitatively controllable pre-fabrication devices and methods for compressor blade impact damage. Current technologies struggle to simulate the complex impact loads experienced by blades in actual flight. Impact tests on materials focus on high-strain-rate constitutive relationships, but existing testing techniques cannot further assess the impact of damage on the material's mechanical properties after impact. The lack of a pre-fabrication device capable of precisely controlling the degree and location of damage limits in-depth research into the effects of blade damage on its mechanical properties and the further development of damage repair technologies.

[0005] To address this technological need, this patent proposes a quantitatively controllable device and method for pre-fabricating compressor blade impact damage. The aim is to provide a new technical means for studying blade damage mechanisms and developing damage repair technologies by accurately simulating and pre-fabricating blade damage. This device can simulate impacts from foreign objects of different velocities, angles, and energies, achieving precise control over the degree and location of blade damage, thereby providing more realistic and reliable experimental data for blade damage research. This method allows for the systematic study of blade performance changes under different damage conditions, providing a scientific basis for damage tolerance analysis and the formulation of repair strategies. Summary of the Invention

[0006] The problem that this invention aims to solve is: The main existing device for testing the impact performance of materials is the Hopkinson bar test system. The Hopkinson bar test controls the test loading strain rate and the strain range of the specimen by controlling the length and speed of the impact bar. It is mainly used to test the dynamic mechanical response performance of materials at high strain rates, but it lacks the ability to control the damage caused by a single impact.

[0007] The purpose of this invention is: To address the aforementioned shortcomings in the existing technology, this invention provides a quantitatively controllable impact damage pre-fabrication device and method, which can solve the technical problem of the lack of effective quantitative pre-fabrication of damage to study the impact of damage on the mechanical properties of materials.

[0008] The technical solution of this invention is: On the one hand, the present invention proposes a quantitatively controllable impact pre-damage testing device for impacting plate impact specimens (7). The device includes: an ejector rod (1), a clamp (2), an incident rod (3), an impact rod (4), an energy absorption device (5), and a data acquisition device (6), wherein: the clamp (2) is used to fix the plate impact specimen (7) between the ejector rod (1) and the incident rod (3) to ensure the stability of the plate impact specimen (7) during the tensile process; one end of the ejector rod (1) is threadedly connected to one end of the clamp (2), and the other end is rigidly fixed; the impact rod (4) is a hollow cylindrical rod that is sleeved on the incident rod (3), and its initial position is fixed at the launch position; when impacting the flange of the incident rod (3) The impact load is transferred to the incident rod (3); one end of the incident rod (3) is threaded to the other end of the clamp (2), and the other end is connected to the flange to withstand the impact of the impact rod (4); the impact rod (4) is capable of impacting one end of the ejector rod (1) at a controllable speed to generate stress waves; the stress wave load passes through the incident rod (3), clamp (2), plate impact specimen (7), ejector rod (1), and energy absorption device (5) in sequence; a rubber gasket is provided on the outside of the flange to buffer and reduce the damage to the incident rod (3) when it impacts the energy absorption device (5) after the impact.

[0009] On the other hand, this invention proposes a quantitatively controllable impact pre-damage test method, which includes the following steps: Step 1: Based on the response and damage of the blade to foreign objects during actual service, determine the amount of damage that the specimen needs to be pre-fabricated, further determine the stress wave that needs to pass through the working section, and thus determine the test impact load. Further determine the specimen response under the load through finite element calculation, adjust the size of the separation notch of the plate impact specimen (7), and ensure the preparation of the corresponding plate impact specimen (7). Step 2: Select appropriate sizes for the ejector rod (1), incident rod (3), and impact rod (4) according to the size of the fixture (2), and attach high-speed dynamic strain gauges to the ejector rod (1) and incident rod (3), connect the oscilloscope and the high-speed dynamic strain acquisition system to form a data acquisition device (6). Step 3: Fix the plate impact test specimen (7) with the corresponding clamp (2), and connect it to the ejector rod (1) and the incident rod (3) by thread, while returning the impact rod (4) to its original position (see Figure 4a for the original position). Step 4: Use the impact rod (4) to impact the incident rod (3) to complete the impact damage pre-fabrication, and use the data acquisition device (6) to collect and analyze the data; Step 5: The working section of the prefabricated plate impact specimen (7) is cut by wire cutting to prepare a vibration fatigue specimen (8), thus completing the preparation of the damaged prefabricated vibration fatigue specimen.

[0010] The advantages and beneficial effects of this invention are: This method can ensure that the separation section of the plate impact specimen (7) breaks during a single impact loading, blocking the transmission of reflected waves and ensuring that the working section of the plate impact specimen (7) is only subjected to one impact stress wave load.

[0011] Compared with existing impact damage pre-fabrication methods, this invention can accurately simulate the evolution of microstructure in blade impact damage, providing a new technical means for the study of blade damage mechanisms and the development of damage repair technology. Through this method, the remaining life and remaining strength of blades under different damage conditions can be systematically evaluated, providing a scientific basis for damage tolerance analysis and the formulation of repair strategies. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention 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.

[0013] Figure 1 This is a schematic diagram of a quantitatively controllable impact damage pretreatment device used in an embodiment of the present invention. Figure 2(a) is a schematic diagram of the dimensions of a plate impact test specimen (7) according to an embodiment of the present invention; Figure 2(b) is a schematic diagram of the structure of a plate impact test specimen (7) according to an embodiment of the present invention; Figure 2(c) is a three-dimensional structural diagram of a plate impact test specimen (7) according to an embodiment of the present invention; Figure 3(a) is a schematic diagram of the connection between the clamp (2) and the shooting rod (1) and the incident rod (3) according to an embodiment of the present invention; Figure 3(b) is a schematic diagram of the clamp (2) and fixing method according to an embodiment of the present invention; Figure 4(a) is a schematic diagram of the working mode (initial test) of the damage prefabrication testing machine according to an embodiment of the present invention; Figure 4(b) is a schematic diagram of the working mode (end of test) of the damage prefabrication testing machine according to an embodiment of the present invention; Figure 5 is a three-dimensional model of a plate impact test specimen (7) according to an embodiment of the present invention; Figure 6(a) is a schematic diagram of a plate impact test specimen (7) according to an embodiment of the present invention; Figure 6(b) is a schematic diagram and coordinate axis of the separation section of the plate impact test specimen (7) according to an embodiment of the present invention; Figure 7 is a schematic diagram comparing the damage theory and experimental values ​​of an embodiment of the present invention; Figure 8 is a schematic diagram of a quantitatively controllable vibration fatigue specimen (8) according to an embodiment of the present invention; Figure 9 is a schematic diagram of the design method of a quantitatively controllable impact damage preform (7) according to an embodiment of the present invention; Figure 10 is a schematic flowchart of a quantitatively controllable impact damage pre-construction test method according to an embodiment of the present invention. Wherein: The components include: ejector rod (1), clamp (2), incident rod (3), impact rod (4), energy absorption device (5), data acquisition device (6), plate impact specimen (7), and quantitatively controllable vibration fatigue specimen (8). Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0016] Referring to the accompanying drawings, the present invention proposes a quantitatively controllable impact damage pre-testing device, including an ejector rod (1), an incident rod (3), an impact rod (4), and an energy absorption device (5).

[0017] The plate impact specimen (7) is fixed between the ejector rod (1) and the incident rod (3) by the corresponding clamp (2) to ensure the stability of the plate impact specimen (7) during the tensile process. The fixing method is shown in Figure 3(a) and Figure 3(b).

[0018] Figure 3(a) is a schematic diagram of the connection between the clamp (2) and the firing rod (1) and the incident rod (3) according to an embodiment of the present invention; Figure 3(b) is a schematic diagram of the clamp (2) and the fixing method according to an embodiment of the present invention. Referring to Figures 3(a) and (b), the firing rod (1) and the incident rod (3) are both cylindrical rods. One end of the firing rod (1) is threadedly connected to one end of the clamp (2), and the other end is rigidly fixed. One end of the incident rod (3) is threadedly connected to the other end of the clamp (2), and the other end is connected to a flange to bear the impact of the impact rod (4). The rubber gasket on the outside of the flange is used to buffer and reduce the damage to the incident rod when it impacts the energy absorption device (5) after the impact. The impact rod (4) is a hollow cylindrical rod that is fitted on the incident rod. Its initial position is fixed at the firing position (Figure 1a). In the test, the impact load is transferred to the incident rod by means of air pressure to launch and impact the flange of the incident rod, and finally stays at the position (Figure 1b). The ejector rod (1), the incident rod (3), and the impact rod (4) are all made of high-strength, high-elastic-modulus metal materials to ensure that they are within the elastic deformation range during the test stress wave loading. The energy absorption device (5) mainly consists of two parts: an energy-absorbing rod and an energy-dissipating rod. It is located at the end of the incident rod (3) and is used to absorb and dissipate stress waves to prevent repeated loading and damage to the working section of the plate impact specimen (7). The energy absorption device (5) works as follows: 1. During loading, the impact rod (4) impacts the flange of the incident rod (3), generating a tensile wave in the incident rod (3) and a compressive wave in the absorbing rod 1; 2. The tensile wave of the incident rod (3) is transmitted to the "incident rod-sample" interface to prepare for loading the sample, while the compression wave of rod 1 is transmitted to rod 2. 3. After the tensile wave of the incident rod (3) loads the sample, a portion of it is reflected back to the incident rod in the form of a compression wave and propagates towards the "incident rod-absorbing rod 1" interface. During this process, the compression wave in rod 2 is reflected back to the "rod 2-rod 1" interface in the form of a tensile wave after reaching the end of the rod. Since the "rod 2-rod 1" interface can only transmit compression waves and cannot transmit tensile waves, rod 2 will separate from rod 1 at this time and the stress wave of rod 2 will no longer be transmitted to rod 1; 4. The compression wave of the incident rod (3) reaches the “incident rod-rod 1” interface and is transmitted to rod 1. 5. The compression wave of rod 1 reaches the end of rod 1, while rod 2 has separated from rod 1, so this compression wave will be reflected back to rod 1 in the form of a tension wave. 6. When the tensile wave of rod 1 reaches the “rod 1-incident rod” interface, similar to the analysis in stage (3), rod 1 will separate from the incident rod, and no stress wave will be transmitted to the incident rod.

[0019] The data acquisition device (6) mainly includes a dynamic strain gauge, an oscilloscope and a control device. The dynamic strain gauge is attached to the ejector rod (1) and the incident rod (3) to collect the propagation of stress waves in the sample in real time and record the deformation and failure process of the sample. The control device adopts an advanced loading coordination algorithm to perform precise time control and data synchronization.

[0020] Figure 1 (a) is a schematic diagram of the working mode of the damage prefabrication testing machine (at the beginning of the test), and Figure 2 (b) is the end of the test.

[0021] Secondly, the present invention uses the above-mentioned test device to provide a quantitatively controllable pre-damage test method for impact damage. This pre-damage impact method is based on the mechanical test to be performed on the test material after damage pre-damage, namely, the test specimen standard required for the vibration fatigue test simulating the actual load of the blade in service. The plate impact specimen (7) adopts a combined design, including two clamping ends in the incident and exit directions, a separation section and a working section, which are fixed on the testing machine by the clamp (2). When loading, the notch between the separation section and the free end of the separated specimen breaks and separates first. At this time, the stress wave stops propagating to the working section. The working section retains the high-speed damage caused by the passage of a single stress wave, so as to accurately control the damage amount by controlling the parameters of the stress wave. After loading is completed, the working section of the pre-made plate impact specimen (7) is cut to prepare a vibration fatigue specimen (8) by wire cutting, which is used for vibration fatigue test, and then the life condition after damage is evaluated. In the data acquisition system, a high-speed strain test system is installed on the incident rod and the exit rod to collect the stress wave flow during the test process.

[0022] In some embodiments, the method includes the following steps.

[0023] Step 1: Prepare plate impact specimens (7).

[0024] The plate impact specimen (7) is designed based on the vibration fatigue standard specimen (8), with the addition of a separation section. The design of the separation section mainly includes the notch feature size and the length of the separation section (that is, the position of the notch from the edge of the specimen). Since the working section of the vibration fatigue standard specimen (8) is relatively narrow and its stress level is relatively large compared to the nominal stress, the notch needs to be designed to generate a large stress concentration. Therefore, an elliptical notch is selected, and the feature parameters are defined as follows: a: length of the semi-major axis of the ellipse, b: length of the semi-minor axis of the ellipse, l: length of the separation section. The constraints are mainly based on the boundary length and the estimated stress concentration factor. The estimated stress concentration factor is selected from the algorithm of the stress concentration factor at the vertex of the major axis of the elliptical hole of an infinitely large plate. The actual stress concentration factor of the elliptical notch will be larger than this value. The boundary satisfies: (Width of the vibration fatigue standard specimen (8)), estimated stress concentration factor satisfy (Maximum stress concentration factor of the working section), thus obtaining .

[0025] The process for determining the optimal design parameters for the separation section is as follows: First, regarding the loading of the specimen, through formulas (1)(2)(3) (where...) and The initial length and cross-sectional area of ​​the specimen (7), E is the elastic modulus of the compression bar, C is the wave velocity of the compression bar, and A is the cross-sectional area of ​​the compression bar; stress and strain are all positive under compression) determine the strain rate, strain and stress of the working section of the specimen (7).

[0026] Then, the notch parameters of the separated section of the specimen (7) were analyzed, and a theoretical model of the stress field of the notch section of the plate impact specimen (7) was established. A function with the notch characteristic position and notch characteristic size as characteristic parameters was established. The notch fracture and the working section of the specimen did not fracture were the main constraints. The position and geometric characteristics of the notch section were determined by parameter optimization. At the same time, attention was paid to the edge being extended to a certain length according to the Saint-Venant principle to avoid interference with the stress wave of the working section and the impact of subsequent cutting operations on the internal damage of the working section.

[0027] The following formulas give the calculation formulas for stress, strain and strain rate inside the plate impact specimen (7) during impact: (1) (2) (3) : The strain of the specimen at time t; The stress on the specimen at time t; : The strain rate of the specimen at time t; Incident strain; Reflected strain; : Outgoing strain; : Length of specimen (7) at the start of the test; : Cross-sectional area of ​​specimen (7) at the start of the test; E: Elastic modulus of the compression bar; C: Wave velocity of the compression bar; A: Cross-sectional area of ​​the compression member.

[0028] This experiment is broadly classified as a high-strain-rate impact tensile test. The JC constitutive model, which considers the effects of strain rate, strain, and temperature, is suitable for this study, and its expression is as follows: (4) (5) The corresponding damage plastic strain is: (6) The damage accumulation function is: (7) That is, in the i-th iteration, based on the stress condition at this time, the damage plastic strain in the i-th step is calculated by formula (4). Divide by the failure plastic strain under this stress condition, as determined by formula (6). The damage level of step i is obtained, and the final cumulative damage is obtained by integrating the whole process according to formula (7). When D reaches 1, it is judged as unit failure.

[0029] Where the parameters are: Equivalent flow stress; Equivalent plastic strain (important data during the experiment); : Yield strength of materials below the reference temperature; Hardening modulus; Material hardening index; : Strain rate hardening parameters; Temperature-related parameters (tested); Reference strain rate (unit: 1); Melting temperature (manual value); Reference temperature (room temperature); Parameters to be determined; Stress triaxiality, where p is hydrostatic pressure and q is equivalent stress, generally using MISES stress.

[0030] (8) (9) (10) in: P: hydrostatic pressure; q: Equivalent stress, generally using MISES stress; First principal stress; Second principal stress; : Third principal stress.

[0031] That is, in the i-th iteration, based on the stress condition at this time, the damage plastic strain in the i-th step is calculated by formula (4). Divide by the failure plastic strain under this stress condition, as determined by formula (6). The damage level of step i is obtained, and the final cumulative damage is obtained by integrating the whole process according to formula (7). When D reaches 1, it is judged as unit failure.

[0032] Analysis of the expression for the damage function reveals that many parameters are constants calibrated through experiments (these constants remain unchanged when the initial conditions of the experiment are fixed). Therefore, the main variables are... , , Regarding temperature changes, the following details how each variable was handled: Equivalent plastic strain and strain rate can be acquired during the test procedure using the data acquisition system (6); Regarding temperature changes, as a room temperature high-speed impact tensile test, the specimen was subjected to loading on a timescale of 10. -4 The time interval is even shorter than s. During this process, it can be considered as adiabatic conditions. Therefore, it can be assumed that there is zero heat transfer to the outside during the test. The internal energy generated by the specimen cannot be dissipated, which leads to an increase in the internal thermal strain of the specimen, resulting in the formation of an adiabatic shear band. After the impact, the specimen will dissipate heat naturally. Therefore, it is necessary to measure the temperature change of the specimen (especially the working section) before and after the test to determine the energy that generates the adiabatic shear band.

[0033] Figure 3 Schematic diagram of the three-dimensional model of the specimen; Figure 4 (a) and (b) Schematic diagram of the separated sections and coordinate axes and sketch parameters. Stress triaxiality It is a scalar representing the loading condition of a unit, and its value affects the strength of the material. Based on the geometric characteristics of the semi-elliptical notch in the specimen design (as shown in Figures 3 and 4(a) and (b)) and the calculation formula, under the assumptions of pure tensile loading, surface plane stress state, and linear superposition of the stress concentrations of the two elliptical notches, the corresponding values ​​are obtained. and The expressed stress triaxiality.

[0034] Introducing stress triaxiality and The calculation formula is used to express this, thereby solving for the stress triaxiality value in real time: (11) in: Stress triaxiality; : Stress in the x-direction; Stress in the z-direction; : Shear stress in the xz plane.

[0035] The detailed result can be obtained using formula (10). , and The expression is used to establish a function with a and b as parameters, and the most suitable parameters are finally obtained based on the optimization constraints.

[0036] The tensile principal stresses are superimposed on two coordinates (a, 0) and (da, 0) (where d is the specimen width), with the center of the elliptical hole as the origin. Substituting the specific values, we obtain the following stress concentration factors. K The formula can be used to calibrate the finite element calculation results using the specific value of this point: (12) in: K Stress concentration factor; a: Length of the semi-major axis of the ellipse; b: Length of the semi-minor axis of the ellipse.

[0037] Step 2: Based on the design results of the plate impact specimen (7) and the size of the ejector rod (1) and incident rod (3) of the test device, design the fixture (2), with the following requirements: 1. The length of the clamp (2) is the same as that of the specimen, and the two ends are reserved for high-strength adhesive bonding with the specimen; 2. The two ends of the fixture (2) and the injection rod (1) and the incident rod (3) of the test device can be threaded together; 3. The stiffness of the fixture (2) is much stronger than that of the plate impact specimen (7) to ensure accurate results; 4. The fixture (2) should not have any resistance in the tensile direction, so as not to affect the actual test load.

[0038] Step 3: Before starting the test, fix the specially designed specimen (7) with the clamp (2) and connect it to the ejector rod (1) and the incident rod (3) by thread. Align the high-speed camera with the specimen (7) and simultaneously return the impact rod (4) to its original position (see the return position). Figure 1 a), and attach high-speed dynamic strain gauges to the outgoing rod (1) and the incoming rod (3), connect the oscilloscope and the high-speed dynamic strain acquisition system, adjust the shutter and shooting position of the high-speed camera, and form a data acquisition device (6). Step 4: Use the impact rod (4) to impact the incident rod (3) to complete the impact damage pre-fabrication, and use the data acquisition device (6) to collect and analyze the data; Step 5: The working section of the prefabricated plate impact specimen (7) is cut by wire cutting to prepare a vibration fatigue specimen (8), thus completing the preparation of the damaged prefabricated vibration fatigue specimen.

[0039] This method can ensure that the separation section of the plate impact specimen (7) breaks during a single impact loading, blocking the transmission of reflected waves and ensuring that the working section of the plate impact specimen (7) is only subjected to one impact stress wave load.

[0040] like Figures 1 to 7 In this embodiment, a quantitatively controllable impact damage pre-fabrication device was built for TC17 titanium alloy used in compressor blades, and damage pre-fabrication was realized. The influence of pre-fabricated damage on fatigue life was also verified.

[0041] Step 1: Prepare impact-type test specimens (7), as shown in Figure 2. The material is TC4 alloy for compressor blades, and a total of 20 test specimens are processed. In this embodiment, a standard specimen for room temperature vibration fatigue is used as the basis, with an overall length of 110 mm, including a smooth working section of 18 mm, a separation section notch with a semi-major axis of 8 mm, a semi-minor axis of 2.5 mm, a finite element calculation stress concentration factor of 15.82, and an analytical calculation value of 15.56 according to formula (20), with an error of 1.67%.

[0042] Step 2, construct the quantitatively controllable impact damage pre-fabrication device, such as... Figure 1The fixture (2) is made of GH4169 alloy and has a diameter of 25mm. The launch rod (1) and the incident rod (3) are made of 18Ni martensitic stainless steel, with a diameter of 25mm and a length of 2000mm. One end of the launch rod (1) is threaded to one end of the fixture (2), and the other end is rigidly fixed; one end of the incident rod (3) is threaded to the other end of the fixture (2), and the other end is connected to a flange to withstand the impact of the impact rod (4). The rubber gasket on the outside of the flange is used to buffer and reduce the damage to the incident rod when it impacts the energy absorption device (5) after the impact. The impact rod (4) is a hollow cylindrical rod made of 18Ni martensitic stainless steel with an inner diameter of 26mm. It is fitted on the incident rod and is initially fixed at the launch position (Figure 4a). During the test, the impact load is transferred to the incident rod by air pressure launch and impacting the incident rod flange, and finally stops at the position shown in Figure 4b. The energy absorption device (5) mainly consists of two parts: an energy-absorbing rod and an energy-dissipating rod. It is located at the end of the incident rod (3) and is used to absorb and dissipate stress waves to prevent the plate from being repeatedly loaded and damaged during the working section of the test specimen (7).

[0043] Step 3: Fix the specimen (7) with the corresponding clamp (2) and connect it to the ejector rod (1) and the incident rod (3) by thread, while returning the impact rod (4) to its original position (see Figure 4a for the original position). Step 4: Perform damage pre-construction operation. The test procedure is shown in Figure 9. Clamp the fixture (2) tightly between the ejector and incident rods (3), ensuring the symmetrical axis of the specimen (7) coincides with the axis of the ejector and incident rods (3). Return the impact rod (4) to its initial position. Adjust the energy absorption device (5) to fit against the right end of the incident rod (3). Adjust the firing pressure of the impact rod (4) according to the test requirements. Start the data acquisition device (6). Check all components of the device, including the ejector rod (1), incident rod (3), impact rod (4), sample clamping device, and data acquisition system, ensuring all components are working properly. Then start and complete the test. Obtain the stress-strain test results of the damage test, such as... Figure 5 As shown.

[0044] The degree of damage to the specimens was controlled by adjusting the actual strain rate. Eleven specimens were divided into five groups, with each group having an impact strain rate set at 550 s⁻¹. -1 Three 1500 s -1 Three 2500s -1 Three 3300s -1 One 4500 s -1 .

[0045] Vibration fatigue specimens (8) were prepared by cutting the working section of the pre-damaged plate impact specimen (7) using wire cutting. Vibration fatigue tests were conducted on the vibration fatigue specimens (8) using an electromagnetic vibration table at a temperature of 300℃ and a maximum stress of 300MPa. The test standard was HB 5277 "Vibration Fatigue Test Method for Engine Blades and Materials".

[0046] Table 1 shows the remaining life, theoretical damage value, and test damage value of the pre-damaged specimens under different load conditions. The test damage value is calculated based on the data collected by the data acquisition system (6) during the actual impact damage pre-damage test, according to the formula ().

[0047] Where, N f,l For the remaining logarithmic fatigue life, N f The logarithmic fatigue life without pre-existing damage is obtained by averaging the values ​​of three specimens in each group.

[0048] As can be seen from Figure 7, the deviation between the theoretical damage value and the damage test value is small.

[0049] Table 1. Remaining life, theoretical damage value, and experimental damage value of pre-damaged specimens under different loads.

[0050] Figure 8 is a schematic diagram of a quantitatively controllable vibration fatigue specimen (8) according to an embodiment of the present invention.

[0051] Figure 9 is a schematic flowchart of a quantitatively controllable impact damage precast specimen (7) design method according to an embodiment of the present invention. (Reference) Figure 9 The design method includes: Step 1: Based on the objective of the next experiment, the criteria for the next experiment are to use morphology and size as a basis and add separation segments; Step 2: Determine the location and dimensional characteristics of the separation section through calculation and analysis, and simulate to determine whether the separation section is working correctly; Step 3: Clamp the device according to the experimental characteristics to ensure that it is fixedly aligned and can successfully complete the interruption test; Step 4: Produce a portion of the designed test specimens for testing and verification. Once the verification is successful, normal production and damage pre-fabrication can proceed.

[0052] Figure 10 is a schematic flowchart of a quantitatively controllable impact damage pre-construction test method according to an embodiment of the present invention. (Reference) Figure 10 The experimental procedure includes the following steps: Step 1: Design the specimen and fixture according to the experimental objective; Step 2: Correctly place the specimen between the input and output rods, return the impact rod to its original position, and set up the energy absorption device; Step 3: Connect the data acquisition system and adjust the appropriate firing pressure; Step 4: Turn on the data acquisition system, trigger the impact and record the test process to obtain the corresponding pre-damaged specimen.

[0053] It should be noted that the above process operations can be combined to varying degrees. For the sake of brevity, the implementation methods of various combinations will not be elaborated here. Those skilled in the art can flexibly adjust the order of the above operation steps or flexibly combine the above steps according to actual needs.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A quantitatively controllable impact pre-damage testing device for impacting sheet metal specimens (7), characterized in that, The device includes: a launch rod (1), a clamp (2), an incident rod (3), an impact rod (4), an energy absorption device (5), and a data acquisition device (6), wherein: The clamp (2) is used to fix the plate impact specimen (7) between the ejector rod (1) and the incident rod (3) to ensure the stability of the plate impact specimen (7) during the tensile process; One end of the ejector rod (1) is threadedly connected to one end of the clamp (2), and the other end is rigidly fixed; The impact rod (4) is a hollow cylindrical rod that is fitted onto the incident rod (3) and is initially fixed at the launching position. When it impacts the flange of the incident rod (3), it transfers the impact load to the incident rod (3). One end of the incident rod (3) is threaded to the other end of the clamp (2), and the other end is connected to a flange plate to withstand the impact of the impact rod (4); The impact rod (4) is capable of impacting one end of the ejector rod (1) at a controllable speed to generate a stress wave; the stress wave load passes sequentially through the incident rod (3), the clamp (2), the plate impact specimen (7), the ejector rod (1), and the energy absorption device (5); A rubber gasket is provided on the outside of the flange to cushion and reduce damage to the incident rod (3) during impact and when it hits the energy absorption device (5).

2. The apparatus according to claim 1, characterized in that, in: The ejector rod (1), the incident rod (3), and the impact rod (4) are all made of high-strength, high-elastic-modulus metal materials to ensure that they are within the elastic deformation range during the test stress wave loading, and to reduce energy loss and improve impact efficiency.

3. The apparatus according to claim 1, characterized in that, in: Both the ejector rod (1) and the incident rod (3) are cylindrical rods.

4. The apparatus according to claim 1, characterized in that, The energy absorption device (5) transmits only the ballast load and not the tensile load. It is located at the end of the incident rod (3) and is used to absorb and dissipate the reflected stress wave, further preventing the reflected wave from interfering with the damage prefabrication result.

5. The apparatus according to claim 1, characterized in that, in: The data acquisition device (6) includes a dynamic strain gauge, an oscilloscope, and a control device; Dynamic strain gauges are attached to the ejector rod (1), the incident rod (3), and the impact rod (4) to collect stress wave propagation in the sample in real time and record the deformation and failure process of the sample. The control device employs a load coordination algorithm for precise time control and data synchronization.

6. The apparatus according to claim 1, characterized in that, in: The plate impact specimen (7) adopts a combined design, including a notched section and a smooth working section. When loaded, the notch between the separation section and the free end of the separated specimen breaks first. At this time, the stress wave is cut off, so that the working section retains high-speed damage but does not cause damage.

7. The apparatus according to claims 1-6, characterized in that, in: The plate impact test specimen (7) and the fixture (2) are connected with high-temperature adhesive to improve the stability of the stress wave.

8. A quantitatively controllable impact pre-damage test method, comprising conducting the test using the quantitatively controllable impact pre-damage test apparatus described in claims 1-7, characterized in that, The method includes the following steps: Step 1: Based on the response and damage of the blade to foreign objects during actual service, determine the amount of damage that the specimen needs to be pre-fabricated, further determine the stress wave that needs to pass through the working section, and thus determine the test impact load. Further determine the specimen response under the load through finite element calculation, adjust the size of the separation notch of the plate impact specimen (7), and ensure the preparation of the corresponding plate impact specimen (7). Step 2: Select appropriate sizes for the ejector rod (1), incident rod (3), and impact rod (4) according to the size of the fixture (2), and attach high-speed dynamic strain gauges to the ejector rod (1) and incident rod (3), connect the oscilloscope and the high-speed dynamic strain acquisition system to form a data acquisition device (6); Step 3: Fix the plate impact sample (7) with the corresponding clamp (2), and connect it to the ejector rod (1) and the incident rod (3) by thread, while returning the impact rod (4) to its original position (see Figure 4a for the original position). Step 4: Use the impact rod (4) to impact the incident rod (3) to complete the impact damage pre-fabrication, and use the data acquisition device (6) to collect and analyze the data; Step 5: The working section of the prefabricated plate impact test specimen (7) is cut by wire cutting to prepare a vibration fatigue test specimen (8), thus completing the preparation of the damaged prefabricated vibration fatigue test specimen.

9. The method according to claim 8, characterized in that, The method also includes: The plate impact test specimen (7) is designed in advance, and is divided into the incident direction clamping end, working section, separation section and exit direction clamping end. The clamping sections at both ends are fixed to the fixture (2) with high temperature glue. The design requires that during the first impact loading of the pre-damage testing machine, the separation notch of the plate impact specimen (7) breaks, blocking the path of the reflected wave to the working section, ensuring that the working section of the plate impact specimen (7) is only subjected to the first impact stress wave load, which facilitates the control of the damage.

10. The method according to claim 8 or 9, characterized in that, The method also includes: After the test is completed, the working section of the prefabricated plate impact specimen (7) can be cut into vibration fatigue specimens (8) by wire cutting to carry out the next stage of testing. Without cumbersome methods, the specimens under the same damage condition can be prepared in batches under the control of the damage condition, which is convenient for the study of the vibration fatigue performance of the specimens.

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