A dynamic force sensor calibration method for an instrumented impact testing machine based on a double-pulse method

Abstract

The application discloses a kind of instrumented impact testing machine dynamic force sensor calibration method based on double-pulse method, standard cuboid sample is generated by using pendulum impact standard, and standard double-pulse force can be traced to sample attribute (sample size, mass and Young's modulus) and pendulum impact velocity (or pendulum effective length) above, and then the calibration method of instrumented impact testing machine dynamic force sensor is traced to source;Propose a kind of design method for the sample required for the sweep frequency calibration of instrumented impact testing machine dynamic force sensor, to achieve the purpose of sweep frequency calibration of instrumented impact testing machine dynamic force sensor.This method can stably, reliably and quickly realize the high-frequency calibration of instrumented impact testing machine dynamic force sensor under the premise of effectively ensuring calibration accuracy, and fills the blank of existing instrumented impact testing machine dynamic force sensor calibration method.

Description

Technical Field

[0001] This invention belongs to the field of impact vibration measurement and testing, and is aimed at high-precision, stable and reliable calibration of dynamic force sensors of instrumented impact testing machines across the entire frequency range. Background Technology

[0002] Instrumented Charpy impact testing machines are increasingly used to measure the fracture toughness of materials, primarily in the field of material quality inspection. Since the measurement accuracy of an instrumented impact testing machine depends almost entirely on the dynamic force sensor mounted on it, the calibration of this sensor is a prerequisite for ensuring the accuracy, reliability, and validity of impact test measurement data. Therefore, research on the calibration of dynamic force sensors in instrumented impact testing machines is of great significance.

[0003] Commonly used dynamic force sensor calibration methods are classified into three main categories: pulse dynamic force calibration, steady-state sinusoidal dynamic force calibration, and step dynamic force calibration. Pulse dynamic force calibration utilizes pulsed force signals to trace the force values ​​of dynamic force sensors. These pulsed force signals are generated by various excitation sources, the most typical being half-sine pulse force signals and rectangular force signals. Many metrology institutions and universities both domestically and internationally have established different standard devices for pulsed dynamic force calibration, as shown in Table 1. In current common designs, the standard device for pulsed dynamic force calibration employs a mass impact technique, using a laser interferometer to measure the acceleration of the mass during the impact process. Newton's second law is then applied to obtain the force on the mass. This method is characterized by its simplicity and rapid analysis, and it can especially obtain dynamic force signals with a wide bandwidth and large force values. However, with further research, researchers have gradually discovered that this method has limitations under certain conditions when generating pulsed force sources. Taking a falling hammer standard device as an example, it needs to meet the rigidity condition of the falling hammer under impact. However, the mass of the falling hammer is usually large, and its volume is also large. Therefore, the condition that the falling hammer can be regarded as an absolutely rigid body may not hold under high-speed impact conditions. Local stress and local deformation are generated at the impact end of the falling hammer, accompanied by the propagation of stress waves. When discussing the magnitude of the impact force at that instant, the acceleration at a certain point on the falling hammer cannot be used as the overall acceleration of the falling hammer for analysis. One solution is to use multiple laser interferometers to form an acceleration acquisition array to measure the acceleration at multiple points of the falling hammer, thereby correcting the measurement results. Another solution is the approach of PTB in Germany, which places the entire device horizontally and uses horizontal air-bearing guide rail technology to replace the falling hammer impact with horizontal impact.

[0004] Table 1: Basic Information of Various Pulse-Type Dynamic Force Standard Devices

[0005]

[0006] The steady-state sinusoidal dynamic force calibration method is a method of tracing the force value of a dynamic force sensor by using a vibration table as the excitation force source to generate a sinusoidal force signal and obtaining the dynamic characteristics of the force sensor through frequency sweeping. The signal analyzer's signal source generates a standard sinusoidal periodic signal of a certain frequency. By changing the amplitude and frequency of the signal source output, different standard sinusoidal signals are obtained, which are then amplified by a power amplifier to drive the vibration table. The force source is generally generated by an electromagnetic vibration table, the basic principle of which is that a current-carrying coil (moving coil) experiences a Lorentz force in a magnetic field. One end of the dynamic force sensor to be calibrated is mounted on the vibration table surface, and the other end is connected to a load mass. The acceleration of the mass can be measured using a standard accelerometer mounted on the mass or a laser interferometer on a vibration isolation platform. By changing the mass of the load, the force value can be changed. By changing the frequency of the signal source output signal within a certain frequency range (frequency sweeping), the sensor sensitivity at different frequency points, i.e., the sensor's dynamic characteristic index, can be obtained. The working principle of the standard devices for the steady-state sinusoidal force calibration method is basically consistent in various countries. Specific details are shown in Table 2.

[0007] Table 2: Basic Information of Each Pulse-Type Dynamic Force Standard Device

[0008]

[0009] The advantages of using this type of force source to calibrate the dynamic characteristics of a force sensor are its simple and clear structure, easy data processing, and high calibration accuracy. However, it also has some disadvantages:

[0010] (1) It is difficult to perform frequency sweep across a wide test frequency band. At the low frequency end, the lateral vibration of the vibration table intensifies, and the accelerometer output will contain more lateral sensitivity components, resulting in a large test error. One solution is to continuously change the installation direction of the accelerometer during the test and then average the test values ​​to achieve higher test accuracy. At the high frequency end, due to the coupling relationship between the sensor and the mass block, their vibration accelerations are no longer equal, causing the vibration frequency of the mass block to be lower than the vibration frequency of the vibration table.

[0011] (2) It is difficult to generate high-power dynamic force at high frequencies. When the excitation signal frequency increases, the current in the winding of the moving coil of the vibration table will decrease due to the increased impedance, and the output force will become smaller. That is, there is a contradiction between the output force value and the output force frequency band in the vibration table method. One solution is to add a power compensation system to compensate for the decrease in current.

[0012] The principle of the step-type dynamic force calibration method is generally to apply a fixed load (the weight of the weight multiplied by the lever's amplification factor) to the sensor using a lever, a metal wire (or other connecting parts made of brittle materials), and weights (or other force-applying devices). Then, the metal wire holding the weight is suddenly cut using electrical or mechanical means, causing the sensor to be suddenly unloaded. In this way, a negative step force is applied to the sensor. Many metrology institutions and universities at home and abroad have established different standard devices for the step-type dynamic force calibration method, as shown in Table 3.

[0013] Table 3: Basic Information on Each Step-Type Dynamic Force Standard Device

[0014]

[0015] Step signals are easy to achieve, especially negative step forces. The key to this method is to cut the connector, such as the metal wire, within an extremely short time to obtain a near-ideal negative step force. Common design approaches include direct-pressure drop hammer impact or shear unloading. If the connector is made of a brittle material, the amplitude of the negative step force depends on the load-bearing capacity of the brittle material, and the lower edge time is closely related to its fracture time. Generally, the greater the load-bearing capacity, the larger the size of the brittle material, which in turn prolongs the material's fracture time. Therefore, selecting a brittle material with appropriate structural dimensions and material properties is crucial. High-purity SiC ceramics, as a brittle material, have been tested to have fracture times ranging from 2 to 20 μs. There is also a method of electrically cutting the metal wire, which uses a charged large-capacity capacitor to rapidly melt and cut the wire with a high current discharge in a short time. When the wire is a tungsten wire with a diameter of 1.06 mm, the cutting time is less than 10 μs. However, rapid cutting is not feasible when the wire is thick, so this method is only suitable for low-force situations.

[0016] The problems with the step dynamic force calibration method are: (1) When the force amplitude is large, it is difficult to guarantee a short falling edge due to the limitation of the size of the connecting parts; (2) Due to the effect of the added mass, the falling edge time of the force acting on the force sensor is actually greater than the material fracture time.

[0017] In addition, the three existing methods for calibrating and tracing dynamic force sensors are difficult to apply to the calibration of dynamic force sensors in instrumented impact testing machines in practice. The main reason is that instrumented impact testing machines are designed to avoid disassembling dynamic force sensors. This is because the installation of dynamic force sensors will affect the rigidity of the connection between the dynamic force sensor and the whole machine, and thus affect its dynamic performance. Therefore, even if the dynamic force sensor is disassembled and calibrated well, its dynamic performance will change after installation.

[0018] In summary, the three existing methods are insufficient to meet the traceability and calibration requirements of dynamic force sensors in instrumented impact testing machines. It is necessary to break free from the existing framework and research new dynamic force traceability methods suitable for instrumented impact testing machines. This invention proposes a novel dynamic force traceability method—the dual-pulse method—based on beam vibration theory, which traces the force through impact results without disassembling the dynamic force sensor. Summary of the Invention

[0019] This invention addresses the problem that current dynamic force sensor calibration methods are unsuitable for calibrating dynamic force sensors in instrumented impact testing machines due to limitations in calibration frequency and practical applications. Based on the pendulum impact velocity of the instrumented impact testing machine, this invention calculates the sample size and material corresponding to the generated double-pulse force at the target frequency using a specific formula. Simultaneously, it calibrates the dynamic force sensor of the instrumented impact testing machine by comparing the calculated first-peak force time span and maximum force value with the first-peak force value and waveform in the experimental results.

[0020] The technical solution adopted in this invention is a targeted and applicable calibration method for dynamic force sensors of instrumented impact testing machines, including: Step 1: Select the target frequency to be calibrated, calculate the corresponding sample size, and if the sample used is a non-cubic prism sample, calculate the equivalent length of the sample used according to the method provided above.

[0021] Step 2: Measure the basic dimensions and relevant parameters of the sample, and calculate the maximum force value of the first peak;

[0022] Step 3: Check whether the instrumented impact testing machine to be calibrated retains the complete impact process. If the complete impact process can be retained, then install the sample on the anvil; if not, place it normally on the anvil.

[0023] Step 4: Conduct a standard instrumented impact test;

[0024] Step 5: Analyze the instrumented impact test and obtain the corresponding results: First, check whether the M-curve shape is distorted. If there is distortion, it is determined that the dynamic force sensor of this instrumented impact testing machine cannot meet the usage requirements at the target frequency. If there is no distortion, compare the maximum force value of the M-curve in the test results with the maximum force value calculated in Step 2 to obtain the dynamic force measurement error at this target frequency. For those installed in the normal way, check the maximum force value at the first peak and compare it with the calculated maximum force value to obtain the dynamic force measurement error at this target frequency.

[0025] Step 6: For dynamic force calibration at a target frequency, perform multiple instrumented impact tests to check the repeatability of the instrumented impact testing machine to be calibrated. It is normal for the dispersion coefficient of the first peak force maximum value to be below 3%. Otherwise, check whether there is a problem with the sample installation or check the instrumented impact testing machine.

[0026] Step 7: Repeat steps 1 to 6 for different target frequencies to achieve frequency sweep calibration of the dynamic force sensor of the instrumented impact testing machine.

[0027] In the instrumented impact test in step 4:

[0028] 1) During the impact process, when the pendulum first contacts the specimen, the vibration caused is a beam vibration mode based on the specimen's own properties, and the time span of the first peak force is calculated.

[0029] 2) During the impact process, the collision between the hammer blade and the sample is a rigid collision.

[0030] 3) For impact testing, if a cuboid specimen is used and it contacts the anvil during installation, the initial peak is the first half of the M-shaped curve. The two parts of the M-shaped curve are identical; therefore, the area enclosed by the initial peak is mv. Given that the force-time waveform of the initial peak is a sinusoidal function, the half-cycle time span of this sinusoidal function, and the area enclosed by the force-time waveform of this half-cycle (mv), the maximum force of the initial peak is obtained. Based on the maximum force value of the initial peak, the dynamic force sensor of the instrumented impact testing machine is calibrated at the target frequency.

[0031] The low-frequency vibration calibration method of the present invention has the following advantages:

[0032] 1. This invention fills the gap in the metrological calibration methods for dynamic force sensors of instrumented impact testing machines, and provides a highly applicable calibration method for the calibration of dynamic force sensors of instrumented impact testing machines.

[0033] 2. The method of the present invention is practical and reliable. It is a calibration method for dynamic force sensors of instrumented impact testing machines that uses instrumented impact testing itself as a calibration means. Calibration can be performed without disassembling the sensor or affecting the sensor's installation rigidity.

[0034] 3. The calibration process of the present invention is simple and the system cost is low. For the calibration of the dynamic force sensor of the instrumented impact testing machine, only one (group) of cuboid specimens at the target frequency are required.

[0035] 4. This method allows for the customization of low-cost calibration samples for the target frequency, thus broadening the calibration frequency range to the megahertz level. Attached Figure Description

[0036] Figure 1 Static simulation of a cuboid specimen (half) under simulated impact conditions.

[0037] Figure 2 Static simulation of a V-shaped specimen (half) under simulated impact conditions.

[0038] Figure 3 : Installation and placement diagram of a 7mm rectangular unnotched sample.

[0039] Figure 4 Experimental data of instrumented Charpy impact test on 7mm rectangular unnotched specimen from NACK Steel Research Institute: force-time curve (top) and magnified view of the first peak (within the frame) (bottom).

[0040] Figure 5 M-peak decomposition diagram.

[0041] Figure 6 Instrumented Charpy impact test data of a certain brand of steel (low, medium and high energy, multiple types of standard V-type specimens): force-time curve (top) and enlarged view of the first peak (the part inside the frame) (bottom). Detailed Implementation

[0042] To address the problem that existing dynamic force sensor calibration methods cannot meet the calibration frequency requirements of dynamic force sensors in instrumented impact testing machines, and also cannot calibrate the dynamic force sensors in practical applications without disassembling them, this invention provides a dynamic force calibration method based on the dual-pulse method for dynamic force sensors in instrumented impact testing machines in their operating frequency domain.

[0043] The technical solution adopted in this invention is a targeted and applicable method for calibrating dynamic force sensors in instrumented impact testing machines, comprising:

[0044] (1) Based on the impact velocity of the pendulum of the instrumented impact testing machine, the sample size and material corresponding to the double pulse force at the target frequency are obtained by calculation formula;

[0045] (2) Based on the calculated first peak force time span and maximum force value and the first peak force value and waveform in the experimental results, the dynamic force sensor of the instrumented impact testing machine is calibrated.

[0046] A calibration method for a dynamic force sensor of an instrumented impact testing machine based on a dual-pulse method, the calibration method comprising the following steps:

[0047] S1: Calculate the thickness of the cuboid sample corresponding to the target frequency to be calibrated (materials other than steel can also be considered), and select a cuboid sample of appropriate size.

[0048] S2: Instrumented impact test is performed on the cuboid sample to obtain the first peak force value;

[0049] S3: Using the maximum force value of the first peak force calculated by the double pulse method formula as the standard, and taking the maximum force value of the first peak force in the experimental results as a reference, the dynamic force sensor of the instrumented impact testing machine is calibrated at the target frequency.

[0050] S4: For other target frequencies, repeat steps S1-S3 to achieve the frequency sweep effect for calibrating the dynamic force sensor.

[0051] In the above steps, the cuboid specimen can be replaced with a V-shaped specimen, but the equivalent impact direction thickness of the V-shaped specimen needs to be obtained, as follows.

[0052] Using the finite element method, the displacement at the contact point of a standard V-shaped specimen (nominal thickness 10 mm) and a 10 mm thick rectangular specimen were compared under the same conditions as in the impact test. The general equivalent thickness of the V-shaped specimen was then calculated using the deflection formula. The simulation results are as follows: Figure 1 and Figure 2 As shown, under the same material (same Young's modulus and Poisson's ratio) and the same load (10kN, located at the contact point between the hammer blade and the specimen, in the direction of impact), the maximum displacement of the standard V-shaped specimen is 0.276mm, and the maximum displacement of the cuboid specimen is 0.221mm.

[0053] According to the deflection formula

[0054]

[0055] Where w is the deflection, F is the load, E is Young's modulus, I is the moment of inertia of the section, and l is the specimen length, substituting into x = l / 2 yields...

[0056]

[0057] Since F, E, and l are consistent in both simulations, the deflections of the V-shaped and cuboid specimens are substituted into the values ​​and divided to obtain the results.

[0058]

[0059] From I = bh 3 / 12 and b V型样 =b 长方体样 =h 长方体样 =10mm to further obtain the general equivalent thickness of the V-shaped sample under this working condition.

[0060]

[0061] Substituting the values, we obtain the general equivalent thickness of the V-shaped sample under this working condition as 9.286 mm.

[0062] The method for calculating the maximum value of the first peak force generated using a cuboid specimen (taking a 7mm thick cuboid specimen as an example) – the double-pulse method – is derived and explained below:

[0063] Vibration mode verification experiment results: A rectangular, unnotched specimen was prepared with dimensions of 55mm × 10mm × 7mm, with the pendulum impact direction dimension being 7mm. Before impact, the specimen was placed 3mm away from the anvil, and all other procedures were performed according to the experimental method. Figure 3 As shown. The experimental results are as follows. Figure 4 As shown, it is very clear that the initial stress curve of the 7mm specimen is M-shaped. This proves that the vibration mode of the specimen after impact should be a beam vibration mode: as shown... Figure 5 As shown, after the sample is impacted, it is first accelerated by force. After the contact point velocity equals the impact velocity, it separates from the hammer blade and the force value returns to zero. However, at this time, the part of the sample outside the contact point has not yet finished accelerating. The sample is in a bent state, which causes the contact point to move back and make a second contact collision, thus forming an M-shaped trend of the force value curve.

[0064] 1) During the impact process, the vibration induced when the pendulum first contacts the specimen is a beam vibration mode based on the specimen's own properties, rather than a rigid body collision. Based on this, the time span of the initial peak force can be calculated.

[0065] According to beam vibration theory, the vibration equation of the specimen is:

[0066]

[0067] Where u is the vibration displacement, ρ is the density, A is the cross-sectional area of ​​the sample, F(t) is the impact force, δ is the Dirac function, L is the sample length, E is the Young's modulus of the sample material, ρ is the density of the sample material, and the independent variables x and t are the position and time, respectively. The boundary conditions corresponding to this differential equation are:

[0068]

[0069] With the hammer blade as the reference inertial frame, the initial conditions are:

[0070]

[0071] Using the method of separation of variables, let but

[0072]

[0073] q(t)=A sinωt+B cosωt (9)

[0074] and

[0075]

[0076] Where I = bh 3 / 12, b is the vertical height of the specimen, and h is the thickness of the specimen in the impact direction. Substituting the boundary condition (6) into equation (8), we get

[0077]

[0078] To ensure that the equation has a nontrivial solution, then

[0079]

[0080] βL has infinitely many solutions, the first of which is βL = 4.7300. Substituting this into equation (10) yields the frequency corresponding to the first peak force. Since the time span of the first peak force is half a cycle, the corresponding target calibration frequency and the time span of the first peak force can be obtained from the following two equations, which are respectively

[0081] and

[0082]

[0083] t0=π / ω (14)

[0084] 2) During the impact, the collision between the hammer blade and the specimen is a rigid collision (the hardness of the hammer blade is above 55 HRC, the hardness of the low-energy V-shaped specimen is 51.0 ± 0.2 HRC, the hardness of the medium-energy V-shaped specimen is 33.5 ± 0.3 HRC, and the hardness of the high-energy V-shaped specimen is 25.8 ± 0.2 HRC). Energy loss during the impact is very small. According to the laws of conservation of momentum and energy, we have...

[0085] Mv=Mv1+mv2 (15)

[0086] Mv 2 =Mv1 2 +mv2 2 (16)

[0087] Where M is the equivalent impact mass of the pendulum, m is the mass of the sample, v is the impact velocity of the pendulum, v1 is the velocity of the pendulum after impact, and v2 is the velocity of the sample after impact. Here, "after impact" refers to the time after the sample and pendulum are completely separated. The solution yields...

[0088]

[0089] The standard V-shaped specimen has a mass of 42.8g, the 7mm specimen has a mass of 30.0g, and the pendulum has a mass of 34142g. The pendulum mass is much greater than the specimen mass, M >> m, therefore Therefore

[0090] v2 = 2v (18)

[0091] This indicates that after a complete impact, the velocity of the ejected specimen should be twice the impact velocity of the pendulum. Therefore, it can be deduced that the area enclosed by integrating the M-shaped curve segment on the force-time curve, ∫F dt, should be equal to 2mv, i.e.

[0092] ∫F dt=2mv (19)

[0093] 3) For a typical impact test, if a cuboid specimen is used and it contacts the anvil during installation, then its initial peak is the first half of the M-shaped curve. Due to the principle of vibration, the two parts of the M-shaped curve are identical. Therefore, the area enclosed by the initial peak is mv. Thus, given that the force-time waveform of the initial peak is a sinusoidal function, the half-cycle time span of this sinusoidal function is known, and the area enclosed by the force-time waveform of this half-cycle is mv, the maximum force of the initial peak is...

[0094]

[0095] Where ρ is the sample density, E is the Young's modulus of the sample, h is the sample thickness in the impact direction, L is the sample length, v is the initial velocity of the pendulum impact, and b is the vertical height of the sample.

[0096] Therefore, the maximum force value of the first peak at the target calibration frequency can be obtained, and then the dynamic force sensor of the instrumented impact testing machine can be calibrated at the target frequency based on this maximum force value.

[0097] The method of the present invention can achieve high accuracy in calibrating the dynamic force sensor of the instrumented impact testing machine at its operating frequency. The present invention will be described in detail below with reference to specific implementation examples.

[0098] The calibration steps of this invention (calibration method for dynamic force sensor of instrumented impact testing machine based on dual-pulse method) are as follows:

[0099] Step 1: Select the target frequency to be calibrated, calculate the corresponding sample size according to formula (13), and if the sample used is a non-cubic prism sample, calculate the equivalent length of the sample used according to the method provided above and substitute it into the formula.

[0100] Step 2: Measure the basic dimensions and related parameters of the sample, and substitute them into formula (20) to obtain the maximum force value of the first peak;

[0101] Step 3: Check whether the instrumented impact testing machine to be calibrated retains the complete impact process (some testing machines cannot record this). Figure 4 As shown in the M-shaped curve, if the complete impact process can be preserved, then the sample should be handled according to... Figure 3Install it on the anvil as shown. If it cannot be installed, place it normally on the anvil.

[0102] Step 4: Conduct a standard instrumented impact test;

[0103] Step 5: Analyze the results obtained, for those according to Figure 3 For installations as shown, first check if the M-curve shape is distorted. If distortion is present, the dynamic force sensor of this instrumented impact testing machine cannot meet the requirements at the target frequency. If no distortion is present, compare the maximum force value of the M-curve in the test results with the maximum force value calculated in step 2 to determine the dynamic force measurement error at the target frequency. For installations installed in the normal manner, check the maximum force value at the first peak (e.g., ...). Figure 6 (As shown), compare it with the calculated maximum force value to obtain the dynamic force measurement error at this target frequency;

[0104] Table 4: Statistical Results of Maximum First Peak Force in Multiple Impact Tests of a Certain Brand's Instrumented Impact Testing Machine

[0105] First Peak Force (N) Energy value (J) Low-energy sample 1 13296 23.97 Low-energy sample 2 13181 22.24 Low-energy sample 3 13261 20.75 Low-energy sample 4 12390 22.67 Medium energy sample 1 13071 99.39 Medium energy sample 2 13093 100.8 Medium energy sample 3 12838 100.8 Medium energy sample 4 12818 99.69 High-energy sample 1 12519 122.9 High-energy sample 2 12721 113.6 High-energy sample 3 13428 127 average value 12965 - Standard deviation 334 - Discrete coefficients 257％ -

[0106] Step 6: For dynamic force calibration at a target frequency, multiple instrumented impact tests can be performed to check the repeatability of the instrumented impact testing machine to be calibrated. According to the experimental results (as shown in Table 4), it is normal to ensure that the dispersion coefficient of the maximum force value of the first peak is below 3%. Otherwise, check whether there is a certain degree of problem with the sample installation, or check the instrumented impact testing machine.

[0107] Step 7: Repeat steps 1 to 6 for different target frequencies to achieve frequency sweep calibration of the dynamic force sensor of the instrumented impact testing machine.

[0108] The foregoing description provides a detailed account of embodiments of the present invention and is not intended to limit the invention in any way. Those skilled in the art can make various optimizations, improvements, and modifications based on this invention. Therefore, the scope of protection of this invention should be defined by the appended claims.

Claims

1. A method for calibrating the dynamic force sensor of an instrumented impact testing machine based on the dual-pulse method, characterized in that, This includes: Step 1: Select the target frequency to be calibrated and calculate the corresponding sample size; Step 2: Measure the basic dimensions and relevant parameters of the sample, and calculate the maximum force value of the first peak; Step 3: Check whether the instrumented impact testing machine to be calibrated retains the complete impact process. If the complete impact process can be retained, then install the sample on the anvil; if not, place it normally on the anvil. Step 4: Conduct a standard instrumented impact test; in the instrumented impact test of Step 4: 1) During the impact process, when the pendulum first contacts the specimen, the vibration caused is a beam vibration mode based on the specimen's own properties, and the time span of the first peak force is calculated. 2) During the impact process, the collision between the hammer blade and the sample is a rigid collision; 3) For impact testing, if a cuboid specimen is used and the specimen contacts the anvil during installation, the first peak is the first half of the M-shaped curve; the two parts of the M-shaped curve are the same; therefore, the area enclosed by the first peak is mv; given that the force-time waveform of the first peak is a sine function, the half-cycle time span of this sine function is known, and the area enclosed by this half-cycle force-time waveform is known to be mv, the maximum value of the first peak force is obtained; based on the maximum force value of the first peak, the dynamic force sensor of the instrumented impact testing machine is calibrated at the target frequency; Step 5: Analyze the instrumented impact test and obtain the corresponding results: First, check whether the M-curve shape is distorted. If there is distortion, it is determined that the dynamic force sensor of this instrumented impact testing machine cannot meet the usage requirements at the target frequency. If there is no distortion, compare the maximum force value of the M-curve in the test results with the maximum force value calculated in Step 2 to obtain the dynamic force measurement error at this target frequency. For those installed in the normal way, check the maximum force value at the first peak and compare it with the calculated maximum force value to obtain the dynamic force measurement error at this target frequency. Step 6: For dynamic force calibration at a target frequency, perform multiple instrumented impact tests to check the repeatability of the instrumented impact testing machine to be calibrated. It is normal for the dispersion coefficient of the first peak force maximum value to be below 3%. Otherwise, check whether there is a problem with the sample installation or check the instrumented impact testing machine. Step 7: Repeat steps 1 to 6 for different target frequencies to achieve frequency sweep calibration of the dynamic force sensor of the instrumented impact testing machine.

2. The method for calibrating a dynamic force sensor of an instrumented impact testing machine based on the dual-pulse method according to claim 1, characterized in that, The specimen used can be a cuboid specimen or a non-cuboid specimen; if it is a non-cuboid specimen, the equivalent length of the non-cuboid specimen used is calculated.

3. The method for calibrating a dynamic force sensor of an instrumented impact testing machine based on the dual-pulse method according to claim 1, characterized in that, If the specimen used is a non-cubic prism specimen, the equivalent length of the non-cubic prism used can be calculated.

4. The method for calibrating a dynamic force sensor of an instrumented impact testing machine based on the dual-pulse method according to claim 1, characterized in that, According to beam vibration theory, the vibration equation of the specimen is: in For vibration displacement, The cross-sectional area of ​​the sample. For impact force, For the Dirac function, Where E is the sample length and E is the Young's modulus of the sample material. The density of the sample material is the independent variable. These represent location and time, respectively; the corresponding boundary conditions are: With the hammer blade as the reference inertial frame, the initial conditions are: Using the method of separation of variables, let ,but in b is the vertical height of the specimen, and h is the thickness of the specimen in the impact direction; substituting the boundary condition (6) into equation (8), we get To ensure that the equation has a nontrivial solution, then There are infinitely many solutions, of which the first solution is... Substituting into equation (10), we obtain the frequency corresponding to the first peak force. Since the time span of the first peak force is half a cycle, we can obtain the corresponding target calibration frequency and the time span of the first peak force according to the following two equations, which are respectively 5. The method for calibrating a dynamic force sensor of an instrumented impact testing machine based on the dual-pulse method according to claim 1, characterized in that, Given that the force-time waveform of the initial peak is a sinusoidal function, the half-cycle time span of this sinusoidal function is known, and the area enclosed by the force-time waveform of this half-cycle is mv, the maximum force of the initial peak is... in, Let be the sample density, E be the Young's modulus of the sample, and h be the sample thickness in the impact direction. denoted as , v is the initial velocity of the pendulum impact, and b is the vertical height of the sample.

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