Equivalent calculation method and system for natural fragment finite element model

Abstract

The application relates to the technical field of electric digital data processing in intelligent manufacturing, and discloses a natural fragment finite element model equivalent calculation method and system, which can reduce the test times and ensure the reliability of simulation results. The method comprises the following steps: randomly selecting part of fragments in a mass interval, establishing a fragment model according to the average length, the average width and the average height; simulating and analyzing the estimated residual mass and the estimated residual velocity of the fragment model and the target plate model after penetration under different contact conditions; comparing the actual residual mass and the actual residual velocity of at least one fragment selected in a real test environment; obtaining correction coefficients corresponding to the estimated residual mass and the estimated residual velocity under different contact conditions; then obtaining the correction interval range corresponding to the estimated residual mass and the estimated residual velocity; and correcting the single-value simulation results corresponding to the residual mass and the residual velocity in the mass interval into interval range values according to the correction interval range.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical digital data processing in intelligent manufacturing, and in particular to a method and system for calculating an equivalent finite element model of natural fragments. Background Art

[0002] To control the shape, quality, and quantity of fragments, as well as for engineering purposes, different fragment types have been developed, primarily including natural fragments, semi-prefabricated fragments, and prefabricated fragments. Prefabricated fragments are commonly used in prefabricated fragment warheads due to their regular shape and ease of processing. They are also easy to model in 3D software and mesh in finite element software, resulting in a relatively mature research landscape for finite element simulation models of prefabricated fragments. The shell structure of semi-prefabricated fragments is intact. By implementing certain technical measures, the warhead shell is shattered in a predetermined manner under the action of the explosion, ultimately forming fragments of relatively regular shape and uniform quality. Natural fragments, however, target the integral shell structure. Upon detonation, the projectile forms a large number of fragments of varying shapes and qualities, which fly in all directions at high speeds.

[0003] Studying natural fragmentation helps measure the degree of shell fragmentation and also helps understand and calculate the lethality of warheads. However, to date, research on calculation methods for finite element simulation models of natural fragmentation is almost nonexistent. This is due to the inherently irregular shapes of natural fragments, making three-dimensional modeling complex and difficult to create high-quality cell meshes. Furthermore, the calculation process requires a large number of cells, which can lead to cell mismatches and low computational efficiency. Summary of the Invention

[0004] The present invention aims to disclose a method and system for calculating the equivalent of a natural fragment finite element model, so as to reduce the number of tests and ensure the reliability of the simulation results.

[0005] To achieve the above-mentioned purpose, the equivalent calculation method of the natural fragment finite element model disclosed in the present invention includes:

[0006] Step S1: Treat each natural fragment as a cuboid and determine the mass range of the natural fragment to be modeled;

[0007] Step S2: Randomly select some fragments within the mass range, measure the length and width of each randomly selected natural fragment, and then calculate the height of each natural fragment if it is regarded as a rectangular parallelepiped based on the mass and density; and calculate the length, width, and height of the selected natural fragments to obtain the average length, average width, and average height;

[0008] Step S3, establishing a fragment model of the mass range in the modeling software according to the average length, average width and average height;

[0009] Step S4: in the modeling software, simulating and analyzing the estimated residual mass and estimated residual velocity of the fragment model and the target plate model after penetrating the target under different contact conditions;

[0010] Step S5: measuring the actual residual mass and actual residual velocity of the at least one selected fragment in a real test environment;

[0011] Step S6: Compare the estimated remaining mass and estimated remaining speed with the actual remaining mass and actual remaining speed respectively to obtain correction coefficients corresponding to the estimated remaining mass and estimated remaining speed under different contact conditions; then extract the maximum and minimum values ​​of the correction coefficients to obtain correction ranges corresponding to the estimated remaining mass and estimated remaining speed respectively;

[0012] Step S8: Correct the single-value simulation results corresponding to the residual mass and the residual speed within the mass interval to interval range values ​​according to the correction interval range.

[0013] Preferably, when the number of fragments measured in the actual test environment in step S5 is at least 2, the obtained actual residual mass and actual residual velocity are the average values ​​of the measured fragments.

[0014] Preferably, when the number of fragments actually measured in the actual test environment in step S5 is only 1, the steps between step S6 and step S8 further include:

[0015] Step S7: Measure the actual remaining mass and actual remaining velocity corresponding to the newly added fragment 1 in a real test environment to determine whether the actual remaining mass and actual remaining velocity are within the allowable error range of the correction range obtained in step S6. If so, confirm that the correction range is accurate and proceed to step S8. Otherwise, take the union of the two measured correction ranges to obtain an expanded correction range and proceed to step S9.

[0016] Step S9: Correct the single-value simulation results corresponding to the residual mass and the residual speed in the mass interval to interval range values ​​according to the expanded correction interval range.

[0017] Preferably, in step S7, the allowable error range of the correction interval obtained in step S6 is 15%.

[0018] Preferably, the step size between two adjacent mass intervals is 1 gram.

[0019] Preferably, the modeling software adopts LS-DYNA software, which is mainly based on the Lagrange algorithm and has both ALE and Euler algorithms. It is a general structural analysis nonlinear finite element program that combines military and civilian applications.

[0020] Preferably, during the modeling process, the target plate has a thickness determined according to the target test environment, and its length and width are centered on the target point. The length and width of the entire model are centered on the target point, and the length and width are both 70 times the larger value of the average length and average width of the fragments. The internal area containing the target point has a dense grid, and the edge area away from the target point has a sparse grid.

[0021] Preferably, in step S5, when the number of fragments measured in the actual test environment in step S5 is at least 3, it also includes: eliminating abnormal data of fragments obtained from a single test, and the abnormal data is data whose difference between the residual mass and / or residual velocity and the mean is greater than or equal to 3 times the overall statistical standard deviation.

[0022] To achieve the above-mentioned purpose, the present invention also discloses a natural fragment finite element model equivalent calculation system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned method when executing the computer program.

[0023] In summary, the core of the method and system of the present invention is: randomly selecting some fragments within the mass range, establishing a fragment model based on the average length, average width and average height; simulating and analyzing the estimated residual mass and estimated residual velocity of the fragment model and the target plate model after penetrating the target under different contact conditions; comparing the actual residual mass and actual residual velocity obtained by measuring at least one selected fragment under a real test environment; obtaining the correction coefficients corresponding to the estimated residual mass and the estimated residual velocity under different contact conditions; and then obtaining the correction interval range corresponding to the estimated residual mass and the estimated residual velocity; and correcting the single-value simulation results corresponding to the residual mass and the residual velocity within the mass range to interval range values ​​according to the correction interval range. Thus, the present invention has the following beneficial effects:

[0024] 1. Based on the measured test results, it is proved that the method of treating the fragments as rectangular blocks and measuring their length and width, and solving the height by equivalently using the relationship between mass, density and volume is logically reasonable and reliable.

[0025] 2. Typically, the number of actual tests is far less than the number of simulations under various contact conditions. By correcting the simulation data using the correction coefficient range determined by limited real-world test data, we can accurately estimate the distribution range of residual mass and residual velocity corresponding to the actual fragment-target contact conditions. This effectively reduces test costs and ensures the high reliability of the final results.

[0026] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 It is a flow chart of the equivalent calculation method of the natural fragment finite element model disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0030] Example 1

[0031] This embodiment discloses a method for calculating the equivalent of a natural fragment finite element model, comprising the following steps:

[0032] Step 1: Rationally divide the natural fragments into mass ranges and select fragments within the mass range.

[0033] In this step, the mass interval can be divided into (m±a) grams, where the value of a varies with m. Preferably, the step size between two adjacent mass intervals is 1 gram. For illustration, the mass interval of (12±0.5) grams is used as an example.

[0034] Step 2: Randomly select natural fragments for statistical analysis.

[0035] Step 2.1: Based on the test outline, randomly select a batch of natural fragments from the recovered natural fragments that meet the mass range. The interference of human factors should be eliminated during the selection process.

[0036] Step 2.2: The number of randomly selected natural fragments should be neither too few nor too many, but should be representative and complete. The sample size of the randomly selected natural fragments should be sufficient and should include fragments within a certain mass range. This will have a better predictive effect on the residual mass and residual velocity of subsequent natural fragments in the same mass range after they penetrate the target.

[0037] The randomly selected natural fragments with a mass range of (12±0.5)g include 11.5g, 11.6g, 11.7g, 11.8g, 11.9g, 12.0g, 12.1g, 12.2g, 12.3g, 12.4g, and 12.5g, which are of positive significance for studying the residual velocity and residual mass of natural fragment groups.

[0038] Step 3: Treat the natural fragments as cuboids and determine the average length, average width, and average height of the cuboids based on statistical data.

[0039] Specifically, a vernier caliper can be used to measure the length a and width b of each randomly selected fragment. The height c of the cuboid can be determined based on the volume formula and the mass-density formula, and the average equatorial length of the randomly selected fragments can be calculated. Average width Calculate the average height based on the mass

[0040] For example, randomly select 20 fragments from a pile of 12g ± 0.5g fragments. Use a ruler or graph paper to calculate the length, width, and height of the 20 fragments. The results are shown in Table 1 below:

[0041] Table 1: a, b, and c values ​​of randomly selected fragments

[0042]

[0043]

[0044] Then, based on the average length of several fragments Average width Calculate the average height based on the mass

[0045] Step 4: Establish a finite element model of the fragments and target plate and perform simulation calculations.

[0046] The core of this step is: To determine the size of the fragment finite element model, determine the length and width of the target plate finite element model to eliminate the impact of the target plate end effect on the target plate penetration process, and determine the thickness of the target plate finite element model based on the experimental conditions of the fragment penetration target plate. Finally, establish the finite element model of the fragment and target plate in the finite element software and calculate the residual mass and residual velocity of the fragments under the same conditions and different target impact postures of the natural fragments. Calculate the average residual mass and average residual velocity of the natural fragments after penetrating the target. Furthermore, this step can be further subdivided into the following sub-steps:

[0047] Step 4.1: According to To determine the size of the established fragment finite element model, to eliminate the influence of the target plate end face effect on the target plate penetration process, to determine the length and width of the established target plate finite element model, according to the test conditions of the fragment penetration target plate, to determine the thickness of the established target plate finite element model, and to establish the finite element model of the fragment and target plate in the finite element software.

[0048] Preferably, during the modeling process, the target plate has a thickness determined according to the target test environment, and its length and width are centered on the target point. The length and width of the entire model are centered on the target point, and the length and width are both 70 times the larger value of the average length and average width of the fragments. The internal area containing the target point has a dense grid, and the edge area away from the target point has a sparse grid.

[0049] Step 4.2: Establish a finite element model of the fragments and target plate in the finite element software and calculate the residual mass and residual velocity of the natural fragments under different target impact postures under the same conditions, and calculate the average residual mass and average residual velocity of the natural fragments after penetrating the target.

[0050] The finite element model of the rectangular fragment and target plate is established in truegrid. The length of the rectangular fragment is a1 = 16 mm, the width is b1 = 16 mm, and c1 = 6 mm. The length and width of the full target plate model are L1 = 70a1 = 70 × 16 = 1120 mm. The thickness of the target plate is determined according to the target plate thickness required for penetration.

[0051] Taking the penetration of 12g rectangular fragments into 10mm 45# steel as an example, the simulation conditions in the finite element software are shown in Table 2.

[0052] Table 2: Simulation conditions

[0053]

[0054]

[0055] Since there are three forms of contact between fragments and target plates at the moment of collision, namely, surface contact, line contact, and point contact, different contact forms can be obtained at the moment of impact due to the certain angles between the rectangular fragments and the central x-axis, y-axis, and z-axis. The values ​​obtained by simulation in LS-DYNA are shown in Table 3, and the simulation data processing part is shown in Table 3.

[0056] Table 3: Values ​​obtained from LS-DYNA simulation

[0057]

[0058]

[0059] Step 5: Modify the simulation results based on the ballistic gun test results.

[0060] Based on this step, the simulation results and subsequent test results can be within the allowable error range. To this end, this step can be further divided into:

[0061] Step 5.1: Collect light ballistic test data under the same conditions as the above simulations and, using the "3σ" principle, eliminate fragments with significantly different residual masses and residual velocities. The "3σ" principle eliminates anomalous fragment data from a single test, defined as data with a residual mass and / or residual velocity that differs from the mean by more than or equal to three times the overall statistical standard deviation.

[0062] The test data of the residual mass and residual velocity obtained when 5 (12±0.5)g fragments vertically penetrated a 10mm 45# steel target plate at a certain initial velocity are shown in Table 4.

[0063] Table 4: Residual mass and residual velocity of fragments obtained from ballistic gun tests

[0064]

[0065]

[0066] Step 5.2: Determine the correction coefficient based on the ratio of each reasonable test value of the fragment to the simulated operating condition, find the range of the correction coefficient, and then obtain the range of the fragment's residual mass and residual velocity. Based on the data in sequence 1, the correction coefficients for the fragment's residual mass and residual velocity are shown in Tables 5 and 6, respectively.

[0067] Table 5: Correction factors for residual mass of fragments

[0068]

[0069]

[0070]

[0071] In other words, the correction interval of the fragment residual mass is [1.03,1.13]m 仿真值 .

[0072] Table 6: Correction factors for residual fragment velocity

[0073]

[0074]

[0075]

[0076] The correction interval of the fragment residual velocity is [1.01,1.18]v 仿真值 .

[0077] Step 5.3: Finally, the remaining fragments to be tested within the mass range can be predicted. If the residual mass and residual velocity of most of the fragments to be tested after the test are within the allowable error range of the residual mass and residual velocity of the fragments obtained above, the equivalent calculation method can be considered reasonable.

[0078] The second ballistic gun test in No. 2 in Table 4 was verified. The average values ​​of the residual mass and residual velocity calculated in LS-DYNA software using the above method were 10.23 g and 371.28 m / s, respectively. Based on the correction ranges of the fragment residual mass and residual velocity, the residual mass and residual velocity of the fragment under the test conditions were predicted to be in the ranges of [10.54, 11.56] g and [374.99, 438.64] m / s, respectively. After comparing these with the actual residual mass of 10.60 and the actual residual velocity of 386.08 corresponding to No. 2 in Table 4, the calculated errors are shown in Table 7.

[0079] Table 7: Comparison of ballistic gun test data errors

[0080] sequence Residual mass error Remaining speed error 1 10.54 -0.55％ 374.99 -2.87％ 2 11.56 9.06％ 438.64 13.6％ Average error 4.81％ Average error 8.24％

[0081] The average error between the residual mass and residual velocity of the fragments predicted by the above method under the ballistic gun test conditions and those measured in the final test is within 15%, which shows that the equivalent calculation method is reasonable.

[0082] As a workaround, it is obvious to those skilled in the art that the correction coefficient can be determined by directly averaging multiple tests and omitting the subsequent verification operation.

[0083] In summary, the core content of the method of this embodiment is as follows: Figure 1 As shown, it can be summarized into the following steps:

[0084] Step S1: each natural fragment is regarded as a cuboid, and the mass range of the natural fragment to be modeled is determined.

[0085] Step S2: Randomly select some fragments within the mass range, measure the length and width of each randomly selected natural fragment, and then calculate the height of each natural fragment if it is regarded as a rectangular parallelepiped based on the mass and density; and calculate the length, width, and height of the selected natural fragments to obtain the average length, average width, and average height.

[0086] Step S3: establishing a fragment model of the mass range in the modeling software according to the average length, average width and average height.

[0087] Step S4: In the modeling software, simulate and analyze the estimated residual mass and estimated residual velocity of the fragment model and the target plate model after penetrating the target under different contact conditions.

[0088] Step S5: measuring the actual residual mass and actual residual velocity of the at least one selected fragment in a real test environment.

[0089] Step S6: Compare the estimated remaining mass and estimated remaining speed with the actual remaining mass and actual remaining speed respectively to obtain correction coefficients corresponding to the estimated remaining mass and estimated remaining speed under different contact conditions; then extract the maximum and minimum values ​​of the correction coefficients to obtain correction ranges corresponding to the estimated remaining mass and estimated remaining speed respectively.

[0090] Step S8: Correct the single-value simulation results corresponding to the residual mass and the residual speed within the mass interval to interval range values ​​according to the correction interval range.

[0091] Optionally, when the number of fragments actually measured in the actual test environment in step S5 is at least 2, the obtained actual residual mass and actual residual velocity are average values ​​of the actually measured fragments.

[0092] Optionally, when the number of fragments actually measured in the actual test environment in step S5 is only 1, the steps between step S6 and step S8 further include:

[0093] In step S7, the actual remaining mass and actual remaining velocity corresponding to the newly added fragment 1 are measured under a real test environment to determine whether the actual remaining mass and actual remaining velocity are within the error range allowed by the correction range obtained in step S6. If so, the correction range is confirmed to be accurate and the process proceeds to step S8; otherwise, the correction ranges obtained from the two actual measurements are combined to obtain an expanded correction range and the process proceeds to step S9.

[0094] Step S9: Correct the single-value simulation results corresponding to the residual mass and the residual speed in the mass interval to interval range values ​​according to the expanded correction interval range.

[0095] Example 2

[0096] Corresponding to the above embodiment, this embodiment discloses a natural fragment finite element model equivalent calculation system, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the series of steps corresponding to the above method embodiment are implemented.

[0097] In summary, the present invention has the following beneficial effects:

[0098] 1. Based on the measured test results, it is proved that the method of treating the fragments as rectangular blocks and measuring their length and width, and solving the height by equivalently using the relationship between mass, density and volume is logically reasonable and reliable.

[0099] 2. Typically, the number of actual tests is far less than the number of simulations under various contact conditions. By correcting the simulation data using the correction coefficient range determined by limited real-world test data, we can accurately estimate the distribution range of residual mass and residual velocity corresponding to the actual fragment-target contact conditions. This effectively reduces test costs and ensures the high reliability of the final results.

[0100] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A natural fragment finite element model equivalent calculation method, characterized in that: include: Step S1: Treat each natural fragment as a cuboid and determine the mass range of the natural fragment to be modeled; Step S2: Randomly select some natural fragments within the mass range, measure the length and width of each selected natural fragment, and then calculate the height of each natural fragment if it is regarded as a cuboid based on the mass and density; and calculate the length, width, and height of the selected natural fragments to obtain an average length, average width, and average height. Step S3, establishing a natural fragment model of the mass interval in the modeling software according to the average length, average width and average height; Step S4: In the modeling software, simulate and analyze the estimated residual mass and estimated residual velocity of the natural fragment model and the target plate model after penetrating the target under different contact conditions; Step S5: measuring the actual residual mass and actual residual velocity of the at least one natural fragment selected in step S2 under a real test environment; Step S6: Compare the estimated remaining mass and estimated remaining speed with the actual remaining mass and actual remaining speed respectively to obtain correction coefficients corresponding to the estimated remaining mass and estimated remaining speed under different contact conditions; then extract the maximum and minimum values ​​of the correction coefficients to obtain correction ranges corresponding to the estimated remaining mass and estimated remaining speed respectively; Step S8: Correcting the single-value simulation results corresponding to the residual mass and the residual velocity of the natural fragment model within the mass range to interval range values ​​according to the correction interval range.

2. The method according to claim 1, characterized in that When the number of natural fragments actually measured under the actual test environment in step S5 is at least 2, the obtained actual residual mass and actual residual velocity are average values ​​of the actually measured natural fragments.

3. The method according to any one of claims 1 to 2, characterized in that: The step size between two adjacent mass intervals is 1 gram.

4. The method according to any one of claims 1 to 2, characterized in that: The finite element analysis software used is LS-DYNA software.

5. The method according to any one of claims 1 to 2, characterized in that: During the modeling process, the thickness of the target plate is determined according to the target test environment. The length and width of the entire model are centered on the target point, and the length and width are both 70 times the larger value of the average length and average width of natural fragments.

6. The method according to claim 5, characterized in that During the target plate modeling process, the mesh of the inner area containing the target is dense, while the mesh of the edge area away from the target is sparse.

7. The method according to any one of claims 1 to 2, characterized in that: In step S5, when the number of natural fragments measured in the actual test environment in step S5 is at least 3, the method further includes: Abnormal data of natural fragments obtained from a single test were eliminated. The abnormal data were data whose difference between the residual mass and / or residual velocity and the mean was greater than or equal to 3 times the overall statistical standard deviation.

8. A natural fragment finite element model equivalent calculation system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

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