A method for evaluating the performance of a dot matrix structure buffer energy absorption of a pyrotechnic device

Abstract

A lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device, which is a lattice structure buffer energy absorption performance evaluation method using small sample multi-rate equivalent load application, comprehensively considers the influence of loading rate on the mechanical behavior of the lattice structure, calculates the lattice structure calculation model parameters under different conditions by presetting the loading rate, and then according to the lattice structure calculation model parameters, the current impact speed is calculated, based on the densification load and the maximum energy absorption characteristic parameters, and the calculation results are used to evaluate the buffer energy absorption performance of the lattice structure under the specified mass and speed impact.

Description

TECHNICAL FIELD

[0001] The application relates to a lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device and belongs to the field of missile body structure separation devices. BACKGROUND

[0002] During the separation process of a missile body structure, a high-speed separation mass is formed after a pyrotechnic device such as an explosive bolt is initiated and unlocked, and if the separation mass directly impacts on the missile body structure, a large impact response is generated, which may further cause damage to adjacent instruments and equipment and affect the safety of a flight mission. An inner concave hexagonal lattice structure is widely used as an energy absorption material for absorbing and dissipating the energy of the high-speed separation mass after the pyrotechnic device is unlocked, so as to reduce the separation impact response and realize a buffer protection effect. The inner concave hexagonal lattice structure is manufactured by additive manufacturing and is a multilayer and porous thin-walled shell structure, and the compression mechanical behavior of the structure is obviously affected by a loading rate. The buffer energy absorption performance of lattice structures with different structure parameters is different under different impact speeds, and how to evaluate the buffer energy absorption performance of the inner concave hexagonal structure under high-speed impact is a problem that needs to be solved in the engineering use of the lattice structure.

[0003] At present, the buffer energy absorption performance evaluation of the lattice structure generally adopts a firing test of a real pyrotechnic separation device structure, and on the one hand, the firing test and testing cost are high, and on the other hand, the test results are greatly different due to the dispersion of the pyrotechnic power source, which affects the evaluation accuracy of the buffer energy absorption performance of the lattice structure.

[0004] In order to reasonably and accurately evaluate the buffer energy absorption performance consistency of the lattice structure under high-speed impact, a small sample and a multi-rate equivalent load application method are adopted, and the buffer energy absorption performance of the lattice buffer structure is evaluated based on the densification load and energy absorption rate characteristics. SUMMARY

[0005] The application solves the technical problem that the evaluation method of the prior art adopts a real pyrotechnic separation device structure for a firing test, and the accuracy is poor and the cost is high, and proposes a lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device.

[0006] The application solves the above technical problem by the following technical scheme:

[0007] A lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device comprises the following steps:

[0008] The mass and impact speed data of the separation mass for buffering and absorbing energy of the lattice structure are collected, and the kinetic energy of the separation mass is calculated;

[0009] The densification displacement of the lattice structure is calculated according to the cell size of the lattice structure;

[0010] The lattice structure compression test under the preset loading rate is carried out by displacement control;

[0011] According to the lattice structure compression test results, the densification load characteristic values of the lattice structure under each preset loading rate are obtained, and the maximum energy absorption characteristic values of the lattice structure under each preset loading rate are determined;

[0012] According to the characteristic value parameters of the lattice structure under each preset loading rate and the corresponding lattice structure densification load, the lattice structure calculation model parameters are calculated;

[0013] The densification load and the maximum energy absorption under the impact speed corresponding to the current kinetic energy parameter are calculated by using all the calculated lattice structure calculation model parameters and the kinetic energy parameters of the separated mass;

[0014] The cushioning and energy absorption performance is evaluated according to the densification load and the maximum energy absorption under the current impact speed.

[0015] The calculation method of the kinetic energy of the separated mass is:

[0016]

[0017] In the formula, the mass of the separated mass is m, and the impact speed is v0;

[0018] The calculation method of the densification displacement of the lattice structure is:

[0019]

[0020] In the formula, the densification displacement of the lattice structure is h d , d is the wall thickness of the lattice structure cell thin-walled shell, L is the cell height, S is the cell width, and H is the total height of the lattice structure.

[0021] The preset loading rates V1, V2 and V3 are preselected, and the preset loading speed values are set according to the maximum energy that can be absorbed by the lattice structure; the lattice structure compression test is carried out according to the selected preset loading rates, and the load-displacement curves under different loading rates are obtained.

[0022] According to the densification load characteristic values of the lattice structure under each preset loading rate, the calculation method of the lattice structure calculation model parameters is determined as follows:

[0023]

[0024] In the formula, F d-v represents the densification load characteristic value of the lattice structure when the loading speed is v, F0 is the load parameter, A represents the speed parameter, which is determined according to the material of the lattice structure, B represents the exponential parameter of the speed, and a specified constant is selected, wherein F0, A and B are the lattice structure calculation model parameters.

[0025] According to the maximum energy absorption characteristic value of the dot matrix structure under each preset loading rate, the calculation method of the dot matrix structure calculation model parameters is determined as follows:

[0026]

[0027] In the formula, W v-max represents the maximum energy absorption of the dot matrix structure when the loading speed is v, W0 is the energy absorption parameter, C is the speed parameter, which is determined according to the material of the dot matrix structure, D represents the exponential parameter of the speed, and a specified constant is selected, wherein W0, C and D are the dot matrix structure calculation model parameters.

[0028] According to the impact speed v0, the dot matrix structure calculation model parameters obtained by solving are re-substituted, and the densification load characteristic value of the dot matrix structure and the expression of the dot matrix structure calculation model parameters, the maximum energy absorption characteristic value of the dot matrix structure and the expression of the dot matrix structure calculation model parameters are used to calculate the densification load F d-v and the maximum energy absorption W v-max of the dot matrix structure under the current impact speed v0.

[0029] The specific standard for evaluating the buffering and energy absorption performance is as follows:

[0030] When the maximum energy absorption W v-max is greater than or equal to the kinetic energy E of the separated mass, the densification load F d-v is inversely proportional to the buffering and energy absorption performance of the dot matrix structure.

[0031] The dot matrix structure is arranged in a concave hexagonal structure, and the maximum energy absorption of the dot matrix structure and the densification displacement of the dot matrix structure in the compression process are related as follows:

[0032]

[0033] In the formula, W max represents the maximum energy absorption of the dot matrix structure; h d represents the densification displacement of the dot matrix structure, that is, the displacement at the moment when the thin-walled shells are in contact and compacted; h is the compression displacement of the dot matrix structure; and F(h) is the stress value corresponding to the compression displacement h.

[0034] The material of the dot matrix structure is an alloy material.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The application provides a lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device, comprehensively considers the influence of a loading rate on the mechanical behavior of the lattice structure, evaluates the buffer energy absorption performance of the lattice structure under a specified mass and speed impact based on densification load and maximum energy absorption characteristic parameters, and can solve the problem that there is no reasonable buffer energy absorption performance evaluation method for the lattice structure of the pyrotechnic device, and proposes a new small sample multi-rate equivalent load application lattice structure buffer energy absorption performance evaluation method, which can reasonably and accurately evaluate the buffer energy absorption performance consistency of the lattice structure under high-speed impact. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A schematic diagram of a concave hexagonal lattice structure for a pyrotechnic device is provided.

[0038] Figure 2 A loading schematic diagram of the concave hexagonal lattice structure is provided.

[0039] Figure 3 A load-displacement curve diagram of the lattice structure under different loading rates is provided.

[0040] Figure 4 A flowchart of the buffer energy absorption performance equivalent evaluation method of the lattice structure is provided. DETAILED DESCRIPTION

[0041] A lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device adopts a small sample multi-rate equivalent load application lattice structure buffer energy absorption performance evaluation method, comprehensively considers the influence of a loading rate on the mechanical behavior of the lattice structure, calculates the lattice structure calculation model parameters under different conditions by presetting the loading rate, and then reversely calculates the current impact speed based on the lattice structure calculation model parameters, densification load and maximum energy absorption characteristic parameters, and evaluates the buffer energy absorption performance of the lattice structure under a specified mass and speed impact according to the calculation results.

[0042] The lattice structure buffer energy absorption performance equivalent evaluation method for a pyrotechnic device has the following specific steps:

[0043] The mass and impact speed data of the separated mass body for the buffer energy absorption of the lattice structure are collected, and the kinetic energy of the separated mass body is calculated.

[0044] The densification displacement of the lattice structure is calculated according to the cell size of the lattice structure.

[0045] The lattice structure compression test under the preset loading rate is carried out by displacement control.

[0046] According to the lattice structure compression test results, the densification load characteristic values of the lattice structure under each preset loading rate are obtained, and the maximum energy absorption characteristic values of the lattice structure under each preset loading rate are determined.

[0047] According to the eigenvalue parameters of the lattice structure under each preset loading rate and the corresponding densification load of the lattice structure, the lattice structure calculation model parameters are calculated;

[0048] Using all the calculated lattice structure calculation model parameters and kinetic energy parameters of the separated mass, the densification load and the maximum absorbed energy at the impact speed corresponding to the current kinetic energy parameters are calculated;

[0049] The cushioning and energy absorption performance is evaluated according to the densification load and the maximum absorbed energy at the current impact speed.

[0050] The calculation method of the kinetic energy of the separated mass is:

[0051]

[0052] In the formula, the mass of the separated mass is m, and the impact speed is v0;

[0053] The calculation method of the densification displacement of the lattice structure is:

[0054]

[0055] In the formula, the densification displacement of the lattice structure is h d , d is the wall thickness of the lattice structure cell thin-walled shell; L is the cell height; S is the cell width; and H is the total height of the lattice structure.

[0056] The preset loading rates V1, V2 and V3 are preselected, and the preset loading speed values are set according to the maximum energy that can be absorbed by the lattice structure; the lattice structure compression test is carried out according to the selected preset loading rate, and the load-displacement curve under different loading rates is obtained.

[0057] According to the densification load eigenvalue of the lattice structure under each preset loading rate, the calculation method of the lattice structure calculation model parameters is determined as follows:

[0058]

[0059] In the formula, F d-v represents the densification load eigenvalue of the lattice structure when the loading speed is v, F0 is the load parameter, A represents the speed parameter, which is determined according to the material of the lattice structure, B represents the exponential parameter of the speed, and a specified constant is selected, wherein F0, A and B are the lattice structure calculation model parameters.

[0060] According to the maximum absorbed energy eigenvalue of the lattice structure under each preset loading rate, the calculation method of the lattice structure calculation model parameters is determined as follows:

[0061]

[0062] In the formula, Wv-max represents the maximum energy absorbed by the dot matrix structure at the loading speed v, W0 is the absorbed energy parameter, C is the speed parameter, which is determined according to the material of the dot matrix structure, D represents the exponential parameter of the speed, and a specified constant is selected, wherein W0, C, and D are dot matrix calculation model parameters.

[0063] According to the impact speed v0, the dot matrix calculation model parameters are re-substituted, and the densification load F0 of the dot matrix structure at the current impact speed v0 is calculated by using the expression of the densification load characteristic value and the dot matrix calculation model parameters, the expression of the maximum absorbed energy characteristic value of the dot matrix structure and the dot matrix calculation model parameters. d-v and the maximum absorbed energy W v-max .

[0064] The specific standard for evaluating the cushioning and energy absorption performance is:

[0065] When the maximum absorbed energy W v-max is greater than or equal to the kinetic energy E of the separated mass, the densification load F d-v is inversely proportional to the cushioning and energy absorption performance of the dot matrix structure.

[0066] The material of the dot matrix structure is an alloy material.

[0067] The following will be further described in combination with the drawings and preferred embodiments of the specification:

[0068] In the current embodiment, in order to solve the problem that there is no reasonable cushioning and energy absorption performance evaluation method for the dot matrix structure used in the current initiating device, an equivalent evaluation method for the cushioning and energy absorption performance of the dot matrix structure is proposed by using a small sample and a multi-rate equivalent load test. The influence of the loading rate on the mechanical behavior of the dot matrix structure is comprehensively considered, and the cushioning and energy absorption performance of the dot matrix structure under the impact of a specified mass and speed is evaluated based on the densification load and the maximum absorbed energy characteristic parameters. Specifically:

[0069] A typical concave hexagonal dot matrix structure used in the initiating device is as shown in Figure 1As shown, the compression process includes three stages of elastic deformation, plastic deformation and densification, the first stage is the elastic deformation stage, the load and displacement are linearly related, the lattice structure is in a small strain range; the second stage is the plastic deformation stage (platform stage), the local stress of the lattice structure gradually exceeds the yield strength to cause plastic deformation, but the thin-walled shell does not immediately contact due to high porosity, the strain increases while the stress remains almost unchanged, which is the main stage of energy absorption; the third stage is the densification stage (compaction stage), a large number of lattice structure units are crushed due to continuous loading, the thin-walled shells contact each other, the structure is completely compacted, the strain changes very little while the stress increases sharply, and the energy absorption capacity of the lattice structure is greatly weakened in this stage, which is similar to the compression of dense metals. The present application aims at the second stage, and forms a lattice structure buffer energy absorption performance evaluation method of small sample low frequency equivalent load application, and the specific technical scheme is as follows:

[0070] 1) Test method

[0071] The compression test under three loading rates is carried out by displacement control, the loading schematic diagram is as shown in Figure 2 The selected three loading rates are V1, V2 and V3, which are all lower than the actual impact speed V, and the load-displacement curves under the three loading rates are obtained, as shown in Figure 3

[0072] 2) Mathematical model

[0073] Assumption 1: The elastic region strain of the concave hexagonal lattice structure is very small, that is, the displacement h s is very small when entering the plastic region, and the strain energy of the lattice structure in this stage can be ignored relative to the energy absorbed by the entire stage lattice structure,

[0074]

[0075] In the formula, W max represents the maximum energy that can be absorbed by the lattice structure; h d represents the densification displacement of the lattice structure, that is, the displacement at the moment when the thin-walled shells are in contact and compacted; h is the compression displacement of the lattice structure; F(h) is the stress value corresponding to the compression displacement h.

[0076] Assumption 2: The cell angle of the concave hexagonal lattice structure is 45°, and the cell size satisfies The densification displacement corresponds to the displacement at the moment when the thin-walled shells of each layer are compacted and fitted, therefore, the calculation formula of the densification displacement of the lattice structure is as follows;

[0077]

[0078] In the formula, d is the wall thickness of the lattice structure cell thin-walled shell; L is the single cell height; S is the single cell width; H is the total height of the lattice structure.​

[0079] Hypothesis 3: The compression mechanical behavior of lattice structure is affected by loading rate, in the case of the same compression displacement, the load and energy absorption efficiency increase with the increase of loading rate, at the same time, with the increase of loading rate, the load increases and the change of energy absorption efficiency is no longer obvious, the following formula can be used to fit:

[0080]

[0081]

[0082] In the formula, F d-v represents the densification load of the lattice structure when the loading speed is v; W v-max represents the maximum energy absorbed by the lattice structure when the loading speed is v; F0 is the load parameter; W0 is the absorbed energy parameter; A and C are speed parameters, which generally take a value of about 0.01 m / s for aluminum alloy; B and D are speed index parameters, and the values of B and D are generally greater than 10.

[0083] 3) Equivalent evaluation method of buffer energy absorption performance

[0084] The equivalent evaluation method of buffer energy absorption performance of the lattice structure is shown in Figure 4 .

[0085] Step 1: Input parameter calculation

[0086] According to the mass m and impact speed v of the separated mass body using the lattice structure for buffer energy absorption, the kinetic energy of the separated mass body is calculated.

[0087]

[0088] According to the cell size of the lattice structure, the densification displacement h d of the lattice structure is calculated according to formula (2).

[0089] Step 2: Perform loading test

[0090] The compression test of the lattice structure under three loading rates is performed by displacement control, and the test samples under each loading rate are not less than 3, the loading rates are 0.0001 m / s, 0.001 m / s and 0.01 m / s respectively, and the load-displacement curve under different loading rates is obtained.

[0091] Step 3: Calculate characteristic value

[0092] According to the load-displacement curve, the densification load characteristic value of the lattice structure under three loading rates is obtained, and the maximum absorbed energy characteristic value of the lattice structure under three loading rates is calculated.

[0093] Step 3: Solve model parameters

[0094] The densification load of the dot matrix structure under three loading rates is substituted into formula (3) to obtain the model parameters F0, A and B.

[0095] The maximum absorption energy of the dot matrix structure under three loading rates is substituted into formula (4) to obtain the model parameters W0, C and D.

[0096] Step 4: Evaluate the buffering energy absorption performance

[0097] The impact velocity of the separated mass is substituted into the model to calculate the densification load F d-v and the maximum absorption energy W v-max of the dot matrix structure under the impact velocity.

[0098] Evaluate the buffering energy absorption performance, in the case that the maximum absorption energy W v-max is greater than or equal to the kinetic energy E of the separated mass, the smaller the densification load F d-v is, the better the buffering performance of the dot matrix structure is.

[0099] Take a buffering dot matrix structure of a certain explosive device as an example, the bolt body flies out after the explosion of the bolt, the mass m of the bolt body is 0.35 kg, the impact velocity v is 70 m / s, the kinetic energy is 857.5 J, the cell wall thickness of the dot matrix structure is 0.5 mm, the inner recess angle is 45°, the cell height L is 4.8 mm, and the height of the dot matrix structure is 75 mm.

[0100] According to the calculation model in the patent, the densification displacement is 43.75 mm, and the displacement from the platform stage to the compaction stage is 42.4 mm-43.2 mm, which is close to the calculated value. According to the load-displacement curve under the loading rates of 0.0001 m / s, 0.001 m / s and 0.01 m / s, the densification load calculation formula is The maximum absorption energy formula is The calculation obtains that the densification load is 19.25 kN and the maximum absorption energy is 822 J when v is 70 m / s. According to the evaluation result, the dot matrix structure cannot completely absorb the impact energy of the bolt body, but it is quite close, and the calculation result is quite close to the test result of the firing test.

[0101] Although the present application has been disclosed with the above preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the present application by using the disclosed methods and technical contents without departing from the spirit and scope of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, which does not deviate from the technical solutions of the present application, belongs to the protection scope of the technical solutions of the present application.

[0102] That which is not described in detail in the specification of the present application is within the knowledge of the skilled person.

Claims

1. A method for evaluating the performance of a lattice structure buffer energy absorber for a pyrotechnic device, characterized by The method comprises the following steps: Collecting the mass of the separated mass and the impact velocity data of the lattice structure buffer energy absorption, and calculating the kinetic energy of the separated mass; According to the cell size of the lattice structure, the densification displacement of the lattice structure is calculated; The displacement control is used for the lattice structure compression test under the preset loading rate; According to the lattice structure compression test results, the densification load characteristic value of the lattice structure under each preset loading rate is obtained, and the maximum energy absorption characteristic value of the lattice structure under each preset loading rate is determined; According to the characteristic value parameters of the lattice structure under each preset loading rate and the corresponding lattice structure densification load, the lattice structure calculation model parameters are calculated; Using all the calculated lattice structure calculation model parameters and the kinetic energy parameters of the separated mass, the densification load and the maximum energy absorption under the impact velocity corresponding to the current kinetic energy parameters are calculated; The buffer energy absorption performance evaluation is carried out according to the densification load and the maximum energy absorption under the current impact velocity.

2. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 1, wherein: The calculation method of the kinetic energy of the separated mass is: In the formula, the mass of the separated mass is m, and the impact velocity is v0; The calculation method of the densification displacement of the lattice structure is: In the formula, the densification displacement of the lattice structure is h d , d is the cell thin shell wall thickness of the lattice structure; L is the cell height; S is the cell width; and H is the total height of the lattice structure.

3. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 1, wherein: The preset loading rate is preselected as V1, V2 and V3, and the preset loading velocity value is set according to the maximum energy that can be absorbed by the lattice structure; the load-displacement curve under different loading rates is obtained by carrying out the lattice structure compression test according to the selected preset loading rate.

4. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 1, wherein: According to the densification load characteristic value of the lattice structure under each preset loading rate, the calculation method of the lattice structure calculation model parameters is: In the formula, F d-v F0 is the load parameter, A represents the speed parameter, which is determined according to the material of the dot matrix structure, B represents the exponential parameter of the speed, and a specified constant is selected. In the formula, F0, A, and B are the calculation model parameters of the dot matrix structure.

5. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 4, wherein: According to the maximum energy absorption characteristic value of the lattice structure under each preset loading rate, the calculation method of the lattice structure calculation model parameters is: In the formula, W v-max represents the maximum energy absorbed by the dot matrix structure at a loading speed of v, W0 is an absorption energy parameter, C is a speed parameter, determined according to the material of the dot matrix structure, and D represents an exponential parameter of the speed, selected as a specified constant, wherein W0, C, and D are dot matrix structure calculation model parameters.

6. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 5, wherein: According to the impact velocity v0, the point array structure calculation model parameters are re-substituted to solve, the densification load characteristic value and the expression of the point array structure calculation model parameters, the maximum absorption energy characteristic value of the point array structure and the expression of the point array structure calculation model parameters are used to calculate the densification load F of the point array structure under the current impact velocity v0 d-v and the maximum absorption energy W v-max .

7. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 6, wherein: The specific standard of the buffer energy absorption performance evaluation is: When the maximum absorption energy W v-max The densification load F d-v is inversely proportional to the cushioning energy absorption performance of the dot matrix structure.

8. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 7, wherein: The lattice structure adopts an inner recessed hexagonal structure, and the relationship between the maximum energy that can be absorbed by the lattice structure and the densification displacement of the lattice structure during the lattice structure compression process is: In the formula, W max represents the maximum energy that the lattice structure can absorb; h d represents the densification displacement of the lattice structure, that is, the displacement at the moment when the thin-walled shells are all in contact and compacted; h is the compression displacement of the lattice structure; and F(h) is the stress value corresponding to the compression displacement h.

9. The lattice structure buffer energy absorption performance equivalent evaluation method for the initiating device according to claim 7, wherein: The material of the lattice structure is an alloy material.

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