A method of controlling pre-control fragment dispersion angle

Abstract

The application provides a method for controlling a pre-control fragmentation angle, a prefabricated groove is processed in a shell, and the prefabricated groove comprises equidistantly arranged annular grooves and longitudinal grooves; wherein the groove width direction of the annular groove is determined as follows: the annular groove is equidistantly arranged along the axial direction according to the height of the fragment, the spacing of the annular groove is determined, a reference circular arc curve is connected with the annular groove and the center of the reference circular arc according to the traditional focusing type or scattering type shell bus, and the direction of the connecting line is the groove width direction of the annular groove; if the reference circular arc is concave, the focusing type fragment is formed; and if the reference circular arc is convex, the scattering type fragment is formed. The pre-control fragmentation angle of the pre-control fragment warhead can be controlled by changing the angle of the annular groove.

Description

Technical Field

[0001] This invention belongs to the field of ammunition design, and in particular to a method for controlling the dispersion of fragments from a pre-controlled warhead. Background Technology

[0002] Pre-controlled fragments are one of the commonly used destructive elements in lethal weapons. After the explosive charge detonates, the high-pressure detonation products drive the fragments at high speed, ultimately penetrating the target and causing damage. To optimize their dispersion design, the fragment dispersion angle needs to be adjusted to achieve different damage requirements. Therefore, some methods for controlling the fragment dispersion angle are proposed.

[0003] In engineering practice, the Shapiro formula is widely used to calculate fragment dispersion angles. Focusing and scattering fragments are controlled by designing the shell generatrix to manage the axial dispersion characteristics of fragments driven by explosives, thus obtaining the fragment dispersion angle distribution as required. The Shapiro formula can be used to design pre-controlled fragment shell curves that achieve different fragment dispersion distributions. Based on the Shapiro formula, the generatrix of the pre-controlled fragment shell can be designed using the infinitesimal element method according to the fragment impact point distribution on the target. Focusing fragment shells are typically designed as waist-shaped (thin in the middle and thick at both ends), while scattering fragment shells are designed as drum-shaped (thick in the middle and thin at both ends).

[0004] Selective laser melting (SLM) evolved from powder bed selective laser sintering. Using metal powder as the raw material, a high-energy-density laser beam melts and deposits the powder layer by layer onto a metal substrate, forming a metal part. For some complex-shaped components that are difficult to manufacture using traditional processes, metal additive manufacturing technology can produce parts that meet the requirements.

[0005] Considering the limitations of both focusing and scattering fragment shells, their shape is restricted by the shape of the carrier compartment. Both waist-shaped and drum-shaped shells will lose some of the charge mass, which is detrimental to the initial fragment velocity and ultimately affects the lethality. Therefore, a method is needed that can control the fragment scattering angle without being restricted by the shape of the carrier compartment or losing the charge mass. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the pre-controlled fragment dispersion angle, which can adjust the fragment dispersion angle based on a cylindrical shell to meet different kill range requirements.

[0007] The technical solution to achieve the purpose of this invention is as follows:

[0008] A method for controlling the pre-controlled fragment scattering angle involves machining pre-fabricated grooves inside a shell, including circumferential grooves and longitudinal grooves arranged at equal intervals.

[0009] The method for determining the width direction of the circumferential groove is as follows: the cylindrical shell is divided axially into equal parts according to the fragment height to determine the spacing of the circumferential groove. The generatrix of the traditional focusing or scattering shell is used as a reference arc curve. The center of the circumferential groove is connected to the center of the reference arc, and the direction of the line is the width direction of the circumferential groove. If the reference arc is concave, a focusing fragment is formed; if the reference arc is convex, a scattering fragment is formed.

[0010] The significant advantages of this invention compared to existing technologies are:

[0011] This invention proposes a method for adjusting the dispersion angle of pre-controlled fragments. Based on additive manufacturing technology, it achieves the effect of controlling the dispersion angle of pre-controlled fragment warhead fragments by changing the angle of the circumferential pre-formed groove. This method can achieve different dispersion angle distributions by adjusting the angle of the circumferential pre-formed groove while ensuring a consistent shape of the casing generatrix. The effectiveness of the method is verified through numerical simulation. Simulation results show that the method can adjust the fragment dispersion angle and can provide a reference for the design of pre-controlled fragment warheads. Attached Figure Description

[0012] Figure 1 These are schematic diagrams of the shell shapes for different types of fragment dispersion. (a) is a focusing fragment shell (waist drum shape); (b) is a dispersion fragment shell (drum shape).

[0013] Figure 2 This is a schematic diagram of the central groove of a pre-controlled fragment cylindrical shell manufactured by additive manufacturing. (a) is a focused pre-controlled fragment cylindrical shell; (b) is a scattered pre-controlled fragment cylindrical shell; (c) is a schematic diagram of the central pre-fabricated groove (longitudinal groove) of the cylindrical shell.

[0014] Figure 3 Schematic diagrams of the stress and dispersion direction of the fragments. (a) is a schematic diagram of the stress analysis of the focused pre-controlled fragments; (b) is a schematic diagram of the stress analysis of the dispersed pre-controlled fragments.

[0015] Figure 4 These are finite element models of additive manufacturing pre-fragmented cylindrical shells. (a) is a focused pre-fragmented cylindrical shell; (b) is a scattered pre-fragmented cylindrical shell.

[0016] Figure 5 The results are from pre-controlled fragment dispersion in additive manufacturing. (a) is focused pre-controlled fragment; (b) is dispersed pre-controlled fragment.

[0017] Figure 6 It is a curve showing the initial velocity distribution of pre-controlled fragments in additive manufacturing.

[0018] Figure 7 It is a curve showing the pre-controlled fragment scattering angle distribution of additive manufacturing. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] This invention relates to a novel additive manufacturing process that allows pre-formed grooves to be created inside the shell wall, while the inner and outer surfaces of the shell remain groove-free. Experiments show that this pre-formed groove ensures shell strength while effectively improving fragmentation rate. Furthermore, the inner and outer surfaces of this fragment shell remain continuously smooth, which is beneficial for loading and storage.

[0021] To achieve fragment focusing, the housing or fragment controller is typically manufactured as follows: Figure 1 (a) shows the shape; if an increased fragment dispersion range is required, the housing or fragment controller should be machined as shown. Figure 1 The shape shown in (b) illustrates this. It can be seen that, under the same maximum diameter constraint, Figure 1 (a) and Figure 1 (b) Compared to a cylindrical shape, the housing or fragment controller volume is smaller, which means the charge is also smaller, resulting in a lower loading ratio and thus a lower initial fragment velocity, which reduces the overall lethality.

[0022] Considering the characteristic that the scattering direction of both focused and scattered fragments is close to the normal direction of the shell generatrix, an additive manufacturing pre-controlled fragment shell is designed. The cylindrical shell is divided axially into sections equal to the fragment height to determine the spacing of the circumferential grooves. Using the generatrix (arc) of a traditional focused or scattered shell as a reference arc curve, the centers of the circumferential grooves and the reference arc are connected. The direction of the connection is the groove width direction (shell thickness direction). A concave reference arc can form focused fragments, such as... Figure 2 As shown in (a); if the reference arc protrudes outward, it will form scattered fragments. Figure 2 As shown in (b). To ensure shell strength while improving fragment formation rate, the width of the circumferential and longitudinal grooves is set to 60% of the shell wall thickness, and the groove thickness is no more than 0.3 mm. Moreover, the smaller the groove thickness, the lower the fragment loss mass. The cylindrical shell is made of a high-strength and high-toughness metal to ensure sufficient penetration capability of the fragments.

[0023] Using circumferential grooves to restrict the axial dispersion of fragments involves utilizing the interaction forces between fragments to change the direction of the total resultant force on each fragment, thereby altering the direction of the fragment velocity and ultimately changing the fragment dispersion angle. For example... Figure 3 As shown in (a), for focused fragments, after the charge center detonates, the detonation wave propagates as a spherical wave, and the detonation wave arrives first. Figure 3 (a) Fragment ① moves under pressure. Simultaneously, fragments ① and ②, due to their material connection, compress each other, resulting in equal but opposite forces, perpendicular to the circumferential groove between the fragments. The forces acting on fragment ① from surrounding fragments do not change its dispersion direction, only affecting its dispersion velocity. Fragment ② experiences pressure F from fragment ③. 32The pressure F of fragment ② on fragment ① is greater than that of fragment ① 12 F 32 and F 12 Under the action of the force, the final force F1 of fragment ② deviates from the direction of the detonation force, thereby changing the velocity direction of fragment ② and ultimately changing the dispersion angle. Fragments ③ and ④ are similar, ultimately enabling the shell to achieve fragment focusing.

[0024] like Figure 3 As shown in (b), for scattering fragments, after the charge center detonates, the detonation wave propagates as a spherical wave, and the detonation wave arrives first. Figure 3 (b) Fragment ① moves under stress. Simultaneously, fragments ① and ②, due to their material connection, stretch each other, resulting in equal but opposite forces that are perpendicular to the circumferential groove between the fragments. The tensile force on fragment ① from the surrounding fragments does not change its dispersion direction, only affecting its dispersion velocity. Fragment ② experiences a tensile force F from fragment ③. 32 The tensile force F exerted by fragment ② on fragment ① is greater than that of fragment ①. 12 F 32 and F 12 Under the action of the force, the final force F1 on fragment ② deviates from the direction of the detonation force, thereby changing the velocity direction of fragment ② and ultimately changing the dispersion angle. Fragments ③ and ④ are similar, ultimately causing the shell to achieve fragment dispersion.

[0025] To verify the effectiveness of the above method, numerical simulations were performed on the designed additively manufactured pre-controlled fragmentation shell fragmentation and dispersion. The ALE method was used to simulate detonation-driven fragments, the Euler algorithm was used for the explosive and air, and the Lagrange algorithm was used for the fragmentation shell. The numerical simulation model included the explosive charge, the additively manufactured shell, and air, neglecting components such as the end cap fuse. The simulation model mainly consisted of three materials: explosive charge, air, and metal. The explosive charge material was 8701, and the explosive density was 1.695 g / cm³. 3 The detonation velocity was 8425 m / s, and the Chapman-Jouguet (CJ) pressure was 29.5 GPa. The equation of state for the high-energy explosive was the Jones-Wilkins-Lee (JWL) equation. The Johnson-Cook (JC) strength model was used to describe the additively manufactured shell. The JC model represents the strength behavior of typical metals under high strain, high strain rate, and high temperature. This model comprehensively considers strain hardening effects, strain rate effects, and temperature effects. The detonation method was a central single-point initiation.

[0026] The established finite element model (1 / 2 model, finite element mesh not displayed) of the pre-controlled additive manufacturing shell is as follows: Figure 4 As shown. Figure 4 (a) is a focusing fragment shell, and Figure 2 (a) Correspondence; Figure 4(b) is a fragmented shell, and Figure 2 (b) Corresponding. The inner diameter of the shell is 70 mm, the outer diameter is 82 mm, and the height is 96 mm. The shell is prefabricated with 15 circumferential grooves, totaling 16 layers of fragments. The longitudinal grooves are shown in 2(a), totaling 32 grooves, with 32 fragments in each layer.

[0027] Numerical simulation results are as follows Figure 5 As shown, the focused fragments are more densely distributed axially than the scattered fragments, and the central fragments of the focused fragments scatter further, indicating a higher initial fragment velocity. Fragment velocity data for both types of shells were extracted, and the velocity after stabilization following the charge was used as the fragment velocity. The velocity of each fragment layer was plotted as a curve, as shown below. Figure 6 As shown. From Figure 6 It can be seen that the initial velocities of the fragments in the middle and both ends of the focused fragment shell are significantly higher, compared to... Figure 5 The conclusions are consistent. Fragment velocity data for both types of shells were extracted. The velocity after stabilization following the charge was used as the initial fragment velocity. The axial velocity of each fragment layer was then extracted, and the scattering angle of each fragment layer was calculated and plotted as a curve, as shown below. Figure 7 As shown. From Figure 7 It can be seen that the fragment scattering angle in the middle of the focused fragment shell changes very gently, almost horizontally, which is consistent with the characteristics of the focused fragment scattering angle.

[0028] Numerical simulation results show that adjusting the angle between the circumferential precast groove and the axis can change the scattering angle distribution of the fragments, thereby achieving the requirement of fragment focusing or scattering.

Claims

1. A method for controlling the pre-controlled fragment scattering angle, characterized in that, Pre-fabricated grooves are machined inside the shell, including circumferential grooves and longitudinal grooves arranged at equal intervals; The shell is a cylindrical metal shell. The method for determining the width direction of the circumferential groove is as follows: the cylindrical shell is divided axially into equal parts according to the fragment height to determine the spacing of the circumferential groove. The generatrix of the traditional focusing or scattering shell is used as a reference arc curve. The center of the circumferential groove is connected to the center of the reference arc. The direction of the connecting line is the width direction of the circumferential groove. If the reference arc is concave, a focusing fragment is formed. If the reference arc is convex, a scattering fragment is formed.

2. The method for controlling the pre-controlled fragment scattering angle according to claim 1, characterized in that, The circumferential groove and the longitudinal shell are formed using additive manufacturing methods.

3. The method for controlling the pre-controlled fragment scattering angle according to claim 1, characterized in that, The width of the circumferential and longitudinal grooves is 60% of the shell wall thickness, and the groove thickness is no more than 0.3 mm.

4. The method for controlling the pre-controlled fragment scattering angle according to claim 1, characterized in that, Adjust the effect of fragment focusing or fragment scattering by changing the radius of the reference arc.

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