KR102290751B1 - Bulletproof performance estimation method for Al composite material - Google Patents

Abstract

According to one aspect of the present invention, it provides a method for predicting the ballistic performance of an aluminum composite. The method for predicting the ballistic performance of the aluminum composite includes: placing a specimen including the aluminum composite in a dynamic compression test apparatus; measuring a dynamic compressive strength (F) value using the dynamic compression test apparatus; calculating a dynamic shock absorption energy (E) value from the dynamic compressive strength (F) value; and predicting the ballistic performance of the aluminum composite by calculating the penetration depth (D) from the calculated dynamic shock absorption energy (E) using Equation 1 below.
[Equation 1]
Penetration depth (D) = -0.03 × Dynamic shock absorption energy (E) + 6.38
(Here, the penetration depth (D) is the damage depth of the mold in contact with the aluminum composite material, and the dynamic shock absorption energy (E) is the value of the shock absorption energy received by the specimen per unit volume)

Description

Bulletproof performance estimation method for Al composite material

The present invention relates to a method for predicting the ballistic performance of an aluminum composite, and to a method for predicting the ballistic performance of an aluminum composite that can easily predict the ballistic performance even when a general ballistic impact test cannot be used.

For bulletproof tests on metal armor, small-caliber AP (Armor Piercing) bullets (Caliber30, Cailber50, 20mm, etc.) and large-caliber AP bullets (90mm, etc.) are used depending on the thickness of the plate. The ballistic velocity (V50), which corresponds to a 50% probability that the test bullet penetrates the plate, is defined as the ballistic limit (BL) and expressed as an index of bulletproof performance.

Penetration of metal armor material during the bulletproof test is judged by applying the protection criteria. This standard is considered complete penetration (CP) when the witness plate installed at the rear is damaged by debris even if the test projectile does not completely penetrate the board. It is a strict standard considering damage. Such bulletproof test procedures are stipulated in detail in the U.S. Military Standards (USATECOM TOP 2-2-710).

On the other hand, unlike other armor materials such as ceramics and polymer composite materials, metal armor materials must be considered not only the ballistic properties of the armor material itself but also the ballistic properties of the welded parts when evaluating the ballistic performance. Most of the metal armor material is used as a welded structure, because the weld joint is relatively weak compared to the base material.

The procedure for the bulletproof test of the weld, called the H-plate bulletproof test, is stipulated in the U.S. Military Standards (MIL-STD-1941). It is evaluated by measuring the crack length generated on the rear side of the weld by colliding a test bullet of a prescribed bullet velocity against an H-shaped weld bead.

However, these bulletproof tests are expensive and not economical, and due to the complexity of ballistic management, there are many procedural steps and time-consuming problems.

In order to solve this problem, the Hopkins method test is widely used because it can evaluate the correlation between material properties and the high-speed deformation characteristic factor required as a bulletproof structure, such as the critical strain required for the formation of adiabatic shear band, relatively easily without actual bulletproof test. have.

However, in the case of the bulletproof test, the results of which factors correlate with the bulletproof performance in what relationship are very limited, so there is a problem that all tests for each material must be conducted and reviewed.

Therefore, the present invention is to solve various problems, including the above problems, by confirming the correlation between the dynamic shock absorption energy and the ballistic penetration depth. The purpose is to provide a prediction method. However, these problems are exemplary, and the scope of the present invention is not limited thereto.

According to one aspect of the present invention for solving the above problems, it provides a method for predicting the ballistic performance of an aluminum composite.

The method for predicting the ballistic performance of the aluminum composite includes: placing a specimen including the aluminum composite in a dynamic compression test apparatus; measuring a dynamic compressive strength (F) value using the dynamic compression test apparatus; calculating a dynamic shock absorption energy (E) value from the dynamic compressive strength (F) value; and predicting the ballistic performance of the aluminum composite by calculating the penetration depth (D) from the calculated dynamic shock absorption energy (E) using Equation 1 below.

[Equation 1]

Penetration depth (D) = -0.03 × Dynamic shock absorption energy (E) + 6.38

(Here, the penetration depth (D) is the damage depth of the mold in contact with the aluminum composite, and the dynamic shock absorption energy (E) is the value of the shock absorption energy received by the specimen per unit volume)

In the method for predicting the ballistic performance of the aluminum composite, the dynamic compression test apparatus may include a Split Hopkinson Pressure Bar test apparatus.

In the anti-ballistic performance prediction method of the aluminum composite, the dynamic compressive strength (F) and the dynamic shock absorption energy (E) may have a proportional relationship with each other.

In the anti-ballistic performance prediction method of the aluminum composite, the dynamic compressive strength (F) and the fracture depth (D) may have an inverse relationship with each other.

In the method for predicting the ballistic performance of the aluminum composite, the deformation rate of the dynamic compression test apparatus may satisfy the range of 2600/s to 2800/s.

In the method for predicting the ballistic performance of the aluminum composite, the aluminum composite may include a ceramic reinforcement dispersed in an aluminum matrix.

In the anti-ballistic performance prediction method of the aluminum composite, the fraction of the ceramic reinforcement may satisfy the range of 30% to 60%.

According to the method for predicting the ballistic performance of the aluminum composite material of the present invention made as described above, it is possible to provide a method for simply predicting the ballistic performance of the aluminum composite material through a dynamic compression test without performing an expensive ballistic test. Of course, the scope of the present invention is not limited by these effects.

1 is a diagram schematically illustrating a dynamic compression experimental apparatus according to an experimental example of the present invention.
2 is a diagram schematically illustrating a ballistic test apparatus according to an experimental example of the present invention.
3 is a schematic diagram schematically illustrating a specimen applicable to the ballistic test apparatus shown in FIG. 2 .
4 and 5 are front and side photos of the aluminum composite specimen after the bulletproof test of the test specimens of the present invention.
6 is a side view of the STS304 base material after the bulletproof test of the test sample of the present invention.
7 is a strain graph according to the dynamic compressive strength after the bulletproof test of the test sample of the present invention.
FIG. 8 is a graph showing the results of fitting the dynamic shock absorption energy value and the penetration depth value calculated from the dynamic compressive strength of FIG. 7 .
9 is a graph showing the results of fitting the quasi-static shock absorption energy value and the penetration depth value calculated from the compressive strength in a quasi-static situation according to a comparative example of the present invention.
10 is a photograph showing the adiabatic shear deformation according to the deformation rate of the sample according to the experimental example of the present invention.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. Examples of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and the scope of the present invention is as follows It is not limited to an Example. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the spirit of the present invention to those skilled in the art.

Hereinafter, the present invention relates to a method for predicting the ballistic performance of an aluminum composite, and provides a method for predicting the ballistic performance of a specimen including the aluminum composite by using a dynamic compression test apparatus. Here, the aluminum composite includes a ceramic reinforcement dispersed in an aluminum matrix. The bulletproof performance varies depending on the degree to which the ceramic reinforcement is included in the aluminum matrix. Since a certain amount of the ceramic reinforcement is contained in the aluminum matrix, in order for the aluminum composite to have bulletproof properties, the fraction of the ceramic reinforcement must be in the range of 30% to 60%. Preferably, the fraction of the reinforcing material should satisfy the range of 35% to 60%, more preferably, it should satisfy the range of 40% to 60%.

The method for predicting ballistic performance of an aluminum composite material according to an embodiment of the present invention comprises the steps of placing a specimen including the aluminum composite in a dynamic compression test apparatus, and measuring the dynamic compressive strength (F) value using the dynamic compression test apparatus Step, calculating the dynamic shock absorption energy (E) value from the dynamic compressive strength (F) value and calculating the penetration depth (D) from the calculated dynamic shock absorption energy (E) using the following Equation 1 , and predicting the ballistic performance of the aluminum composite.

[Equation 1]

Penetration depth (D) = -0.03 × Dynamic shock absorption energy (E) + 6.38

(Here, the penetration depth (D) is the damage depth of the mold in contact with the aluminum composite, and the dynamic shock absorption energy (E) is the value of the shock absorption energy received by the specimen per unit volume)

Referring to Equation 1, the dynamic compressive strength (F) and the dynamic shock absorption energy (E) have a proportional relationship with each other, and the dynamic compressive strength (F) and the fracture depth (D) are inversely proportional to each other. have The above correlation is a very important factor, for example, it does not appear in a quasi-static situation. Here, the quasi-static situation refers to a general compression test test, and the correlation as in Equation 1 does not appear at a deformation rate that is relatively lower than the movement velocity of the ballistic during a general ballistic test.

In general, a ballistic impact test is known at a strain rate ^{of 10 4} /s to 10 ^{5 /s.} After the ballistic impact test, the aluminum composite specimen is fractured together with radical cracks. In the dynamic compression test for predicting bulletproof performance, after compression, at a low deformation rate, only cracks mainly occur in the shear direction, and fragmentation occurs actively from ^{10 3 /s.}

Therefore, in order to predict the ballistic performance of the aluminum composite, the deformation rate above a certain level must be maintained. However, even if the deformation rate is too fast, the aluminum composite material is damaged and the ballistic performance cannot be predicted. That is, the deformation rate of the dynamic compression test apparatus should satisfy the range of 2600/s to 2800/s. A dynamic compression test apparatus that satisfies this may use, for example, a Split Hopkinson Pressure Bar test apparatus, but if there is a compression test apparatus that satisfies the above strain rate range, it may be used.

<Experimental example>

An aluminum composite in which a ceramic reinforcement is dispersed in an Al7075 base material with a size of Φ5mm × 5mm was placed in the red marked area (Specimen) of the split Hopkins bar device having a similar strain rate and history experienced by the material during the bulletproof test shown in FIG. Then, a dynamic compression test was performed at a deformation rate of 2600/s to 2800/s to measure dynamic compressive strength and dynamic shock absorption energy.

As shown in FIG. 2 , an STS304 mold having a size of 300 mm × 300 mm × 20 mm in which a groove having a size of 100 mm × 100 mm × 10 mm was formed in the center was prepared. A specimen was prepared by loading the same aluminum composite material used in Experimental Example 1 into the groove provided in the mold. Thereafter, as shown in FIG. 3, using a projectile of M80 bullet, lead core, Φ7.62 × 51 mm, 9.6 g, each ballistic test was performed at a bullet velocity of 700 m/s and 850 m/s to destroy the aluminum composite. The depth and penetration depth of the STS304 mold were measured. At this time, as shown in the Side View of FIG. 2, the position of the aluminum composite was arranged in the direction in which the trajectory was flying.

<Comparative example>

A semi-static compression test was performed using a general compression test apparatus (not shown) in which the deformation rate experienced by the material during the ballistic test of the same aluminum composite material used in Experimental Example 1 was 10 ^{-3 .} Hereinafter, Comparative Example 2 may be understood as a quasi-static compression test result.

Table 1 below summarizes the types of specimens used in Experimental Examples and Comparative Examples.

Psalter ceramic
reinforcement ceramic
Reinforcement size
(μm) ceramic
Reinforcement fraction (%) dynamic compression
Strength (MPa) shock absorption
energy
(MJ/㎥) Composite
depth of destruction
(mm) base material
penetration depth
(mm) Experimental Example 1 SiC 7.9 ± 2.0 54.1 ± 1.5 1355 ± 20 96.8 5.8 3.5 Experimental Example 2 B ₄ C 4.3 ± 1.7 51.7 ± 2.1 1268 ± 113 81.8 6.7 3.8 Experimental Example 3 SiC 30.5 ± 14.1 49.5 ± 2.7 866 ± 43 110.9 8.3 3.2 Experimental Example 4 B ₄ C 38.2 ± 16.2 52.7 ± 2.3 1356 ± 106 124.9 7.5 2.7 Experimental Example 5 SiC
B ₄ C 8.3 ± 2.0
4.4 ± 1.9 30.1 ± 1.1
29.2 ± 1.6 1530 ± 85 160.0 4.9 1.5 Experimental Example 6 SiC 8.1 ± 1.9 11.2 ± 0.4 717 ± 41 148.9 9.0 5.6 Experimental Example 7 SiC 8.3 ± 2.3 29.7 ± 0.9 868 ± 57 111.7 8.7 4.6 Comparative Example 1 SiC 7.9 ± 2.0 54.1 ± 1.5 - 42.2 - 3.5 Comparative Example 2 B ₄ C 4.3 ± 1.7 51.7 ± 2.1 - 45.0 - 3.8 Comparative Example 3 SiC
B ₄ C 8.3 ± 2.0
4.4 ± 1.9 30.1 ± 1.1
29.2 ± 1.6 - 59.6 - 1.5 Comparative Example 4 SiC 30.5 ± 14.1 49.5 ± 2.7 - 43.6 - 3.2 Comparative Example 5 B ₄ C 38.2 ± 16.2 52.7 ± 2.3 - 48.2 - 2.7

In Table 1, the fracture depth of the composite material is a result of measuring the fractured depth from the surface of the composite material on a side-by-side basis, and the base material penetration depth is a result of measuring the fractured depth due to the impact from the surface of the parent material. Here, the composite fracture depth and base metal penetration depth values of the specimens of Experimental Examples 1 to 7 represent the measurement results at a strain rate of 850 m/s.

4 and 5 are a front photograph and a side photograph of an aluminum composite specimen after the bulletproof test of the experimental sample of the present invention, and FIG. 6 is a side photograph of the STS304 base material after the bulletproof test of the experimental specimen of the present invention.

4 and 5, when an impact was applied to the specimen at a speed of 700 m/s, there was no damage to the STS304 base material, and only the aluminum composite material was destroyed. On the other hand, according to FIG. 6, when an impact was applied to the specimen at a speed of 850 m/s, the aluminum composite did not penetrate during the impact, but the STS304 base material was damaged and warped.

7 is a strain graph according to the dynamic compressive strength after the bulletproof test of the test sample of the present invention.

The results of dynamic shock absorption energy calculated from the dynamic compressive strength are summarized in Table 1, and referring to FIG. 7, in the specimens of Experimental Examples 1 to 5, dynamic compressive strength, dynamic shock absorption energy and STS304 It can be seen that the penetration depth of the base material is inversely proportional to each other.

On the other hand, the specimens of Experimental Example 6 and Experimental Example 7 were specimens containing ceramic reinforcement at a fraction of 11.2% and 29.7%, respectively, and the penetration depth of the STS304 base material was 4 mm or more, indicating that it was not suitable as a bulletproof material. For this reason, when implementing an aluminum composite material, it was confirmed that an appropriate amount of ceramic reinforcement (the proportion of the ceramic reinforcement in the aluminum matrix must be at least 30% to predict the ballistic performance through the dynamic compressive strength test) must be contained.

8 is a graph showing the results of fitting the dynamic strain energy density and the depth of penetration calculated from the dynamic compressive strength of FIG. 7 , and FIG. 9 is a graph of the present invention. It is a graph showing the result of fitting the quasi-static shock absorption energy value and the penetration depth value calculated from the compressive strength in the quasi-static situation according to the comparative example.

Referring to FIG. 8 , the dynamic shock absorption energy value and the penetration depth have an inverse relationship with each other, and are expressed by the relational expression of Equation 1 above. Comparing the measured value with the actual value, it was confirmed that the error rate was also measured fairly accurately with 0.98002. Therefore, based on Equation 1, the penetration depth can be predicted through the results of the dynamic compressive strength test.

Referring to FIG. 9 , there was no correlation between the static strain energy density and the depth of penetration when the compression was evaluated at a ^{deformation rate of 10 -3.} In quasi-static compression conditions, it is limited by the difference in strain rate and heat generation from the ballistic test conditions. For example, ^{during compression at a deformation rate of about 10 3} /s, the temperature rises by about 300° C. to 500° C. due to heat generation. In fact, it is impossible to simulate at a low strain rate because thermal energy of 500°C or higher is generated during the ballistic test.

10 is a photograph showing the adiabatic shear deformation according to the deformation rate of the sample according to the experimental example of the present invention.

Strain Rate
(s ^-1 ) Cracking
of SiC _p s SiC _p /matrix Interfacial Debonding Local Deformation
of Al Matrix 10-3 51 41 8 2800 45 25 30

Referring to FIG. 10 and Table 2, an adiabatic shear band actively occurs in a general high-speed test, and a very large amount of adiabatic shear deformation was observed in the specimen after performing the ballistic test. In addition, in the case of an aluminum matrix with a low melting point due to heat generation during high-speed deformation, melting occurs, and many were found at a deformation rate of 2800/s, confirming that it is similar to the bulletproof test environment. On the other hand, in the low-speed deformation, relatively little melting or matrix deformation of the aluminum matrix was observed.

Although the present invention has been described with reference to the embodiment shown in the drawings, which is merely exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims (7)

placing a specimen comprising an aluminum composite in a dynamic compression test apparatus;
measuring a dynamic compressive strength (F) value using the dynamic compression test apparatus;
calculating a dynamic shock absorption energy (E) value from the dynamic compressive strength (F) value; and
Predicting the ballistic performance of the aluminum composite by calculating the penetration depth (D) using the following Equation 1 from the calculated dynamic shock absorption energy (E);
including,
The aluminum composite includes a ceramic reinforcement dispersed in an aluminum matrix, and the fraction of the ceramic reinforcement satisfies the range of 30% to 60%,
A method for predicting the bulletproof performance of aluminum composites.
[Equation 1]
Penetration depth (D) = -0.03 × Dynamic shock absorption energy (E) + 6.38
(Here, the penetration depth (D) is the damage depth of the mold in contact with the aluminum composite material, and the dynamic shock absorption energy (E) is the value of the shock absorption energy received by the specimen per unit volume) The method of claim 1,
The dynamic compression test apparatus includes a Split Hopkinson Pressure Bar test apparatus,
A method for predicting the bulletproof performance of aluminum composites. The method of claim 1,
The dynamic compressive strength (F) and the dynamic shock absorption energy (E) have a proportional relationship with each other,
A method for predicting the bulletproof performance of aluminum composites. The method of claim 1,
The dynamic compressive strength (F) and the penetration depth (D) have an inverse relationship with each other,
A method for predicting the bulletproof performance of aluminum composites. The method of claim 1,
The strain rate of the dynamic compression test apparatus satisfies the range of 2600 / s to 2800 / s,
A method for predicting the bulletproof performance of aluminum composites. delete delete

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