RU2486512C2 - Method of determining working efficiency of explosives - Google Patents

Abstract

FIELD: blasting operations.

SUBSTANCE: weighed portion of the explosive of a predetermined mass is initiated, and the medium pressure level is recorded in the point remote from the test sample of the explosive at a predetermined distance.

EFFECT: improvement of certain characteristics, such as improvement of accuracy of evaluating the properties of explosives, reducing the required amount of explosives for testing, and simplification of the test procedure.

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Description

The invention relates to the field of testing explosives (EXPLOSIVES), in particular to determining the operability of explosives.

An analogue of the proposed method is a method for determining the performance of explosives in a lead bomb, described in [1]. This method is based on determining the expansion of the bomb channel by the explosive charge explosion products and extends to powdery, granular, liquid, viscous and plastic explosives with a critical detonation diameter of not more than 20 mm.

The disadvantages of a similar method for determining the working capacity of explosives include:

- large quantities of explosives used for testing, for example, for testing use three experiments with explosive weights of 10 g each;

- the high cost of materials used in the tests, for example, the equipment used in the lead bomb method is disposed of after each test and is not reused;

- insufficient efficiency of the methods.

As a prototype method, the method described in the patent [2] is selected. In the prototype method, a sample of explosives with a detonator is installed in a sealed chamber, in the housing of which a pressure sensor is mounted. Using the detonator, the test explosive is blown up and its characteristics are estimated by the magnitude of the quasistatic pressure in the chamber after the explosion.

The disadvantage of the prototype is that the tests are carried out in a special sealed chamber that complicates the test procedure, and the presence of a detonator reduces the accuracy of the evaluation of the properties of the test explosive, in addition, large explosive samples (30 g) are required for testing.

The technical result of the present invention is to improve the accuracy of evaluating the properties of explosives, reducing the required number of explosives for testing, as well as simplifying the test procedure.

The technical result is achieved by the fact that from the measured values of the pressure of the medium arising under the action of the energy of the explosion in an elastic medium, the characteristic of the power of acoustic vibrations is calculated, which is taken as the absolute characteristic of the working capacity of the explosive, and then the ratio of the measured characteristic of the power of acoustic vibrations of the investigated explosive to the characteristic power of acoustic vibrations of the reference explosive and the resulting value is taken in as a relative measure of explosive performance.

The essence of the proposed method lies in the fact that the parameters of the shock waves (maximum pressure and momentum of the compression and rarefaction phases in the front of the shock wave) and sound vibrations are determined by the same explosive properties that determine their operability (explosiveness), including the heat of explosion, the volume of detonation products, and detonation velocity [3]. The performance of explosives based on the analysis of sound generated by detonation is proposed to be calculated by the formula

$$\sigma =\max \left(\frac{\mathrm{one}}{t}{\displaystyle \underset{0}{\overset{t}{\int }}{s}^{2}dt}\right)(\mathrm{one})$$

where s is the realization of the measured sound pressure signal, t is time.

In practice, when using analog-to-digital conversion of a sound pressure signal with uniform sampling and quantization, expression (1) is converted to the form (2):

$$\sigma =\max \left({\frac{{\displaystyle \sum _{i=0}^j{s}_i^2}}{j\Delta t}|}_{j=\mathrm{0\; ..}N}\right)(2)$$

where s _i is the value of the sound pressure reading, Δt is the sampling interval of the sound pressure signal, N is the number of the last reading of the signal implementation.

The values of σ calculated by the formula (2) allow us to unambiguously differentiate explosives by their operability, which justifies the applicability of this method.

To create oscillations of the medium with levels reliably recorded by measuring equipment, much smaller quantities of explosives (tenths and hundredths of a gram) are required than in standard methods for testing energy-saturated materials (from 10 g to 200 g). This allows you to minimize the amount of explosives required for testing.

In addition, in the inventive method, it is proposed to detonate the test specimen of the explosive without an initiating explosive (for example, using a fire beam, impact on the pile, etc.), which allows to exclude the contribution of the initiating explosive from the measured sound pressure.

Moreover, the inventive method does not require additional special equipment in the form of cameras, bombs, etc., which simplifies its practical implementation.

The proposed method is carried out in the following steps. Take a sample of the test explosive of a certain mass, the minimum value of which is due to the critical size of the detonation, placed in the shell (for example, a cap) or without a shell (for example, in the form of a checker). The sample is suspended in air so that it is at a certain distance from the sound pressure sensor, provided that the reflected waves are weaker than the direct wave. Then, an explosive is initiated and the sound pressure value is measured, digitized and recorded. Then, according to the characteristics of the measured signal, the absolute operability value is calculated by the formula (2). To assess the relative working capacity, the absolute working capacity is additionally measured by the above method for a substance that is taken as a standard (for example, TNT). Then find the ratio of the health of the test explosive to the health of the reference explosive.

$$B=\frac{{\displaystyle \sum _{i=0}^n{s}_{xi}^2}}{{\displaystyle \sum _{i=0}^n{s}_{0i}^2}},(2)$$

where s _x is the signal received during the “sample” of the substance with the required working capacity, s ₀ is the signal received during the “sample” of the substance with the reference working capacity (TNT).

Example. The experimental design is shown in Fig. 1, where 1 is a sound pressure sensor (microphone), 2 is an amplifier, 3 is a power source and polarization voltage, 4 is an ADC, 5 is a computer, 6 is a copra column, 7 is a load, 8 is a roller instrument with test sample, 9 - anvil.

Testing explosives for performance, in accordance with the claimed method, was carried out as follows. To initiate the explosive transformation of explosive bombs, the mechanical effect of a falling load weighing 10 kg from a height of 1 m was used. To create the indicated shock loads, a K-44-2 coper was used. Sampling, preparation and weighing of samples were carried out in accordance with the methodology described in GOST 4545-88. During the experiments, a test substance weighing 50 mg was weighed on a balance that provided an absolute error of not more than 1 mg, and was placed in a roller device according to GOST 4545-88. The sound pressure signal caused by the explosive transformation of explosives was recorded by a free field microphone with a sensitivity of 4 mV / Pa, type 40BF from GRAS with a 26AA preamplifier. The microphone was mounted in the direction of the test sample at a distance of 1 meter. The preamplifier output was connected to the input of a power source and a polarization voltage of type 12AR. The output signal was subjected to analog-to-digital conversion with an accuracy corresponding to 13 binary bits per voltage range ± 10 V.

In the process of testing, 10 samples of TNT, TENA, RDX, and tetryl were initiated. The recorded sound pressure signals were digitally aligned in time, averaged, and the accumulated sums of squares of the signal samples were determined.

As a result of processing the sound pressure signals according to the formula (2), the values of relative working capacity normalized to TNT were obtained. Comparison of normalized health data on the value of the health of the heating element, calculated in accordance with the proposed method and the standard method of a lead bomb, is shown in figure 2.

Used Books

1. GOST 4546-81. Explosives. Methods for determining the explosiveness.

2. US Patent No. 7669460. Small-scale shock reactivity and internal blast test / Harold W. Sandusky, Richard H. Granholm, Douglas G. Bohl. Date of patent: Mar. 2, 2010.

3. Explosion Physics / Under. Ed. L.P. Orlenko. - Ed. 3rd, rev. - In 2 vols. - M .: FIZMATLIT, 2002. - 832 p.

Claims (1)

The method for determining the performance of explosives, which consists in initiating a sample of explosive of a certain mass and recording the level of pressure of the medium at a point remote from the test sample of explosive at a certain distance, characterized in that according to the measured values of the pressure of the medium arising under the influence of the explosion energy in an elastic medium, the characteristic of the power of acoustic vibrations is calculated, which is taken as the absolute performance characteristic of explosives second substance, and then finding the ratio of the measured power characteristic acoustic vibrations of the test explosive power to the characteristic acoustic vibrations reference explosive and the obtained value is taken as a relative measure of performance of the explosive.

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