SU1670469A2 - Device for impact testing - Google Patents

Abstract

This invention relates to a testing technique. The purpose of the invention is to improve working conditions by reducing impulse noise without increasing the length of the device. The device comprises a barrel 1, a piston 2 installed therein for accommodating a test article 3, a high pressure chamber 4 connected by a channel 5 to a valve 6 with a pre-piston cavity 7 of the barrel 1, an additional piston 8, a clamp 9 of the piston 2, a trap 10 of the piston 2, a fixture stopping the piston 8 upon rebound, means for forming a shock pulse in the form of holes 16, in part of which plugs 17 are installed, and in the other — chokes 18 and a silencer including a gas collecting chamber 24, covering the part of the barrel 1 between pistons 2 and 8, and communicated with camera 2 4 by channel 26 of the exhaust pipe 25, the length of which is selected from the condition of reducing the pressure of the exhaust gases at the outlet of the pipe 25 to ambient pressure. The presence of such a silencer eliminates exhaust gases under high pressure, accompanied by impulse noise. 1 il.

Description

The invention relates to a testing technique, in particular, to devices for testing products for the impact of a shock load, and is an improvement of the basic invention according to the authors. St. No. 1295252.

The purpose of the invention is to improve working conditions by reducing impulse noise without increasing the length of the device.

The goal is achieved by supplying the device with a silencer in the form of a gas collecting chamber and an exhaust pipe connected to it, the length of which is chosen because of the pressure of the exhaust gases at the exit from the pipe to the ambient pressure.

The drawing shows the described device for shock tests.

The device comprises a barrel 1, a piston 2 mounted therein for accommodating

the test article 3, the high-pressure chamber 4 connected by channel 5 to the valve 6 with the pre-piston cavity 7 of the barrel 1, an additional piston 8 placed in the pre-piston cavity 7, the clamp 9 of the piston 2 made in the form of a breakable element installed in the wall of the barrel 1, a trap 10 piston 2, a device for stopping an additional piston 8 during a rebound, made in the form of protruding inside the barrel 1 through the longitudinal grooves 11 in its wall springed by means of an elastic ring 12 one-sided stops 13, which are fixed to by the power of the hinges 14 on the friction element 15, and the means for forming the shock pulse, which are a system of holes 16 along the length of the barrel 1 along which the plugs 17 are installed, and the chokes 18 in the other.

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A channel 5 has an inlet throttle washer 19. The high pressure chamber 4 is connected to a high pressure source (not shown) through the opening 20. The pressing force of the friction element 15 is controlled by a clamp 21. A plastic damping gasket 22 is fixed to the rear end of the auxiliary piston 8. The barrel 1, the trap 10 and the high pressure chamber 4 are mounted on the base 23. The device also comprises an assembly gas chamber 24 installed axially of the barrel 1, covering a section of barrel 1 between pistons 8 and 2, communicating with the chamber 24 and open at tor- ATC exhaust pipe 25 disposed parallel to the barrel 1. The gas-collection chamber 24 and the pipe 25 communicated by a channel 26. Tube 25 is set on the basis of 23.

The length of the exhaust pipe 25 is selected because of the pressure of the exhaust gases at the exit from the pipe to the pressure of the surrounding medium. This condition is satisfied when the following relations are satisfied:

Uo (Pi / k - Pj / k) - Pj / k F Li Tp

; (D

LTP UT; (2)

s; F, (3)

where LTp is the length of the exhaust pipe 25;

Uo is the volume of chamber 4 of high pressure;

Ro is the initial gas pressure in the high-pressure chamber 4;

K is the adiabatic constant of the gas enclosed in the high-pressure chamber 4;

PC is the pressure in the environment;

F is the cross-sectional area of the bore 1;

LI - the length of the upper part of the barrel 1;

S is the cross-sectional area of the exhaust pipe 25;

CT - stem length 1.

A similar effect of reducing impulse noise can be achieved with a corresponding increase in the length of the accelerating part of the barrel 1. To do this, it is necessary to reduce the gas pressure that accelerates the additional piston 8 to the ambient pressure when the additional piston 8 reaches the required maximum speed. However, calculations show that this requirement leads to an unacceptable increase in the length of the trunk and in practice. hence the entire device.

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The percussion test device operates as follows.

An additional piston 8 is installed in the barrel 1. Thereafter, the piston 2 is installed in the barrel 1 with the product 3. In accordance with the test conditions, the openings 16 in the barrel 1 are opened (by unscrewing the threaded plugs 17). This necessarily opens a part of the holes 16 in the area of the barrel 1 between the pistons 2 and 8, the number of which and the location are determined by the test conditions of the product 3. The chokes 18 are installed in the open holes 16.

A washer 19 is installed in channel 5. The position of piston 2 is fixed by latch 9. Compressed gas (air) is fed into chamber 4 from source of pressure through opening 20. Then opening 20 is blocked, in this state the device is prepared for testing the product.

When the valve 6 is activated, the compressed air from the chamber 4 through the channel 5 through the washer 19 enters the pre-piston cavity 7, the air pressure in it increases.

When the pressure of air in the cavity 7 on the piston 8 reaches a value sufficient to overcome the friction force, the rest of this piston 8. The latter begins, accelerating, to move in the barrel 1. The speed of the piston 8 increases. The compacted air formed in front of the piston 8 is discharged through the holes 1 b, the grooves 11 located in the section of the barrel 1 between the pistons 2 and 8, the gas collection chamber 24, the channel 26 and the exhaust pipe 25 to the atmosphere. When the piston 8 moves in the area of the barrel 1 until it passes through the open holes 16, the piston 2 remains stationary, as it is fixed by a latch 9. At the time of the passage of the holes 16 and the slots 11, the piston 8 acquires maximum speed. With a constant initial air pressure in the chamber 4, the speed of the piston 8 can be controlled by the number of open holes 16 in the barrel and by changing the flow area of the washer 19. During forward stroke, the piston 8 pushes the stops 13, which deviate in the radial direction at the hinges 14 and are displaced from the channel trunk 1. Due to the presence of the elastic ring 12 and the choice of the appropriate profile of the contacting surfaces of the piston 8 and the stop 13 during the forward stroke of the piston 8, this interaction does not significantly impede the movement of the piston 8. After the right Boating piston 8 of openings 16 and slots 11 located on the trunk portion 1 between the pistons 2 and 8, the stops 13 hold the starting

position. After the piston passes through the openings 16 and the grooves 11 ohms, it begins to compress the air in the part of the barrel 1 formed by the piston 8 and the piston 2 (in the initial state, the air in the barrel 1 is under atmospheric pressure). When the air pressure on the piston 2 exceeds a certain value, the latch 9 collapses and the piston 2 is released. As the piston 8 continues to move, the air pressure on the piston 2 increases and reaches its maximum value at the time of the closest approach of the pistons 8 and 2. At this time, a peak value is formed of the shock acceleration acting on article 1, After energy is exchanged between pistons 8 and 2, piston 2 acquires maximum speed. After exiting the barrel 1, the piston 2 is braked by the gun 10 at the level of braking acceleration acceptable for product 3. The trap 10 is made, for example, in the form of dampers-i and masses placed in the guides.

Reproducible shock acceleration parameters can be adjusted by collecting a portion of the air from the barrel 1 to the atmosphere through the holes 16 and throttles 18.

In the absence of a device to stop the piston 8, the latter, moving in the opposite direction, compresses the air in the pre-piston cavity 7 The compressed air of the cavity 7 expands and re-accelerates the piston 8, which can lead to a repeated direct (very intense) collision of the pistons 8 and 2 , but already outside the barrel 1, which ultimately leads to an unacceptable repeated shock loading of the product 3. Due to the availability of a means for stopping the additional piston 6 during a rebound, the non-operational action of the shock acceleration is tested emoe product 3 is eliminated.

After the end of the working interaction of the pistons 2 and 8, the last one at the rebound

moves in the opposite direction, reaches the stops 13 and, interacting with them through the damping gasket 22, stops. The energy of the reverse stroke of the piston 8

dissipates due to friction losses when the stops 13 are moved relative to the barrel 1 (in the axial direction).

When the working acceleration of the additional piston 8 at the time of passage of the piston

8 open holes 16 and grooves 11, it acquires the desired maximum speed. The exhaust gas (behind the piston 8), which is the main source of impulse noise during operation of the device, is discharged

into the atmosphere, passage through the chamber 24, channel 26. the pipe 25 into the atmosphere, the parameters of the pipe 25 according to the above ratios are chosen so that the pressure of the exhaust gases is equal to the pressure of the environment, which reduces the rate of gas outflow to the atmosphere, and consequently, impulse noise level. The length of the pipe does not exceed the length of the stand,

Thus, supplying a shock test device with a silencer reduces impulse noise during operation and does not increase its length.

Claims (1)

Invention Formula Device for impact tests on the author. St. N: 1295252, characterized in that, in order to improve working conditions by reducing impulse noise without increasing the length of the device, it is equipped with a gas collecting chamber covering the barrel in the section between the pistons and communicated with this chamber and an exhaust pipe open at both ends parallel to the trunk, the length of which is chosen from the condition of reducing the pressure of exhaust gases at the exit of the pipe to the environment. W 465 7 lit 15 ft 13 12 # „W.L.D ... / .. /. / N U 18 ® 1 10