SU1555628A2 - Method and apparatus for exciting damped vibrations of object - Google Patents

Abstract

This invention relates to a testing technique. The purpose of the additional invention is to increase the reliability of the tests when using a piston located between two hydraulic springs to excite oscillations of the object due to a more accurate setting of the initial differential pressure in the springs. The goal is achieved by creating a pressure differential by pushing a body of the required volume into one of the hydraulic springs. The device that implements the described method includes a housing 1, in the cavity 2 of which a piston 3 is installed with a rod 4 supported on a ruptured membrane 5, a two-stage piston 7, a step of larger diameter which is placed in an additional cavity 8 communicated with the cavity 2 by an axial bore 9, gunpowder charge 11 installed in cavity 6, and additional charge 12 placed in cavity 8. Piston 3 divides cavity 2 into chambers 15 and 16 for liquid. A stop 17 is formed in the cavity 8. The housing 1 is fixed to the object under test 18. When the charge 12 is ignited, the piston 7 is pushed into the chamber 15 and creates a well-defined pressure drop. When charge 11 is triggered, the membrane 5 is destroyed, and the piston 3 begins to oscillate, transmitted through the housing 1 to the object 18. 1 sludge.

Description

The invention relates to a testing technique, in particular, methods for initiating damped oscillations of a test object and devices for carrying out this method, and is an improvement of the invention according to the author. St. No. 1359004.

The purpose of the invention is to increase the reliability of tests when a massive piston located between two hydraulic springs is used to excite the oscillations of an object of oscillations due to a more precise setting of the initial pressure difference in the hydraulic springs.

This goal is achieved due to the fact that the initial pressure drop is created by pushing the required volume into one of the hydraulic springs of the body.

The drawing shows a device that implements a method for initiating damped oscillations of an object.

The device comprises a housing 1, in the cavity 2 of which a piston 3 is installed with a rod 4 supported on a retaining element in the form of a destructible membrane 5 placed in cavity 6, a two-stage piston 7, the stage of which having a larger diameter is placed in an additional cavity 8 which is communicated with cavity 2 through axial opening 9 in partition dividing these cavities 10, powder charge 11, which serves to destroy the membrane 5 and placed in cavity 6, and additional powder charge 12, which creates pressure that ensures The first stages of the piston 7 are of smaller diameter into the cavity 2. The cavities 2 and 6 are separated by a partition 13, in which an axial bore 14 is made, through which the piston rod 4 of the piston 3 is passed. The piston 3 divides according to

bridge 2 on the piston 15 and the rod 16 camera. When these chambers are filled with liquid, hydraulic springs are formed, between which the piston 3 can oscillate. In the cavity 8, a stop 17 for the piston 7 is formed. The housing 1 is attached to the test object 18. The stop 17 provides such a free stroke of the piston 7, so that in chamber 15 the required maximum pressure P.

When this is the necessary free running of the DH piston 7 is determined from the condition

dx z3 & - dx f

(one)

five

Q Q

five

where V0 is the initial volume of the chamber 15; K - compressibility factor

liquids;

F - the area of the end of the stage of smaller diameter of the piston 7.

The method for initiating damped oscillations of an object is carried out as follows.

The housing 1 of the device is attached to the test object 18. The chambers 15 and 16 are filled with the working fluid. Based on the required maximum amplitude of the excited oscillations, the required differential pressure between chambers 15 and 16 is determined. To achieve this difference, the free stroke of the piston 7 is determined by expression (1) and the piston 7 is installed. thus, adjusting the stop 17. The powder charge ignites. The pressure in the cavity 8 rises, as a result of which a stage of smaller diameter of the piston 7 is pushed into the chamber 15 until the stop of a larger diameter stops the partition 10. At the same time, the pressure in the chamber 15 rises to the desired

5155

values, and the piston 7 is held in this position throughout the entire time of the oscillatory process. The force acting on the piston in this case is equal to 85-90% of the effort to destroy the membrane 5, which keeps the piston 3 from moving. The characteristics of charge 12 are chosen in such a way that the additional dynamic force acting on the piston 3 due to the quick pull-out of the piston 7 does not exceed 10% of the force of the destruction of the membrane 5. To do this, the retracting speed

piston 7 hlaks does not have to exceed

values

 , 0Л1-ЈР,

And "ax -

where is the initial pressure drop between the hydraulic springs in chambers 15 and 16, and is the density of the working fluid

a is the speed of sound in a liquid. The damping time of wave processes occurring in chamber 15 when the piston 7 is sharply moved in is about 0.001 s.

Thus, after 0.001 seconds after the piston 7 is pushed in, it is possible to destroy the membrane 5 to release the piston 3. For this, an additional force from an autonomous exciter is applied to the membrane 5, so that the total force acting on the membrane 5 is 110-115% from the effort of its destruction (i.e., guaranteed destruction of the membrane 5 would be ensured). This additional force is created by igniting the charge 11 in the cavity 6. The ignition of the charge 11 should not occur later than 0.01 s to eliminate the influence of the possible flow of fluid from the chamber 15 to the chamber 16 through the piston seal 3. The required time interval it is ensured by the selection of ballistic parameters of charges 11 and 12 or by an appropriate ignition delay of charge 11.

When the membrane 5 is destroyed, the piston 3 is released and under the action of the initial pressure differential in the chambers 15 and 16 begins to oscillate, whereby the test object 18 through the housing 1 will be subjected to powerful high-frequency damped oscillations.

Q

0

five

0

five

0

five

0

five

The initial oscillation amplitude, the piston 3 is determined by the initial pressure differential between the chambers 15 and 16, which can be set quite accurately by strictly regulated reduction of the volume of fluid in the chamber 15 by pushing the piston 7 into it by a predetermined value. High reproduction accuracy of a given dynamic load is also provided by the fact that this load does not depend on the force of destruction of the membrane 5, which is carried out using an autonomous power driver (charge 11).

The proposed method for initiating damped oscillations and a device for its implementation provide reproduction of the initial acceleration of the test object with an accuracy of about 5%.

Claims (2)

1. The method of initiating damped oscillations of an object according to ed. St. No. 1359004, characterized in that, in order to increase the reliability of testing using hydraulic springs due to more precise setting of the initial pressure drop in the hydraulic springs, the initial pressure drop is created by reducing the volume of one of the hydraulic springs by a specified amount by pushing the body of the required volume with a speed of no more ° .i 8. 5 area where rp is the required initial pressure drop between the hydraulic springs, n / m 2, O is the density of the liquid, kg / m-, and is the speed of sound in the liquid, m / s and an additional force from the autonomous energizer is applied 0.001-0.01 s after the creation of the pressure drop. 2. A device for initiating damped oscillations of an object according to the ed. St. No. 1359004, characterized in that, in order to increase the reliability of testing when using hydraulic springs due to 7155 more accurate setting of the initial differential pressure in hydraulic springs, it is equipped with a two-stage piston, a step of larger diameter is placed in an additional cavity, which is made in the housing and communicated with the piston chamber of the main cavity through an axial bore in the partition separating these cavities, introduced into the axial bore, and an additional powder charge to create pressure, which ensures that the piston of a smaller diameter moves into the piston chamber of the axle ovnoy cavity into the secondary cavity by the charge is formed eight stop for the piston, and the free stroke & X of the two-stage piston is selected from the condition Bx Vo- F TO where P is the required maximum pressure in the piston chamber, n / m ", V0 - the initial volume of fluid in the piston chamber, m3, K - coefficient of compressibility of the liquid, m / n, F is the area of a torus of a smaller diameter of a two-stage piston, mV.