RU2710870C1 - Accelerating carriages braking tray - Google Patents

Abstract

FIELD: test equipment.SUBSTANCE: invention relates to engineering, particularly, to equipment for high-speed track testing of articles for impact action. Tray for braking of acceleration carriages comprises cavity formed by bottom, front, rear and side walls, filled with energy-absorbing liquid medium, at that cavity along tray length is sectioned by means of transverse easily disintegrating partitions, and liquid energy-absorbing mediums filling separate sections have different rheological characteristics, with increase in consistency coefficient and corresponding change in flow index, in direction of carriage movement subject to braking.EFFECT: reduced length of brake section of track with provision of reliable and safe braking of high-speed rail acceleration carriages, as well as increased accuracy of results of tests accompanying tests.3 cl, 3 dwg

Description

The present invention relates to the field of technology, and specifically to equipment for high-speed track testing of products for impact.

During track tests of various products, they are installed on the accelerating carriage of the track and are accelerated with its help to a predetermined speed, after which the carriage is braked while the product is undocked from it, and its further free flight until it hits an obstacle. For braking of booster carriages during experimental research on the track, various types of braking devices are used.

A device for braking carriages / 1 / is a friction shoe driven by a powder pressure accumulator (PAD). When the igniter is located in a closed cylindrical gas cavity of the brake cylinder, the powder bomb ignites. Powder gases push the piston acting on the fluid in the working cavity of the brake cylinder, through which the force is transmitted to the friction elements in contact with the rail.

The disadvantages of this device are as follows:

- increased wear of rail track guides when exposed to them during braking of friction shoes;

- the complexity of the synchronous operation of PADs when used on two-track tracks.

In the device / 2 / the guides are made of flexible stretched steel ropes, diverging at an angle to each other in the direction of movement of the carriage. The carriage with the product is braked due to the divergence of the ropes, bringing them together, and the kinetic energy of the carriage is spent on friction and elastic deformation of the guides.

When braking using this device, along with frictional wear of the guides, some loss of the strength characteristics of the guides due to the accumulation of fatigue phenomena during reversible deformations can also occur.

A separate group of braking devices is hydrodynamic, in which the braking of high-speed objects is carried out by a liquid, mainly water.

So, for example, in devices / 3, 4 / it is proposed that the accelerated object be braked by a counter flow of water.

These devices work well for braking mostly small objects. However, their drawback is the need for additional pumping equipment, and in relation to large tracks - the need for significant amounts of water.

Closest to the proposed invention in technical essence and the achieved result is a tray for braking accelerating carriages / 5 /, containing a cavity filled with energy-absorbing liquid medium (water), formed by the bottom, front, rear and side walls. When the accelerating carriage reaches the brake section of the track, it falls into the tray, partially immersed in the water located in it, and due to the hydrodynamic interaction of the immersed carriage elements with water, it is decelerated.

The disadvantage of this device is that for complete braking of the carriage with water, it must have a large length, up to several tens of meters.

As already described above, when testing the product for impact, it is first accelerated to a predetermined speed using the accelerating carriage, and at the beginning of the brake section, it is undocked and further free to collide with the obstacle. Obviously, the smaller the distance from the beginning of the brake section of the track to the obstacle, the less will be the loss of speed of the product when moving in free flight, the more accurate it will be in the specified area of the obstacle, the more adequate and accurate the results of the corresponding measurements.

The technical task of the invention is to reduce the length of the brake section of the track with the provision of reliable and safe braking of high-speed rail accelerating carriages, as well as improving the accuracy of the results of related measurements.

The solution to this problem is achieved by the fact that in the known tray for braking booster carriages containing a cavity filled with an energy-absorbing liquid medium formed by the bottom, front, rear and side walls, in accordance with the invention, the cavity along the length of the tray is made sectionalized by transverse easily destroyed partitions, and separate sections of liquid energy-absorbing media have different rheological characteristics, - with an increase in the coefficient of consistency and corresponding changes m flow index in the direction of accelerating the carriage to be braked.

The necessity and sufficiency of the above distinctive features of the proposed technical solution can be explained as follows.

The separation of the initially large cavity of the tray into separate sections will eliminate the mixing of energy-absorbing liquid media filling them with different rheological characteristics before the carriage brakes, and the separating sections of easily destructible partitions will not impede the successive movement of the carriage along the tray sections when it is braked.

The use of liquid energy-absorbing media with various rheological characteristics for filling the tray sections will allow them to provide effective braking conditions for the accelerating carriage, corresponding to its speed at the current time and the conditions of contact interaction of its structural elements with the medium.

As energy-absorbing liquid media can be used, for example, dilatant liquids with varying degrees of consistency, or electrorheological suspensions.

The viscosity of dilatant fluids, unlike Newtonian ones, is unstable - it increases with an increase in the shear rate gradient. Clay suspensions, sand-water systems, a suspension of starch in water, suspensions of potassium silicate, etc., possess dilatant properties.

Electrorheological fluids are capable of rapidly reversible changes in viscosity under the influence of an electric field. They are suspensions consisting of particles of polarizable materials distributed in dielectric liquids, for example silica with particle sizes not exceeding 1 μm. Dispersion media can be non-polar or weakly polar organic liquids with a sufficiently high electrical resistance, for example, kerosene, thickened with small additives of polyisobutylene, etc. In the absence of an electric field, electrorheological liquids behave like most ordinary suspensions, and when an electric field is applied, they almost instantly occur. a sharp (by several orders of magnitude) increase in viscosity due to the formation of chain structures directed parallel to electric power lines sky field.

When using rheological fluid as an energy-absorbing medium for braking the accelerating carriages, the tray should be equipped with electrodes located on the inside of the side walls of its sections and connected to an adjustable constant voltage source.

During acceleration, the carriage acquires kinetic energy:

where M is the mass of the carriage, kg;

V _Kр - speed of the accelerated carriage before braking, m / s.

Along with some losses on the destruction of the front wall of the tray and then its partitions, when braking in a liquid medium filling the sections of the tray, this energy is spent on giving speed in different directions to individual volumes of liquid and their movement, internal turbulization, wave formation, increment of the free surface, drop formation heating fluid and carriage elements, etc. A complete theoretical description of these processes is difficult, however, due to the fact that their initial cause is the force interaction of the carriage elements with the liquid, the braking process can be qualitatively analyzed taking into account the indicated force factors.

The fluid drag force F _{T, which} brakes the carriage, at a given moment in time consists of two components:

F where _F - the force of the hydrodynamic interaction of fluid with the front of the carriage elements, H;

F _{G + B} is the force of the hydrodynamic interaction of a fluid with horizontal and vertical carriage elements, N.

By virtue of Newton’s third law, equal in magnitude and oppositely directed forces act on the liquid side of the carriage, leading to a change in its energy characteristics.

When used for braking non-Newtonian fluids, in particular water, these components of the instantaneous force inhibiting the carriage can be described as:

where S _Ф - the area of the frontal elements of the carriage interacting with water, m ² ;

ρ is the density of the liquid (water), kg / m ³ ;

V _K - current carriage speed, m / s.

AND

и m - соответственно количество горизонтальных и вертикальных поверхностей каретки, контактирующих с жидкостью;Where

and m are, respectively, the number of horizontal and vertical surfaces of the carriage in contact with the liquid;

S _Гi is the area of a separate horizontal element of the carriage interacting with the liquid, m ² ;

S _Bj is the area of a separate vertical element of the carriage interacting with the liquid, m ² ;

τ _Гi , τ _Bj - tangential stresses in the fluid, acting respectively in the horizontal and vertical planes on the individual surfaces of the carriage interacting with the fluid, Pa;

μ - dynamic viscosity, for a Newtonian fluid independent of shear rate, Pa⋅s;

- градиент скорости сдвига жидкости в направлениях, перпендикулярных скорости движения каретки (вертикальном и горизонтальном), с^-1;

- gradient of fluid shear rate in directions perpendicular to the speed of the carriage (vertical and horizontal), s ^-1 ;

A force component equal to F _Ф acting on the adjacent fluid layers from the side of the carriage is a source for driving a certain volume of fluid adjacent to the front surfaces of the carriage, which will be prevented, first of all, by shear stresses (tangential) arising in it with respect to the unperturbed layers. Thus, the decrease in the kinetic energy of the carriage and its braking (speed reduction) under the action of the force F _{Ф is} carried out mainly by overcoming the forces of internal viscous friction between the fluid layers.

Component F _{Г + B} describes the manifestation of viscous friction forces due to the action of shear stresses on individual horizontal and vertical elements of the carriage during its movement in the fluid. Those. the energy loss of the moving carriage under the action of the component F _{Г + B} occurs due to overcoming the friction forces of the corresponding elements of the carriage against the liquid. Moreover, in the case of water with a low dynamic viscosity μ (for example, at a temperature of 20 ° C of only 1004⋅10 ^-6 Pa⋅s), the contribution of this force factor to the braking of the carriage is very small.

An analysis of dependencies (3) and (4) shows that as it decreases, due to energy loss during braking of the current carriage speed V _K , both the braking force component F _Ф and F _{Г + B} will accordingly decrease.

If, as a inhibitory energy-absorbing medium, a non-Newtonian fluid is used, which has, in particular, dilatant properties, then

равном единице), Па⋅сⁿ;where k is the coefficient of consistency of the liquid medium (can be defined as the viscosity of the medium with a shear rate gradient

equal to one), Pa⋅s ⁿ ;

n> 1 is the flow index, which determines the increase in the effective viscosity of the medium with increasing shear rate.

If we introduce the concept of effective viscosity

then dependence (5) can be represented similarly to (4) in the form

соответственно выше и их энергопоглощающая способность, обусловленная действием сил вязкого трения, - как межслойного, генерируемого составляющей F_Ф, так и по поверхностям каретки под действием составляющей F_Г+B.The effective viscosity and density of dilatant fluids (and electrorheological), due to their composition, are significantly higher than that of water, therefore, at the same values

respectively, their energy-absorbing ability is higher, due to the action of viscous friction forces, both of the interlayer generated component F _Ф and along the surfaces of the carriage under the action of the component F _{Г + B.}

- градиента скорости сдвига жидкости в направлениях перпендикулярных вектору скорости каретки. При достаточно больших значениях величин k и n жидкость по отношению к каретке может проявить себя практически как жестко-упругое тело. Т.е. первый же контакт «каретка-жидкость» будет фактически ударным взаимодействием, что чревато разрушением отдельных элементов каретки, ее опрокидыванию и т.д.During the initial contact of the carriage with the energy-absorbing dilatant liquid in the first section of the tray, when the speed of the carriage V _Kp is large, accordingly, the value

- gradient of fluid shear rate in directions perpendicular to the carriage speed vector. At sufficiently large values of k and n, the fluid with respect to the carriage can manifest itself practically as a rigid-elastic body. Those. the first “carriage-liquid” contact will actually be a shock interaction, which is fraught with destruction of individual elements of the carriage, its overturning, etc.

(см. (6)), определяемой в свою очередь текущей скоростью каретки V_К и, как следствие, приблизительно равные тормозные факторы, обусловленные вязкостным трением под действием сил F_Ф и F_Г+B. Т.е. каретка будет тормозиться практически с постоянным замедлением, а тормозной путь вплоть до полного ее останова, и соответственно необходимая длина лотка, будут меньшими, чем в случае лотка с водяным торможением.Therefore, filling individual sections of the tray with liquid energy-absorbing media having different rheological characteristics, with an increase in the consistency coefficient and a corresponding change in the flow index in the direction of movement of the carriage to be braked, will ensure that the carriage first enters the first section of the tray without destroying its elements, and then as it moves along the tray with deceleration, maintaining approximately the same conditions of viscous friction when moving from section to section. So, if in the first section along the braking of the tray the energy-absorbing liquid medium has rheological characteristics k and n, and in the subsequent ones k 'and n', k '' and n '', etc., then under the condition k <k '<k''<... and n≤n'≤n''≤ ... ... in each section of the tray, you can get close in value of the effective viscosity of the medium μ _eff (corresponding to

(see (6)), which in turn is determined by the current carriage speed V _K and, as a result, approximately equal braking factors due to viscous friction under the action of forces F _Ф and F _{Г + B.} Those. the carriage will be braked with almost constant deceleration, and the braking distance until it stops completely, and accordingly the required length of the tray, will be less than in the case of a tray with water braking.

When using electrorheological suspensions for braking carriages, the value of effective viscosity is possible in two ways:

1 - sections of the tray are filled with suspensions with different initial rheological characteristics for each section with the condition k <k '<k' '<... and n≤n'≤n''≤ ..., and on the electrodes located on the inner side of the side walls of the sections tray, from an adjustable source a constant voltage of the same magnitude is applied to all sections;

2 - sections of the tray are filled with suspensions with the same initial rheological characteristics k = k '= k' '= ... and n = n' = n '' = ..., in this case, on the electrodes located on the inner side of the side walls of the sections of the tray, from adjustable the source is supplied with a constant voltage of different sizes for all sections, whereby the condition k <k '<k' '<... and n≤n'≤n''≤ ...

As with the dilatant liquid, both of these options will provide in each section of the tray close values of the effective viscosity of the medium μ _eff , and accordingly approximately equal braking factors.

The design of the device is illustrated by the following graphic information (the number of tray sections is not limited to three, presented in the illustrations only as an example):

In FIG. 1 is a schematic side view of a tray and an accelerating carriage with a test article before braking in a dilated ECG-absorbing medium.

In FIG. 2 also schematically shows a top view of a tray and an accelerating carriage with a test article before braking in a dilated energy-absorbing medium.

In FIG. 3 is a schematic top view of a tray and an accelerating carriage with a test article before braking in an electrorheological energy absorbing medium.

The arrows in the illustrations show the direction of movement of the carriage with the product to the braking device.

The tray for braking the booster carriages contains a cavity filled with an energy-absorbing liquid medium formed by the bottom 1, front 2, rear 3 and side walls 4. The cavity along the length of the tray is partitioned by transverse easily destructible partitions 5. Separate sections of the tray are filled with liquid energy-absorbing media 6, 6 ' , 6 '' with different rheological characteristics, consistency coefficients k (k> k '> k' ') and flow indices n (n≥n'≥n' '). The carriage 7 accelerates along the rail guides 8 by means of jet engines 9 and carries the test product 10.

For use when braking the carriages as an energy-absorbing medium 6, 6 ', 6' 'of rheological fluid (Fig. 3), the tray is equipped with electrodes 11, 12, 11', 12 ', 11' ', 12' 'located on the inner side of the side the walls of its sections and connected to a source of adjustable constant voltage 13, with the possibility of a separate connection by means of keys 14, 14 ', 14' '.

The operation of the device is as follows.

The tray sections (Figs. 1, 2) formed by the common bottom 1, front 2, rear 3 and side walls 4 and internal easily destructible partitions 5 are filled with liquid energy-absorbing media 6, 6 ', 6' 'with various rheological characteristics before testing.

The carriage 7 with the test product 10 by means of jet engines 9 moves along the rail guides 8 of the track to the braking zone, where the carriage collides with the easily destructible front wall of the tray 2. At this moment, the product 10 is undocked from the carriage 7 and then moves along the specified path before hitting the obstacle.

When the carriage 7 collides with the front wall of the tray 2, the wall collapses, the carriage enters the tray, and due to the interaction of its individual elements with the liquid energy-absorbing medium 6 located in the first compartment of the tray, hydrodynamic braking begins. Moving along the tray, the carriage, successively destroying the partitions 5, from the first section enters the second with an energy-absorbing medium 6 ', then into the third (with an energy-absorbing medium 6''), etc. Energy-absorbing media in different sections have different rheological characteristics (with an increase in the consistency coefficient and a corresponding change in the flow index, in the direction of movement of the carriage - k <k '<k''<... and n≤n'≤n''≤ ...), which allows to obtain in them close values of the effective viscosity μ _eff (determined by the current carriage speed V _K ) of the media and, as a result, approximately equal braking factors due to viscous friction under the action of forces F _Ф and F _{Г + B} , as a result of which the carriage 7 is practically inhibited with constant th slowdown.

In the case of filling the sections of the tray with energy-absorbing media 6, 6 ', 6'', having electrorheological properties (Fig. 3), to ensure that they have close values of the effective viscosity μ _eff on the electrodes 11, 12, 11', 12 ', 11 '', 12 '', located on the inner side of the side walls 4 of its sections, a constant voltage is supplied from the regulated source 13 through the keys 14, 14 ', 14''.

As a result, in both cases, the carriage 7 is braked until it stops completely with almost constant deceleration on a smaller braking distance than in the case of a tray with water braking.

Thus, the proposed device provides reliable and safe braking of high-speed rail accelerating carriages with a decrease in the required length of the brake section of the track, i.e. in fact, the length of the tray, as well as improving the accuracy of the results of the measurements associated with the tests, due to the decrease in the distance covered by the tested product from the moment of undocking from the carriage to the obstacle, and as a result, less loss of speed of the product when moving in free flight and its more accurate hit specified area of the barrier.

Sources of information taken into account when filling out the application:

1) V. Balakin, Missile tracks - M.: Science and Life, No. 2, 2006, - p. 38-39.

2) RF Patent No. 2235302, G01M 7/08, G01N 3/313, Impact test bench, booster booster device, brake booth device, 2004.

3) French Patent 22534649, F16F 9/00, F42B 13/00, G01M 19/00, Method and device for recuperating projectiles, 1984.

4) Japanese Patent No. 3028700, F42B 35/00, G01P 3/66, Bullet body speed measuring device for scoop type soft recovering apparatus, 1991.

5) RF patent №112420, Mobile device for heating the brake section of a rocket track, G01M 15/02, 2012.

Claims (3)

1. A tray for braking booster carriages, containing a cavity formed by an energy-absorbing liquid medium formed by the bottom, front, rear and side walls, characterized in that the cavity along the length of the tray is partitioned by transverse easily destructible partitions, and liquid energy-absorbing media filling separate sections have different rheological characteristics, - with an increase in the consistency coefficient and a corresponding change in the flow index, in the direction of movement of the carriage to be braked eniyu. 2. The tray according to claim 1, characterized in that dilatant liquids are used as filling sections of the energy-absorbing liquid media. 3. The tray according to claim 1, characterized in that electrorheological suspensions are used as filling sections of the energy-absorbing liquid media, the tray containing electrodes located on the inside of the side walls of its sections connected to a source of adjustable constant voltage.

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