RU2414690C1 - Stand for testing objects on alternating-sign impact loads - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: stand has a base with guides, a shaft for accelerating a striker, a decelerating device and a platform which moves in between on guides for placing two cylindrical reservoirs with liquid on its opposite sides in line with the shaft and the test object in a container. A first profiled tip is attached to the front end of he striker coaxially with it and with possibility of entering the input opening of the first reservoir with liquid closed by a membrane. The deceleration device is in form of a second profiled tip attached to the base opposite the shaft and coaxial with it with possibility of entering the input opening of the second reservoir with liquid, covered with a membrane. Placing the platform between the tips, whose profiles are defined by the form and parametres of the alternating-sign overloading pulse, as well as installation at the output of the shaft at least one crusher for decelerating the tip after formation of the positive phase of the overloading pulse and normally closed check valve in the bottom area of the first reservoir with liquid, provides independent formation of positive and negative phases of the alternating-sign overloading pulse for testing articles.

EFFECT: testing and article with a single alternating-sign overloading pulse with predetermined form and parametres, as well as with imitation of its location in flooded condition at given depth in the liquid.

9 cl, 7 dwg

Description

The invention relates to testing equipment, in particular, to stands for testing objects with single alternating shock pulses of a load (overload).

A known stand for full-scale testing of products for alternating shock overloads containing a flyover, a hammer with one hydraulic spring, a working platform for mounting the test product, movable in the direction of impact, a brake device and a buffer mass with another hydraulic spring installed between the working platform and the brake device. The buffer mass is made with the possibility of controlling stiffness, equipped with removable weights and can move in the direction of impact (see AS USSR No. 315075, IPC G01M 7/00, publ. 21.IX.1971. Bull. No. 28).

The disadvantage of this stand is that the formation of an alternating overload pulse is carried out by hydraulic springs in conjunction with the contacting elements of the hammer, working platform and buffer mass, in which plastic deformations are inevitable and even necessary to ensure the required durations of the positive and negative phases of the pulse. At this stand it is impossible to provide a predetermined arbitrary law of change in overload in time. In addition, the stand as a mechanical system with gaps, with moving and contacting elements without cutting off the influence of the elements creating the first positive phase of the overload pulse on the formation of the second negative phase of the overload pulse, does not have the ability to provide a continuous, without time delay, transition of the positive phase of the pulse in the negative phase. Preliminary calibration of the stand for this is time-consuming and inefficient, since the stability and accuracy of reproduction of overload pulses from experience to experience on a stand with the described formation of an overload pulse is obviously small.

In addition, repeated collisions of the working platform with the hammer due to the elastic component of the force interaction of the working platform with the hydraulic springs of the hammer and the buffer mass are not ruled out. This is possible because There are no limits for moving the hammer and the work platform. The hammer at the end of the first positive phase of the overload impulse, having bounced off the working platform, can enter the overpass. After the second exit from the overpass, having acquired the initial speed, the hammer will be ready for subsequent interaction with the working platform. Moreover, the speed of the working platform may no longer be zero, as it was during the first interaction with the hammer, since the working platform, after interacting with the buffer mass, can move towards the hammer rolling down from the flyover at a certain speed.

The closest analogue of the claimed stand, selected as a prototype, is a stand for testing products for alternating loads, containing a base with rails installed in the rails of a movable platform for mounting the test product, located on opposite sides of the platform and interacting with it, a drummer and a movable buffer mass, the first elastic element (spring) mounted on the buffer mass from the platform side, which is attached to the plateau in order to reproduce a lot of cyclic load my mass buffer braking device, a device for impactor acceleration of the trunk associated with the source of pressurized gas, a second elastic member mounted on the platform from the stem (see. AS USSR №690352, IPC ² G01M 7/00, publ 05.10.1979. Bull. No. 37).

The disadvantages of this stand are the impossibility of creating a single alternating overload pulse and the use of elastic springs and additional buffer mass as a shaper of overload pulses, with the help of which it is impossible to set the desired pulse shape and parameters in advance and reproduce it from experience to experience with the given stability and accuracy. In addition, for this reason, for the same reason as at the previous stand, a continuous, without time delay, transition of the positive phase of the pulse to the negative phase cannot be provided.

The problem solved by the claimed invention is to develop a stand that allows to conduct studies of the health of objects that, during operation, are subjected to a single alternating overload pulse with predetermined shape and parameters and may be under hydrostatic pressure of a liquid column when the object is freely immersed at a given depth.

The technical result, which can be obtained by using the inventive stand, is to provide studies of the test object with a single alternating overload pulse with a predetermined shape and parameters, including with an imitation of being in a flooded state at a given depth in the liquid, the process of creating positive and negative phases of alternating impulse overload, affecting the test object (OI), occurs without mutual influence between them, which ensures maximum compliance with the shape and parameters of the specified overload pulse is given.

The specified technical result is achieved by using a test bench for alternating impact loads containing a base with guides, a barrel for accelerating the striker, a platform for placing the test object, moving along the guides in the direction of impact, a braking device that differs from the prototype in that it is additionally equipped with the first and the second cylindrical reservoirs of liquid mounted on both sides of the platform coaxially with the barrel, the first shaped tip is mounted on the front end of the ud nick coaxially to input it into the inlet opening closed by a membrane, the first fluid reservoir, the braking device is designed as a second profiled tip, mounted to the base opposite the stem is coaxially to input it into the inlet opening closed by a membrane, the second liquid reservoir.

The barrel may be provided with openings for bleeding gas after the drummer reaches a predetermined speed. At least one crusher can be installed at the exit of the barrel, designed to support the hammer after the formation of a positive phase of the pulse.

On the outer end surface of the inlet openings of the first and second reservoirs, coaxially to the tanks can be installed in a ring, the cross section of which is made in the form of a rectangular trapezoid and oriented so that the larger base of the ring is adjacent to the outer end surface of the inlet of the corresponding reservoir, and the diameter of the inlet formed the sharp edge of the ring is less than the diameter of the inner side surface of the corresponding reservoir, and the area of the annular gap between the corresponding yuschim sharp edge tip and ring is less than the area of the annular gap between the inner lateral surface of the respective reservoir and respective tip.

A normally closed non-return valve may be installed in the first tank, which can be activated when a vacuum occurs inside the liquid of the first tank.

The platform of the stand can be made with the possibility of placing OI in a container with liquid in a flooded state and with the ability to adjust the pressure of the liquid filling the container.

The stand can be equipped with a damper made of porous material placed in the barrel behind the drummer in the direction of its movement.

The radii of the cross section of the first r ₁ (z ₁ ) and second r ₂ (z ₂ ) shaped tips, respectively, at a distance of z ₁ and z ₁ from their sock can be selected from the condition:

where r _i is the radius of the inlet of the first (i = 1) or second (i = 2) tank;

ψ _i (z _i ) is the dimensionless profile function of the corresponding tip, is determined from the corresponding expression:

или

or

in which

m _UN ; m _PE - respectively, the total mass of the drummer and the tip or platform with the elements placed on it (tanks, test object and container for it);

ρ ₁ , ρ ₂ - the density of the liquid, respectively, in the first and second reservoir;

- площадь входного отверстия соответственно в первом и втором резервуаре;

- the area of the inlet in the first and second reservoir, respectively;

a _CN (z ₁ ), a _PE (z ₂ ) - respectively, the acceleration of the centers of mass of the drummer with the first tip and the platform with the elements placed on it, depending on the penetration of the tip of the tips into the first or second reservoir, respectively, by the values of z ₁ and z ₂ ;

V _CN (z ₁ ); V _PE (z ₂ ) is, respectively, the velocity of the centers of mass of the striker with the first tip and the platform with elements placed on it, depending on the penetration of the tip of the tips into the first or second reservoir, respectively, by the value of z ₁ and z ₂ .

Supply the stand with the first and second cylindrical reservoirs of liquid mounted on both sides of the platform, the first profiled tip mounted on the front end of the drummer coaxially with the possibility of introducing into the inlet, closed by the membrane, the first reservoir of fluid, the braking device in the form of a second profiled tip fixed on the base opposite the barrel coaxially with it with the possibility of introducing into the inlet, closed by a membrane, a second reservoir with liquid, I provide loading the test object alternating pulse overload predetermined shapes and parameters without mutual influence of the positive and negative pulse phases, which improves the accuracy of the pulse-defined parameters.

Placing a damper made of a porous material in the barrel behind the drummer in the direction of the drummer makes it possible to smooth out sharp pressure peaks during acceleration of the drummer in the barrel, which will facilitate control of the drummer acceleration and increase the accuracy of the set parameters of the overload pulse.

The holes in the barrel make it possible, after the drummer reaches the set speed to realize the positive phase of the overload pulse, to pit the gas from the barrel so that the further movement of the drummer is carried out by inertia, thereby bringing the loading conditions closer to the set ones.

The implementation of the container with the possibility of placing OI in a flooded state in a container with a liquid with pressure control in it allows you to simulate the impact of both shock load and hydrostatic pressure on the OI at a given depth in the liquid.

The implementation of the radii of the cross section of the first and second shaped tips at a distance of z ₁ and z ₂ from the toe of the corresponding tip from the condition (1) allows you to set various shapes and parameters of alternating overload pulses.

Installing at least one crusher at the barrel exit, designed to support the hammer after the formation of a positive pulse phase, allows the hammer to stop, thereby eliminating its distorting force effect on the formation of the negative pulse phase.

Installation on the outer end surface of the inlet openings of the first and second reservoirs coaxially to the reservoirs in a ring with predetermined parameters of their cross-section allows the positive and negative phases of the overload pulse to be formed with several local extremes, which makes it possible to use a test bench for OI subjected to a monotonically alternating alternating overload pulse with superimposed oscillations.

Installing a non-return valve in the first tank, which is triggered when a rarefaction occurs in the liquid when the first profiled tip leaves the first reservoir due to the stop of the hammer by the cracker, will provide a break in the mechanical connection of the first profiled tip with the first reservoir and unimpeded movement of the platform with OI during the formation of the negative phase of the overload pulse.

The invention is illustrated by drawings.

Figure 1 shows a section of the inventive stand for testing objects for alternating shock loads.

Figure 2 shows the position of the elements of the stand at the end of the formation of the positive phase of an alternating impulse overload, at the moment the drummer touches the crash.

Figure 3 shows a diagram of the operation of the stand during the formation of the positive phase of the pulse n ⁺ (t) before the introduction of the first tip into the first tank (dotted line) and in the process of implementation.

.Figure 4 shows graphs of changes in speeds V * _UN (t); and V _PE (t), respectively, of the striker and the first tip (with a total mass of ( _mU ) and a platform with tanks placed on it, the test object and a container for it (with a total mass of m _PE ) during the formation of a positive pulse phase n ⁺ (t), and also their relative speed

.

Figure 5 shows a diagram of the installation of a normally closed check valve in the first tank in the initial position (dotted line) and after operation.

Figure 6 shows a diagram of the operation of the stand during the formation of the negative phase of the pulse n ^- (t) during the implementation of the second profiled tip in the second tank.

Figure 7 shows the shape of a given alternating impulse overload pulse, the field of tolerances for implementation during testing according to GOST 28213-89 and its possible implementation on the proposed stand.

The test bench for objects under alternating loads (see Fig. 1) contains a base 1 with guides 15, on which a second profiled tip 2 and a cylindrical barrel 3 are mounted coaxially with each other for acceleration of the hammer 6. In between the barrel 3 and the second profiled tip 2 freely, strictly along the line connecting their centers, is moved using a sliding pair 16 or a rolling pair 22 along the guides 15 of the platform 8, on which a container 9 with OI 10 and the first and W eye fluid reservoir 11 and 12, respectively. The brake device is made in the form of a second profiled tip 2, mounted on a base 1 opposite the barrel 3 coaxially to it.

Inside the barrel 5 for acceleration of the striker 6 there may be a high-pressure chamber 4 with a charge 5 of gunpowder or explosive placed inside it or the high-pressure chamber 4 can be connected through a valve to a pressure air accumulator (VAD, not shown in FIG. 1) and there is a drummer 6 freely movable along it. The drummer 6 can be separated from the high-pressure chamber 4 by a damper 7 made of porous material to smooth out sharp peaks of gas pressure from the involved charge 5 or when air is supplied from the VAD′a. At the front end of the striker 6, the first profiled tip 19 is coaxially fixed to it, the midsection of which is less than the diameter of the striker 6 so that at least one crusher 18 can rest on the inside of the open part of the barrel 3, which is supported on the ledge thus formed, ensuring the stop of the hammer 6 after the formation of the positive phase of the pulse n ⁺ (t). On the platform 8, from the side facing the barrel 3, and coaxially mounted thereto, the first reservoir 11 with liquid and with a normally closed check valve 23, and on the other side facing the second profiled tip 2, and the second reservoir 12 with fluid coaxially mounted .

In order to eliminate the distorting effect on the positive phase of the force overload pulse generated by the first profiled tip 19 from the introduction of the second profiled tip 2 into the second reservoir 12, the inlet in the second reservoir 12 at the initial moment should be located at a distance Δ from the toe of the second profiled tip 2, determined from the expression :

where g = 9,806 m / s ² - gravitational acceleration. This is the distance that platform 8 will move when the positive phase of the overload pulse n ⁺ (t) is exposed to it.

The inlets in the tanks 11 and 12 filled with liquid are closed by membranes 14 and 13, respectively, and are arranged with the possibility of sequentially introducing the first 19 and second 2 tips respectively.

In the central part of the barrel body 3, a series of holes 17 can be located so that after the striker 6 reaches a predetermined speed to realize the positive phase of the overload pulse n ⁺ (t), the gas from the high-pressure chamber 4 is vented, and further movement of the striker 6 is carried out by inertia, which brings the loading conditions closer to the given conditions.

OI 10 in the container 9 can be fixed traditionally using various transition elements of a certain stiffness or to exclude the influence on the loading of the OI of the fastening elements to be in the container 9 in a flooded state by immersion in a liquid with a given buoyancy q:

,

,

where G is the weight of the OI, _Pout is the force that pushes the OI out of the liquid. By varying the buoyancy q, it is possible to influence the amplitude of the overload n ^* (t) acting on the OI:

n ^* (t) = qn (t),

where n (t) is the overload acting on the container with OI filled with liquid.

When the OI 10 is placed in the container 9 in a flooded state, the necessary pressure can be created in the liquid, for example, using a gas bubble in the container, to simulate the effect of hydrostatic pressure on the OI located at a certain depth in the liquid.

The first and second profiled tips 19 and 2, when sequentially introduced in opposite directions respectively into the first and second tanks 11 and 12, have a predetermined alternating force effect on the OI 10 placed in the container 9 on the platform 8. The profiles of the first and second tips 19 and 2 are performed in accordance with the above expression (1). In this case, the profile of the first tip 19 must be made taking into account the influence on the generated impulse of the overload displacement of the first tank 11 located on an unsecured platform 8.

Installation on the outer end surfaces of the inlets of the first reservoir 11 and the second reservoir 12 (see FIGS. 1 and 2), respectively, of the first ring 20 and the second ring 21, the cross section of which is made in the form of a rectangular trapezoid and oriented so that the larger base of the ring is adjacent to the outer end surface of the inlet of the corresponding reservoir, the area of the annular gaps between the sharp edges of these rings and the profiled tips 19 and 2 will be less than the area of the annular gaps between the corresponding and internal lateral surfaces of reservoirs and tips, ensures the formation of positive and negative phases of the overload pulse with several local extremes, which can be used for autonomous tests of the internal element of the OI, subjected to a monotonously changing alternating overload pulse with superimposed oscillations.

A normally closed check valve 23 (see FIG. 5) is installed in the bottom zone of the first tank 11 so that when introducing the first profiled tip 19 into the first tank 11, possible fluid swirls inside the tank could not lead to premature valve actuation.

The stand works as follows.

(см. фиг.3) и приобретает скорость V_ПЭ0, равную скорости V_УНК ударника 6 в конце формирования положительной фазы импульса перегрузки (V_ПЭ0=V_УНК). Сопротивлением движению платформы 8 по направляющим 15 с использованием скользящей пары 16 или пары качения 22 при этом можно пренебречь.After opening the VAD'a valve or from activating the charge 5 in the chamber 4, a high gas pressure arises, which through the damper 7 or directly acts on the hammer 6 and accelerates it in the barrel 3 to a predetermined speed. After the drummer 6 reaches a predetermined speed in the barrel 3, due to the release of the holes of the drummer body 17 in the barrel 3 from the high-pressure chamber 4, the gas is vented. The drummer 6 by inertia moves along the barrel 3 and the first profiled tip 19 with a given speed V _UH0 , tearing the membrane 14, is introduced into the first reservoir 11, which was at rest on the platform 8. Due to inertial forces when the fluid passes through the annular gap between the first profiled the tip 19 and the inlet in the first tank 11 forms a positive phase n ⁺ (t) alternating overload pulse. Under the influence of this impulse, the striker 6 is braked, and the platform 8 with the OI 10 placed on it is accelerated by Newton’s third law:

(cm. 3) and acquires the speed V _PE0 equal speed V _UNK striker 6 at the end of formation of the positive phase overload pulse (V = V _{PE0 UNK).} The resistance to the movement of the platform 8 along the guides 15 using a sliding pair 16 or a rolling pair 22 can be neglected.

Drummer 6, after the first profiled tip 19 is fully inserted into the first reservoir 11, comes into contact with the crasher 18 and is braked. In this case, the exit of the first profiled tip 19, rigidly connected with the hammer 6, from the first tank 11, which continues to inertia move together with the platform 8 with a speed V _PE0 , is prevented by the rarefaction in the liquid of the first tank 11, which leads to distortion of the generated pulse. Under the influence of this vacuum, the check valve 23 is activated (see FIG. 5), through which the cavity of the first reservoir 11 communicates with the liquid with the atmosphere and the mechanical connection between the first shaped tip 19 and the first reservoir 11 installed on the platform 8 is broken.

Moving together with the platform 8 to this point in time at a distance Δ, the second tank 12 with an initial speed V _PE0 = V _UNK , stumbles on the second profiled tip 2. The second profiled tip 2 breaks the membrane 13 on the second reservoir 12, enters it and forms on the platform 8 and the loaded OI 10, the negative phase n ^- (t) of the alternating overload pulse.

Here is an example of a test bench for loading the assembly as part of OI 10 in container 9, two reservoirs 11 and 12 with liquid and platform 8 with a total mass m _PE = 20,000 kg of an alternating overload pulse n (t), represented by expression (4) and in graphical form on Fig.7. This is a sequence of two semi-sinusoidal pulses with different parameters:

where t is the current time;

., τ⁺=5 мс - соответственно максимальная величина перегрузки и длительность положительной фазы импульса;

., τ ⁺ = 5 ms - respectively, the maximum value of the overload and the duration of the positive phase of the pulse;

., τ^-=5.55…мс - соответственно максимальная величина перегрузки и длительность отрицательной фазы импульса.

., τ ^- = 5.55 ... ms - respectively, the maximum value of the overload and the duration of the negative phase of the pulse.

The parameters of the positive n ⁺ (t) and negative phases n ^- (t) of the alternating overload pulse n (t} should be consistent with each other on the basis of equal modulus values of the phase pulses.The phases of the alternating overload pulse n (t) are half-sinusoidal because they relate to standard pulse shapes for which tolerance fields are determined according to GOST 28213-89 when reproduced under real test conditions, and they can also be calculated in an analytical form.

The process of creating positive n ⁺ (t) and negative n ^- (t) phases of an alternating overload pulse affecting the assembly with OI 10 will be considered independently of each other, since there is no structural interference between them, and therefore the pulse generated by the stand is at maximum degree will be close to a predefined pulse.

The positive phase n ⁺ (t) of an alternating overload pulse at OI 10 is created by the interaction of two masses m _CN and m _PE . For one of them (m _УН = 1000 kg), the total mass of the striker 6 with the first profiled tip 19, moving with the initial speed V _УН0 , and the other (m _PE = 20,000 kg) - the resting platform total mass (V _ПЕ0 = 0), were _taken 8 with a container 9, OI 10 and two reservoirs 11 and 12 with liquid placed on it. The interaction of the masses is schematically presented in figure 3.

The necessary to eliminate the influence of the positive phase of the pulse on the negative and, conversely, the initial distance Δ between the inlet in the second tank 12 and the second profiled tip 2 is determined by double integration of the positive phase of the overload pulse n ⁺ (t) during its operation τ ⁺ = 5 ms :

.

.

и равенства импульсов перегрузки, действующих на эти взаимодействующие массы, получим, что при торможении массы m_УН на нее должен действовать импульс перегрузки n_УН(t), определяемый из следующего выражения:Based on the accepted mass ratio

and the equality of the overload pulses acting on these interacting masses, we get that when braking the mass m _UN , the overload impulse n _UN (t) should act on it, determined from the following expression:

.

.

, которую определим путем интегрирования импульса перегрузки n_УН(t):For such an overload pulse to be realized during braking of the mass m _UN , it must have an initial velocity

, which is determined by integrating the overload pulse n _UN (t):

.

.

Under the influence of the momentum n _VN (t), the mass m _{VN is} inhibited, and its speed will change according to the law

,

,

and the mass m _PE under the influence of the same pulse will accelerate and gain speed

.

.

The relative velocity of the mutual displacement of the masses m _UN and m _PE in this case will occur according to the law:

and it vanishes at time equal to

.

.

масса m_ПЭ (сборка с ОИ) не приобретет требуемую для реализации отрицательной фазы импульса n^-(t) скорость V_ПЭ0. Поэтому определенная выше начальная скорость

должна быть увеличена на величину V_ПЭ0=V_ПЭ(τ⁺), т.е. начальная скорость V_УН0 ударника 6 с первым профилированным наконечником 19 должна быть равна

.In magnitude, it is less than the specified duration τ ⁺ = 5 ms of the positive phase of the pulse n ⁺ (t) (see Fig. 4), and by the time

mass m _PE (assembly with OI) does not acquire the velocity V _PE0 required for the implementation of the negative phase of the pulse n ^- (t). Therefore, the initial velocity determined above

should be increased by the value of V _PE0 = V _PE (τ ⁺ ), i.e. the initial speed V _{UN0 of the} hammer 6 with the first profiled tip 19 should be equal

.

Then, for the initial speed V _{VN0 of the} hammer 6 obtained in this way and for a given overload pulse n ⁺ (t), the profile of the first tip 19, which will provide both a given pulse and its residual velocity equal to the speed of platform 8, is necessary to realize the negative phase of the pulse, must be calculated according to the above expression (1) in the following form:

where r ₁ (z ₁ ) is the radius of the first profiled tip 19 in cross section at a distance z ₁ from its toe;

r ₁ is the radius of the inlet of the first tank 11;

ψ ₁ (z ₁ ) is the dimensionless function of the profile of the first tip, determined from the expression

wherein

- площадь входного отверстия первого резервуара 11;

- the area of the inlet of the first tank 11;

a _CN (z ₁ ) is the acceleration of the center of mass of the impactor 6 and the first profiled tip 19, depending on the penetration of the toe of the first profiled tip 19 into the first reservoir 11 by a value of z ₁ ;

V _UN (z ₁ ) is the velocity of the center of mass of the impactor 6 and the first profiled tip 19, depending on the penetration of the toe of the first profiled tip 19 into the first reservoir 11 by a value of z ₁ .

The dependences a _VN (z ₁ ) and V _VN (z ₁ ) required for the calculation are easily determined, since overload pulses n _VN (t) and n _PE (t) are known for masses m _VN and m _PE .

Immediately after the formation of the positive phase of the pulse n ⁺ (t), the gap Δ is sampled and the second reservoir 12 accelerated to the speed V _PE0 bumps into the second profiled tip 2 and the formation of the second negative phase n ^- (t) of the alternating overload pulse begins. The interaction diagram of the inertial element m _PE with the second profiled tip 2 rigidly fixed on the base 1 is presented in Fig.6.

In Fig.6 (in addition to the designation of structural elements that correspond to the designation of the elements in figure 1) is indicated:

r ₂ is the inner radius of the inlet of the second tank 12;

r ₂ (z ₂ ) is the radius of the cross section of the second profiled tip 2 at a distance z ₂ from its toe;

V _PE is the speed of the loaded assembly under the influence of the negative phase of the pulse n ^- (t).

The profile of the second profiled tip 2 for creating a negative phase n ^- {t) sign on the mass m _{PE of an} alternating overload pulse is determined by the above dependences (5) and (6) with the substitution of subscript indices of the CN with PE and 1 with 2, respectively. In addition, with if necessary, it is possible to take into account the decrease in the mass of m _PE by the value of the mass of the displaced liquid from the first reservoir 11 when the positive phase of the overload pulse n ⁺ (t) is formed.

The obtained alternating impulse momentum n (t) at the proposed stand with an indication of the tolerance field for its implementation according to GOST 28213-89 is shown in Fig.7.

Slight deviations from the desired shape of the ends of the positive and negative phases of the pulse, not exceeding the tolerance range according to GOST 28213-89, are associated with the implementation of the design features of profiled tips (reducing their midsection in the tail parts in order to eliminate technological difficulties in ensuring the required profiling during manufacture, and also installation of the cone in their bow parts to exclude a flat impact on the surface of the liquid in the tanks).

For the adopted parameters of an alternating impulse with a maximum overload of 100 units, acting on test object 10 (see Fig. 1) as part of an assembly with a total mass of 20,000 kg and internal radii of the tanks 11 and 12 r ₁ = r ₂ = 300 mm barrel 3 may have a length of 2 ... 3 m with a diameter of ≈1 m, and elements (OI 10, tanks 11 and 12 and container 9) installed on a movable platform 8, depending on the dimensions of OI 10, can have a length of 1.5 ... 8 m and the total length of the stand can be approximately 10 m. In the high-pressure chamber 4 and in the tanks with liquid 11 and 12 can A pressure of approximately 4MPa is generated. Such a pressure with a wall thickness of about 50 mm can withstand with a double margin such material as 30KhGSA.

Thus, the proposed stand is put into practice, especially with the smaller dimensions and mass of the test object. On it alternating overload pulses of arbitrary shape with a total duration of up to several tens of milliseconds and with a maximum level of overload of up to several hundred units can be realized.

Claims (9)

1. A bench for testing objects for alternating shock loads, containing a base with guides, a barrel for accelerating the striker, a platform for placing the test object, moving along the guides in the direction of impact, a brake device, characterized in that it is additionally equipped with first and second cylindrical tanks with liquid mounted on both sides of the platform coaxially with the barrel, the first profiled tip mounted on the front end of the drummer coaxially with the possibility of entering into the inlet, closed The braking device, which was washed by the membrane of the first reservoir with liquid, is made in the form of a second profiled tip fixed to the base opposite the barrel coaxially with it with the possibility of introducing into the inlet, closed by the membrane, a second reservoir of fluid. 2. The stand according to claim 1, characterized in that the barrel is equipped with holes for bleeding gas after the drummer reaches a predetermined speed. 3. The stand according to claim 1, characterized in that at least one crusher is installed at the output of the barrel, designed to stop the hammer in it after the formation of the positive phase of the pulse. 4. Stand 1, characterized in that the platform is configured to place the test object in a flooded state in a container with liquid. 5. The stand according to claim 4, characterized in that the container is configured to adjust the pressure of the liquid filling it. 6. The stand according to claim 1, characterized in that a damper made of porous material is placed in the barrel behind the drummer in the direction of its movement. 7. The stand according to claim 1, characterized in that the radii of the cross section of the first r ₁ (z ₁ ) and second r ₂ (z ₂ ) shaped tips at a distance of z ₁ and z ₂ from the tip of the corresponding tip are selected from the condition:

where r _i is the radius of the inlet of the first (i = 1) or second (i = 2) tank;
ψ _i (z _i ) is the dimensionless profile function of the corresponding tip, is determined from the corresponding expression:

or

in which
m _yn ; m _pe - respectively, the total mass of the drummer and the tip or platform with the elements placed on it (tanks, test object and container for it);
ρ ₁ , ρ ₂ - the density of the liquid, respectively, in the first and second reservoir;

,

- the area of the inlet in the first and second reservoir, respectively;
and _un (z ₁ ) and _pe (z ₂ ) are, respectively, the acceleration of the centers of mass of the striker with the first tip and the platform with elements placed on it, depending on the penetration of the tip of the tips into the first or second reservoir, respectively, by the values of z ₁ and z ₂ ;
V _yn (z ₁ ); V _pe (z ₂ ) - respectively, the speed of the centers of mass of the striker with the first tip and the platform with the elements placed on it, depending on the penetration of the tip of the tips into the first or second reservoir, respectively, by the value of z ₁ and z ₂ . 8. The stand according to claim 1, characterized in that a normally closed non-return valve is installed in the first tank, which is capable of triggering when a vacuum occurs inside the liquid inside it. 9. The stand according to claim 1, characterized in that on the outer end surface of the inlet openings of the first and second tanks coaxially to the tanks is installed in a ring, the cross section of which is made in the form of a rectangular trapezoid and oriented so that the larger base of the ring is adjacent to the outer end surface of the input the holes of the corresponding reservoir, and the diameter of the inlet formed by the sharp edge of the ring is less than the diameter of the inner side surface of the corresponding reservoir, and the area of the annular the gap between the corresponding tip and the sharp edge of the ring is less than the area of the annular gap between the inner side surface of the tank and the corresponding tip.

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